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Blip_Buffer.cpp
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Blip_Buffer.cpp
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// Blip_Buffer 0.4.1. http://www.slack.net/~ant/
#include "Blip_Buffer.h"
#include <assert.h>
#include <limits.h>
#include <string.h>
#include <stdlib.h>
#include <math.h>
/* Copyright (C) 2003-2006 Shay Green. This module is free software; you
can redistribute it and/or modify it under the terms of the GNU Lesser
General Public License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version. This
module is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
details. You should have received a copy of the GNU Lesser General Public
License along with this module; if not, write to the Free Software Foundation,
Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA */
#ifdef BLARGG_ENABLE_OPTIMIZER
#include BLARGG_ENABLE_OPTIMIZER
#endif
int const silent_buf_size = 1; // size used for Silent_Blip_Buffer
Blip_Buffer::Blip_Buffer()
{
factor_ = (blip_ulong)-1 / 2;
offset_ = 0;
buffer_ = 0;
buffer_size_ = 0;
sample_rate_ = 0;
reader_accum_ = 0;
bass_shift_ = 0;
clock_rate_ = 0;
bass_freq_ = 16;
length_ = 0;
// assumptions code makes about implementation-defined features
#ifndef NDEBUG
// right shift of negative value preserves sign
buf_t_ i = -0x7FFFFFFE;
assert( (i >> 1) == -0x3FFFFFFF );
// casting to short truncates to 16 bits and sign-extends
i = 0x18000;
assert( (short) i == -0x8000 );
#endif
}
Blip_Buffer::~Blip_Buffer()
{
if ( buffer_size_ != silent_buf_size )
free( buffer_ );
}
Silent_Blip_Buffer::Silent_Blip_Buffer()
{
factor_ = 0;
buffer_ = buf;
buffer_size_ = silent_buf_size;
memset( buf, 0, sizeof buf ); // in case machine takes exception for signed overflow
}
void Blip_Buffer::clear( int entire_buffer )
{
offset_ = 0;
reader_accum_ = 0;
modified_ = 0;
if ( buffer_ )
{
long count = (entire_buffer ? buffer_size_ : samples_avail());
memset( buffer_, 0, (count + blip_buffer_extra_) * sizeof (buf_t_) );
}
}
Blip_Buffer::blargg_err_t Blip_Buffer::set_sample_rate( long new_rate, int msec )
{
if ( buffer_size_ == silent_buf_size )
{
assert( 0 );
return "Internal (tried to resize Silent_Blip_Buffer)";
}
// start with maximum length that resampled time can represent
long new_size = (UINT_MAX >> BLIP_BUFFER_ACCURACY) - blip_buffer_extra_ - 64;
if ( msec != blip_max_length )
{
long s = (new_rate * (msec + 1) + 999) / 1000;
if ( s < new_size )
new_size = s;
else
assert( 0 ); // fails if requested buffer length exceeds limit
}
if ( buffer_size_ != new_size )
{
void* p = realloc( buffer_, (new_size + blip_buffer_extra_) * sizeof *buffer_ );
if ( !p )
return "Out of memory";
buffer_ = (buf_t_*) p;
}
buffer_size_ = new_size;
assert( buffer_size_ != silent_buf_size );
// update things based on the sample rate
sample_rate_ = new_rate;
length_ = new_size * 1000 / new_rate - 1;
if ( msec )
assert( length_ == msec ); // ensure length is same as that passed in
if ( clock_rate_ )
clock_rate( clock_rate_ );
bass_freq( bass_freq_ );
clear();
return 0; // success
}
blip_resampled_time_t Blip_Buffer::clock_rate_factor( long rate ) const
{
double ratio = (double) sample_rate_ / rate;
blip_long factor = (blip_long) floor( ratio * (1L << BLIP_BUFFER_ACCURACY) + 0.5 );
assert( factor > 0 || !sample_rate_ ); // fails if clock/output ratio is too large
return (blip_resampled_time_t) factor;
}
void Blip_Buffer::bass_freq( int freq )
{
bass_freq_ = freq;
int shift = 31;
if ( freq > 0 )
{
shift = 13;
long f = (freq << 16) / sample_rate_;
while ( (f >>= 1) && --shift ) { }
}
bass_shift_ = shift;
}
void Blip_Buffer::end_frame( blip_time_t t )
{
offset_ += t * factor_;
