CoCalc -- controls.xml

GitHub Repository: awilliam/linux-vfio
Path: blob/master/Documentation/DocBook/v4l/controls.xml
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  <section id="control">
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    <title>User Controls</title>
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    <para>Devices typically have a number of user-settable controls
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such as brightness, saturation and so on, which would be presented to
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the user on a graphical user interface. But, different devices
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will have different controls available, and furthermore, the range of
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possible values, and the default value will vary from device to
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device. The control ioctls provide the information and a mechanism to
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create a nice user interface for these controls that will work
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correctly with any device.</para>
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    <para>All controls are accessed using an ID value. V4L2 defines
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several IDs for specific purposes. Drivers can also implement their
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own custom controls using <constant>V4L2_CID_PRIVATE_BASE</constant>
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and higher values. The pre-defined control IDs have the prefix
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<constant>V4L2_CID_</constant>, and are listed in <xref
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linkend="control-id" />. The ID is used when querying the attributes of
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a control, and when getting or setting the current value.</para>
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    <para>Generally applications should present controls to the user
22
without assumptions about their purpose. Each control comes with a
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name string the user is supposed to understand. When the purpose is
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non-intuitive the driver writer should provide a user manual, a user
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interface plug-in or a driver specific panel application. Predefined
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IDs were introduced to change a few controls programmatically, for
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example to mute a device during a channel switch.</para>
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29
    <para>Drivers may enumerate different controls after switching
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the current video input or output, tuner or modulator, or audio input
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or output. Different in the sense of other bounds, another default and
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current value, step size or other menu items. A control with a certain
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<emphasis>custom</emphasis> ID can also change name and
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type.<footnote>
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	<para>It will be more convenient for applications if drivers
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make use of the <constant>V4L2_CTRL_FLAG_DISABLED</constant> flag, but
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that was never required.</para>
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      </footnote> Control values are stored globally, they do not
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change when switching except to stay within the reported bounds. They
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also do not change &eg; when the device is opened or closed, when the
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tuner radio frequency is changed or generally never without
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application request. Since V4L2 specifies no event mechanism, panel
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applications intended to cooperate with other panel applications (be
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they built into a larger application, as a TV viewer) may need to
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regularly poll control values to update their user
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interface.<footnote>
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	<para>Applications could call an ioctl to request events.
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After another process called &VIDIOC-S-CTRL; or another ioctl changing
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shared properties the &func-select; function would indicate
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readability until any ioctl (querying the properties) is
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called.</para>
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      </footnote></para>
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54
    <table pgwide="1" frame="none" id="control-id">
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      <title>Control IDs</title>
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      <tgroup cols="3">
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	&cs-def;
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	<thead>
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	  <row>
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	    <entry>ID</entry>
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	    <entry>Type</entry>
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	    <entry>Description</entry>
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	  </row>
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	</thead>
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	<tbody valign="top">
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	  <row>
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	    <entry><constant>V4L2_CID_BASE</constant></entry>
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	    <entry></entry>
69
	    <entry>First predefined ID, equal to
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<constant>V4L2_CID_BRIGHTNESS</constant>.</entry>
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	  </row>
72
	  <row>
73
	    <entry><constant>V4L2_CID_USER_BASE</constant></entry>
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	    <entry></entry>
75
	    <entry>Synonym of <constant>V4L2_CID_BASE</constant>.</entry>
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	  </row>
77
	  <row>
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	    <entry><constant>V4L2_CID_BRIGHTNESS</constant></entry>
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	    <entry>integer</entry>
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	    <entry>Picture brightness, or more precisely, the black
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level.</entry>
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	  </row>
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	  <row>
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	    <entry><constant>V4L2_CID_CONTRAST</constant></entry>
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	    <entry>integer</entry>
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	    <entry>Picture contrast or luma gain.</entry>
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	  </row>
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	  <row>
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	    <entry><constant>V4L2_CID_SATURATION</constant></entry>
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	    <entry>integer</entry>
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	    <entry>Picture color saturation or chroma gain.</entry>
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	  </row>
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	  <row>
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	    <entry><constant>V4L2_CID_HUE</constant></entry>
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	    <entry>integer</entry>
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	    <entry>Hue or color balance.</entry>
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	  </row>
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	  <row>
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	    <entry><constant>V4L2_CID_AUDIO_VOLUME</constant></entry>
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	    <entry>integer</entry>
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	    <entry>Overall audio volume. Note some drivers also
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provide an OSS or ALSA mixer interface.</entry>
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	  </row>
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	  <row>
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	    <entry><constant>V4L2_CID_AUDIO_BALANCE</constant></entry>
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	    <entry>integer</entry>
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	    <entry>Audio stereo balance. Minimum corresponds to all
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the way left, maximum to right.</entry>
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	  </row>
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	  <row>
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	    <entry><constant>V4L2_CID_AUDIO_BASS</constant></entry>
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	    <entry>integer</entry>
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	    <entry>Audio bass adjustment.</entry>
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	  </row>
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	  <row>
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	    <entry><constant>V4L2_CID_AUDIO_TREBLE</constant></entry>
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	    <entry>integer</entry>
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	    <entry>Audio treble adjustment.</entry>
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	  </row>
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	  <row>
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	    <entry><constant>V4L2_CID_AUDIO_MUTE</constant></entry>
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	    <entry>boolean</entry>
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	    <entry>Mute audio, &ie; set the volume to zero, however
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without affecting <constant>V4L2_CID_AUDIO_VOLUME</constant>. Like
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ALSA drivers, V4L2 drivers must mute at load time to avoid excessive
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noise. Actually the entire device should be reset to a low power
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consumption state.</entry>
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	  </row>
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	  <row>
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	    <entry><constant>V4L2_CID_AUDIO_LOUDNESS</constant></entry>
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	    <entry>boolean</entry>
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	    <entry>Loudness mode (bass boost).</entry>
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	  </row>
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	  <row>
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	    <entry><constant>V4L2_CID_BLACK_LEVEL</constant></entry>
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	    <entry>integer</entry>
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	    <entry>Another name for brightness (not a synonym of
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<constant>V4L2_CID_BRIGHTNESS</constant>). This control is deprecated
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and should not be used in new drivers and applications.</entry>
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	  </row>
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	  <row>
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	    <entry><constant>V4L2_CID_AUTO_WHITE_BALANCE</constant></entry>
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	    <entry>boolean</entry>
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	    <entry>Automatic white balance (cameras).</entry>
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	  </row>
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	  <row>
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	    <entry><constant>V4L2_CID_DO_WHITE_BALANCE</constant></entry>
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	    <entry>button</entry>
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	    <entry>This is an action control. When set (the value is
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ignored), the device will do a white balance and then hold the current
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setting. Contrast this with the boolean
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<constant>V4L2_CID_AUTO_WHITE_BALANCE</constant>, which, when
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activated, keeps adjusting the white balance.</entry>
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	  </row>
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	  <row>
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	    <entry><constant>V4L2_CID_RED_BALANCE</constant></entry>
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	    <entry>integer</entry>
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	    <entry>Red chroma balance.</entry>
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	  </row>
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	  <row>
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	    <entry><constant>V4L2_CID_BLUE_BALANCE</constant></entry>
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	    <entry>integer</entry>
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	    <entry>Blue chroma balance.</entry>
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	  </row>
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	  <row>
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	    <entry><constant>V4L2_CID_GAMMA</constant></entry>
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	    <entry>integer</entry>
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	    <entry>Gamma adjust.</entry>
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	  </row>
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	  <row>
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	    <entry><constant>V4L2_CID_WHITENESS</constant></entry>
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	    <entry>integer</entry>
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	    <entry>Whiteness for grey-scale devices. This is a synonym
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for <constant>V4L2_CID_GAMMA</constant>. This control is deprecated
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and should not be used in new drivers and applications.</entry>
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	  </row>
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	  <row>
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	    <entry><constant>V4L2_CID_EXPOSURE</constant></entry>
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	    <entry>integer</entry>
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	    <entry>Exposure (cameras). [Unit?]</entry>
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	  </row>
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	  <row>
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	    <entry><constant>V4L2_CID_AUTOGAIN</constant></entry>
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	    <entry>boolean</entry>
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	    <entry>Automatic gain/exposure control.</entry>
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	  </row>
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	  <row>
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	    <entry><constant>V4L2_CID_GAIN</constant></entry>
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	    <entry>integer</entry>
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	    <entry>Gain control.</entry>
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	  </row>
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	  <row>
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	    <entry><constant>V4L2_CID_HFLIP</constant></entry>
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	    <entry>boolean</entry>
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	    <entry>Mirror the picture horizontally.</entry>
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	  </row>
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	  <row>
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	    <entry><constant>V4L2_CID_VFLIP</constant></entry>
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	    <entry>boolean</entry>
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	    <entry>Mirror the picture vertically.</entry>
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	  </row>
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	<row>
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	  <entry><constant>V4L2_CID_HCENTER_DEPRECATED</constant> (formerly <constant>V4L2_CID_HCENTER</constant>)</entry>
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	    <entry>integer</entry>
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	    <entry>Horizontal image centering. This control is
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deprecated. New drivers and applications should use the <link
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linkend="camera-controls">Camera class controls</link>
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<constant>V4L2_CID_PAN_ABSOLUTE</constant>,
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<constant>V4L2_CID_PAN_RELATIVE</constant> and
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<constant>V4L2_CID_PAN_RESET</constant> instead.</entry>
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	  </row>
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	  <row>
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	    <entry><constant>V4L2_CID_VCENTER_DEPRECATED</constant>
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	    (formerly <constant>V4L2_CID_VCENTER</constant>)</entry>
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	    <entry>integer</entry>
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	    <entry>Vertical image centering. Centering is intended to
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<emphasis>physically</emphasis> adjust cameras. For image cropping see
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<xref linkend="crop" />, for clipping <xref linkend="overlay" />. This
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control is deprecated. New drivers and applications should use the
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<link linkend="camera-controls">Camera class controls</link>
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<constant>V4L2_CID_TILT_ABSOLUTE</constant>,
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<constant>V4L2_CID_TILT_RELATIVE</constant> and
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<constant>V4L2_CID_TILT_RESET</constant> instead.</entry>
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	  </row>
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	  <row id="v4l2-power-line-frequency">
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	    <entry><constant>V4L2_CID_POWER_LINE_FREQUENCY</constant></entry>
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	    <entry>enum</entry>
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	    <entry>Enables a power line frequency filter to avoid
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flicker. Possible values for <constant>enum v4l2_power_line_frequency</constant> are:
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<constant>V4L2_CID_POWER_LINE_FREQUENCY_DISABLED</constant> (0),
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<constant>V4L2_CID_POWER_LINE_FREQUENCY_50HZ</constant> (1) and
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<constant>V4L2_CID_POWER_LINE_FREQUENCY_60HZ</constant> (2).</entry>
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	  </row>
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	  <row>
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	    <entry><constant>V4L2_CID_HUE_AUTO</constant></entry>
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	    <entry>boolean</entry>
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	    <entry>Enables automatic hue control by the device. The
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effect of setting <constant>V4L2_CID_HUE</constant> while automatic
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hue control is enabled is undefined, drivers should ignore such
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request.</entry>
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	  </row>
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	  <row>
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	    <entry><constant>V4L2_CID_WHITE_BALANCE_TEMPERATURE</constant></entry>
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	    <entry>integer</entry>
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	    <entry>This control specifies the white balance settings
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as a color temperature in Kelvin. A driver should have a minimum of
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2800 (incandescent) to 6500 (daylight). For more information about
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color temperature see <ulink
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url="http://en.wikipedia.org/wiki/Color_temperature">Wikipedia</ulink>.</entry>
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	  </row>
251
	  <row>
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	    <entry><constant>V4L2_CID_SHARPNESS</constant></entry>
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	    <entry>integer</entry>
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	    <entry>Adjusts the sharpness filters in a camera. The
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minimum value disables the filters, higher values give a sharper
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picture.</entry>
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	  </row>
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	  <row>
259
	    <entry><constant>V4L2_CID_BACKLIGHT_COMPENSATION</constant></entry>
260
	    <entry>integer</entry>
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	    <entry>Adjusts the backlight compensation in a camera. The
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minimum value disables backlight compensation.</entry>
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	  </row>
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	  <row>
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	    <entry><constant>V4L2_CID_CHROMA_AGC</constant></entry>
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	    <entry>boolean</entry>
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	    <entry>Chroma automatic gain control.</entry>
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	  </row>
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	  <row>
270
	    <entry><constant>V4L2_CID_CHROMA_GAIN</constant></entry>
271
	    <entry>integer</entry>
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	    <entry>Adjusts the Chroma gain control (for use when chroma AGC
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	    is disabled).</entry>
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	  </row>
275
	  <row>
276
	    <entry><constant>V4L2_CID_COLOR_KILLER</constant></entry>
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	    <entry>boolean</entry>
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	    <entry>Enable the color killer (&ie; force a black &amp; white image in case of a weak video signal).</entry>
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	  </row>
280
	  <row id="v4l2-colorfx">
281
	    <entry><constant>V4L2_CID_COLORFX</constant></entry>
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	    <entry>enum</entry>
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	    <entry>Selects a color effect. Possible values for
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<constant>enum v4l2_colorfx</constant> are:
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<constant>V4L2_COLORFX_NONE</constant> (0),
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<constant>V4L2_COLORFX_BW</constant> (1),
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<constant>V4L2_COLORFX_SEPIA</constant> (2),
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<constant>V4L2_COLORFX_NEGATIVE</constant> (3),
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<constant>V4L2_COLORFX_EMBOSS</constant> (4),
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<constant>V4L2_COLORFX_SKETCH</constant> (5),
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<constant>V4L2_COLORFX_SKY_BLUE</constant> (6),
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<constant>V4L2_COLORFX_GRASS_GREEN</constant> (7),
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<constant>V4L2_COLORFX_SKIN_WHITEN</constant> (8) and
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<constant>V4L2_COLORFX_VIVID</constant> (9).</entry>
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	  </row>
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	  <row>
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	    <entry><constant>V4L2_CID_ROTATE</constant></entry>
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	    <entry>integer</entry>
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	    <entry>Rotates the image by specified angle. Common angles are 90,
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	    270 and 180. Rotating the image to 90 and 270 will reverse the height
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	    and width of the display window. It is necessary to set the new height and
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	    width of the picture using the &VIDIOC-S-FMT; ioctl according to
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	    the rotation angle selected.</entry>
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	  </row>
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	  <row>
306
	    <entry><constant>V4L2_CID_BG_COLOR</constant></entry>
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	    <entry>integer</entry>
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	    <entry>Sets the background color on the current output device.
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	    Background color needs to be specified in the RGB24 format. The
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	    supplied 32 bit value is interpreted as bits 0-7 Red color information,
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	    bits 8-15 Green color information, bits 16-23 Blue color
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	    information and bits 24-31 must be zero.</entry>
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	  </row>
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	  <row>
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	    <entry><constant>V4L2_CID_ILLUMINATORS_1</constant>
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		<constant>V4L2_CID_ILLUMINATORS_2</constant></entry>
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	    <entry>boolean</entry>
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	    <entry>Switch on or off the illuminator 1 or 2 of the device
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		(usually a microscope).</entry>
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	  </row>
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	  <row>
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	    <entry><constant>V4L2_CID_LASTP1</constant></entry>
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	    <entry></entry>
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	    <entry>End of the predefined control IDs (currently
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<constant>V4L2_CID_ILLUMINATORS_2</constant> + 1).</entry>
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	  </row>
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	  <row>
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	    <entry><constant>V4L2_CID_PRIVATE_BASE</constant></entry>
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	    <entry></entry>
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	    <entry>ID of the first custom (driver specific) control.
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Applications depending on particular custom controls should check the
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driver name and version, see <xref linkend="querycap" />.</entry>
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	  </row>
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	</tbody>
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      </tgroup>
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    </table>
337

