Blip_Buffer.h

// Band-limited sound synthesis and buffering

// Blip_Buffer 0.4.0

#ifndef BLIP_BUFFER_H
#define BLIP_BUFFER_H

// Time unit at source clock rate
typedef long blip_time_t;

// Output samples are 16-bit signed, with a range of -32768 to 32767
typedef short blip_sample_t;
enum { blip_sample_max = 32767 };

class Blip_Buffer {
public:
	typedef const char* blargg_err_t;
	
	// Set output sample rate and buffer length in milliseconds (1/1000 sec, defaults
	// to 1/4 second), then clear buffer. Returns NULL on success, otherwise if there
	// isn't enough memory, returns error without affecting current buffer setup.
	blargg_err_t set_sample_rate( long samples_per_sec, int msec_length = 1000 / 4 );
	
	// Set number of source time units per second
	void clock_rate( long );
	
	// End current time frame of specified duration and make its samples available
	// (along with any still-unread samples) for reading with read_samples(). Begins
	// a new time frame at the end of the current frame.
	void end_frame( blip_time_t time );
	
	// Read at most 'max_samples' out of buffer into 'dest', removing them from from
	// the buffer. Returns number of samples actually read and removed. If stereo is
	// true, increments 'dest' one extra time after writing each sample, to allow
	// easy interleving of two channels into a stereo output buffer.
	long read_samples( blip_sample_t* dest, long max_samples, int stereo = 0 );
	
// Additional optional features

	// Current output sample rate
	long sample_rate() const;
	
	// Length of buffer, in milliseconds
	int length() const;
	
	// Number of source time units per second
	long clock_rate() const;
	
	// Set frequency high-pass filter frequency, where higher values reduce bass more
	void bass_freq( int frequency );
	
	// Number of samples delay from synthesis to samples read out
	int output_latency() const;
	
	// Remove all available samples and clear buffer to silence. If 'entire_buffer' is
	// false, just clears out any samples waiting rather than the entire buffer.
	void clear( int entire_buffer = 1 );
	
	// Number of samples available for reading with read_samples()
	long samples_avail() const;
	
	// Remove 'count' samples from those waiting to be read
	void remove_samples( long count );
	
// Experimental features
	
	// Number of raw samples that can be mixed within frame of specified duration.
	long count_samples( blip_time_t duration ) const;
	
	// Mix 'count' samples from 'buf' into buffer.
	void mix_samples( blip_sample_t const* buf, long count );
	
	// Count number of clocks needed until 'count' samples will be available.
	// If buffer can't even hold 'count' samples, returns number of clocks until
	// buffer becomes full.
	blip_time_t count_clocks( long count ) const;
	
	// not documented yet
	typedef unsigned long blip_resampled_time_t;
	void remove_silence( long count );
	blip_resampled_time_t resampled_duration( int t ) const     { return t * factor_; }
	blip_resampled_time_t resampled_time( blip_time_t t ) const { return t * factor_ + offset_; }
	blip_resampled_time_t clock_rate_factor( long clock_rate ) const;
public:
	Blip_Buffer();
	~Blip_Buffer();
	
	// Deprecated
	typedef blip_resampled_time_t resampled_time_t;
	blargg_err_t sample_rate( long r ) { return set_sample_rate( r ); }
	blargg_err_t sample_rate( long r, int msec ) { return set_sample_rate( r, msec ); }
private:
	// noncopyable
	Blip_Buffer( const Blip_Buffer& );
	Blip_Buffer& operator = ( const Blip_Buffer& );
public:
	typedef long buf_t_;
	unsigned long factor_;
	blip_resampled_time_t offset_;
	buf_t_* buffer_;
	long buffer_size_;
private:
	long reader_accum;
	int bass_shift;
	long sample_rate_;
	long clock_rate_;
	int bass_freq_;
	int length_;
	friend class Blip_Reader;
};

#ifdef HAVE_CONFIG_H
	#include "config.h"
#endif

// Number of bits in resample ratio fraction. Higher values give a more accurate ratio
// but reduce maximum buffer size.
#ifndef BLIP_BUFFER_ACCURACY
	#define BLIP_BUFFER_ACCURACY 16
#endif

// Number bits in phase offset. Fewer than 6 bits (64 phase offsets) results in
// noticeable broadband noise when synthesizing high frequency square waves.
// Affects size of Blip_Synth objects since they store the waveform directly.
#ifndef BLIP_PHASE_BITS
	#define BLIP_PHASE_BITS 6
#endif

