Mercurial > repos > blastem
diff psg.c @ 483:3e1573fa22cf
Implement turbo/slow motion feature that overclocks or underclocks the entire system at the push of a button
| author | Mike Pavone <pavone@retrodev.com> |
|---|---|
| date | Tue, 01 Oct 2013 23:51:16 -0700 |
| parents | 140af5509ce7 |
| children | b7b7a1cab44a |
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--- a/psg.c Wed Sep 18 19:10:54 2013 -0700 +++ b/psg.c Tue Oct 01 23:51:16 2013 -0700 @@ -1,6 +1,6 @@ /* Copyright 2013 Michael Pavone - This file is part of BlastEm. + This file is part of BlastEm. BlastEm is free software distributed under the terms of the GNU General Public License version 3 or greater. See COPYING for full license text. */ #include "psg.h" @@ -13,15 +13,23 @@ memset(context, 0, sizeof(*context)); context->audio_buffer = malloc(sizeof(*context->audio_buffer) * samples_frame); context->back_buffer = malloc(sizeof(*context->audio_buffer) * samples_frame); - double clock_rate = (double)master_clock / (double)clock_div; - context->buffer_inc = ((double)sample_rate / (double)master_clock) * clock_div; context->clock_inc = clock_div; + context->sample_rate = sample_rate; context->samples_frame = samples_frame; + psg_adjust_master_clock(context, master_clock); for (int i = 0; i < 4; i++) { context->volume[i] = 0xF; } } +#define BUFFER_INC_RES 1000000000UL + +void psg_adjust_master_clock(psg_context * context, uint32_t master_clock) +{ + uint64_t old_inc = context->buffer_inc; + context->buffer_inc = ((BUFFER_INC_RES * (uint64_t)context->sample_rate) / (uint64_t)master_clock) * (uint64_t)context->clock_inc; +} + void psg_write(psg_context * context, uint8_t value) { if (value & 0x80) { @@ -70,7 +78,7 @@ //table shamelessly swiped from PSG doc from smspower.org int16_t volume_table[16] = { 32767/PSG_VOL_DIV, 26028/PSG_VOL_DIV, 20675/PSG_VOL_DIV, 16422/PSG_VOL_DIV, 13045/PSG_VOL_DIV, 10362/PSG_VOL_DIV, - 8231/PSG_VOL_DIV, 6568/PSG_VOL_DIV, 5193/PSG_VOL_DIV, 4125/PSG_VOL_DIV, 3277/PSG_VOL_DIV, 2603/PSG_VOL_DIV, + 8231/PSG_VOL_DIV, 6568/PSG_VOL_DIV, 5193/PSG_VOL_DIV, 4125/PSG_VOL_DIV, 3277/PSG_VOL_DIV, 2603/PSG_VOL_DIV, 2067/PSG_VOL_DIV, 1642/PSG_VOL_DIV, 1304/PSG_VOL_DIV, 0 }; @@ -97,8 +105,8 @@ } } context->buffer_fraction += context->buffer_inc; - if (context->buffer_fraction >= 1.0) { - context->buffer_fraction -= 1.0; + if (context->buffer_fraction >= BUFFER_INC_RES) { + context->buffer_fraction -= BUFFER_INC_RES; int16_t acc = 0; for (int i = 0; i < 3; i++) { if (context->output_state[i]) {