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    <para>Applications can enumerate the available controls with the
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&VIDIOC-QUERYCTRL; and &VIDIOC-QUERYMENU; ioctls, get and set a
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control value with the &VIDIOC-G-CTRL; and &VIDIOC-S-CTRL; ioctls.
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Drivers must implement <constant>VIDIOC_QUERYCTRL</constant>,
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<constant>VIDIOC_G_CTRL</constant> and
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<constant>VIDIOC_S_CTRL</constant> when the device has one or more
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controls, <constant>VIDIOC_QUERYMENU</constant> when it has one or
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more menu type controls.</para>
346

347
    <example>
348
      <title>Enumerating all controls</title>
349

350
      <programlisting>
351
&v4l2-queryctrl; queryctrl;
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&v4l2-querymenu; querymenu;
353

354
static void
355
enumerate_menu (void)
356
{
357
	printf ("  Menu items:\n");
358

359
	memset (&amp;querymenu, 0, sizeof (querymenu));
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	querymenu.id = queryctrl.id;
361

362
	for (querymenu.index = queryctrl.minimum;
363
	     querymenu.index &lt;= queryctrl.maximum;
364
	      querymenu.index++) {
365
		if (0 == ioctl (fd, &VIDIOC-QUERYMENU;, &amp;querymenu)) {
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			printf ("  %s\n", querymenu.name);
367
		}
368
	}
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}
370

371
memset (&amp;queryctrl, 0, sizeof (queryctrl));
372

373
for (queryctrl.id = V4L2_CID_BASE;
374
     queryctrl.id &lt; V4L2_CID_LASTP1;
375
     queryctrl.id++) {
376
	if (0 == ioctl (fd, &VIDIOC-QUERYCTRL;, &amp;queryctrl)) {
377
		if (queryctrl.flags &amp; V4L2_CTRL_FLAG_DISABLED)
378
			continue;
379

380
		printf ("Control %s\n", queryctrl.name);
381

382
		if (queryctrl.type == V4L2_CTRL_TYPE_MENU)
383
			enumerate_menu ();
384
	} else {
385
		if (errno == EINVAL)
386
			continue;
387

388
		perror ("VIDIOC_QUERYCTRL");
389
		exit (EXIT_FAILURE);
390
	}
391
}
392

393
for (queryctrl.id = V4L2_CID_PRIVATE_BASE;;
394
     queryctrl.id++) {
395
	if (0 == ioctl (fd, &VIDIOC-QUERYCTRL;, &amp;queryctrl)) {
396
		if (queryctrl.flags &amp; V4L2_CTRL_FLAG_DISABLED)
397
			continue;
398

399
		printf ("Control %s\n", queryctrl.name);
400

401
		if (queryctrl.type == V4L2_CTRL_TYPE_MENU)
402
			enumerate_menu ();
403
	} else {
404
		if (errno == EINVAL)
405
			break;
406

407
		perror ("VIDIOC_QUERYCTRL");
408
		exit (EXIT_FAILURE);
409
	}
410
}
411
</programlisting>
412
    </example>
413

414
    <example>
415
      <title>Changing controls</title>
416

417
      <programlisting>
418
&v4l2-queryctrl; queryctrl;
419
&v4l2-control; control;
420

421
memset (&amp;queryctrl, 0, sizeof (queryctrl));
422
queryctrl.id = V4L2_CID_BRIGHTNESS;
423

424
if (-1 == ioctl (fd, &VIDIOC-QUERYCTRL;, &amp;queryctrl)) {
425
	if (errno != EINVAL) {
426
		perror ("VIDIOC_QUERYCTRL");
427
		exit (EXIT_FAILURE);
428
	} else {
429
		printf ("V4L2_CID_BRIGHTNESS is not supported\n");
430
	}
431
} else if (queryctrl.flags &amp; V4L2_CTRL_FLAG_DISABLED) {
432
	printf ("V4L2_CID_BRIGHTNESS is not supported\n");
433
} else {
434
	memset (&amp;control, 0, sizeof (control));
435
	control.id = V4L2_CID_BRIGHTNESS;
436
	control.value = queryctrl.default_value;
437

438
	if (-1 == ioctl (fd, &VIDIOC-S-CTRL;, &amp;control)) {
439
		perror ("VIDIOC_S_CTRL");
440
		exit (EXIT_FAILURE);
441
	}
442
}
443

444
memset (&amp;control, 0, sizeof (control));
445
control.id = V4L2_CID_CONTRAST;
446

447
if (0 == ioctl (fd, &VIDIOC-G-CTRL;, &amp;control)) {
448
	control.value += 1;
449

450
	/* The driver may clamp the value or return ERANGE, ignored here */
451

452
	if (-1 == ioctl (fd, &VIDIOC-S-CTRL;, &amp;control)
453
	    &amp;&amp; errno != ERANGE) {
454
		perror ("VIDIOC_S_CTRL");
455
		exit (EXIT_FAILURE);
456
	}
457
/* Ignore if V4L2_CID_CONTRAST is unsupported */
458
} else if (errno != EINVAL) {
459
	perror ("VIDIOC_G_CTRL");
460
	exit (EXIT_FAILURE);
461
}
462

463
control.id = V4L2_CID_AUDIO_MUTE;
464
control.value = TRUE; /* silence */
465

466
/* Errors ignored */
467
ioctl (fd, VIDIOC_S_CTRL, &amp;control);
468
</programlisting>
469
    </example>
470
  </section>
471

472
  <section id="extended-controls">
473
    <title>Extended Controls</title>
474

475
    <section>
476
      <title>Introduction</title>
477

478
      <para>The control mechanism as originally designed was meant
479
to be used for user settings (brightness, saturation, etc). However,
480
it turned out to be a very useful model for implementing more
481
complicated driver APIs where each driver implements only a subset of
482
a larger API.</para>
483

484
      <para>The MPEG encoding API was the driving force behind
485
designing and implementing this extended control mechanism: the MPEG
486
standard is quite large and the currently supported hardware MPEG
487
encoders each only implement a subset of this standard. Further more,
488
many parameters relating to how the video is encoded into an MPEG
489
stream are specific to the MPEG encoding chip since the MPEG standard
490
only defines the format of the resulting MPEG stream, not how the
491
video is actually encoded into that format.</para>
492

493
      <para>Unfortunately, the original control API lacked some
494
features needed for these new uses and so it was extended into the
495
(not terribly originally named) extended control API.</para>
496

497
      <para>Even though the MPEG encoding API was the first effort
498
to use the Extended Control API, nowadays there are also other classes
499
of Extended Controls, such as Camera Controls and FM Transmitter Controls.
500
The Extended Controls API as well as all Extended Controls classes are
501
described in the following text.</para>
502
    </section>
503

504
    <section>
505
      <title>The Extended Control API</title>
506

507
      <para>Three new ioctls are available: &VIDIOC-G-EXT-CTRLS;,
508
&VIDIOC-S-EXT-CTRLS; and &VIDIOC-TRY-EXT-CTRLS;. These ioctls act on
509
arrays of controls (as opposed to the &VIDIOC-G-CTRL; and
510
&VIDIOC-S-CTRL; ioctls that act on a single control). This is needed
511
since it is often required to atomically change several controls at
512
once.</para>
513

514
      <para>Each of the new ioctls expects a pointer to a
515
&v4l2-ext-controls;. This structure contains a pointer to the control
516
array, a count of the number of controls in that array and a control
517
class. Control classes are used to group similar controls into a
518
single class. For example, control class
519
<constant>V4L2_CTRL_CLASS_USER</constant> contains all user controls
520
(&ie; all controls that can also be set using the old
521
<constant>VIDIOC_S_CTRL</constant> ioctl). Control class
522
<constant>V4L2_CTRL_CLASS_MPEG</constant> contains all controls
523
relating to MPEG encoding, etc.</para>
524

525
      <para>All controls in the control array must belong to the
526
specified control class. An error is returned if this is not the
527
case.</para>
528

529
      <para>It is also possible to use an empty control array (count
530
== 0) to check whether the specified control class is
531
supported.</para>
532

533
      <para>The control array is a &v4l2-ext-control; array. The
534
<structname>v4l2_ext_control</structname> structure is very similar to
535
&v4l2-control;, except for the fact that it also allows for 64-bit
536
values and pointers to be passed.</para>
537

538
      <para>It is important to realize that due to the flexibility of
539
controls it is necessary to check whether the control you want to set
540
actually is supported in the driver and what the valid range of values
541
is. So use the &VIDIOC-QUERYCTRL; and &VIDIOC-QUERYMENU; ioctls to
542
check this. Also note that it is possible that some of the menu
543
indices in a control of type <constant>V4L2_CTRL_TYPE_MENU</constant>
544
may not be supported (<constant>VIDIOC_QUERYMENU</constant> will
545
return an error). A good example is the list of supported MPEG audio
546
bitrates. Some drivers only support one or two bitrates, others
547
support a wider range.</para>
548
    </section>
549

550
    <section>
551
      <title>Enumerating Extended Controls</title>
552

553
      <para>The recommended way to enumerate over the extended
554
controls is by using &VIDIOC-QUERYCTRL; in combination with the
555
<constant>V4L2_CTRL_FLAG_NEXT_CTRL</constant> flag:</para>
556

557
      <informalexample>
558
	<programlisting>
559
&v4l2-queryctrl; qctrl;
560

561
qctrl.id = V4L2_CTRL_FLAG_NEXT_CTRL;
562
while (0 == ioctl (fd, &VIDIOC-QUERYCTRL;, &amp;qctrl)) {
563
	/* ... */
564
	qctrl.id |= V4L2_CTRL_FLAG_NEXT_CTRL;
565
}
566
</programlisting>
567
      </informalexample>
568

569
      <para>The initial control ID is set to 0 ORed with the
570
<constant>V4L2_CTRL_FLAG_NEXT_CTRL</constant> flag. The
571
<constant>VIDIOC_QUERYCTRL</constant> ioctl will return the first
572
control with a higher ID than the specified one. When no such controls
573
are found an error is returned.</para>
574

575
      <para>If you want to get all controls within a specific control
576
class, then you can set the initial
577
<structfield>qctrl.id</structfield> value to the control class and add
578
an extra check to break out of the loop when a control of another
579
control class is found:</para>
580

581
      <informalexample>
582
	<programlisting>
583
qctrl.id = V4L2_CTRL_CLASS_MPEG | V4L2_CTRL_FLAG_NEXT_CTRL;
584
while (0 == ioctl (fd, &VIDIOC-QUERYCTRL;, &amp;qctrl)) {
585
	if (V4L2_CTRL_ID2CLASS (qctrl.id) != V4L2_CTRL_CLASS_MPEG)
586
		break;
587
		/* ... */
588
		qctrl.id |= V4L2_CTRL_FLAG_NEXT_CTRL;
589
	}
590
</programlisting>
591
      </informalexample>
592