	// Internal
	typedef unsigned long blip_resampled_time_t;
	int const blip_widest_impulse_ = 16;
	int const blip_res = 1 << BLIP_PHASE_BITS;
	class blip_eq_t;
	
	class Blip_Synth_ {
		double volume_unit_;
		short* const impulses;
		int const width;
		long kernel_unit;
		int impulses_size() const { return blip_res / 2 * width + 1; }
		void adjust_impulse();
	public:
		Blip_Buffer* buf;
		int last_amp;
		int delta_factor;
		
		Blip_Synth_( short* impulses, int width );
		void treble_eq( blip_eq_t const& );
		void volume_unit( double );
	};

// Quality level. Start with blip_good_quality.
const int blip_med_quality  = 8;
const int blip_good_quality = 12;
const int blip_high_quality = 16;

// Range specifies the greatest expected change in amplitude. Calculate it
// by finding the difference between the maximum and minimum expected
// amplitudes (max - min).
template<int quality,int range>
class Blip_Synth {
public:
	// Set overall volume of waveform
	void volume( double v ) { impl.volume_unit( v * (1.0 / (range < 0 ? -range : range)) ); }
	
	// Configure low-pass filter (see notes.txt)
	void treble_eq( blip_eq_t const& eq )       { impl.treble_eq( eq ); }
	
	// Get/set Blip_Buffer used for output
	Blip_Buffer* output() const                 { return impl.buf; }
	void output( Blip_Buffer* b )               { impl.buf = b; impl.last_amp = 0; }
	
	// Update amplitude of waveform at given time. Using this requires a separate
	// Blip_Synth for each waveform.
	void update( blip_time_t time, int amplitude );

// Low-level interface

	// Add an amplitude transition of specified delta, optionally into specified buffer
	// rather than the one set with output(). Delta can be positive or negative.
	// The actual change in amplitude is delta * (volume / range)
	void offset( blip_time_t, int delta, Blip_Buffer* ) const;
	void offset( blip_time_t t, int delta ) const { offset( t, delta, impl.buf ); }
	
	// Works directly in terms of fractional output samples. Contact author for more.
	void offset_resampled( blip_resampled_time_t, int delta, Blip_Buffer* ) const;
	
	// Same as offset(), except code is inlined for higher performance
	void offset_inline( blip_time_t t, int delta, Blip_Buffer* buf ) const {
		offset_resampled( t * buf->factor_ + buf->offset_, delta, buf );
	}
	void offset_inline( blip_time_t t, int delta ) const {
		offset_resampled( t * impl.buf->factor_ + impl.buf->offset_, delta, impl.buf );
	}
	
public:
	Blip_Synth() : impl( impulses, quality ) { }
private:
	typedef short imp_t;
	imp_t impulses [blip_res * (quality / 2) + 1];
	Blip_Synth_ impl;
};

// Low-pass equalization parameters
class blip_eq_t {
public:
	// Logarithmic rolloff to treble dB at half sampling rate. Negative values reduce
	// treble, small positive values (0 to 5.0) increase treble.
	blip_eq_t( double treble_db = 0 );
	
	// See notes.txt
	blip_eq_t( double treble, long rolloff_freq, long sample_rate, long cutoff_freq = 0 );
	
private:
	double treble;
	long rolloff_freq;
	long sample_rate;
	long cutoff_freq;
	void generate( float* out, int count ) const;
	friend class Blip_Synth_;
};

int const blip_sample_bits = 30;

// Optimized inline sample reader for custom sample formats and mixing of Blip_Buffer samples
class Blip_Reader {
public:
	// Begin reading samples from buffer. Returns value to pass to next() (can
	// be ignored if default bass_freq is acceptable).
	int begin( Blip_Buffer& );
	
	// Current sample
	long read() const               { return accum >> (blip_sample_bits - 16); }
	
	// Current raw sample in full internal resolution
	long read_raw() const           { return accum; }
	
	// Advance to next sample
	void next( int bass_shift = 9 )         { accum += *buf++ - (accum >> bass_shift); }
	
	// End reading samples from buffer. The number of samples read must now be removed
	// using Blip_Buffer::remove_samples().
	void end( Blip_Buffer& b )              { b.reader_accum = accum; }
	
private:
	const Blip_Buffer::buf_t_* buf;
	long accum;
};


