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