593
      <para>The 32-bit <structfield>qctrl.id</structfield> value is
594
subdivided into three bit ranges: the top 4 bits are reserved for
595
flags (&eg; <constant>V4L2_CTRL_FLAG_NEXT_CTRL</constant>) and are not
596
actually part of the ID. The remaining 28 bits form the control ID, of
597
which the most significant 12 bits define the control class and the
598
least significant 16 bits identify the control within the control
599
class. It is guaranteed that these last 16 bits are always non-zero
600
for controls. The range of 0x1000 and up are reserved for
601
driver-specific controls. The macro
602
<constant>V4L2_CTRL_ID2CLASS(id)</constant> returns the control class
603
ID based on a control ID.</para>
604

605
      <para>If the driver does not support extended controls, then
606
<constant>VIDIOC_QUERYCTRL</constant> will fail when used in
607
combination with <constant>V4L2_CTRL_FLAG_NEXT_CTRL</constant>. In
608
that case the old method of enumerating control should be used (see
609
1.8). But if it is supported, then it is guaranteed to enumerate over
610
all controls, including driver-private controls.</para>
611
    </section>
612

613
    <section>
614
      <title>Creating Control Panels</title>
615

616
      <para>It is possible to create control panels for a graphical
617
user interface where the user can select the various controls.
618
Basically you will have to iterate over all controls using the method
619
described above. Each control class starts with a control of type
620
<constant>V4L2_CTRL_TYPE_CTRL_CLASS</constant>.
621
<constant>VIDIOC_QUERYCTRL</constant> will return the name of this
622
control class which can be used as the title of a tab page within a
623
control panel.</para>
624

625
      <para>The flags field of &v4l2-queryctrl; also contains hints on
626
the behavior of the control. See the &VIDIOC-QUERYCTRL; documentation
627
for more details.</para>
628
    </section>
629

630
    <section id="mpeg-controls">
631
      <title>MPEG Control Reference</title>
632

633
      <para>Below all controls within the MPEG control class are
634
described. First the generic controls, then controls specific for
635
certain hardware.</para>
636

