mirror of
https://github.com/ekeeke/Genesis-Plus-GX.git
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305 lines
6.5 KiB
C
305 lines
6.5 KiB
C
/* Game_Music_Emu 0.5.2. http://www.slack.net/~ant/ */
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/* Copyright (C) 2004-2006 Shay Green. */
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/* C Conversion by Eke-Eke for use in Genesis Plus (2009). */
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#include "Fir_Resampler.h"
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#include <assert.h>
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#include <string.h>
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#include <stdlib.h>
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#include <stdio.h>
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#include <math.h>
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/* sound buffer */
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static sample_t *buffer = NULL;
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static int buffer_size = 0;
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static sample_t impulses[MAX_RES][WIDTH];
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static sample_t* write_pos = NULL;
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static int res = 1;
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static int imp_phase = 0;
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static unsigned long skip_bits = 0;
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static int step = STEREO;
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static int input_per_cycle;
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static double ratio = 1.0;
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static void gen_sinc(double rolloff, int width, double offset, double spacing, double scale, int count, short *out )
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{
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double const maxh = 256;
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double const fstep = M_PI / maxh * spacing;
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double const to_w = maxh * 2 / width;
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double const pow_a_n = pow( rolloff, maxh );
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scale /= maxh * 2;
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double angle = (count / 2 - 1 + offset) * -fstep;
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while ( count-- )
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{
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*out++ = 0;
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double w = angle * to_w;
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if ( fabs( w ) < M_PI )
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{
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double rolloff_cos_a = rolloff * cos( angle );
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double num = 1 - rolloff_cos_a -
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pow_a_n * cos( maxh * angle ) +
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pow_a_n * rolloff * cos( (maxh - 1) * angle );
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double den = 1 - rolloff_cos_a - rolloff_cos_a + rolloff * rolloff;
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double sinc = scale * num / den - scale;
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out [-1] = (short) (cos( w ) * sinc + sinc);
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}
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angle += fstep;
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}
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}
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static int available( unsigned long input_count )
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{
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int cycle_count = input_count / input_per_cycle;
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int output_count = cycle_count * res * STEREO;
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input_count -= cycle_count * input_per_cycle;
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unsigned long skip = skip_bits >> imp_phase;
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int remain = res - imp_phase;
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while ( input_count >= 0 )
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{
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input_count -= step + (skip & 1) * STEREO;
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skip >>= 1;
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if ( !--remain )
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{
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skip = skip_bits;
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remain = res;
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}
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output_count += 2;
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}
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return output_count;
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}
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int Fir_Resampler_initialize( int new_size )
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{
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buffer = (sample_t *) realloc( buffer, (new_size + WRITE_OFFSET) * sizeof (sample_t) );
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if ( !buffer && new_size ) return 0;
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buffer_size = new_size + WRITE_OFFSET;
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write_pos = 0;
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res = 1;
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imp_phase = 0;
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skip_bits = 0;
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step = STEREO;
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ratio = 1.0;
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Fir_Resampler_clear();
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return 1;
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}
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void Fir_Resampler_shutdown( void )
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{
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if (buffer) free(buffer);
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buffer = 0;
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buffer_size = 0;
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write_pos = 0;
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}
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void Fir_Resampler_clear()
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{
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imp_phase = 0;
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if ( buffer_size )
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{
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write_pos = &buffer [WRITE_OFFSET];
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memset( buffer, 0, buffer_size * sizeof (sample_t) );
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}
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}
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double Fir_Resampler_time_ratio( double new_factor )
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{
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ratio = new_factor;
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int i, r;
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double fstep = 0.0;
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double least_error = 2;
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double pos = 0.0;
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res = -1;
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for ( r = 1; r <= MAX_RES; r++ )
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{
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pos += ratio;
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double nearest = floor( pos + 0.5 );
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double error = fabs( pos - nearest );
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if ( error < least_error )
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{
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res = r;
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fstep = nearest / res;
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least_error = error;
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}
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}
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skip_bits = 0;
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step = STEREO * (int) floor( fstep );
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ratio = fstep;
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fstep = fmod( fstep, 1.0 );
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double filter = (ratio < 1.0) ? 1.0 : 1.0 / ratio;
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pos = 0.0;
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input_per_cycle = 0;
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for ( i = 0; i < res; i++ )
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{
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gen_sinc( ROLLOFF, (int) (WIDTH * filter + 1) & ~1, pos, filter,
