annotate vgm.c @ 2228:0db9dc6a9020

Some minor refresh emulation improvements
author Michael Pavone <pavone@retrodev.com>
date Mon, 05 Sep 2022 23:37:49 -0700
parents 327332138c5c
children
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rev   line source
1909
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1 #include <stdlib.h>
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2 #include <string.h>
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3 #include <stddef.h>
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4 #include "vgm.h"
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5
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6 vgm_writer *vgm_write_open(char *filename, uint32_t rate, uint32_t clock, uint32_t cycle)
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7 {
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8 FILE *f = fopen(filename, "wb");
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9 if (!f) {
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10 return NULL;
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11 }
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12 vgm_writer *writer = calloc(sizeof(vgm_writer), 1);
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13 memcpy(writer->header.ident, "Vgm ", 4);
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14 writer->header.version = 0x150;
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15 writer->header.data_offset = sizeof(writer->header) - offsetof(vgm_header, data_offset);
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16 writer->header.rate = rate;
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17 writer->f = f;
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18 if (1 != fwrite(&writer->header, sizeof(writer->header), 1, f)) {
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19 free(writer);
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20 fclose(f);
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21 return NULL;
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22 }
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23 writer->master_clock = clock;
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24 writer->last_cycle = cycle;
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25
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26 return writer;
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27 }
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28
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29 void vgm_sn76489_init(vgm_writer *writer, uint32_t clock, uint16_t feedback, uint8_t shift_reg_size, uint8_t flags)
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30 {
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31 if (flags && writer->header.version < 0x151) {
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32 writer->header.version = 0x151;
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33 }
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34 writer->header.sn76489_clk = clock,
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35 writer->header.sn76489_fb = feedback;
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36 writer->header.sn76489_shift = shift_reg_size;
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37 writer->header.sn76489_flags = flags;
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38 }
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39
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40 static void wait_commands(vgm_writer *writer, uint32_t delta)
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41 {
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42 if (!delta) {
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43 return;
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44 }
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45 if (delta <= 0x10) {
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46 fputc(CMD_WAIT_SHORT + (delta - 1), writer->f);
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47 } else if (delta >= 735 && delta <= (735 + 0x10)) {
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48 fputc(CMD_WAIT_60, writer->f);
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49 wait_commands(writer, delta - 735);
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50 } else if (delta >= 882 && delta <= (882 + 0x10)) {
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51 fputc(CMD_WAIT_50, writer->f);
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52 wait_commands(writer, delta - 882);
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53 } else if (delta > 0xFFFF) {
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54 uint8_t cmd[3] = {CMD_WAIT, 0xFF, 0xFF};
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55 fwrite(cmd, 1, sizeof(cmd), writer->f);
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56 wait_commands(writer, delta - 0xFFFF);
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57 } else {
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58 uint8_t cmd[3] = {CMD_WAIT, delta, delta >> 8};
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59 fwrite(cmd, 1, sizeof(cmd), writer->f);
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60 }
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61 }
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62
2002
fc8fd89aeba9 Fix VGM delay calculation overflow when a YM-2612 write follows a PSG write in close succession
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63 #include "util.h"
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64 static void add_wait(vgm_writer *writer, uint32_t cycle)
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65 {
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66 if (cycle < writer->last_cycle) {
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67 //This can happen when a YM-2612 write happens immediately after a PSG write
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68 //due to the relatively low granularity of the PSG's internal clock
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69 //given that VGM only has a granularity of 44.1 kHz ignoring this is harmless
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70 return;
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71 }
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72 uint64_t last_sample = (uint64_t)writer->last_cycle * (uint64_t)44100;
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73 last_sample /= (uint64_t)writer->master_clock;
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74 uint64_t sample = ((uint64_t)cycle + (uint64_t)writer->extra_delta) * (uint64_t)44100;
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75 sample /= (uint64_t)writer->master_clock;
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76 uint32_t delta = sample - last_sample;
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77
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78 writer->last_cycle = cycle;
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79 writer->extra_delta = 0;
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80 writer->header.num_samples += delta;
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81 wait_commands(writer, delta);
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82 }
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83
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84 static uint8_t last_cmd;
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85 void vgm_sn76489_write(vgm_writer *writer, uint32_t cycle, uint8_t value)
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86 {
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87 add_wait(writer, cycle);
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88 uint8_t cmd[2] = {CMD_PSG, value};
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89 last_cmd = CMD_PSG;
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90 fwrite(cmd, 1, sizeof(cmd), writer->f);
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91 }
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92
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93 void vgm_ym2612_init(vgm_writer *writer, uint32_t clock)
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94 {
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95 writer->header.ym2612_clk = clock;
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96 }
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97
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98 void vgm_ym2612_part1_write(vgm_writer *writer, uint32_t cycle, uint8_t reg, uint8_t value)
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99 {
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100 add_wait(writer, cycle);
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101 uint8_t cmd[3] = {CMD_YM2612_0, reg, value};
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102 last_cmd = CMD_YM2612_0;
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103 fwrite(cmd, 1, sizeof(cmd), writer->f);
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104 }
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105
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106 void vgm_ym2612_part2_write(vgm_writer *writer, uint32_t cycle, uint8_t reg, uint8_t value)
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107 {
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108 add_wait(writer, cycle);
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109 uint8_t cmd[3] = {CMD_YM2612_1, reg, value};
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110 last_cmd = CMD_YM2612_1;
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111 fwrite(cmd, 1, sizeof(cmd), writer->f);
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112 }
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113
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114 void vgm_adjust_cycles(vgm_writer *writer, uint32_t deduction)
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115 {
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116 if (deduction > writer->last_cycle) {
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117 writer->extra_delta += deduction - writer->last_cycle;
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118 writer->last_cycle = 0;
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119 } else {
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120 writer->last_cycle -= deduction;
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121 }
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122 }
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123
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124 void vgm_close(vgm_writer *writer)
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125 {
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126 uint8_t cmd = 0x66;
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127 fwrite(&cmd, 1, sizeof(cmd), writer->f);
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128 writer->header.eof_offset = ftell(writer->f) - offsetof(vgm_header, eof_offset);
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129 fseek(writer->f, SEEK_SET, 0);
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130 fwrite(&writer->header, sizeof(writer->header), 1, writer->f);
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131 fclose(writer->f);
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132 free(writer);
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133 }