637
      <section>
638
	<title>Generic MPEG Controls</title>
639

640
	<table pgwide="1" frame="none" id="mpeg-control-id">
641
	  <title>MPEG Control IDs</title>
642
	  <tgroup cols="4">
643
	    <colspec colname="c1" colwidth="1*" />
644
	    <colspec colname="c2" colwidth="6*" />
645
	    <colspec colname="c3" colwidth="2*" />
646
	    <colspec colname="c4" colwidth="6*" />
647
	    <spanspec namest="c1" nameend="c2" spanname="id" />
648
	    <spanspec namest="c2" nameend="c4" spanname="descr" />
649
	    <thead>
650
	      <row>
651
		<entry spanname="id" align="left">ID</entry>
652
		<entry align="left">Type</entry>
653
	      </row><row rowsep="1"><entry spanname="descr" align="left">Description</entry>
654
	      </row>
655
	    </thead>
656
	    <tbody valign="top">
657
	      <row><entry></entry></row>
658
	      <row>
659
		<entry spanname="id"><constant>V4L2_CID_MPEG_CLASS</constant>&nbsp;</entry>
660
		<entry>class</entry>
661
	      </row><row><entry spanname="descr">The MPEG class
662
descriptor. Calling &VIDIOC-QUERYCTRL; for this control will return a
663
description of this control class. This description can be used as the
664
caption of a Tab page in a GUI, for example.</entry>
665
	      </row>
666
	      <row><entry></entry></row>
667
	      <row id="v4l2-mpeg-stream-type">
668
		<entry spanname="id"><constant>V4L2_CID_MPEG_STREAM_TYPE</constant>&nbsp;</entry>
669
		<entry>enum&nbsp;v4l2_mpeg_stream_type</entry>
670
	      </row><row><entry spanname="descr">The MPEG-1, -2 or -4
671
output stream type. One cannot assume anything here. Each hardware
672
MPEG encoder tends to support different subsets of the available MPEG
673
stream types. The currently defined stream types are:</entry>
674
	      </row>
675
	      <row>
676
		<entrytbl spanname="descr" cols="2">
677
		  <tbody valign="top">
678
		    <row>
679
		      <entry><constant>V4L2_MPEG_STREAM_TYPE_MPEG2_PS</constant>&nbsp;</entry>
680
		      <entry>MPEG-2 program stream</entry>
681
		    </row>
682
		    <row>
683
		      <entry><constant>V4L2_MPEG_STREAM_TYPE_MPEG2_TS</constant>&nbsp;</entry>
684
		      <entry>MPEG-2 transport stream</entry>
685
		    </row>
686
		    <row>
687
		      <entry><constant>V4L2_MPEG_STREAM_TYPE_MPEG1_SS</constant>&nbsp;</entry>
688
		      <entry>MPEG-1 system stream</entry>
689
		    </row>
690
		    <row>
691
		      <entry><constant>V4L2_MPEG_STREAM_TYPE_MPEG2_DVD</constant>&nbsp;</entry>
692
		      <entry>MPEG-2 DVD-compatible stream</entry>
693
		    </row>
694
		    <row>
695
		      <entry><constant>V4L2_MPEG_STREAM_TYPE_MPEG1_VCD</constant>&nbsp;</entry>
696
		      <entry>MPEG-1 VCD-compatible stream</entry>
697
		    </row>
698
		    <row>
699
		      <entry><constant>V4L2_MPEG_STREAM_TYPE_MPEG2_SVCD</constant>&nbsp;</entry>
700
		      <entry>MPEG-2 SVCD-compatible stream</entry>
701
		    </row>
702
		  </tbody>
703
		</entrytbl>
704
	      </row>
705
	      <row><entry></entry></row>
706
	      <row>
707
		<entry spanname="id"><constant>V4L2_CID_MPEG_STREAM_PID_PMT</constant>&nbsp;</entry>
708
		<entry>integer</entry>
709
	      </row><row><entry spanname="descr">Program Map Table
710
Packet ID for the MPEG transport stream (default 16)</entry>
711
	      </row>
712
	      <row><entry></entry></row>
713
	      <row>
714
		<entry spanname="id"><constant>V4L2_CID_MPEG_STREAM_PID_AUDIO</constant>&nbsp;</entry>
715
		<entry>integer</entry>
716
	      </row><row><entry spanname="descr">Audio Packet ID for
717
the MPEG transport stream (default 256)</entry>
718
	      </row>
719
	      <row><entry></entry></row>
720
	      <row>
721
		<entry spanname="id"><constant>V4L2_CID_MPEG_STREAM_PID_VIDEO</constant>&nbsp;</entry>
722
		<entry>integer</entry>
723
	      </row><row><entry spanname="descr">Video Packet ID for
724
the MPEG transport stream (default 260)</entry>
725
	      </row>
726
	      <row><entry></entry></row>
727
	      <row>
728
		<entry spanname="id"><constant>V4L2_CID_MPEG_STREAM_PID_PCR</constant>&nbsp;</entry>
729
		<entry>integer</entry>
730
	      </row><row><entry spanname="descr">Packet ID for the
731
MPEG transport stream carrying PCR fields (default 259)</entry>
732
	      </row>
733
	      <row><entry></entry></row>
734
	      <row>
735
		<entry spanname="id"><constant>V4L2_CID_MPEG_STREAM_PES_ID_AUDIO</constant>&nbsp;</entry>
736
		<entry>integer</entry>
737
	      </row><row><entry spanname="descr">Audio ID for MPEG
738
PES</entry>
739
	      </row>
740
	      <row><entry></entry></row>
741
	      <row>
742
		<entry spanname="id"><constant>V4L2_CID_MPEG_STREAM_PES_ID_VIDEO</constant>&nbsp;</entry>
743
		<entry>integer</entry>
744
	      </row><row><entry spanname="descr">Video ID for MPEG
745
PES</entry>
746
	      </row>
747
	      <row><entry></entry></row>
748
	      <row id="v4l2-mpeg-stream-vbi-fmt">
749
		<entry spanname="id"><constant>V4L2_CID_MPEG_STREAM_VBI_FMT</constant>&nbsp;</entry>
750
		<entry>enum&nbsp;v4l2_mpeg_stream_vbi_fmt</entry>
751
	      </row><row><entry spanname="descr">Some cards can embed
752
VBI data (&eg; Closed Caption, Teletext) into the MPEG stream. This
753
control selects whether VBI data should be embedded, and if so, what
754
embedding method should be used. The list of possible VBI formats
755
depends on the driver. The currently defined VBI format types
756
are:</entry>
757
	      </row>
758
	      <row>
759
		<entrytbl spanname="descr" cols="2">
760
		  <tbody valign="top">
761
		    <row>
762
		      <entry><constant>V4L2_MPEG_STREAM_VBI_FMT_NONE</constant>&nbsp;</entry>
763
		      <entry>No VBI in the MPEG stream</entry>
764
		    </row>
765
		    <row>
766
		      <entry><constant>V4L2_MPEG_STREAM_VBI_FMT_IVTV</constant>&nbsp;</entry>
767
		      <entry>VBI in private packets, IVTV format (documented
768
in the kernel sources in the file <filename>Documentation/video4linux/cx2341x/README.vbi</filename>)</entry>
769
		    </row>
770
		  </tbody>
771
		</entrytbl>
772
	      </row>
773
	      <row><entry></entry></row>
774
	      <row id="v4l2-mpeg-audio-sampling-freq">
775
		<entry spanname="id"><constant>V4L2_CID_MPEG_AUDIO_SAMPLING_FREQ</constant>&nbsp;</entry>
776
		<entry>enum&nbsp;v4l2_mpeg_audio_sampling_freq</entry>
777
	      </row><row><entry spanname="descr">MPEG Audio sampling
778
frequency. Possible values are:</entry>
779
	      </row>
780
	      <row>
781
		<entrytbl spanname="descr" cols="2">
782
		  <tbody valign="top">
783
		    <row>
784
		      <entry><constant>V4L2_MPEG_AUDIO_SAMPLING_FREQ_44100</constant>&nbsp;</entry>
785
		      <entry>44.1 kHz</entry>
786
		    </row>
787
		    <row>
788
		      <entry><constant>V4L2_MPEG_AUDIO_SAMPLING_FREQ_48000</constant>&nbsp;</entry>
789
		      <entry>48 kHz</entry>
790
		    </row>
791
		    <row>
792
		      <entry><constant>V4L2_MPEG_AUDIO_SAMPLING_FREQ_32000</constant>&nbsp;</entry>
793
		      <entry>32 kHz</entry>
794
		    </row>
795
		  </tbody>
796
		</entrytbl>
797
	      </row>
798
	      <row><entry></entry></row>
799
	      <row id="v4l2-mpeg-audio-encoding">
800
		<entry spanname="id"><constant>V4L2_CID_MPEG_AUDIO_ENCODING</constant>&nbsp;</entry>
801
		<entry>enum&nbsp;v4l2_mpeg_audio_encoding</entry>
802
	      </row><row><entry spanname="descr">MPEG Audio encoding.
803
Possible values are:</entry>
804
	      </row>
805
	      <row>
806
		<entrytbl spanname="descr" cols="2">
807
		  <tbody valign="top">
808
		    <row>
809
		      <entry><constant>V4L2_MPEG_AUDIO_ENCODING_LAYER_1</constant>&nbsp;</entry>
810
		      <entry>MPEG-1/2 Layer I encoding</entry>
811
		    </row>
812
		    <row>
813
		      <entry><constant>V4L2_MPEG_AUDIO_ENCODING_LAYER_2</constant>&nbsp;</entry>
814
		      <entry>MPEG-1/2 Layer II encoding</entry>
815
		    </row>
816
		    <row>
817
		      <entry><constant>V4L2_MPEG_AUDIO_ENCODING_LAYER_3</constant>&nbsp;</entry>
818
		      <entry>MPEG-1/2 Layer III encoding</entry>
819
		    </row>
820
		    <row>
821
		      <entry><constant>V4L2_MPEG_AUDIO_ENCODING_AAC</constant>&nbsp;</entry>
822
		      <entry>MPEG-2/4 AAC (Advanced Audio Coding)</entry>
823
		    </row>
824
		    <row>
825
		      <entry><constant>V4L2_MPEG_AUDIO_ENCODING_AC3</constant>&nbsp;</entry>
826
		      <entry>AC-3 aka ATSC A/52 encoding</entry>
827
		    </row>
828
		  </tbody>
829
		</entrytbl>
830
	      </row>
831
	      <row><entry></entry></row>
832
	      <row id="v4l2-mpeg-audio-l1-bitrate">
833
		<entry spanname="id"><constant>V4L2_CID_MPEG_AUDIO_L1_BITRATE</constant>&nbsp;</entry>
834
		<entry>enum&nbsp;v4l2_mpeg_audio_l1_bitrate</entry>
835
	      </row><row><entry spanname="descr">MPEG-1/2 Layer I bitrate.
836
Possible values are:</entry>
837
	      </row>
838
	      <row>
839
		<entrytbl spanname="descr" cols="2">
840
		  <tbody valign="top">
841
		    <row>
842
		      <entry><constant>V4L2_MPEG_AUDIO_L1_BITRATE_32K</constant>&nbsp;</entry>
843
		      <entry>32 kbit/s</entry></row>
844
		    <row>
845
		      <entry><constant>V4L2_MPEG_AUDIO_L1_BITRATE_64K</constant>&nbsp;</entry>
846
		      <entry>64 kbit/s</entry>
847
		    </row>
848
		    <row>
849
		      <entry><constant>V4L2_MPEG_AUDIO_L1_BITRATE_96K</constant>&nbsp;</entry>
850
		      <entry>96 kbit/s</entry>
851
		    </row>
852
		    <row>
853
		      <entry><constant>V4L2_MPEG_AUDIO_L1_BITRATE_128K</constant>&nbsp;</entry>
854
		      <entry>128 kbit/s</entry>
855
		    </row>
856
		    <row>
857
		      <entry><constant>V4L2_MPEG_AUDIO_L1_BITRATE_160K</constant>&nbsp;</entry>
858
		      <entry>160 kbit/s</entry>
859
		    </row>
860
		    <row>
861
		      <entry><constant>V4L2_MPEG_AUDIO_L1_BITRATE_192K</constant>&nbsp;</entry>
862
		      <entry>192 kbit/s</entry>
863
		    </row>
864
		    <row>
865
		      <entry><constant>V4L2_MPEG_AUDIO_L1_BITRATE_224K</constant>&nbsp;</entry>
866
		      <entry>224 kbit/s</entry>
867
		    </row>
868
		    <row>
869
		      <entry><constant>V4L2_MPEG_AUDIO_L1_BITRATE_256K</constant>&nbsp;</entry>
870
		      <entry>256 kbit/s</entry>
871
		    </row>
872
		    <row>
873
		      <entry><constant>V4L2_MPEG_AUDIO_L1_BITRATE_288K</constant>&nbsp;</entry>
874
		      <entry>288 kbit/s</entry>
875
		    </row>
876
		    <row>
877
		      <entry><constant>V4L2_MPEG_AUDIO_L1_BITRATE_320K</constant>&nbsp;</entry>
878
		      <entry>320 kbit/s</entry>
879
		    </row>
880
		    <row>
881
		      <entry><constant>V4L2_MPEG_AUDIO_L1_BITRATE_352K</constant>&nbsp;</entry>
882
		      <entry>352 kbit/s</entry>
883
		    </row>
884
		    <row>
885
		      <entry><constant>V4L2_MPEG_AUDIO_L1_BITRATE_384K</constant>&nbsp;</entry>
886
		      <entry>384 kbit/s</entry>
887
		    </row>
888
		    <row>
889
		      <entry><constant>V4L2_MPEG_AUDIO_L1_BITRATE_416K</constant>&nbsp;</entry>
890
		      <entry>416 kbit/s</entry>
891
		    </row>
892
		    <row>
893
		      <entry><constant>V4L2_MPEG_AUDIO_L1_BITRATE_448K</constant>&nbsp;</entry>
894
		      <entry>448 kbit/s</entry>
895
		    </row>
896
		  </tbody>
897
		</entrytbl>
898
	      </row>
899
	      <row><entry></entry></row>
900
	      <row id="v4l2-mpeg-audio-l2-bitrate">
901
		<entry spanname="id"><constant>V4L2_CID_MPEG_AUDIO_L2_BITRATE</constant>&nbsp;</entry>
902
		<entry>enum&nbsp;v4l2_mpeg_audio_l2_bitrate</entry>
903
	      </row><row><entry spanname="descr">MPEG-1/2 Layer II bitrate.
904
Possible values are:</entry>
905
	      </row>
906
	      <row>
907
		<entrytbl spanname="descr" cols="2">
908
		  <tbody valign="top">
909
		    <row>
910
		      <entry><constant>V4L2_MPEG_AUDIO_L2_BITRATE_32K</constant>&nbsp;</entry>
911
		      <entry>32 kbit/s</entry>
912
		    </row>
913
		    <row>
914
		      <entry><constant>V4L2_MPEG_AUDIO_L2_BITRATE_48K</constant>&nbsp;</entry>
915
		      <entry>48 kbit/s</entry>
916
		    </row>
917
		    <row>
918
		      <entry><constant>V4L2_MPEG_AUDIO_L2_BITRATE_56K</constant>&nbsp;</entry>
919
		      <entry>56 kbit/s</entry>
920
		    </row>
921
		    <row>
922
		      <entry><constant>V4L2_MPEG_AUDIO_L2_BITRATE_64K</constant>&nbsp;</entry>
923
		      <entry>64 kbit/s</entry>
924
		    </row>
925
		    <row>
926
		      <entry><constant>V4L2_MPEG_AUDIO_L2_BITRATE_80K</constant>&nbsp;</entry>
927
		      <entry>80 kbit/s</entry>
928
		    </row>
929
		    <row>
930
		      <entry><constant>V4L2_MPEG_AUDIO_L2_BITRATE_96K</constant>&nbsp;</entry>
931
		      <entry>96 kbit/s</entry>
932
		    </row>
933
		    <row>
934
		      <entry><constant>V4L2_MPEG_AUDIO_L2_BITRATE_112K</constant>&nbsp;</entry>
935
		      <entry>112 kbit/s</entry>
936
		    </row>
937
		    <row>
938
		      <entry><constant>V4L2_MPEG_AUDIO_L2_BITRATE_128K</constant>&nbsp;</entry>
939
		      <entry>128 kbit/s</entry>
940
		    </row>
941
		    <row>
942
		      <entry><constant>V4L2_MPEG_AUDIO_L2_BITRATE_160K</constant>&nbsp;</entry>
943
		      <entry>160 kbit/s</entry>
944
		    </row>
945
		    <row>
946
		      <entry><constant>V4L2_MPEG_AUDIO_L2_BITRATE_192K</constant>&nbsp;</entry>
947
		      <entry>192 kbit/s</entry>
948
		    </row>
949
		    <row>
950
		      <entry><constant>V4L2_MPEG_AUDIO_L2_BITRATE_224K</constant>&nbsp;</entry>
951
		      <entry>224 kbit/s</entry>
952
		    </row>
953
		    <row>
954
		      <entry><constant>V4L2_MPEG_AUDIO_L2_BITRATE_256K</constant>&nbsp;</entry>
955
		      <entry>256 kbit/s</entry>
956
		    </row>
957
		    <row>
958
		      <entry><constant>V4L2_MPEG_AUDIO_L2_BITRATE_320K</constant>&nbsp;</entry>
959
		      <entry>320 kbit/s</entry>
960
		    </row>
961
		    <row>
962
		      <entry><constant>V4L2_MPEG_AUDIO_L2_BITRATE_384K</constant>&nbsp;</entry>
963
		      <entry>384 kbit/s</entry>
964
		    </row>
965
		  </tbody>
966
		</entrytbl>
967
	      </row>
968
	      <row><entry></entry></row>
969
	      <row id="v4l2-mpeg-audio-l3-bitrate">
970
		<entry spanname="id"><constant>V4L2_CID_MPEG_AUDIO_L3_BITRATE</constant>&nbsp;</entry>
971
		<entry>enum&nbsp;v4l2_mpeg_audio_l3_bitrate</entry>
972
	      </row><row><entry spanname="descr">MPEG-1/2 Layer III bitrate.
973
Possible values are:</entry>
974
	      </row>
975
	      <row>
976
		<entrytbl spanname="descr" cols="2">
977
		  <tbody valign="top">
978
		    <row>
979
		      <entry><constant>V4L2_MPEG_AUDIO_L3_BITRATE_32K</constant>&nbsp;</entry>
980
		      <entry>32 kbit/s</entry>
981
		    </row>
982
		    <row>
983
		      <entry><constant>V4L2_MPEG_AUDIO_L3_BITRATE_40K</constant>&nbsp;</entry>
984
		      <entry>40 kbit/s</entry>
985
		    </row>
986
		    <row>
987
		      <entry><constant>V4L2_MPEG_AUDIO_L3_BITRATE_48K</constant>&nbsp;</entry>
988
		      <entry>48 kbit/s</entry>
989
		    </row>
990
		    <row>
991
		      <entry><constant>V4L2_MPEG_AUDIO_L3_BITRATE_56K</constant>&nbsp;</entry>
992
		      <entry>56 kbit/s</entry>
993
		    </row>
994
		    <row>
995
		      <entry><constant>V4L2_MPEG_AUDIO_L3_BITRATE_64K</constant>&nbsp;</entry>
996
		      <entry>64 kbit/s</entry>
997
		    </row>
998
		    <row>
999
		      <entry><constant>V4L2_MPEG_AUDIO_L3_BITRATE_80K</constant>&nbsp;</entry>
1000
		      <entry>80 kbit/s</entry>
1001
		    </row>
1002
		    <row>
1003
		      <entry><constant>V4L2_MPEG_AUDIO_L3_BITRATE_96K</constant>&nbsp;</entry>
1004
		      <entry>96 kbit/s</entry>
1005
		    </row>
1006
		    <row>
1007
		      <entry><constant>V4L2_MPEG_AUDIO_L3_BITRATE_112K</constant>&nbsp;</entry>
1008
		      <entry>112 kbit/s</entry>
1009
		    </row>
1010
		    <row>
1011
		      <entry><constant>V4L2_MPEG_AUDIO_L3_BITRATE_128K</constant>&nbsp;</entry>
1012
		      <entry>128 kbit/s</entry>
1013
		    </row>
1014
		    <row>
1015
		      <entry><constant>V4L2_MPEG_AUDIO_L3_BITRATE_160K</constant>&nbsp;</entry>
1016
		      <entry>160 kbit/s</entry>
1017
		    </row>
1018
		    <row>
1019
		      <entry><constant>V4L2_MPEG_AUDIO_L3_BITRATE_192K</constant>&nbsp;</entry>
1020
		      <entry>192 kbit/s</entry>
1021
		    </row>
1022
		    <row>
1023
		      <entry><constant>V4L2_MPEG_AUDIO_L3_BITRATE_224K</constant>&nbsp;</entry>