assert( samples_avail() <= (long) buffer_size_ ); // time outside buffer length
}
void Blip_Buffer::remove_silence( long count )
{
assert( count <= samples_avail() ); // tried to remove more samples than available
offset_ -= (blip_resampled_time_t) count << BLIP_BUFFER_ACCURACY;
}
long Blip_Buffer::count_samples( blip_time_t t ) const
{
unsigned long last_sample = resampled_time( t ) >> BLIP_BUFFER_ACCURACY;
unsigned long first_sample = offset_ >> BLIP_BUFFER_ACCURACY;
return (long) (last_sample - first_sample);
}
blip_time_t Blip_Buffer::count_clocks( long count ) const
{
if ( !factor_ )
{
assert( 0 ); // sample rate and clock rates must be set first
return 0;
}
if ( count > buffer_size_ )
count = buffer_size_;
blip_resampled_time_t time = (blip_resampled_time_t) count << BLIP_BUFFER_ACCURACY;
return (blip_time_t) ((time - offset_ + factor_ - 1) / factor_);
}
void Blip_Buffer::remove_samples( long count )
{
if ( count )
{
remove_silence( count );
// copy remaining samples to beginning and clear old samples
long remain = samples_avail() + blip_buffer_extra_;
memmove( buffer_, buffer_ + count, remain * sizeof *buffer_ );
memset( buffer_ + remain, 0, count * sizeof *buffer_ );
}
}
// Blip_Synth_
Blip_Synth_Fast_::Blip_Synth_Fast_()
{
buf = 0;
last_amp = 0;
delta_factor = 0;
}
void Blip_Synth_Fast_::volume_unit( double new_unit )
{
delta_factor = int (new_unit * (1L << blip_sample_bits) + 0.5);
}
#if !BLIP_BUFFER_FAST
Blip_Synth_::Blip_Synth_( short* p, int w ) :
impulses( p ),
width( w )
{
volume_unit_ = 0.0;
kernel_unit = 0;
buf = 0;
last_amp = 0;
delta_factor = 0;
}
#undef PI
#define PI 3.1415926535897932384626433832795029
static void gen_sinc( float* out, int count, double oversample, double treble, double cutoff )
{
if ( cutoff >= 0.999 )
cutoff = 0.999;
if ( treble < -300.0 )
treble = -300.0;
if ( treble > 5.0 )
treble = 5.0;
double const maxh = 4096.0;
double const rolloff = pow( 10.0, 1.0 / (maxh * 20.0) * treble / (1.0 - cutoff) );
double const pow_a_n = pow( rolloff, maxh - maxh * cutoff );
double const to_angle = PI / 2 / maxh / oversample;
for ( int i = 0; i < count; i++ )
{
double angle = ((i - count) * 2 + 1) * to_angle;
double c = rolloff * cos( (maxh - 1.0) * angle ) - cos( maxh * angle );
double cos_nc_angle = cos( maxh * cutoff * angle );
double cos_nc1_angle = cos( (maxh * cutoff - 1.0) * angle );
double cos_angle = cos( angle );
c = c * pow_a_n - rolloff * cos_nc1_angle + cos_nc_angle;
double d = 1.0 + rolloff * (rolloff - cos_angle - cos_angle);
double b = 2.0 - cos_angle - cos_angle;
double a = 1.0 - cos_angle - cos_nc_angle + cos_nc1_angle;
out [i] = (float) ((a * d + c * b) / (b * d)); // a / b + c / d
}
}
void blip_eq_t::generate( float* out, int count ) const
{
// lower cutoff freq for narrow kernels with their wider transition band
// (8 points->1.49, 16 points->1.15)
double oversample = blip_res * 2.25 / count + 0.85;
double half_rate = sample_rate * 0.5;
if ( cutoff_freq )
oversample = half_rate / cutoff_freq;
double cutoff = rolloff_freq * oversample / half_rate;
gen_sinc( out, count, blip_res * oversample, treble, cutoff );
// apply (half of) hamming window
double to_fraction = PI / (count - 1);
for ( int i = count; i--; )
out [i] *= 0.54f - 0.46f * (float) cos( i * to_fraction );
}
void Blip_Synth_::adjust_impulse()
{
// sum pairs for each phase and add error correction to end of first half
int const size = impulses_size();
for ( int p = blip_res; p-- >= blip_res / 2; )
{
int p2 = blip_res - 2 - p;
long error = kernel_unit;
for ( int i = 1; i < size; i += blip_res )
{
error -= impulses [i + p ];
error -= impulses [i + p2];
}
if ( p == p2 )
error /= 2; // phase = 0.5 impulse uses same half for both sides
