345 lines
10 KiB
C
345 lines
10 KiB
C
/* blip_buf $vers. http://www.slack.net/~ant/ */
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#include "blip_buf.h"
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#include <assert.h>
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#include <limits.h>
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#include <string.h>
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#include <stdlib.h>
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/* Library Copyright (C) 2003-2009 Shay Green. This library is free software;
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you can redistribute it and/or modify it under the terms of the GNU Lesser
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General Public License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version. This
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library is distributed in the hope that it will be useful, but WITHOUT ANY
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WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
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A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
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details. You should have received a copy of the GNU Lesser General Public
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License along with this module; if not, write to the Free Software Foundation,
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Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA */
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#if defined (BLARGG_TEST) && BLARGG_TEST
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#include "blargg_test.h"
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#endif
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/* Equivalent to ULONG_MAX >= 0xFFFFFFFF00000000.
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Avoids constants that don't fit in 32 bits. */
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#if ULONG_MAX/0xFFFFFFFF > 0xFFFFFFFF
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typedef unsigned long fixed_t;
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enum { pre_shift = 32 };
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#elif defined(ULLONG_MAX)
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typedef unsigned long long fixed_t;
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enum { pre_shift = 32 };
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#else
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typedef unsigned fixed_t;
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enum { pre_shift = 0 };
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#endif
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enum { time_bits = pre_shift + 20 };
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static fixed_t const time_unit = (fixed_t) 1 << time_bits;
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enum { bass_shift = 9 }; /* affects high-pass filter breakpoint frequency */
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enum { end_frame_extra = 2 }; /* allows deltas slightly after frame length */
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enum { half_width = 8 };
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enum { buf_extra = half_width*2 + end_frame_extra };
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enum { phase_bits = 5 };
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enum { phase_count = 1 << phase_bits };
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enum { delta_bits = 15 };
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enum { delta_unit = 1 << delta_bits };
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enum { frac_bits = time_bits - pre_shift };
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/* We could eliminate avail and encode whole samples in offset, but that would
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limit the total buffered samples to blip_max_frame. That could only be
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increased by decreasing time_bits, which would reduce resample ratio accuracy.
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*/
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/** Sample buffer that resamples to output rate and accumulates samples
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until they're read out */
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struct blip_t
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{
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fixed_t factor;
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fixed_t offset;
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int avail;
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int size;
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int integrator;
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};
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typedef int buf_t;
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/* probably not totally portable */
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#define SAMPLES( buf ) ((buf_t*) ((buf) + 1))
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/* Arithmetic (sign-preserving) right shift */
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#define ARITH_SHIFT( n, shift ) \
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((n) >> (shift))
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enum { max_sample = +32767 };
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enum { min_sample = -32768 };
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#define CLAMP( n ) \
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{\
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if ( (short) n != n )\
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n = ARITH_SHIFT( n, 16 ) ^ max_sample;\
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}
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static void check_assumptions( void )
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{
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int n;
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#if INT_MAX < 0x7FFFFFFF || UINT_MAX < 0xFFFFFFFF
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#error "int must be at least 32 bits"
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#endif
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assert( (-3 >> 1) == -2 ); /* right shift must preserve sign */
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n = max_sample * 2;
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CLAMP( n );
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assert( n == max_sample );
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n = min_sample * 2;
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CLAMP( n );
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assert( n == min_sample );
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assert( blip_max_ratio <= time_unit );
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assert( blip_max_frame <= (fixed_t) -1 >> time_bits );
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}
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blip_t* blip_new( int size )
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{
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blip_t* m;
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assert( size >= 0 );
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m = (blip_t*) malloc( sizeof *m + (size + buf_extra) * sizeof (buf_t) );
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if ( m )
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{
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m->factor = time_unit / blip_max_ratio;
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m->size = size;
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blip_clear( m );
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check_assumptions();
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}
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return m;
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}
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void blip_delete( blip_t* m )
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{
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if ( m != NULL )
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{
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/* Clear fields in case user tries to use after freeing */
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memset( m, 0, sizeof *m );
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free( m );
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}
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}
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void blip_set_rates( blip_t* m, double clock_rate, double sample_rate )
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{
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double factor = time_unit * sample_rate / clock_rate;
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m->factor = (fixed_t) factor;
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/* Fails if clock_rate exceeds maximum, relative to sample_rate */
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assert( 0 <= factor - m->factor && factor - m->factor < 1 );
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/* Avoid requiring math.h. Equivalent to
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m->factor = (int) ceil( factor ) */
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if ( m->factor < factor )
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m->factor++;
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/* At this point, factor is most likely rounded up, but could still
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have been rounded down in the floating-point calculation. */
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}
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void blip_clear( blip_t* m )
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{
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/* We could set offset to 0, factor/2, or factor-1. 0 is suitable if
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factor is rounded up. factor-1 is suitable if factor is rounded down.