1024
		      <entry>224 kbit/s</entry>
1025
		    </row>
1026
		    <row>
1027
		      <entry><constant>V4L2_MPEG_AUDIO_L3_BITRATE_256K</constant>&nbsp;</entry>
1028
		      <entry>256 kbit/s</entry>
1029
		    </row>
1030
		    <row>
1031
		      <entry><constant>V4L2_MPEG_AUDIO_L3_BITRATE_320K</constant>&nbsp;</entry>
1032
		      <entry>320 kbit/s</entry>
1033
		    </row>
1034
		  </tbody>
1035
		</entrytbl>
1036
	      </row>
1037
	      <row><entry></entry></row>
1038
	      <row>
1039
		<entry spanname="id"><constant>V4L2_CID_MPEG_AUDIO_AAC_BITRATE</constant>&nbsp;</entry>
1040
		<entry>integer</entry>
1041
	      </row><row><entry spanname="descr">AAC bitrate in bits per second.</entry>
1042
	      </row>
1043
	      <row><entry></entry></row>
1044
	      <row id="v4l2-mpeg-audio-ac3-bitrate">
1045
		<entry spanname="id"><constant>V4L2_CID_MPEG_AUDIO_AC3_BITRATE</constant>&nbsp;</entry>
1046
		<entry>enum&nbsp;v4l2_mpeg_audio_ac3_bitrate</entry>
1047
	      </row><row><entry spanname="descr">AC-3 bitrate.
1048
Possible values are:</entry>
1049
	      </row>
1050
	      <row>
1051
		<entrytbl spanname="descr" cols="2">
1052
		  <tbody valign="top">
1053
		    <row>
1054
		      <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_32K</constant>&nbsp;</entry>
1055
		      <entry>32 kbit/s</entry>
1056
		    </row>
1057
		    <row>
1058
		      <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_40K</constant>&nbsp;</entry>
1059
		      <entry>40 kbit/s</entry>
1060
		    </row>
1061
		    <row>
1062
		      <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_48K</constant>&nbsp;</entry>
1063
		      <entry>48 kbit/s</entry>
1064
		    </row>
1065
		    <row>
1066
		      <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_56K</constant>&nbsp;</entry>
1067
		      <entry>56 kbit/s</entry>
1068
		    </row>
1069
		    <row>
1070
		      <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_64K</constant>&nbsp;</entry>
1071
		      <entry>64 kbit/s</entry>
1072
		    </row>
1073
		    <row>
1074
		      <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_80K</constant>&nbsp;</entry>
1075
		      <entry>80 kbit/s</entry>
1076
		    </row>
1077
		    <row>
1078
		      <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_96K</constant>&nbsp;</entry>
1079
		      <entry>96 kbit/s</entry>
1080
		    </row>
1081
		    <row>
1082
		      <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_112K</constant>&nbsp;</entry>
1083
		      <entry>112 kbit/s</entry>
1084
		    </row>
1085
		    <row>
1086
		      <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_128K</constant>&nbsp;</entry>
1087
		      <entry>128 kbit/s</entry>
1088
		    </row>
1089
		    <row>
1090
		      <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_160K</constant>&nbsp;</entry>
1091
		      <entry>160 kbit/s</entry>
1092
		    </row>
1093
		    <row>
1094
		      <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_192K</constant>&nbsp;</entry>
1095
		      <entry>192 kbit/s</entry>
1096
		    </row>
1097
		    <row>
1098
		      <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_224K</constant>&nbsp;</entry>
1099
		      <entry>224 kbit/s</entry>
1100
		    </row>
1101
		    <row>
1102
		      <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_256K</constant>&nbsp;</entry>
1103
		      <entry>256 kbit/s</entry>
1104
		    </row>
1105
		    <row>
1106
		      <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_320K</constant>&nbsp;</entry>
1107
		      <entry>320 kbit/s</entry>
1108
		    </row>
1109
		    <row>
1110
		      <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_384K</constant>&nbsp;</entry>
1111
		      <entry>384 kbit/s</entry>
1112
		    </row>
1113
		    <row>
1114
		      <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_448K</constant>&nbsp;</entry>
1115
		      <entry>448 kbit/s</entry>
1116
		    </row>
1117
		    <row>
1118
		      <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_512K</constant>&nbsp;</entry>
1119
		      <entry>512 kbit/s</entry>
1120
		    </row>
1121
		    <row>
1122
		      <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_576K</constant>&nbsp;</entry>
1123
		      <entry>576 kbit/s</entry>
1124
		    </row>
1125
		    <row>
1126
		      <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_640K</constant>&nbsp;</entry>
1127
		      <entry>640 kbit/s</entry>
1128
		    </row>
1129
		  </tbody>
1130
		</entrytbl>
1131
	      </row>
1132
	      <row><entry></entry></row>
1133
	      <row id="v4l2-mpeg-audio-mode">
1134
		<entry spanname="id"><constant>V4L2_CID_MPEG_AUDIO_MODE</constant>&nbsp;</entry>
1135
		<entry>enum&nbsp;v4l2_mpeg_audio_mode</entry>
1136
	      </row><row><entry spanname="descr">MPEG Audio mode.
1137
Possible values are:</entry>
1138
	      </row>
1139
	      <row>
1140
		<entrytbl spanname="descr" cols="2">
1141
		  <tbody valign="top">
1142
		    <row>
1143
		      <entry><constant>V4L2_MPEG_AUDIO_MODE_STEREO</constant>&nbsp;</entry>
1144
		      <entry>Stereo</entry>
1145
		    </row>
1146
		    <row>
1147
		      <entry><constant>V4L2_MPEG_AUDIO_MODE_JOINT_STEREO</constant>&nbsp;</entry>
1148
		      <entry>Joint Stereo</entry>
1149
		    </row>
1150
		    <row>
1151
		      <entry><constant>V4L2_MPEG_AUDIO_MODE_DUAL</constant>&nbsp;</entry>
1152
		      <entry>Bilingual</entry>
1153
		    </row>
1154
		    <row>
1155
		      <entry><constant>V4L2_MPEG_AUDIO_MODE_MONO</constant>&nbsp;</entry>
1156
		      <entry>Mono</entry>
1157
		    </row>
1158
		  </tbody>
1159
		</entrytbl>
1160
	      </row>
1161
	      <row><entry></entry></row>
1162
	      <row id="v4l2-mpeg-audio-mode-extension">
1163
		<entry spanname="id"><constant>V4L2_CID_MPEG_AUDIO_MODE_EXTENSION</constant>&nbsp;</entry>
1164
		<entry>enum&nbsp;v4l2_mpeg_audio_mode_extension</entry>
1165
	      </row><row><entry spanname="descr">Joint Stereo
1166
audio mode extension. In Layer I and II they indicate which subbands
1167
are in intensity stereo. All other subbands are coded in stereo. Layer
1168
III is not (yet) supported. Possible values
1169
are:</entry>
1170
	      </row>
1171
	      <row>
1172
		<entrytbl spanname="descr" cols="2">
1173
		  <tbody valign="top">
1174
		    <row>
1175
		      <entry><constant>V4L2_MPEG_AUDIO_MODE_EXTENSION_BOUND_4</constant>&nbsp;</entry>
1176
		      <entry>Subbands 4-31 in intensity stereo</entry>
1177
		    </row>
1178
		    <row>
1179
		      <entry><constant>V4L2_MPEG_AUDIO_MODE_EXTENSION_BOUND_8</constant>&nbsp;</entry>
1180
		      <entry>Subbands 8-31 in intensity stereo</entry>
1181
		    </row>
1182
		    <row>
1183
		      <entry><constant>V4L2_MPEG_AUDIO_MODE_EXTENSION_BOUND_12</constant>&nbsp;</entry>
1184
		      <entry>Subbands 12-31 in intensity stereo</entry>
1185
		    </row>
1186
		    <row>
1187
		      <entry><constant>V4L2_MPEG_AUDIO_MODE_EXTENSION_BOUND_16</constant>&nbsp;</entry>
1188
		      <entry>Subbands 16-31 in intensity stereo</entry>
1189
		    </row>
1190
		  </tbody>
1191
		</entrytbl>
1192
	      </row>
1193
	      <row><entry></entry></row>
1194
	      <row id="v4l2-mpeg-audio-emphasis">
1195
		<entry spanname="id"><constant>V4L2_CID_MPEG_AUDIO_EMPHASIS</constant>&nbsp;</entry>
1196
		<entry>enum&nbsp;v4l2_mpeg_audio_emphasis</entry>
1197
	      </row><row><entry spanname="descr">Audio Emphasis.
1198
Possible values are:</entry>
1199
	      </row>
1200
	      <row>
1201
		<entrytbl spanname="descr" cols="2">
1202
		  <tbody valign="top">
1203
		    <row>
1204
		      <entry><constant>V4L2_MPEG_AUDIO_EMPHASIS_NONE</constant>&nbsp;</entry>
1205
		      <entry>None</entry>
1206
		    </row>
1207
		    <row>
1208
		      <entry><constant>V4L2_MPEG_AUDIO_EMPHASIS_50_DIV_15_uS</constant>&nbsp;</entry>
1209
		      <entry>50/15 microsecond emphasis</entry>
1210
		    </row>
1211
		    <row>
1212
		      <entry><constant>V4L2_MPEG_AUDIO_EMPHASIS_CCITT_J17</constant>&nbsp;</entry>
1213
		      <entry>CCITT J.17</entry>
1214
		    </row>
1215
		  </tbody>
1216
		</entrytbl>
1217
	      </row>
1218
	      <row><entry></entry></row>
1219
	      <row id="v4l2-mpeg-audio-crc">
1220
		<entry spanname="id"><constant>V4L2_CID_MPEG_AUDIO_CRC</constant>&nbsp;</entry>
1221
		<entry>enum&nbsp;v4l2_mpeg_audio_crc</entry>
1222
	      </row><row><entry spanname="descr">CRC method. Possible
1223
values are:</entry>
1224
	      </row>
1225
	      <row>
1226
		<entrytbl spanname="descr" cols="2">
1227
		  <tbody valign="top">
1228
		    <row>
1229
		      <entry><constant>V4L2_MPEG_AUDIO_CRC_NONE</constant>&nbsp;</entry>
1230
		      <entry>None</entry>
1231
		    </row>
1232
		    <row>
1233
		      <entry><constant>V4L2_MPEG_AUDIO_CRC_CRC16</constant>&nbsp;</entry>
1234
		      <entry>16 bit parity check</entry>
1235
		    </row>
1236
		  </tbody>
1237
		</entrytbl>
1238
	      </row>
1239
	      <row><entry></entry></row>
1240
	      <row>
1241
		<entry spanname="id"><constant>V4L2_CID_MPEG_AUDIO_MUTE</constant>&nbsp;</entry>
1242
		<entry>boolean</entry>
1243
	      </row><row><entry spanname="descr">Mutes the audio when
1244
capturing. This is not done by muting audio hardware, which can still
1245
produce a slight hiss, but in the encoder itself, guaranteeing a fixed
1246
and reproducible audio bitstream. 0 = unmuted, 1 = muted.</entry>
1247
	      </row>
1248
	      <row><entry></entry></row>
1249
	      <row id="v4l2-mpeg-video-encoding">
1250
		<entry spanname="id"><constant>V4L2_CID_MPEG_VIDEO_ENCODING</constant>&nbsp;</entry>
1251
		<entry>enum&nbsp;v4l2_mpeg_video_encoding</entry>
1252
	      </row><row><entry spanname="descr">MPEG Video encoding
1253
method. Possible values are:</entry>
1254
	      </row>
1255
	      <row>
1256
		<entrytbl spanname="descr" cols="2">
1257
		  <tbody valign="top">
1258
		    <row>
1259
		      <entry><constant>V4L2_MPEG_VIDEO_ENCODING_MPEG_1</constant>&nbsp;</entry>
1260
		      <entry>MPEG-1 Video encoding</entry>
1261
		    </row>
1262
		    <row>
1263
		      <entry><constant>V4L2_MPEG_VIDEO_ENCODING_MPEG_2</constant>&nbsp;</entry>
1264
		      <entry>MPEG-2 Video encoding</entry>
1265
		    </row>
1266
		    <row>
1267
		      <entry><constant>V4L2_MPEG_VIDEO_ENCODING_MPEG_4_AVC</constant>&nbsp;</entry>
1268
		      <entry>MPEG-4 AVC (H.264) Video encoding</entry>
1269
		    </row>
1270
		  </tbody>
1271
		</entrytbl>
1272
	      </row>
1273
	      <row><entry></entry></row>
1274
	      <row id="v4l2-mpeg-video-aspect">
1275
		<entry spanname="id"><constant>V4L2_CID_MPEG_VIDEO_ASPECT</constant>&nbsp;</entry>
1276
		<entry>enum&nbsp;v4l2_mpeg_video_aspect</entry>
1277
	      </row><row><entry spanname="descr">Video aspect.
1278
Possible values are:</entry>
1279
	      </row>
1280
	      <row>
1281
		<entrytbl spanname="descr" cols="2">
1282
		  <tbody valign="top">
1283
		    <row>
1284
		      <entry><constant>V4L2_MPEG_VIDEO_ASPECT_1x1</constant>&nbsp;</entry>
1285
		    </row>
1286
		    <row>
1287
		      <entry><constant>V4L2_MPEG_VIDEO_ASPECT_4x3</constant>&nbsp;</entry>
1288
		    </row>
1289
		    <row>
1290
		      <entry><constant>V4L2_MPEG_VIDEO_ASPECT_16x9</constant>&nbsp;</entry>
1291
		    </row>
1292
		    <row>
1293
		      <entry><constant>V4L2_MPEG_VIDEO_ASPECT_221x100</constant>&nbsp;</entry>
1294
		    </row>
1295
		  </tbody>
1296
		</entrytbl>
1297
	      </row>
1298
	      <row><entry></entry></row>
1299
	      <row>
1300
		<entry spanname="id"><constant>V4L2_CID_MPEG_VIDEO_B_FRAMES</constant>&nbsp;</entry>
1301
		<entry>integer</entry>
1302
	      </row><row><entry spanname="descr">Number of B-Frames
1303
(default 2)</entry>
1304
	      </row>
1305
	      <row><entry></entry></row>
1306
	      <row>
1307
		<entry spanname="id"><constant>V4L2_CID_MPEG_VIDEO_GOP_SIZE</constant>&nbsp;</entry>
1308
		<entry>integer</entry>
1309
	      </row><row><entry spanname="descr">GOP size (default
1310
12)</entry>
1311
	      </row>
1312
	      <row><entry></entry></row>
1313
	      <row>
1314
		<entry spanname="id"><constant>V4L2_CID_MPEG_VIDEO_GOP_CLOSURE</constant>&nbsp;</entry>
1315
		<entry>boolean</entry>
1316
	      </row><row><entry spanname="descr">GOP closure (default
1317
1)</entry>
1318
	      </row>
1319
	      <row><entry></entry></row>
1320
	      <row>
1321
		<entry spanname="id"><constant>V4L2_CID_MPEG_VIDEO_PULLDOWN</constant>&nbsp;</entry>
1322
		<entry>boolean</entry>
1323
	      </row><row><entry spanname="descr">Enable 3:2 pulldown
1324
(default 0)</entry>
1325
	      </row>
1326
	      <row><entry></entry></row>
1327
	      <row id="v4l2-mpeg-video-bitrate-mode">
1328
		<entry spanname="id"><constant>V4L2_CID_MPEG_VIDEO_BITRATE_MODE</constant>&nbsp;</entry>
1329
		<entry>enum&nbsp;v4l2_mpeg_video_bitrate_mode</entry>
1330
	      </row><row><entry spanname="descr">Video bitrate mode.
1331
Possible values are:</entry>
1332
	      </row>
1333
	      <row>
1334
		<entrytbl spanname="descr" cols="2">
1335
		  <tbody valign="top">
1336
		    <row>
1337
		      <entry><constant>V4L2_MPEG_VIDEO_BITRATE_MODE_VBR</constant>&nbsp;</entry>
1338
		      <entry>Variable bitrate</entry>
1339
		    </row>
1340
		    <row>
1341
		      <entry><constant>V4L2_MPEG_VIDEO_BITRATE_MODE_CBR</constant>&nbsp;</entry>
1342
		      <entry>Constant bitrate</entry>
1343
		    </row>
1344
		  </tbody>
1345
		</entrytbl>
1346
	      </row>
1347
	      <row><entry></entry></row>
1348
	      <row>
1349
		<entry spanname="id"><constant>V4L2_CID_MPEG_VIDEO_BITRATE</constant>&nbsp;</entry>
1350
		<entry>integer</entry>
1351
	      </row><row><entry spanname="descr">Video bitrate in bits
1352
per second.</entry>
1353
	      </row>
1354
	      <row><entry></entry></row>
1355
	      <row>
1356
		<entry spanname="id"><constant>V4L2_CID_MPEG_VIDEO_BITRATE_PEAK</constant>&nbsp;</entry>
1357
		<entry>integer</entry>
1358
	      </row><row><entry spanname="descr">Peak video bitrate in
1359
bits per second. Must be larger or equal to the average video bitrate.
1360
It is ignored if the video bitrate mode is set to constant
1361
bitrate.</entry>
1362
	      </row>
1363
	      <row><entry></entry></row>
1364
	      <row>
1365
		<entry spanname="id"><constant>V4L2_CID_MPEG_VIDEO_TEMPORAL_DECIMATION</constant>&nbsp;</entry>
1366
		<entry>integer</entry>
1367
	      </row><row><entry spanname="descr">For every captured
1368
frame, skip this many subsequent frames (default 0).</entry>
1369
	      </row>
1370
	      <row><entry></entry></row>
1371
	      <row>
1372
		<entry spanname="id"><constant>V4L2_CID_MPEG_VIDEO_MUTE</constant>&nbsp;</entry>
1373
		<entry>boolean</entry>
1374
	      </row>
1375
	      <row><entry spanname="descr">"Mutes" the video to a
1376
fixed color when capturing. This is useful for testing, to produce a
1377
fixed video bitstream. 0 = unmuted, 1 = muted.</entry>
1378
	      </row>
1379
	      <row><entry></entry></row>
1380
	      <row>
1381
		<entry spanname="id"><constant>V4L2_CID_MPEG_VIDEO_MUTE_YUV</constant>&nbsp;</entry>
1382
		<entry>integer</entry>
1383
	      </row><row><entry spanname="descr">Sets the "mute" color
1384
of the video. The supplied 32-bit integer is interpreted as follows (bit
1385
0 = least significant bit):</entry>
1386
	      </row>
1387
	      <row>
1388
		<entrytbl spanname="descr" cols="2">
1389
		  <tbody valign="top">
1390
		    <row>
1391
		      <entry>Bit 0:7</entry>
1392
		      <entry>V chrominance information</entry>
1393
		    </row>
1394
		    <row>
1395
		      <entry>Bit 8:15</entry>
1396
		      <entry>U chrominance information</entry>
1397
		    </row>
1398
		    <row>
1399
		      <entry>Bit 16:23</entry>
1400
		      <entry>Y luminance information</entry>
1401
		    </row>
1402
		    <row>
1403
		      <entry>Bit 24:31</entry>
1404
		      <entry>Must be zero.</entry>
1405
		    </row>
1406
		  </tbody>
1407
		</entrytbl>
1408
	      </row>
1409
	    </tbody>
1410
	  </tgroup>
1411
	</table>
1412
      </section>
1413