// End of public interface


#include <assert.h>

// Compatibility with older version
const long blip_unscaled = 65535;
const int blip_low_quality  = blip_med_quality;
const int blip_best_quality = blip_high_quality;

#define BLIP_FWD( i ) {                     \
	long t0 = i0 * delta + buf [fwd + i];   \
	long t1 = imp [blip_res * (i + 1)] * delta + buf [fwd + 1 + i]; \
	i0 = imp [blip_res * (i + 2)];          \
	buf [fwd + i] = t0;                     \
	buf [fwd + 1 + i] = t1; }

#define BLIP_REV( r ) {                     \
	long t0 = i0 * delta + buf [rev - r];   \
	long t1 = imp [blip_res * r] * delta + buf [rev + 1 - r];   \
	i0 = imp [blip_res * (r - 1)];          \
	buf [rev - r] = t0;                     \
	buf [rev + 1 - r] = t1; }

template<int quality,int range>
inline void Blip_Synth<quality,range>::offset_resampled( blip_resampled_time_t time,
		int delta, Blip_Buffer* blip_buf ) const
{
	// Fails if time is beyond end of Blip_Buffer, due to a bug in caller code or the
	// need for a longer buffer as set by set_sample_rate().
	assert( (long) (time >> BLIP_BUFFER_ACCURACY) < blip_buf->buffer_size_ );
	delta *= impl.delta_factor;
	int phase = (int) (time >> (BLIP_BUFFER_ACCURACY - BLIP_PHASE_BITS) & (blip_res - 1));
	imp_t const* imp = impulses + blip_res - phase;
	long* buf = blip_buf->buffer_ + (time >> BLIP_BUFFER_ACCURACY);
	long i0 = *imp;
	
	int const fwd = (blip_widest_impulse_ - quality) / 2;
	int const rev = fwd + quality - 2;
	
	BLIP_FWD( 0 )
	if ( quality > 8  ) BLIP_FWD( 2 )
	if ( quality > 12 ) BLIP_FWD( 4 )
	{
		int const mid = quality / 2 - 1;
		long t0 = i0 * delta + buf [fwd + mid - 1];
		long t1 = imp [blip_res * mid] * delta + buf [fwd + mid];
		imp = impulses + phase;
		i0 = imp [blip_res * mid];
		buf [fwd + mid - 1] = t0;
		buf [fwd + mid] = t1;
	}
	if ( quality > 12 ) BLIP_REV( 6 )
	if ( quality > 8  ) BLIP_REV( 4 )
	BLIP_REV( 2 )
	
	long t0 = i0 * delta + buf [rev];
	long t1 = *imp * delta + buf [rev + 1];
	buf [rev] = t0;
	buf [rev + 1] = t1;
}

#undef BLIP_FWD
#undef BLIP_REV

template<int quality,int range>
void Blip_Synth<quality,range>::offset( blip_time_t t, int delta, Blip_Buffer* buf ) const
{
	offset_resampled( t * buf->factor_ + buf->offset_, delta, buf );
}

template<int quality,int range>
void Blip_Synth<quality,range>::update( blip_time_t t, int amp )
{
	int delta = amp - impl.last_amp;
	impl.last_amp = amp;
	offset_resampled( t * impl.buf->factor_ + impl.buf->offset_, delta, impl.buf );
}

inline blip_eq_t::blip_eq_t( double t ) :
		treble( t ), rolloff_freq( 0 ), sample_rate( 44100 ), cutoff_freq( 0 ) { }
inline blip_eq_t::blip_eq_t( double t, long rf, long sr, long cf ) :
		treble( t ), rolloff_freq( rf ), sample_rate( sr ), cutoff_freq( cf ) { }

inline int  Blip_Buffer::length() const         { return length_; }
inline long Blip_Buffer::samples_avail() const  { return (long) (offset_ >> BLIP_BUFFER_ACCURACY); }
inline long Blip_Buffer::sample_rate() const    { return sample_rate_; }
inline int  Blip_Buffer::output_latency() const { return blip_widest_impulse_ / 2; }
inline long Blip_Buffer::clock_rate() const     { return clock_rate_; }
inline void Blip_Buffer::clock_rate( long cps ) { factor_ = clock_rate_factor( clock_rate_ = cps ); }

inline int Blip_Reader::begin( Blip_Buffer& blip_buf )
{
	buf = blip_buf.buffer_;
	accum = blip_buf.reader_accum;
	return blip_buf.bass_shift;
}

int const blip_max_length = 0;
int const blip_default_length = 250;

#endif