fmt123.h

/*
	libmpg123: MPEG Audio Decoder library

	separate header just for audio format definitions not tied to
	library code

	copyright 1995-2020 by the mpg123 project
	free software under the terms of the LGPL 2.1
	see COPYING and AUTHORS files in distribution or http://mpg123.org
*/

#ifndef MPG123_ENC_H
#define MPG123_ENC_H

/** \file fmt123.h Audio format definitions. */

/** \defgroup mpg123_enc mpg123 PCM sample encodings
 *  These are definitions for audio formats used by libmpg123 and
 *  libout123.
 *
 * @{
 */

/** An enum over all sample types possibly known to mpg123.
 *  The values are designed as bit flags to allow bitmasking for encoding
 *  families.
 *  This is also why the enum is not used as type for actual encoding variables,
 *  plain integers (at least 16 bit, 15 bit being used) cover the possible
 *  combinations of these flags.
 *
 *  Note that (your build of) libmpg123 does not necessarily support all these.
 *  Usually, you can expect the 8bit encodings and signed 16 bit.
 *  Also 32bit float will be usual beginning with mpg123-1.7.0 .
 *  What you should bear in mind is that (SSE, etc) optimized routines may be
 *  absent for some formats. We do have SSE for 16, 32 bit and float, though.
 *  24 bit integer is done via postprocessing of 32 bit output -- just cutting
 *  the last byte, no rounding, even. If you want better, do it yourself.
 *
 *  All formats are in native byte order. If you need different endinaness, you
 *  can simply postprocess the output buffers (libmpg123 wouldn't do anything
 * else). The macro MPG123_SAMPLESIZE() can be helpful there.
 */
enum mpg123_enc_enum
{
/* 0000 0000 0000 1111 Some 8 bit  integer encoding. */
	MPG123_ENC_8      = 0x00f
/* 0000 0000 0100 0000 Some 16 bit integer encoding. */
,	MPG123_ENC_16     = 0x040
/* 0100 0000 0000 0000 Some 24 bit integer encoding. */
,	MPG123_ENC_24     = 0x4000
/* 0000 0001 0000 0000 Some 32 bit integer encoding. */
,	MPG123_ENC_32     = 0x100
/* 0000 0000 1000 0000 Some signed integer encoding. */
,	MPG123_ENC_SIGNED = 0x080
/* 0000 1110 0000 0000 Some float encoding. */
,	MPG123_ENC_FLOAT  = 0xe00
/* 0000 0000 1101 0000 signed 16 bit */
,	MPG123_ENC_SIGNED_16   = (MPG123_ENC_16|MPG123_ENC_SIGNED|0x10)
/* 0000 0000 0110 0000 unsigned 16 bit */
,	MPG123_ENC_UNSIGNED_16 = (MPG123_ENC_16|0x20)
/* 0000 0000 0000 0001 unsigned 8 bit */
,	MPG123_ENC_UNSIGNED_8  = 0x01
/* 0000 0000 1000 0010 signed 8 bit */
,	MPG123_ENC_SIGNED_8    = (MPG123_ENC_SIGNED|0x02)
/* 0000 0000 0000 0100 ulaw 8 bit */
,	MPG123_ENC_ULAW_8      = 0x04
/* 0000 0000 0000 1000 alaw 8 bit */
,	MPG123_ENC_ALAW_8      = 0x08
/* 0001 0001 1000 0000 signed 32 bit */
,	MPG123_ENC_SIGNED_32   = MPG123_ENC_32|MPG123_ENC_SIGNED|0x1000
/* 0010 0001 0000 0000 unsigned 32 bit */
,	MPG123_ENC_UNSIGNED_32 = MPG123_ENC_32|0x2000
/* 0101 0000 1000 0000 signed 24 bit */
,	MPG123_ENC_SIGNED_24   = MPG123_ENC_24|MPG123_ENC_SIGNED|0x1000
/* 0110 0000 0000 0000 unsigned 24 bit */
,	MPG123_ENC_UNSIGNED_24 = MPG123_ENC_24|0x2000
/* 0000 0010 0000 0000 32bit float */
,	MPG123_ENC_FLOAT_32    = 0x200
/* 0000 0100 0000 0000 64bit float */
,	MPG123_ENC_FLOAT_64    = 0x400
/* Any possibly known encoding from the list above. */
,	MPG123_ENC_ANY = ( MPG123_ENC_SIGNED_16  | MPG123_ENC_UNSIGNED_16
	                 | MPG123_ENC_UNSIGNED_8 | MPG123_ENC_SIGNED_8
	                 | MPG123_ENC_ULAW_8     | MPG123_ENC_ALAW_8
	                 | MPG123_ENC_SIGNED_32  | MPG123_ENC_UNSIGNED_32
	                 | MPG123_ENC_SIGNED_24  | MPG123_ENC_UNSIGNED_24
	                 | MPG123_ENC_FLOAT_32   | MPG123_ENC_FLOAT_64    )
};