1414
      <section>
1415
	<title>CX2341x MPEG Controls</title>
1416

1417
	<para>The following MPEG class controls deal with MPEG
1418
encoding settings that are specific to the Conexant CX23415 and
1419
CX23416 MPEG encoding chips.</para>
1420

1421
	<table pgwide="1" frame="none" id="cx2341x-control-id">
1422
	  <title>CX2341x Control IDs</title>
1423
	  <tgroup cols="4">
1424
	    <colspec colname="c1" colwidth="1*" />
1425
	    <colspec colname="c2" colwidth="6*" />
1426
	    <colspec colname="c3" colwidth="2*" />
1427
	    <colspec colname="c4" colwidth="6*" />
1428
	    <spanspec namest="c1" nameend="c2" spanname="id" />
1429
	    <spanspec namest="c2" nameend="c4" spanname="descr" />
1430
	    <thead>
1431
	      <row>
1432
		<entry spanname="id" align="left">ID</entry>
1433
		<entry align="left">Type</entry>
1434
	      </row><row><entry spanname="descr" align="left">Description</entry>
1435
	      </row>
1436
	    </thead>
1437
	    <tbody valign="top">
1438
	      <row><entry></entry></row>
1439
	      <row id="v4l2-mpeg-cx2341x-video-spatial-filter-mode">
1440
		<entry spanname="id"><constant>V4L2_CID_MPEG_CX2341X_VIDEO_SPATIAL_FILTER_MODE</constant>&nbsp;</entry>
1441
		<entry>enum&nbsp;v4l2_mpeg_cx2341x_video_spatial_filter_mode</entry>
1442
	      </row><row><entry spanname="descr">Sets the Spatial
1443
Filter mode (default <constant>MANUAL</constant>). Possible values
1444
are:</entry>
1445
	      </row>
1446
	      <row>
1447
		<entrytbl spanname="descr" cols="2">
1448
		  <tbody valign="top">
1449
		    <row>
1450
		      <entry><constant>V4L2_MPEG_CX2341X_VIDEO_SPATIAL_FILTER_MODE_MANUAL</constant>&nbsp;</entry>
1451
		      <entry>Choose the filter manually</entry>
1452
		    </row>
1453
		    <row>
1454
		      <entry><constant>V4L2_MPEG_CX2341X_VIDEO_SPATIAL_FILTER_MODE_AUTO</constant>&nbsp;</entry>
1455
		      <entry>Choose the filter automatically</entry>
1456
		    </row>
1457
		  </tbody>
1458
		</entrytbl>
1459
	      </row>
1460
	      <row><entry></entry></row>
1461
	      <row>
1462
		<entry spanname="id"><constant>V4L2_CID_MPEG_CX2341X_VIDEO_SPATIAL_FILTER</constant>&nbsp;</entry>
1463
		<entry>integer&nbsp;(0-15)</entry>
1464
	      </row><row><entry spanname="descr">The setting for the
1465
Spatial Filter. 0 = off, 15 = maximum. (Default is 0.)</entry>
1466
	      </row>
1467
	      <row><entry></entry></row>
1468
	      <row id="luma-spatial-filter-type">
1469
		<entry spanname="id"><constant>V4L2_CID_MPEG_CX2341X_VIDEO_LUMA_SPATIAL_FILTER_TYPE</constant>&nbsp;</entry>
1470
		<entry>enum&nbsp;v4l2_mpeg_cx2341x_video_luma_spatial_filter_type</entry>
1471
	      </row><row><entry spanname="descr">Select the algorithm
1472
to use for the Luma Spatial Filter (default
1473
<constant>1D_HOR</constant>). Possible values:</entry>
1474
	      </row>
1475
	      <row>
1476
		<entrytbl spanname="descr" cols="2">
1477
		  <tbody valign="top">
1478
		    <row>
1479
		      <entry><constant>V4L2_MPEG_CX2341X_VIDEO_LUMA_SPATIAL_FILTER_TYPE_OFF</constant>&nbsp;</entry>
1480
		      <entry>No filter</entry>
1481
		    </row>
1482
		    <row>
1483
		      <entry><constant>V4L2_MPEG_CX2341X_VIDEO_LUMA_SPATIAL_FILTER_TYPE_1D_HOR</constant>&nbsp;</entry>
1484
		      <entry>One-dimensional horizontal</entry>
1485
		    </row>
1486
		    <row>
1487
		      <entry><constant>V4L2_MPEG_CX2341X_VIDEO_LUMA_SPATIAL_FILTER_TYPE_1D_VERT</constant>&nbsp;</entry>
1488
		      <entry>One-dimensional vertical</entry>
1489
		    </row>
1490
		    <row>
1491
		      <entry><constant>V4L2_MPEG_CX2341X_VIDEO_LUMA_SPATIAL_FILTER_TYPE_2D_HV_SEPARABLE</constant>&nbsp;</entry>
1492
		      <entry>Two-dimensional separable</entry>
1493
		    </row>
1494
		    <row>
1495
		      <entry><constant>V4L2_MPEG_CX2341X_VIDEO_LUMA_SPATIAL_FILTER_TYPE_2D_SYM_NON_SEPARABLE</constant>&nbsp;</entry>
1496
		      <entry>Two-dimensional symmetrical
1497
non-separable</entry>
1498
		    </row>
1499
		  </tbody>
1500
		</entrytbl>
1501
	      </row>
1502
	      <row><entry></entry></row>
1503
	      <row id="chroma-spatial-filter-type">
1504
		<entry spanname="id"><constant>V4L2_CID_MPEG_CX2341X_VIDEO_CHROMA_SPATIAL_FILTER_TYPE</constant>&nbsp;</entry>
1505
		<entry>enum&nbsp;v4l2_mpeg_cx2341x_video_chroma_spatial_filter_type</entry>
1506
	      </row><row><entry spanname="descr">Select the algorithm
1507
for the Chroma Spatial Filter (default <constant>1D_HOR</constant>).
1508
Possible values are:</entry>
1509
	      </row>
1510
	      <row>
1511
		<entrytbl spanname="descr" cols="2">
1512
		  <tbody valign="top">
1513
		    <row>
1514
		      <entry><constant>V4L2_MPEG_CX2341X_VIDEO_CHROMA_SPATIAL_FILTER_TYPE_OFF</constant>&nbsp;</entry>
1515
		      <entry>No filter</entry>
1516
		    </row>
1517
		    <row>
1518
		      <entry><constant>V4L2_MPEG_CX2341X_VIDEO_CHROMA_SPATIAL_FILTER_TYPE_1D_HOR</constant>&nbsp;</entry>
1519
		      <entry>One-dimensional horizontal</entry>
1520
		    </row>
1521
		  </tbody>
1522
		</entrytbl>
1523
	      </row>
1524
	      <row><entry></entry></row>
1525
	      <row id="v4l2-mpeg-cx2341x-video-temporal-filter-mode">
1526
		<entry spanname="id"><constant>V4L2_CID_MPEG_CX2341X_VIDEO_TEMPORAL_FILTER_MODE</constant>&nbsp;</entry>
1527
		<entry>enum&nbsp;v4l2_mpeg_cx2341x_video_temporal_filter_mode</entry>
1528
	      </row><row><entry spanname="descr">Sets the Temporal
1529
Filter mode (default <constant>MANUAL</constant>). Possible values
1530
are:</entry>
1531
	      </row>
1532
	      <row>
1533
		<entrytbl spanname="descr" cols="2">
1534
		  <tbody valign="top">
1535
		    <row>
1536
		      <entry><constant>V4L2_MPEG_CX2341X_VIDEO_TEMPORAL_FILTER_MODE_MANUAL</constant>&nbsp;</entry>
1537
		      <entry>Choose the filter manually</entry>
1538
		    </row>
1539
		    <row>
1540
		      <entry><constant>V4L2_MPEG_CX2341X_VIDEO_TEMPORAL_FILTER_MODE_AUTO</constant>&nbsp;</entry>
1541
		      <entry>Choose the filter automatically</entry>
1542
		    </row>
1543
		  </tbody>
1544
		</entrytbl>
1545
	      </row>
1546
	      <row><entry></entry></row>
1547
	      <row>
1548
		<entry spanname="id"><constant>V4L2_CID_MPEG_CX2341X_VIDEO_TEMPORAL_FILTER</constant>&nbsp;</entry>
1549
		<entry>integer&nbsp;(0-31)</entry>
1550
	      </row><row><entry spanname="descr">The setting for the
1551
Temporal Filter. 0 = off, 31 = maximum. (Default is 8 for full-scale
1552
capturing and 0 for scaled capturing.)</entry>
1553
	      </row>
1554
	      <row><entry></entry></row>
1555
	      <row id="v4l2-mpeg-cx2341x-video-median-filter-type">
1556
		<entry spanname="id"><constant>V4L2_CID_MPEG_CX2341X_VIDEO_MEDIAN_FILTER_TYPE</constant>&nbsp;</entry>
1557
		<entry>enum&nbsp;v4l2_mpeg_cx2341x_video_median_filter_type</entry>
1558
	      </row><row><entry spanname="descr">Median Filter Type
1559
(default <constant>OFF</constant>). Possible values are:</entry>
1560
	      </row>
1561
	      <row>
1562
		<entrytbl spanname="descr" cols="2">
1563
		  <tbody valign="top">
1564
		    <row>
1565
		      <entry><constant>V4L2_MPEG_CX2341X_VIDEO_MEDIAN_FILTER_TYPE_OFF</constant>&nbsp;</entry>
1566
		      <entry>No filter</entry>
1567
		    </row>
1568
		    <row>
1569
		      <entry><constant>V4L2_MPEG_CX2341X_VIDEO_MEDIAN_FILTER_TYPE_HOR</constant>&nbsp;</entry>
1570
		      <entry>Horizontal filter</entry>
1571
		    </row>
1572
		    <row>
1573
		      <entry><constant>V4L2_MPEG_CX2341X_VIDEO_MEDIAN_FILTER_TYPE_VERT</constant>&nbsp;</entry>
1574
		      <entry>Vertical filter</entry>
1575
		    </row>
1576
		    <row>
1577
		      <entry><constant>V4L2_MPEG_CX2341X_VIDEO_MEDIAN_FILTER_TYPE_HOR_VERT</constant>&nbsp;</entry>
1578
		      <entry>Horizontal and vertical filter</entry>
1579
		    </row>
1580
		    <row>
1581
		      <entry><constant>V4L2_MPEG_CX2341X_VIDEO_MEDIAN_FILTER_TYPE_DIAG</constant>&nbsp;</entry>
1582
		      <entry>Diagonal filter</entry>
1583
		    </row>
1584
		  </tbody>
1585
		</entrytbl>
1586
	      </row>
1587
	      <row><entry></entry></row>
1588
	      <row>
1589
		<entry spanname="id"><constant>V4L2_CID_MPEG_CX2341X_VIDEO_LUMA_MEDIAN_FILTER_BOTTOM</constant>&nbsp;</entry>
1590
		<entry>integer&nbsp;(0-255)</entry>
1591
	      </row><row><entry spanname="descr">Threshold above which
1592
the luminance median filter is enabled (default 0)</entry>
1593
	      </row>
1594
	      <row><entry></entry></row>
1595
	      <row>
1596
		<entry spanname="id"><constant>V4L2_CID_MPEG_CX2341X_VIDEO_LUMA_MEDIAN_FILTER_TOP</constant>&nbsp;</entry>
1597
		<entry>integer&nbsp;(0-255)</entry>
1598
	      </row><row><entry spanname="descr">Threshold below which
1599
the luminance median filter is enabled (default 255)</entry>
1600
	      </row>
1601
	      <row><entry></entry></row>
1602
	      <row>
1603
		<entry spanname="id"><constant>V4L2_CID_MPEG_CX2341X_VIDEO_CHROMA_MEDIAN_FILTER_BOTTOM</constant>&nbsp;</entry>
1604
		<entry>integer&nbsp;(0-255)</entry>
1605
	      </row><row><entry spanname="descr">Threshold above which
1606
the chroma median filter is enabled (default 0)</entry>
1607
	      </row>
1608
	      <row><entry></entry></row>
1609
	      <row>
1610
		<entry spanname="id"><constant>V4L2_CID_MPEG_CX2341X_VIDEO_CHROMA_MEDIAN_FILTER_TOP</constant>&nbsp;</entry>
1611
		<entry>integer&nbsp;(0-255)</entry>
1612
	      </row><row><entry spanname="descr">Threshold below which
1613
the chroma median filter is enabled (default 255)</entry>
1614
	      </row>
1615
	      <row><entry></entry></row>
1616
	      <row>
1617
		<entry spanname="id"><constant>V4L2_CID_MPEG_CX2341X_STREAM_INSERT_NAV_PACKETS</constant>&nbsp;</entry>
1618
		<entry>boolean</entry>
1619
	      </row>
1620
	      <row><entry spanname="descr">The CX2341X MPEG encoder
1621
can insert one empty MPEG-2 PES packet into the stream between every
1622
four video frames. The packet size is 2048 bytes, including the
1623
packet_start_code_prefix and stream_id fields. The stream_id is 0xBF
1624
(private stream 2). The payload consists of 0x00 bytes, to be filled
1625
in by the application. 0 = do not insert, 1 = insert packets.</entry>
1626
	      </row>
1627
	    </tbody>
1628
	  </tgroup>
1629
	</table>
1630
      </section>
1631
    </section>
1632