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(double) (0x7FFF * GAIN * filter),
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(int) WIDTH, impulses[i] );
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pos += fstep;
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input_per_cycle += step;
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if ( pos >= 0.9999999 )
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{
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pos -= 1.0;
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skip_bits |= 1 << i;
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input_per_cycle++;
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}
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}
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Fir_Resampler_clear();
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return ratio;
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}
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/* Current ratio */
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double Fir_Resampler_ratio( void )
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{
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return ratio;
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}
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/* Number of input samples that can be written */
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int Fir_Resampler_max_write( void )
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{
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return buffer + buffer_size - write_pos;
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}
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/* Pointer to place to write input samples */
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sample_t* Fir_Resampler_buffer( void )
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{
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return write_pos;
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}
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/* Number of input samples in buffer */
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int Fir_Resampler_written( void )
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{
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return write_pos - &buffer [WRITE_OFFSET];
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}
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/* Number of output samples available */
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int Fir_Resampler_avail( void )
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{
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return available( write_pos - &buffer [WIDTH * STEREO] );
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}
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void Fir_Resampler_write( long count )
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{
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write_pos += count;
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assert( write_pos <= ( buffer + buffer_size ) );
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}
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int Fir_Resampler_read( sample_t** out, unsigned long count )
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{
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sample_t* out_l = out[0];
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sample_t* out_r = out[1];
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const sample_t* in = buffer;
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sample_t* end_pos = write_pos;
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unsigned long skip = skip_bits >> imp_phase;
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sample_t const* imp = impulses [imp_phase];
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int remain = res - imp_phase;
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int n;
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if ( end_pos - in >= WIDTH * STEREO )
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{
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end_pos -= WIDTH * STEREO;
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do
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{
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count--;
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/* accumulate in extended precision */
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unsigned long l = 0;
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unsigned long r = 0;
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const sample_t* i = in;
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if ( count < 0 )
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break;
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for ( n = WIDTH / 2; n; --n )
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{
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int pt0 = imp [0];
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l += pt0 * i [0];
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r += pt0 * i [1];
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int pt1 = imp [1];
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imp += 2;
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l += pt1 * i [2];
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r += pt1 * i [3];
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i += 4;
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}
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remain--;
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l >>= 15;
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r >>= 15;
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in += (skip * STEREO) & STEREO;
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skip >>= 1;
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in += step;
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if ( !remain )
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{
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imp = impulses [0];
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skip = skip_bits;
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remain = res;
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}
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*out_l++ = (sample_t) l;
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*out_r++ = (sample_t) r;
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}
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while ( in <= end_pos );
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}
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imp_phase = res - remain;
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int left = write_pos - in;
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write_pos = &buffer [left];
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memmove( buffer, in, left * sizeof *in );
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return out_l - out[0];
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}
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int Fir_Resampler_input_needed( unsigned long output_count )
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{
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unsigned long input_count = 0;
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unsigned long skip = skip_bits >> imp_phase;
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int remain = res - imp_phase;
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while ( (output_count) > 0 ) /* fixed (Eke_Eke) */
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{
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input_count += step + (skip & 1) * STEREO;
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skip >>= 1;
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if ( !--remain )
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{
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skip = skip_bits;
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remain = res;
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}
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output_count -= 2;
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}
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long input_extra = input_count - (write_pos - &buffer [(WIDTH - 1) * STEREO]);
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if ( input_extra < 0 )
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input_extra = 0;
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return input_extra;
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}
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int Fir_Resampler_skip_input( long count )
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{
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int remain = write_pos - buffer;
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int max_count = remain - WIDTH * STEREO;
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if ( count > max_count )
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count = max_count;
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remain -= count;
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write_pos = &buffer [remain];
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memmove( buffer, &buffer [count], remain * sizeof buffer [0] );
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return count;
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}
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