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Since we don't know rounding direction, factor/2 accommodates either,
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with the slight loss of showing an error in half the time. Since for
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a 64-bit factor this is years, the halving isn't a problem. */
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m->offset = m->factor / 2;
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m->avail = 0;
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m->integrator = 0;
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memset( SAMPLES( m ), 0, (m->size + buf_extra) * sizeof (buf_t) );
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}
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int blip_clocks_needed( const blip_t* m, int samples )
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{
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fixed_t needed;
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/* Fails if buffer can't hold that many more samples */
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assert( samples >= 0 && m->avail + samples <= m->size );
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needed = (fixed_t) samples * time_unit;
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if ( needed < m->offset )
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return 0;
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return (needed - m->offset + m->factor - 1) / m->factor;
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}
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void blip_end_frame( blip_t* m, unsigned t )
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{
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fixed_t off = t * m->factor + m->offset;
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m->avail += off >> time_bits;
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m->offset = off & (time_unit - 1);
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/* Fails if buffer size was exceeded */
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assert( m->avail <= m->size );
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}
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int blip_samples_avail( const blip_t* m )
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{
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return m->avail;
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}
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static void remove_samples( blip_t* m, int count )
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{
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buf_t* buf = SAMPLES( m );
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int remain = m->avail + buf_extra - count;
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m->avail -= count;
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memmove( &buf [0], &buf [count], remain * sizeof buf [0] );
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memset( &buf [remain], 0, count * sizeof buf [0] );
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}
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int blip_read_samples( blip_t* m, short out [], int count, int stereo )
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{
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assert( count >= 0 );
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if ( count > m->avail )
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count = m->avail;
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if ( count )
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{
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int const step = stereo ? 2 : 1;
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buf_t const* in = SAMPLES( m );
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buf_t const* end = in + count;
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int sum = m->integrator;
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do
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{
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/* Eliminate fraction */
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int s = ARITH_SHIFT( sum, delta_bits );
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sum += *in++;
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CLAMP( s );
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*out = s;
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out += step;
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/* High-pass filter */
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sum -= s << (delta_bits - bass_shift);
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}
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while ( in != end );
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m->integrator = sum;
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remove_samples( m, count );
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}
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return count;
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}
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/* Things that didn't help performance on x86:
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__attribute__((aligned(128)))
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#define short int
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restrict
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*/
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/* Sinc_Generator( 0.9, 0.55, 4.5 ) */
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static short const bl_step [phase_count + 1] [half_width] =
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{
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{ 43, -115, 350, -488, 1136, -914, 5861,21022},
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{ 44, -118, 348, -473, 1076, -799, 5274,21001},
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{ 45, -121, 344, -454, 1011, -677, 4706,20936},
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{ 46, -122, 336, -431, 942, -549, 4156,20829},
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{ 47, -123, 327, -404, 868, -418, 3629,20679},
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{ 47, -122, 316, -375, 792, -285, 3124,20488},
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{ 47, -120, 303, -344, 714, -151, 2644,20256},
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{ 46, -117, 289, -310, 634, -17, 2188,19985},
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{ 46, -114, 273, -275, 553, 117, 1758,19675},
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{ 44, -108, 255, -237, 471, 247, 1356,19327},