1633
    <section id="camera-controls">
1634
      <title>Camera Control Reference</title>
1635

1636
      <para>The Camera class includes controls for mechanical (or
1637
equivalent digital) features of a device such as controllable lenses
1638
or sensors.</para>
1639

1640
    <table pgwide="1" frame="none" id="camera-control-id">
1641
      <title>Camera Control IDs</title>
1642
      <tgroup cols="4">
1643
	<colspec colname="c1" colwidth="1*" />
1644
	<colspec colname="c2" colwidth="6*" />
1645
	<colspec colname="c3" colwidth="2*" />
1646
	<colspec colname="c4" colwidth="6*" />
1647
	<spanspec namest="c1" nameend="c2" spanname="id" />
1648
	<spanspec namest="c2" nameend="c4" spanname="descr" />
1649
	<thead>
1650
	  <row>
1651
	    <entry spanname="id" align="left">ID</entry>
1652
	    <entry align="left">Type</entry>
1653
	  </row><row rowsep="1"><entry spanname="descr" align="left">Description</entry>
1654
	  </row>
1655
	</thead>
1656
	<tbody valign="top">
1657
	  <row><entry></entry></row>
1658
	  <row>
1659
	    <entry spanname="id"><constant>V4L2_CID_CAMERA_CLASS</constant>&nbsp;</entry>
1660
	    <entry>class</entry>
1661
	  </row><row><entry spanname="descr">The Camera class
1662
descriptor. Calling &VIDIOC-QUERYCTRL; for this control will return a
1663
description of this control class.</entry>
1664
	  </row>
1665
	  <row><entry></entry></row>
1666

1667
	  <row id="v4l2-exposure-auto-type">
1668
	    <entry spanname="id"><constant>V4L2_CID_EXPOSURE_AUTO</constant>&nbsp;</entry>
1669
	    <entry>enum&nbsp;v4l2_exposure_auto_type</entry>
1670
	  </row><row><entry spanname="descr">Enables automatic
1671
adjustments of the exposure time and/or iris aperture. The effect of
1672
manual changes of the exposure time or iris aperture while these
1673
features are enabled is undefined, drivers should ignore such
1674
requests. Possible values are:</entry>
1675
	  </row>
1676
	  <row>
1677
	    <entrytbl spanname="descr" cols="2">
1678
	      <tbody valign="top">
1679
		<row>
1680
		  <entry><constant>V4L2_EXPOSURE_AUTO</constant>&nbsp;</entry>
1681
		      <entry>Automatic exposure time, automatic iris
1682
aperture.</entry>
1683
		</row>
1684
		<row>
1685
		  <entry><constant>V4L2_EXPOSURE_MANUAL</constant>&nbsp;</entry>
1686
		  <entry>Manual exposure time, manual iris.</entry>
1687
		</row>
1688
		<row>
1689
		  <entry><constant>V4L2_EXPOSURE_SHUTTER_PRIORITY</constant>&nbsp;</entry>
1690
		  <entry>Manual exposure time, auto iris.</entry>
1691
		</row>
1692
		<row>
1693
		  <entry><constant>V4L2_EXPOSURE_APERTURE_PRIORITY</constant>&nbsp;</entry>
1694
		  <entry>Auto exposure time, manual iris.</entry>
1695
		</row>
1696
	      </tbody>
1697
	    </entrytbl>
1698
	  </row>
1699
	  <row><entry></entry></row>
1700

1701
	  <row>
1702
	    <entry spanname="id"><constant>V4L2_CID_EXPOSURE_ABSOLUTE</constant>&nbsp;</entry>
1703
	    <entry>integer</entry>
1704
	  </row><row><entry spanname="descr">Determines the exposure
1705
time of the camera sensor. The exposure time is limited by the frame
1706
interval. Drivers should interpret the values as 100 &micro;s units,
1707
where the value 1 stands for 1/10000th of a second, 10000 for 1 second
1708
and 100000 for 10 seconds.</entry>
1709
	  </row>
1710
	  <row><entry></entry></row>
1711

1712
	  <row>
1713
	    <entry spanname="id"><constant>V4L2_CID_EXPOSURE_AUTO_PRIORITY</constant>&nbsp;</entry>
1714
	    <entry>boolean</entry>
1715
	  </row><row><entry spanname="descr">When
1716
<constant>V4L2_CID_EXPOSURE_AUTO</constant> is set to
1717
<constant>AUTO</constant> or <constant>APERTURE_PRIORITY</constant>,
1718
this control determines if the device may dynamically vary the frame
1719
rate. By default this feature is disabled (0) and the frame rate must
1720
remain constant.</entry>
1721
	  </row>
1722
	  <row><entry></entry></row>
1723

1724
	  <row>
1725
	    <entry spanname="id"><constant>V4L2_CID_PAN_RELATIVE</constant>&nbsp;</entry>
1726
	    <entry>integer</entry>
1727
	  </row><row><entry spanname="descr">This control turns the
1728
camera horizontally by the specified amount. The unit is undefined. A
1729
positive value moves the camera to the right (clockwise when viewed
1730
from above), a negative value to the left. A value of zero does not
1731
cause motion. This is a write-only control.</entry>
1732
	  </row>
1733
	  <row><entry></entry></row>
1734

1735
	  <row>
1736
	    <entry spanname="id"><constant>V4L2_CID_TILT_RELATIVE</constant>&nbsp;</entry>
1737
	    <entry>integer</entry>
1738
	  </row><row><entry spanname="descr">This control turns the
1739
camera vertically by the specified amount. The unit is undefined. A
1740
positive value moves the camera up, a negative value down. A value of
1741
zero does not cause motion. This is a write-only control.</entry>
1742
	  </row>
1743
	  <row><entry></entry></row>
1744

1745
	  <row>
1746
	    <entry spanname="id"><constant>V4L2_CID_PAN_RESET</constant>&nbsp;</entry>
1747
	    <entry>button</entry>
1748
	  </row><row><entry spanname="descr">When this control is set,
1749
the camera moves horizontally to the default position.</entry>
1750
	  </row>
1751
	  <row><entry></entry></row>
1752

1753
	  <row>
1754
	    <entry spanname="id"><constant>V4L2_CID_TILT_RESET</constant>&nbsp;</entry>
1755
	    <entry>button</entry>
1756
	  </row><row><entry spanname="descr">When this control is set,
1757
the camera moves vertically to the default position.</entry>
1758
	  </row>
1759
	  <row><entry></entry></row>
1760

1761
	  <row>
1762
	    <entry spanname="id"><constant>V4L2_CID_PAN_ABSOLUTE</constant>&nbsp;</entry>
1763
	    <entry>integer</entry>
1764
	  </row><row><entry spanname="descr">This control
1765
turns the camera horizontally to the specified position. Positive
1766
values move the camera to the right (clockwise when viewed from above),
1767
negative values to the left. Drivers should interpret the values as arc
1768
seconds, with valid values between -180 * 3600 and +180 * 3600
1769
inclusive.</entry>
1770
	  </row>
1771
	  <row><entry></entry></row>
1772

1773
	  <row>
1774
	    <entry spanname="id"><constant>V4L2_CID_TILT_ABSOLUTE</constant>&nbsp;</entry>
1775
	    <entry>integer</entry>
1776
	  </row><row><entry spanname="descr">This control
1777
turns the camera vertically to the specified position. Positive values
1778
move the camera up, negative values down. Drivers should interpret the
1779
values as arc seconds, with valid values between -180 * 3600 and +180
1780
* 3600 inclusive.</entry>
1781
	  </row>
1782
	  <row><entry></entry></row>
1783

1784
	  <row>
1785
	    <entry spanname="id"><constant>V4L2_CID_FOCUS_ABSOLUTE</constant>&nbsp;</entry>
1786
	    <entry>integer</entry>
1787
	  </row><row><entry spanname="descr">This control sets the
1788
focal point of the camera to the specified position. The unit is
1789
undefined. Positive values set the focus closer to the camera,
1790
negative values towards infinity.</entry>
1791
	  </row>
1792
	  <row><entry></entry></row>
1793

1794
	  <row>
1795
	    <entry spanname="id"><constant>V4L2_CID_FOCUS_RELATIVE</constant>&nbsp;</entry>
1796
	    <entry>integer</entry>
1797
	  </row><row><entry spanname="descr">This control moves the
1798
focal point of the camera by the specified amount. The unit is
1799
undefined. Positive values move the focus closer to the camera,
1800
negative values towards infinity. This is a write-only control.</entry>
1801
	  </row>
1802
	  <row><entry></entry></row>
1803

1804
	  <row>
1805
	    <entry spanname="id"><constant>V4L2_CID_FOCUS_AUTO</constant>&nbsp;</entry>
1806
	    <entry>boolean</entry>
1807
	  </row><row><entry spanname="descr">Enables automatic focus
1808
adjustments. The effect of manual focus adjustments while this feature
1809
is enabled is undefined, drivers should ignore such requests.</entry>
1810
	  </row>
1811
	  <row><entry></entry></row>
1812

1813
	  <row>
1814
	    <entry spanname="id"><constant>V4L2_CID_ZOOM_ABSOLUTE</constant>&nbsp;</entry>
1815
	    <entry>integer</entry>
1816
	  </row><row><entry spanname="descr">Specify the objective lens
1817
focal length as an absolute value. The zoom unit is driver-specific and its
1818
value should be a positive integer.</entry>
1819
	  </row>
1820
	  <row><entry></entry></row>
1821

1822
	  <row>
1823
	    <entry spanname="id"><constant>V4L2_CID_ZOOM_RELATIVE</constant>&nbsp;</entry>
1824
	    <entry>integer</entry>
1825
	  </row><row><entry spanname="descr">Specify the objective lens
1826
focal length relatively to the current value. Positive values move the zoom
1827
lens group towards the telephoto direction, negative values towards the
1828
wide-angle direction. The zoom unit is driver-specific. This is a write-only control.</entry>
1829
	  </row>
1830
	  <row><entry></entry></row>
1831

1832
	  <row>
1833
	    <entry spanname="id"><constant>V4L2_CID_ZOOM_CONTINUOUS</constant>&nbsp;</entry>
1834
	    <entry>integer</entry>
1835
	  </row><row><entry spanname="descr">Move the objective lens group
1836
at the specified speed until it reaches physical device limits or until an
1837
explicit request to stop the movement. A positive value moves the zoom lens
1838
group towards the telephoto direction. A value of zero stops the zoom lens
1839
group movement. A negative value moves the zoom lens group towards the
1840
wide-angle direction. The zoom speed unit is driver-specific.</entry>
1841
	  </row>
1842
	  <row><entry></entry></row>
1843

1844
	  <row>
1845
	    <entry spanname="id"><constant>V4L2_CID_IRIS_ABSOLUTE</constant>&nbsp;</entry>
1846
	    <entry>integer</entry>
1847
	  </row><row><entry spanname="descr">This control sets the
1848
camera's aperture to the specified value. The unit is undefined.
1849
Larger values open the iris wider, smaller values close it.</entry>
1850
	  </row>
1851
	  <row><entry></entry></row>
1852

