minor 68k timing tuning
[picodrive.git] / platform / common / mp3.c
... / ...
CommitLineData
1/*
2 * PicoDrive
3 * (C) notaz, 2010,2013
4 *
5 * This work is licensed under the terms of MAME license.
6 * See COPYING file in the top-level directory.
7 */
8#include <stdio.h>
9#include <string.h>
10
11#include <pico/pico_int.h>
12#include <pico/sound/mix.h>
13#include "mp3.h"
14
15static FILE *mp3_current_file;
16static int mp3_file_len, mp3_file_pos;
17static int cdda_out_pos;
18static int decoder_active;
19
20unsigned short mpeg1_l3_bitrates[16] = {
21 0, 32, 40, 48, 56, 64, 80, 96, 112, 128, 160, 192, 224, 256, 320
22};
23
24int mp3_find_sync_word(const unsigned char *buf, int size)
25{
26 const unsigned char *p, *pe;
27
28 /* find byte-aligned syncword - need 12 (MPEG 1,2) or 11 (MPEG 2.5) matching bits */
29 for (p = buf, pe = buf + size - 3; p <= pe; p++)
30 {
31 int pn;
32 if (p[0] != 0xff)
33 continue;
34 pn = p[1];
35 if ((pn & 0xf8) != 0xf8 || // currently must be MPEG1
36 (pn & 6) == 0) { // invalid layer
37 p++; continue;
38 }
39 pn = p[2];
40 if ((pn & 0xf0) < 0x20 || (pn & 0xf0) == 0xf0 || // bitrates
41 (pn & 0x0c) != 0) { // not 44kHz
42 continue;
43 }
44
45 return p - buf;
46 }
47
48 return -1;
49}
50
51static int try_get_bitrate(unsigned char *buf, int buf_size)
52{
53 int offs1, offs = 0;
54 int ret;
55
56 while (1)
57 {
58 offs1 = mp3_find_sync_word(buf + offs, buf_size - offs);
59 if (offs1 < 0)
60 return -2;
61 offs += offs1;
62 if (buf_size - offs < 4)
63 return -3;
64
65 // printf("trying header %08x\n", *(int *)(buf + offs));
66
67 ret = mpeg1_l3_bitrates[buf[offs + 2] >> 4];
68 if (ret > 0)
69 return ret;
70 }
71
72 return -2;
73}
74
75int mp3_get_bitrate(void *f_, int len)
76{
77 unsigned char buf[2048];
78 FILE *f = f_;
79 int retval = -1;
80 int ret;
81
82 memset(buf, 0, sizeof(buf));
83
84 fseek(f, 0, SEEK_SET);
85 ret = fread(buf, 1, sizeof(buf), f);
86 if (ret != sizeof(buf))
87 goto out;
88
89 ret = try_get_bitrate(buf, sizeof(buf));
90 if (ret <= 0) {
91 // try to read somewhere around the middle
92 fseek(f, len / 2, SEEK_SET);
93 fread(buf, 1, sizeof(buf), f);
94 ret = try_get_bitrate(buf, sizeof(buf));
95 }
96 if (ret > 0)
97 retval = ret;
98
99 //printf("bitrate: %i\n", retval);
100
101out:
102 fseek(f, 0, SEEK_SET);
103 return retval;
104}
105
106void mp3_start_play(void *f_, int pos)
107{
108 unsigned char buf[2048];
109 FILE *f = f_;
110 int ret;
111
112 mp3_file_len = mp3_file_pos = 0;
113 mp3_current_file = NULL;
114 cdda_out_pos = 0;
115 decoder_active = 0;
116
117 if (!(PicoOpt & POPT_EN_MCD_CDDA) || f == NULL) // cdda disabled or no file?
118 return;
119
120 ret = mp3dec_start();
121 if (ret != 0)
122 return;
123
124 decoder_active = 1;
125
126 mp3_current_file = f;
127 fseek(f, 0, SEEK_END);
128 mp3_file_len = ftell(f);
129
130 // search for first sync word, skipping stuff like ID3 tags
131 while (mp3_file_pos < 128*1024) {
132 int offs, bytes;
133
134 fseek(f, mp3_file_pos, SEEK_SET);
135 bytes = fread(buf, 1, sizeof(buf), f);
136 if (bytes < 4)
137 break;
138 offs = mp3_find_sync_word(buf, bytes);
139 if (offs >= 0) {
140 mp3_file_pos += offs;
141 break;
142 }
143 mp3_file_pos += bytes - 3;
144 }
145
146 // seek..
147 if (pos) {
148 unsigned long long pos64 = mp3_file_len - mp3_file_pos;
149 pos64 *= pos;
150 mp3_file_pos += pos64 >> 10;
151 }
152
153 mp3dec_decode(mp3_current_file, &mp3_file_pos, mp3_file_len);
154}
155
156void mp3_update(int *buffer, int length, int stereo)
157{
158 int length_mp3, shr = 0;
159 void (*mix_samples)(int *dest_buf, short *mp3_buf, int count) = mix_16h_to_32;
160
161 if (mp3_current_file == NULL || mp3_file_pos >= mp3_file_len)
162 return; /* no file / EOF */
163
164 if (!decoder_active)
165 return;
166
167 length_mp3 = length;
168 if (PsndRate <= 11025 + 100) {
169 mix_samples = mix_16h_to_32_s2;
170 length_mp3 <<= 2; shr = 2;
171 }
172 else if (PsndRate <= 22050 + 100) {
173 mix_samples = mix_16h_to_32_s1;
174 length_mp3 <<= 1; shr = 1;
175 }
176
177 if (1152 - cdda_out_pos >= length_mp3) {
178 mix_samples(buffer, cdda_out_buffer + cdda_out_pos * 2,
179 length * 2);
180
181 cdda_out_pos += length_mp3;
182 } else {
183 int ret, left = 1152 - cdda_out_pos;
184
185 mix_samples(buffer, cdda_out_buffer + cdda_out_pos * 2,
186 (left >> shr) * 2);
187
188 ret = mp3dec_decode(mp3_current_file, &mp3_file_pos,
189 mp3_file_len);
190 if (ret == 0) {
191 cdda_out_pos = length_mp3 - left;
192 mix_samples(buffer + (left >> shr) * 2,
193 cdda_out_buffer,
194 (cdda_out_pos >> shr) * 2);
195 } else
196 cdda_out_pos = 0;
197 }
198}
199