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comparison src/audio.c @ 24:4c9dbfa30a66

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Implemented audio
author Michael Pavone <pavone@retrodev.com>
date Thu, 31 Mar 2016 00:07:37 -0700
parents
children 23bea9b9569f
comparison
equal deleted inserted replaced
23:a085f17b79e9 24:4c9dbfa30a66
1 #include <stdint.h>
2 #include <stdlib.h>
3 #include <string.h>
4 #include "audio.h"
5 #include "system.h"
6
7 #define BUFFER_INC_RES 1000000000UL
8
9 audio *alloc_audio(uint32_t master_clock, uint32_t clock_div, int sample_rate, int buffer_size)
10 {
11 size_t alloc_size = sizeof(audio) + buffer_size * sizeof(int16_t) * 2;
12 audio *context = malloc(alloc_size);
13 memset(context, 0, alloc_size);
14 context->writebuffer = context->buffer;
15 context->playbuffer = context->buffer + buffer_size;
16
17 context->buffer_size = buffer_size;
18 context->clock_inc = clock_div;
19 context->buffer_inc = ((BUFFER_INC_RES * (uint64_t)sample_rate) / (uint64_t)master_clock) * clock_div;
20 for (int i = 0; i < NUM_CHANNELS; i++)
21 {
22 context->value[i] = context->volume[i] << 5;
23 }
24 }
25
26 void audio_run(audio *context, uint32_t target)
27 {
28 while (context->cycles < target)
29 {
30 for (int i = 0; i < 4; i++)
31 {
32 if (context->timer_cur[i]) {
33 context->timer_cur[i]--;
34 if (!context->timer_cur[i]) {
35 context->value[i] = context->value[i] ? 0 : (context->volume[i] << 5);
36 }
37 } else {
38 context->timer_cur[i] = context->timer_load[i];
39 }
40 }
41 context->buffer_fraction += context->buffer_inc;
42 if (context->buffer_fraction >= BUFFER_INC_RES) {
43 context->buffer_fraction -= BUFFER_INC_RES;
44 context->writebuffer[context->buffer_pos++] =
45 context->value[0] + context->value[1] + context->value[2] + context->value[3];
46 if (context->buffer_pos == context->buffer_size) {
47 int16_t *tmp = context->playbuffer;
48 context->playbuffer = context->writebuffer;
49 context->writebuffer = tmp;
50 system_present_audio(context->playbuffer);
51 context->buffer_pos = 0;
52 }
53 }
54 context->cycles += context->clock_inc;
55 }
56 }
57
58 void audio_write_freq(audio *context, int channel, uint16_t value)
59 {
60 context->timer_cur[channel] = context->timer_load[channel] = value;
61 }
62
63 void audio_write_vol(audio *context, int pair, uint16_t value)
64 {
65 int channel = pair * 2;
66 context->value[channel] = context->volume[channel] = value >> 8;
67 channel++;
68 context->value[channel] = context->volume[channel] = value;
69 }