1853
	  <row>
1854
	    <entry spanname="id"><constant>V4L2_CID_IRIS_RELATIVE</constant>&nbsp;</entry>
1855
	    <entry>integer</entry>
1856
	  </row><row><entry spanname="descr">This control modifies the
1857
camera's aperture by the specified amount. The unit is undefined.
1858
Positive values open the iris one step further, negative values close
1859
it one step further. This is a write-only control.</entry>
1860
	  </row>
1861
	  <row><entry></entry></row>
1862

1863
	  <row>
1864
	    <entry spanname="id"><constant>V4L2_CID_PRIVACY</constant>&nbsp;</entry>
1865
	    <entry>boolean</entry>
1866
	  </row><row><entry spanname="descr">Prevent video from being acquired
1867
by the camera. When this control is set to <constant>TRUE</constant> (1), no
1868
image can be captured by the camera. Common means to enforce privacy are
1869
mechanical obturation of the sensor and firmware image processing, but the
1870
device is not restricted to these methods. Devices that implement the privacy
1871
control must support read access and may support write access.</entry>
1872
	  </row>
1873

1874
	  <row>
1875
	    <entry spanname="id"><constant>V4L2_CID_BAND_STOP_FILTER</constant>&nbsp;</entry>
1876
	    <entry>integer</entry>
1877
	  </row><row><entry spanname="descr">Switch the band-stop filter of a
1878
camera sensor on or off, or specify its strength. Such band-stop filters can
1879
be used, for example, to filter out the fluorescent light component.</entry>
1880
	  </row>
1881
	  <row><entry></entry></row>
1882
	</tbody>
1883
      </tgroup>
1884
    </table>
1885
  </section>
1886

1887
    <section id="fm-tx-controls">
1888
      <title>FM Transmitter Control Reference</title>
1889

1890
      <para>The FM Transmitter (FM_TX) class includes controls for common features of
1891
FM transmissions capable devices. Currently this class includes parameters for audio
1892
compression, pilot tone generation, audio deviation limiter, RDS transmission and
1893
tuning power features.</para>
1894

1895
      <table pgwide="1" frame="none" id="fm-tx-control-id">
1896
      <title>FM_TX Control IDs</title>
1897

1898
      <tgroup cols="4">
1899
	<colspec colname="c1" colwidth="1*" />
1900
	<colspec colname="c2" colwidth="6*" />
1901
	<colspec colname="c3" colwidth="2*" />
1902
	<colspec colname="c4" colwidth="6*" />
1903
	<spanspec namest="c1" nameend="c2" spanname="id" />
1904
	<spanspec namest="c2" nameend="c4" spanname="descr" />
1905
	<thead>
1906
	  <row>
1907
	    <entry spanname="id" align="left">ID</entry>
1908
	    <entry align="left">Type</entry>
1909
	  </row><row rowsep="1"><entry spanname="descr" align="left">Description</entry>
1910
	  </row>
1911
	</thead>
1912
	<tbody valign="top">
1913
	  <row><entry></entry></row>
1914
	  <row>
1915
	    <entry spanname="id"><constant>V4L2_CID_FM_TX_CLASS</constant>&nbsp;</entry>
1916
	    <entry>class</entry>
1917
	  </row><row><entry spanname="descr">The FM_TX class
1918
descriptor. Calling &VIDIOC-QUERYCTRL; for this control will return a
1919
description of this control class.</entry>
1920
	  </row>
1921
	  <row>
1922
	    <entry spanname="id"><constant>V4L2_CID_RDS_TX_DEVIATION</constant>&nbsp;</entry>
1923
	    <entry>integer</entry>
1924
	  </row>
1925
	  <row><entry spanname="descr">Configures RDS signal frequency deviation level in Hz.
1926
The range and step are driver-specific.</entry>
1927
	  </row>
1928
	  <row>
1929
	    <entry spanname="id"><constant>V4L2_CID_RDS_TX_PI</constant>&nbsp;</entry>
1930
	    <entry>integer</entry>
1931
	  </row>
1932
	  <row><entry spanname="descr">Sets the RDS Programme Identification field
1933
for transmission.</entry>
1934
	  </row>
1935
	  <row>
1936
	    <entry spanname="id"><constant>V4L2_CID_RDS_TX_PTY</constant>&nbsp;</entry>
1937
	    <entry>integer</entry>
1938
	  </row>
1939
	  <row><entry spanname="descr">Sets the RDS Programme Type field for transmission.
1940
This encodes up to 31 pre-defined programme types.</entry>
1941
	  </row>
1942
	  <row>
1943
	    <entry spanname="id"><constant>V4L2_CID_RDS_TX_PS_NAME</constant>&nbsp;</entry>
1944
	    <entry>string</entry>
1945
	  </row>
1946
	  <row><entry spanname="descr">Sets the Programme Service name (PS_NAME) for transmission.
1947
It is intended for static display on a receiver. It is the primary aid to listeners in programme service
1948
identification and selection.  In Annex E of <xref linkend="en50067" />, the RDS specification,
1949
there is a full description of the correct character encoding for Programme Service name strings.
1950
Also from RDS specification, PS is usually a single eight character text. However, it is also possible
1951
to find receivers which can scroll strings sized as 8 x N characters. So, this control must be configured
1952
with steps of 8 characters. The result is it must always contain a string with size multiple of 8.</entry>
1953
	  </row>
1954
	  <row>
1955
	    <entry spanname="id"><constant>V4L2_CID_RDS_TX_RADIO_TEXT</constant>&nbsp;</entry>
1956
	    <entry>string</entry>
1957
	  </row>
1958
	  <row><entry spanname="descr">Sets the Radio Text info for transmission. It is a textual description of
1959
what is being broadcasted. RDS Radio Text can be applied when broadcaster wishes to transmit longer PS names,
1960
programme-related information or any other text. In these cases, RadioText should be used in addition to
1961
<constant>V4L2_CID_RDS_TX_PS_NAME</constant>. The encoding for Radio Text strings is also fully described
1962
in Annex E of <xref linkend="en50067" />. The length of Radio Text strings depends on which RDS Block is being
1963
used to transmit it, either 32 (2A block) or 64 (2B block).  However, it is also possible
1964
to find receivers which can scroll strings sized as 32 x N or 64 x N characters. So, this control must be configured
1965
with steps of 32 or 64 characters. The result is it must always contain a string with size multiple of 32 or 64. </entry>
1966
	  </row>
1967
	  <row>
1968
	    <entry spanname="id"><constant>V4L2_CID_AUDIO_LIMITER_ENABLED</constant>&nbsp;</entry>
1969
	    <entry>boolean</entry>
1970
	  </row>
1971
	  <row><entry spanname="descr">Enables or disables the audio deviation limiter feature.
1972
The limiter is useful when trying to maximize the audio volume, minimize receiver-generated
1973
distortion and prevent overmodulation.
1974
</entry>
1975
	  </row>
1976
	  <row>
1977
	    <entry spanname="id"><constant>V4L2_CID_AUDIO_LIMITER_RELEASE_TIME</constant>&nbsp;</entry>
1978
	    <entry>integer</entry>
1979
	  </row>
1980
	  <row><entry spanname="descr">Sets the audio deviation limiter feature release time.
1981
Unit is in useconds. Step and range are driver-specific.</entry>
1982
	  </row>
1983
	  <row>
1984
	    <entry spanname="id"><constant>V4L2_CID_AUDIO_LIMITER_DEVIATION</constant>&nbsp;</entry>
1985
	    <entry>integer</entry>
1986
	  </row>
1987
	  <row><entry spanname="descr">Configures audio frequency deviation level in Hz.
1988
The range and step are driver-specific.</entry>
1989
	  </row>
1990
	  <row>
1991
	    <entry spanname="id"><constant>V4L2_CID_AUDIO_COMPRESSION_ENABLED</constant>&nbsp;</entry>
1992
	    <entry>boolean</entry>
1993
	  </row>
1994
	  <row><entry spanname="descr">Enables or disables the audio compression feature.
1995
This feature amplifies signals below the threshold by a fixed gain and compresses audio
1996
signals above the threshold by the ratio of Threshold/(Gain + Threshold).</entry>
1997
	  </row>
1998
	  <row>
1999
	    <entry spanname="id"><constant>V4L2_CID_AUDIO_COMPRESSION_GAIN</constant>&nbsp;</entry>
2000
	    <entry>integer</entry>
2001
	  </row>
2002
	  <row><entry spanname="descr">Sets the gain for audio compression feature. It is
2003
a dB value. The range and step are driver-specific.</entry>
2004
	  </row>
2005
	  <row>
2006
	    <entry spanname="id"><constant>V4L2_CID_AUDIO_COMPRESSION_THRESHOLD</constant>&nbsp;</entry>
2007
	    <entry>integer</entry>
2008
	  </row>
2009
	  <row><entry spanname="descr">Sets the threshold level for audio compression freature.
2010
It is a dB value. The range and step are driver-specific.</entry>
2011
	  </row>
2012
	  <row>
2013
	    <entry spanname="id"><constant>V4L2_CID_AUDIO_COMPRESSION_ATTACK_TIME</constant>&nbsp;</entry>
2014
	    <entry>integer</entry>
2015
	  </row>
2016
	  <row><entry spanname="descr">Sets the attack time for audio compression feature.
2017
It is a useconds value. The range and step are driver-specific.</entry>
2018
	  </row>
2019
	  <row>
2020
	    <entry spanname="id"><constant>V4L2_CID_AUDIO_COMPRESSION_RELEASE_TIME</constant>&nbsp;</entry>
2021
	    <entry>integer</entry>
2022
	  </row>
2023
	  <row><entry spanname="descr">Sets the release time for audio compression feature.
2024
It is a useconds value. The range and step are driver-specific.</entry>
2025
	  </row>
2026
	  <row>
2027
	    <entry spanname="id"><constant>V4L2_CID_PILOT_TONE_ENABLED</constant>&nbsp;</entry>
2028
	    <entry>boolean</entry>
2029
	  </row>
2030
	  <row><entry spanname="descr">Enables or disables the pilot tone generation feature.</entry>
2031
	  </row>
2032
	  <row>
2033
	    <entry spanname="id"><constant>V4L2_CID_PILOT_TONE_DEVIATION</constant>&nbsp;</entry>
2034
	    <entry>integer</entry>
2035
	  </row>
2036
	  <row><entry spanname="descr">Configures pilot tone frequency deviation level. Unit is
2037
in Hz. The range and step are driver-specific.</entry>
2038
	  </row>
2039
	  <row>
2040
	    <entry spanname="id"><constant>V4L2_CID_PILOT_TONE_FREQUENCY</constant>&nbsp;</entry>
2041
	    <entry>integer</entry>
2042
	  </row>
2043
	  <row><entry spanname="descr">Configures pilot tone frequency value. Unit is
2044
in Hz. The range and step are driver-specific.</entry>
2045
	  </row>
2046
	  <row>
2047
	    <entry spanname="id"><constant>V4L2_CID_TUNE_PREEMPHASIS</constant>&nbsp;</entry>
2048
	    <entry>integer</entry>
2049
	  </row>
2050
	  <row id="v4l2-preemphasis"><entry spanname="descr">Configures the pre-emphasis value for broadcasting.
2051
A pre-emphasis filter is applied to the broadcast to accentuate the high audio frequencies.
2052
Depending on the region, a time constant of either 50 or 75 useconds is used. The enum&nbsp;v4l2_preemphasis
2053
defines possible values for pre-emphasis. Here they are:</entry>
2054
	</row><row>
2055
	<entrytbl spanname="descr" cols="2">
2056
		  <tbody valign="top">
2057
		    <row>
2058
		      <entry><constant>V4L2_PREEMPHASIS_DISABLED</constant>&nbsp;</entry>
2059
		      <entry>No pre-emphasis is applied.</entry>
2060
		    </row>
2061
		    <row>
2062
		      <entry><constant>V4L2_PREEMPHASIS_50_uS</constant>&nbsp;</entry>
2063
		      <entry>A pre-emphasis of 50 uS is used.</entry>
2064
		    </row>
2065
		    <row>
2066
		      <entry><constant>V4L2_PREEMPHASIS_75_uS</constant>&nbsp;</entry>
2067
		      <entry>A pre-emphasis of 75 uS is used.</entry>
2068
		    </row>
2069
		  </tbody>
2070
		</entrytbl>
2071

2072
	  </row>
2073
	  <row>
2074
	    <entry spanname="id"><constant>V4L2_CID_TUNE_POWER_LEVEL</constant>&nbsp;</entry>
2075
	    <entry>integer</entry>
2076
	  </row>
2077
	  <row><entry spanname="descr">Sets the output power level for signal transmission.
2078
Unit is in dBuV. Range and step are driver-specific.</entry>
2079
	  </row>
2080
	  <row>
2081
	    <entry spanname="id"><constant>V4L2_CID_TUNE_ANTENNA_CAPACITOR</constant>&nbsp;</entry>
2082
	    <entry>integer</entry>
2083
	  </row>
2084
	  <row><entry spanname="descr">This selects the value of antenna tuning capacitor
2085
manually or automatically if set to zero. Unit, range and step are driver-specific.</entry>
2086
	  </row>
2087
	  <row><entry></entry></row>
2088
	</tbody>
2089
      </tgroup>
2090
      </table>
2091

2092
<para>For more details about RDS specification, refer to
2093
<xref linkend="en50067" /> document, from CENELEC.</para>
2094
    </section>
2095
</section>
2096

2097
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2098
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2099
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2100
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2101
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2102
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