impulses [size - blip_res + p] += (short) error;
//printf( "error: %ld\n", error );
}
//for ( int i = blip_res; i--; printf( "\n" ) )
// for ( int j = 0; j < width / 2; j++ )
// printf( "%5ld,", impulses [j * blip_res + i + 1] );
}
void Blip_Synth_::treble_eq( blip_eq_t const& eq )
{
float fimpulse [blip_res / 2 * (blip_widest_impulse_ - 1) + blip_res * 2];
int const half_size = blip_res / 2 * (width - 1);
eq.generate( &fimpulse [blip_res], half_size );
int i;
// need mirror slightly past center for calculation
for ( i = blip_res; i--; )
fimpulse [blip_res + half_size + i] = fimpulse [blip_res + half_size - 1 - i];
// starts at 0
for ( i = 0; i < blip_res; i++ )
fimpulse [i] = 0.0f;
// find rescale factor
double total = 0.0;
for ( i = 0; i < half_size; i++ )
total += fimpulse [blip_res + i];
//double const base_unit = 44800.0 - 128 * 18; // allows treble up to +0 dB
//double const base_unit = 37888.0; // allows treble to +5 dB
double const base_unit = 32768.0; // necessary for blip_unscaled to work
double rescale = base_unit / 2 / total;
kernel_unit = (long) base_unit;
// integrate, first difference, rescale, convert to int
double sum = 0.0;
double next = 0.0;
int const impulses_size = this->impulses_size();
for ( i = 0; i < impulses_size; i++ )
{
impulses [i] = (short) floor( (next - sum) * rescale + 0.5 );
sum += fimpulse [i];
next += fimpulse [i + blip_res];
}
adjust_impulse();
// volume might require rescaling
double vol = volume_unit_;
if ( vol )
{
volume_unit_ = 0.0;
volume_unit( vol );
}
}
void Blip_Synth_::volume_unit( double new_unit )
{
if ( new_unit != volume_unit_ )
{
// use default eq if it hasn't been set yet
if ( !kernel_unit )
treble_eq( -8.0 );
volume_unit_ = new_unit;
double factor = new_unit * (1L << blip_sample_bits) / kernel_unit;
if ( factor > 0.0 )
{
int shift = 0;
// if unit is really small, might need to attenuate kernel
while ( factor < 2.0 )
{
shift++;
factor *= 2.0;
}
if ( shift )
{
kernel_unit >>= shift;
assert( kernel_unit > 0 ); // fails if volume unit is too low
// keep values positive to avoid round-towards-zero of sign-preserving
// right shift for negative values
long offset = 0x8000 + (1 << (shift - 1));
long offset2 = 0x8000 >> shift;
for ( int i = impulses_size(); i--; )
impulses [i] = (short) (((impulses [i] + offset) >> shift) - offset2);
adjust_impulse();
}
}
delta_factor = (int) floor( factor + 0.5 );
//printf( "delta_factor: %d, kernel_unit: %d\n", delta_factor, kernel_unit );
}
}
#endif
long Blip_Buffer::read_samples( blip_sample_t* BLIP_RESTRICT out, long max_samples, int stereo )
{
long count = samples_avail();
if ( count > max_samples )
count = max_samples;
if ( count )
{
int const bass = BLIP_READER_BASS( *this );
BLIP_READER_BEGIN( reader, *this );
if ( !stereo )
{
for ( blip_long n = count; n; --n )
{
blip_long s = BLIP_READER_READ( reader );
if ( (blip_sample_t) s != s )
s = 0x7FFF - (s >> 24);
*out++ = (blip_sample_t) s;
BLIP_READER_NEXT( reader, bass );
}
}
else
{
for ( blip_long n = count; n; --n )
{
blip_long s = BLIP_READER_READ( reader );
if ( (blip_sample_t) s != s )
s = 0x7FFF - (s >> 24);
*out = (blip_sample_t) s;
out += 2;
BLIP_READER_NEXT( reader, bass );
}
}
BLIP_READER_END( reader, *this );
remove_samples( count );
}
return count;
}
void Blip_Buffer::mix_samples( blip_sample_t const* in, long count )
{
if ( buffer_size_ == silent_buf_size )
{
assert( 0 );
return;
}
buf_t_* out = buffer_ + (offset_ >> BLIP_BUFFER_ACCURACY) + blip_widest_impulse_ / 2;
int const sample_shift = blip_sample_bits - 16;
int prev = 0;
while ( count-- )
{
blip_long s = (blip_long) *in++ << sample_shift;
*out += s - prev;
prev = s;
++out;
}
*out -= prev;
}

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