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BlipBuffer.h
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BlipBuffer.h
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// 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 -32767 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_ = 0;
blip_resampled_time_t offset_ = 0;
buf_t_* buffer_ = nullptr;
long buffer_size_ = 0;
private:
long reader_accum = 0;
int bass_shift = 0;
long sample_rate_ = 0;
long clock_rate_ = 0;
int bass_freq_ = 0;
int length_ = 0;
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_ = 0.0;
short* const impulses = nullptr;
int const width = 0;
long kernel_unit = 0;
int impulses_size() const { return blip_res / 2 * width + 1; }
void adjust_impulse();
public:
Blip_Buffer* buf = nullptr;
int last_amp = 0;
int delta_factor = 0;
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 = nullptr;
long accum = 0;
};
// 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