/** Get size of one PCM sample with given encoding.
 *  This is included both in libmpg123 and libout123. Both offer
 *  an API function to provide the macro results from library
 *  compile-time, not that of you application. This most likely
 *  does not matter as I do not expect any fresh PCM sample
 *  encoding to appear. But who knows? Perhaps the encoding type
 *  will be abused for funny things in future, not even plain PCM.
 *  And, by the way: Thomas really likes the ?: operator.
 * \param enc the encoding (mpg123_enc_enum value)
 * \return size of one sample in bytes
 */
#define MPG123_SAMPLESIZE(enc) ( \
	(enc) < 1 \
	?	0 \
	:	( (enc) & MPG123_ENC_8 \
		?	1 \
		:	( (enc) & MPG123_ENC_16 \
			?	2 \
			:	( (enc) & MPG123_ENC_24 \
				?	3 \
				:	( (  (enc) & MPG123_ENC_32 \
					  || (enc) == MPG123_ENC_FLOAT_32 ) \
					?	4 \
					:	( (enc) == MPG123_ENC_FLOAT_64 \
						?	8 \
						:	0 \
)	)	)	)	)	)

/** Representation of zero in differing encodings.
 *  This exists to define proper silence in various encodings without
 *  having to link to libsyn123 to do actual conversions at runtime.
 *  You have to handle big/little endian order yourself, though.
 *  This takes the shortcut that any signed encoding has a zero with
 *  all-zero bits. Unsigned linear encodings just have the highest bit set
 *  (2^(n-1) for n bits), while the nonlinear 8-bit ones are special.
 *  \param enc the encoding (mpg123_enc_enum value)
 *  \param siz bytes per sample (return value of MPG123_SAMPLESIZE(enc))
 *  \param off byte (octet) offset counted from LSB
 *  \return unsigned byte value for the designated octet
 */
#define MPG123_ZEROSAMPLE(enc, siz, off) ( \
	(enc) == MPG123_ENC_ULAW_8 \
	?	(off == 0 ? 0xff : 0x00) \
	:	( (enc) == MPG123_ENC_ALAW_8 \
		?	(off == 0 ? 0xd5 : 0x00) \
		:	( (((enc) & (MPG123_ENC_SIGNED|MPG123_ENC_FLOAT)) || (siz) != ((off)+1)) \
			?	0x00 \
			:	0x80 \
	)	)	)

/** Structure defining an audio format.
 *  Providing the members as individual function arguments to define a certain
 *  output format is easy enough. This struct makes is more comfortable to deal
 *  with a list of formats.
 *  Negative values for the members might be used to communicate use of default
 *  values.
 */
struct mpg123_fmt
{
	long rate;    /**< sampling rate in Hz  */
	int channels; /**< channel count */
	/** encoding code, can be single value or bitwise or of members of
	 *  mpg123_enc_enum */
	int encoding;
};

/** @} */

#endif