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{ 43, -103, 237, -199, 390, 373, 981,18944},
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{ 42, -98, 218, -160, 310, 495, 633,18527},
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{ 40, -91, 198, -121, 231, 611, 314,18078},
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{ 38, -84, 178, -81, 153, 722, 22,17599},
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{ 36, -76, 157, -43, 80, 824, -241,17092},
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{ 34, -68, 135, -3, 8, 919, -476,16558},
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{ 32, -61, 115, 34, -60, 1006, -683,16001},
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{ 29, -52, 94, 70, -123, 1083, -862,15422},
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{ 27, -44, 73, 106, -184, 1152,-1015,14824},
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{ 25, -36, 53, 139, -239, 1211,-1142,14210},
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{ 22, -27, 34, 170, -290, 1261,-1244,13582},
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{ 20, -20, 16, 199, -335, 1301,-1322,12942},
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{ 18, -12, -3, 226, -375, 1331,-1376,12293},
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{ 15, -4, -19, 250, -410, 1351,-1408,11638},
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{ 13, 3, -35, 272, -439, 1361,-1419,10979},
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{ 11, 9, -49, 292, -464, 1362,-1410,10319},
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{ 9, 16, -63, 309, -483, 1354,-1383, 9660},
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{ 7, 22, -75, 322, -496, 1337,-1339, 9005},
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{ 6, 26, -85, 333, -504, 1312,-1280, 8355},
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{ 4, 31, -94, 341, -507, 1278,-1205, 7713},
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{ 3, 35, -102, 347, -506, 1238,-1119, 7082},
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{ 1, 40, -110, 350, -499, 1190,-1021, 6464},
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{ 0, 43, -115, 350, -488, 1136, -914, 5861}
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};
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/* Shifting by pre_shift allows calculation using unsigned int rather than
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possibly-wider fixed_t. On 32-bit platforms, this is likely more efficient.
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And by having pre_shift 32, a 32-bit platform can easily do the shift by
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simply ignoring the low half. */
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void blip_add_delta( blip_t* m, unsigned time, int delta )
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{
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unsigned fixed = (unsigned) ((time * m->factor + m->offset) >> pre_shift);
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buf_t* out = SAMPLES( m ) + m->avail + (fixed >> frac_bits);
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int const phase_shift = frac_bits - phase_bits;
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int phase = fixed >> phase_shift & (phase_count - 1);
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short const* in = bl_step [phase];
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short const* rev = bl_step [phase_count - phase];
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int interp = fixed >> (phase_shift - delta_bits) & (delta_unit - 1);
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int delta2 = (delta * interp) >> delta_bits;
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delta -= delta2;
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/* Fails if buffer size was exceeded */
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assert( out <= &SAMPLES( m ) [m->size + end_frame_extra] );
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out [0] += in[0]*delta + in[half_width+0]*delta2;
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out [1] += in[1]*delta + in[half_width+1]*delta2;
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out [2] += in[2]*delta + in[half_width+2]*delta2;
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out [3] += in[3]*delta + in[half_width+3]*delta2;
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out [4] += in[4]*delta + in[half_width+4]*delta2;
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out [5] += in[5]*delta + in[half_width+5]*delta2;
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out [6] += in[6]*delta + in[half_width+6]*delta2;
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out [7] += in[7]*delta + in[half_width+7]*delta2;
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in = rev;
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out [ 8] += in[7]*delta + in[7-half_width]*delta2;
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out [ 9] += in[6]*delta + in[6-half_width]*delta2;
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out [10] += in[5]*delta + in[5-half_width]*delta2;
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out [11] += in[4]*delta + in[4-half_width]*delta2;
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out [12] += in[3]*delta + in[3-half_width]*delta2;
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out [13] += in[2]*delta + in[2-half_width]*delta2;
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out [14] += in[1]*delta + in[1-half_width]*delta2;
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out [15] += in[0]*delta + in[0-half_width]*delta2;
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}
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void blip_add_delta_fast( blip_t* m, unsigned time, int delta )
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{
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unsigned fixed = (unsigned) ((time * m->factor + m->offset) >> pre_shift);
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buf_t* out = SAMPLES( m ) + m->avail + (fixed >> frac_bits);
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int interp = fixed >> (frac_bits - delta_bits) & (delta_unit - 1);
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int delta2 = delta * interp;
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/* Fails if buffer size was exceeded */
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assert( out <= &SAMPLES( m ) [m->size + end_frame_extra] );
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out [7] += delta * delta_unit - delta2;
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out [8] += delta2;
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}
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