Mercurial > repos > blastem

comparison vgm.c @ 2053:3414a4423de1 segacd

Find changesets by keywords (author, files, the commit message), revision number or hash, or revset expression.
Merge from default
author Michael Pavone <pavone@retrodev.com>
date Sat, 15 Jan 2022 13:15:21 -0800
parents 327332138c5c
children 7e1215d17571
comparison
equal deleted inserted replaced
1692:5dacaef602a7 2053:3414a4423de1
1 #include <stdlib.h>
2 #include <string.h>
3 #include <stddef.h>
4 #include "vgm.h"
5
6 vgm_writer *vgm_write_open(char *filename, uint32_t rate, uint32_t clock, uint32_t cycle)
7 {
8 FILE *f = fopen(filename, "wb");
9 if (!f) {
10 return NULL;
11 }
12 vgm_writer *writer = calloc(sizeof(vgm_writer), 1);
13 memcpy(writer->header.ident, "Vgm ", 4);
14 writer->header.version = 0x150;
15 writer->header.data_offset = sizeof(writer->header) - offsetof(vgm_header, data_offset);
16 writer->header.rate = rate;
17 writer->f = f;
18 if (1 != fwrite(&writer->header, sizeof(writer->header), 1, f)) {
19 free(writer);
20 fclose(f);
21 return NULL;
22 }
23 writer->master_clock = clock;
24 writer->last_cycle = cycle;
25
26 return writer;
27 }
28
29 void vgm_sn76489_init(vgm_writer *writer, uint32_t clock, uint16_t feedback, uint8_t shift_reg_size, uint8_t flags)
30 {
31 if (flags && writer->header.version < 0x151) {
32 writer->header.version = 0x151;
33 }
34 writer->header.sn76489_clk = clock,
35 writer->header.sn76489_fb = feedback;
36 writer->header.sn76489_shift = shift_reg_size;
37 writer->header.sn76489_flags = flags;
38 }
39
40 static void wait_commands(vgm_writer *writer, uint32_t delta)
41 {
42 if (!delta) {
43 return;
44 }
45 if (delta <= 0x10) {
46 fputc(CMD_WAIT_SHORT + (delta - 1), writer->f);
47 } else if (delta >= 735 && delta <= (735 + 0x10)) {
48 fputc(CMD_WAIT_60, writer->f);
49 wait_commands(writer, delta - 735);
50 } else if (delta >= 882 && delta <= (882 + 0x10)) {
51 fputc(CMD_WAIT_50, writer->f);
52 wait_commands(writer, delta - 882);
53 } else if (delta > 0xFFFF) {
54 uint8_t cmd[3] = {CMD_WAIT, 0xFF, 0xFF};
55 fwrite(cmd, 1, sizeof(cmd), writer->f);
56 wait_commands(writer, delta - 0xFFFF);
57 } else {
58 uint8_t cmd[3] = {CMD_WAIT, delta, delta >> 8};
59 fwrite(cmd, 1, sizeof(cmd), writer->f);
60 }
61 }
62
63 #include "util.h"
64 static void add_wait(vgm_writer *writer, uint32_t cycle)
65 {
66 if (cycle < writer->last_cycle) {
67 //This can happen when a YM-2612 write happens immediately after a PSG write
68 //due to the relatively low granularity of the PSG's internal clock
69 //given that VGM only has a granularity of 44.1 kHz ignoring this is harmless
70 return;
71 }
72 uint64_t last_sample = (uint64_t)writer->last_cycle * (uint64_t)44100;
73 last_sample /= (uint64_t)writer->master_clock;
74 uint64_t sample = ((uint64_t)cycle + (uint64_t)writer->extra_delta) * (uint64_t)44100;
75 sample /= (uint64_t)writer->master_clock;
76 uint32_t delta = sample - last_sample;
77
78 writer->last_cycle = cycle;
79 writer->extra_delta = 0;
80 writer->header.num_samples += delta;
81 wait_commands(writer, delta);
82 }
83
84 static uint8_t last_cmd;
85 void vgm_sn76489_write(vgm_writer *writer, uint32_t cycle, uint8_t value)
86 {
87 add_wait(writer, cycle);
88 uint8_t cmd[2] = {CMD_PSG, value};
89 last_cmd = CMD_PSG;
90 fwrite(cmd, 1, sizeof(cmd), writer->f);
91 }
92
93 void vgm_ym2612_init(vgm_writer *writer, uint32_t clock)
94 {
95 writer->header.ym2612_clk = clock;
96 }
97
98 void vgm_ym2612_part1_write(vgm_writer *writer, uint32_t cycle, uint8_t reg, uint8_t value)
99 {
100 add_wait(writer, cycle);
101 uint8_t cmd[3] = {CMD_YM2612_0, reg, value};
102 last_cmd = CMD_YM2612_0;
103 fwrite(cmd, 1, sizeof(cmd), writer->f);
104 }
105
106 void vgm_ym2612_part2_write(vgm_writer *writer, uint32_t cycle, uint8_t reg, uint8_t value)
107 {
108 add_wait(writer, cycle);
109 uint8_t cmd[3] = {CMD_YM2612_1, reg, value};
110 last_cmd = CMD_YM2612_1;
111 fwrite(cmd, 1, sizeof(cmd), writer->f);
112 }
113
114 void vgm_adjust_cycles(vgm_writer *writer, uint32_t deduction)
115 {
116 if (deduction > writer->last_cycle) {
117 writer->extra_delta += deduction - writer->last_cycle;
118 writer->last_cycle = 0;
119 } else {
120 writer->last_cycle -= deduction;
121 }
122 }
123
124 void vgm_close(vgm_writer *writer)
125 {
126 uint8_t cmd = 0x66;
127 fwrite(&cmd, 1, sizeof(cmd), writer->f);
128 writer->header.eof_offset = ftell(writer->f) - offsetof(vgm_header, eof_offset);
129 fseek(writer->f, SEEK_SET, 0);
130 fwrite(&writer->header, sizeof(writer->header), 1, writer->f);
131 fclose(writer->f);
132 free(writer);
133 }