mirror of
https://github.com/RaySollium99/picodrive.git
synced 2025-09-05 23:37:46 -04:00
cff531af94
- PicoDrive was originally released by fDave with simple
"free for non-commercial use / For commercial use, separate licencing
terms must be obtained" license and I kept it in my releases.
- in 2011, fDave re-released his code (same that I used as base
many years ago) dual licensed with GPLv2 and MAME licenses:
https://code.google.com/p/cyclone68000/
Based on the above I now proclaim that the whole source code is licensed
under the MAME license as more elaborate form of "for non-commercial use".
If that raises any doubt, I announce that all my modifications (which
is the vast majority of code by now) is licensed under the MAME license,
as it reads in COPYING file in this commit.
This does not affect ym2612.c/sn76496.c that were MAME licensed already
from the beginning.
120 lines
3 KiB
C
120 lines
3 KiB
C
/*
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* PicoDrive
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* (C) notaz, 2008
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*
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* This work is licensed under the terms of MAME license.
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* See COPYING file in the top-level directory.
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*
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* The following ADPCM algorithm was stolen from MAME aica driver.
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* I'm quite sure it's not the right one, but it's the
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* best sounding of the ones that I tried.
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*/
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#include "../pico_int.h"
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#define ADPCMSHIFT 8
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#define ADFIX(f) (int) ((double)f * (double)(1<<ADPCMSHIFT))
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/* limitter */
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#define Limit(val, max, min) { \
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if ( val > max ) val = max; \
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else if ( val < min ) val = min; \
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}
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static const int TableQuant[8] =
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{
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ADFIX(0.8984375),
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ADFIX(0.8984375),
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ADFIX(0.8984375),
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ADFIX(0.8984375),
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ADFIX(1.19921875),
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ADFIX(1.59765625),
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ADFIX(2.0),
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ADFIX(2.3984375)
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};
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// changed using trial and error..
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//static const int quant_mul[16] = { 1, 3, 5, 7, 9, 11, 13, 15, -1, -3, -5, -7, -9, -11, -13, -15 };
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static const int quant_mul[16] = { 1, 3, 5, 7, 9, 11, 13, -1, -1, -3, -5, -7, -9, -11, -13, -15 };
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static int sample = 0, quant = 0, sgn = 0;
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static int stepsamples = (44100<<10)/16000;
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PICO_INTERNAL void PicoPicoPCMReset(void)
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{
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sample = sgn = 0;
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quant = 0x7f;
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memset(PicoPicohw.xpcm_buffer, 0, sizeof(PicoPicohw.xpcm_buffer));
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}
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PICO_INTERNAL void PicoPicoPCMRerate(int xpcm_rate)
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{
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stepsamples = (PsndRate<<10)/xpcm_rate;
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}
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#define XSHIFT 6
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#define do_sample() \
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{ \
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int delta = quant * quant_mul[srcval] >> XSHIFT; \
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sample += delta - (delta >> 2); /* 3/4 */ \
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quant = (quant * TableQuant[srcval&7]) >> ADPCMSHIFT; \
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Limit(quant, 0x6000, 0x7f); \
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Limit(sample, 32767*3/4, -32768*3/4); \
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}
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PICO_INTERNAL void PicoPicoPCMUpdate(short *buffer, int length, int stereo)
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{
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unsigned char *src = PicoPicohw.xpcm_buffer;
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unsigned char *lim = PicoPicohw.xpcm_ptr;
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int srcval, needsamples = 0;
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if (src == lim) goto end;
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for (; length > 0 && src < lim; src++)
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{
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srcval = *src >> 4;
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do_sample();
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for (needsamples += stepsamples; needsamples > (1<<10) && length > 0; needsamples -= (1<<10), length--) {
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*buffer++ += sample;
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if (stereo) { buffer[0] = buffer[-1]; buffer++; }
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}
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srcval = *src & 0xf;
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do_sample();
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for (needsamples += stepsamples; needsamples > (1<<10) && length > 0; needsamples -= (1<<10), length--) {
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*buffer++ += sample;
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if (stereo) { buffer[0] = buffer[-1]; buffer++; }
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}
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// lame normalization stuff, needed due to wrong adpcm algo
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sgn += (sample < 0) ? -1 : 1;
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if (sgn < -16 || sgn > 16) sample -= sample >> 5;
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}
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if (src < lim) {
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int di = lim - src;
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memmove(PicoPicohw.xpcm_buffer, src, di);
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PicoPicohw.xpcm_ptr = PicoPicohw.xpcm_buffer + di;
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elprintf(EL_PICOHW, "xpcm update: over %i", di);
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// adjust fifo
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PicoPicohw.fifo_bytes = di;
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return;
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}
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elprintf(EL_PICOHW, "xpcm update: under %i", length);
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PicoPicohw.xpcm_ptr = PicoPicohw.xpcm_buffer;
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end:
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if (stereo)
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// still must expand SN76496 to stereo
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for (; length > 0; buffer+=2, length--)
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buffer[1] = buffer[0];
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sample = sgn = 0;
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quant = 0x7f;
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}
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