mp3dec: use named constants for Xing header flags
[libav.git] / libavformat / mp3dec.c
1 /*
2 * MP3 demuxer
3 * Copyright (c) 2003 Fabrice Bellard
4 *
5 * This file is part of Libav.
6 *
7 * Libav is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU Lesser General Public
9 * License as published by the Free Software Foundation; either
10 * version 2.1 of the License, or (at your option) any later version.
11 *
12 * Libav is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 * Lesser General Public License for more details.
16 *
17 * You should have received a copy of the GNU Lesser General Public
18 * License along with Libav; if not, write to the Free Software
19 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20 */
21
22 #include "libavutil/avstring.h"
23 #include "libavutil/intreadwrite.h"
24 #include "libavutil/dict.h"
25 #include "libavutil/mathematics.h"
26 #include "avformat.h"
27 #include "internal.h"
28 #include "id3v2.h"
29 #include "id3v1.h"
30 #include "libavcodec/mpegaudiodecheader.h"
31
32 #define XING_FLAG_FRAMES 0x01
33 #define XING_FLAG_SIZE 0x02
34
35 /* mp3 read */
36
37 static int mp3_read_probe(AVProbeData *p)
38 {
39 int max_frames, first_frames = 0;
40 int fsize, frames, sample_rate;
41 uint32_t header;
42 uint8_t *buf, *buf0, *buf2, *end;
43 AVCodecContext avctx;
44
45 buf0 = p->buf;
46 end = p->buf + p->buf_size - sizeof(uint32_t);
47 while(buf0 < end && !*buf0)
48 buf0++;
49
50 max_frames = 0;
51 buf = buf0;
52
53 for(; buf < end; buf= buf2+1) {
54 buf2 = buf;
55
56 for(frames = 0; buf2 < end; frames++) {
57 header = AV_RB32(buf2);
58 fsize = avpriv_mpa_decode_header(&avctx, header, &sample_rate, &sample_rate, &sample_rate, &sample_rate);
59 if(fsize < 0)
60 break;
61 buf2 += fsize;
62 }
63 max_frames = FFMAX(max_frames, frames);
64 if(buf == buf0)
65 first_frames= frames;
66 }
67 // keep this in sync with ac3 probe, both need to avoid
68 // issues with MPEG-files!
69 if (first_frames >= 4) return AVPROBE_SCORE_MAX / 2 + 1;
70
71 if (max_frames) {
72 int pes = 0, i;
73 unsigned int code = -1;
74
75 #define VIDEO_ID 0x000001e0
76 #define AUDIO_ID 0x000001c0
77 /* do a search for mpegps headers to be able to properly bias
78 * towards mpegps if we detect this stream as both. */
79 for (i = 0; i<p->buf_size; i++) {
80 code = (code << 8) + p->buf[i];
81 if ((code & 0xffffff00) == 0x100) {
82 if ((code & 0x1f0) == VIDEO_ID) pes++;
83 else if((code & 0x1e0) == AUDIO_ID) pes++;
84 }
85 }
86
87 if (pes)
88 max_frames = (max_frames + pes - 1) / pes;
89 }
90 if (max_frames > 500) return AVPROBE_SCORE_MAX / 2;
91 else if (max_frames >= 4) return AVPROBE_SCORE_MAX / 4;
92 else if (max_frames >= 1) return 1;
93 else return 0;
94 //mpegps_mp3_unrecognized_format.mpg has max_frames=3
95 }
96
97 /**
98 * Try to find Xing/Info/VBRI tags and compute duration from info therein
99 */
100 static int mp3_parse_vbr_tags(AVFormatContext *s, AVStream *st, int64_t base)
101 {
102 uint32_t v, spf;
103 unsigned frames = 0; /* Total number of frames in file */
104 unsigned size = 0; /* Total number of bytes in the stream */
105 const int64_t xing_offtbl[2][2] = {{32, 17}, {17,9}};
106 MPADecodeHeader c;
107 int vbrtag_size = 0;
108
109 v = avio_rb32(s->pb);
110 if(ff_mpa_check_header(v) < 0)
111 return -1;
112
113 if (avpriv_mpegaudio_decode_header(&c, v) == 0)
114 vbrtag_size = c.frame_size;
115 if(c.layer != 3)
116 return -1;
117
118 /* Check for Xing / Info tag */
119 avio_skip(s->pb, xing_offtbl[c.lsf == 1][c.nb_channels == 1]);
120 v = avio_rb32(s->pb);
121 if(v == MKBETAG('X', 'i', 'n', 'g') || v == MKBETAG('I', 'n', 'f', 'o')) {
122 v = avio_rb32(s->pb);
123 if(v & XING_FLAG_FRAMES)
124 frames = avio_rb32(s->pb);
125 if(v & XING_FLAG_SIZE)
126 size = avio_rb32(s->pb);
127 }
128
129 /* Check for VBRI tag (always 32 bytes after end of mpegaudio header) */
130 avio_seek(s->pb, base + 4 + 32, SEEK_SET);
131 v = avio_rb32(s->pb);
132 if(v == MKBETAG('V', 'B', 'R', 'I')) {
133 /* Check tag version */
134 if(avio_rb16(s->pb) == 1) {
135 /* skip delay and quality */
136 avio_skip(s->pb, 4);
137 size = avio_rb32(s->pb);
138 frames = avio_rb32(s->pb);
139 }
140 }
141
142 if(!frames && !size)
143 return -1;
144
145 /* Skip the vbr tag frame */
146 avio_seek(s->pb, base + vbrtag_size, SEEK_SET);
147
148 spf = c.lsf ? 576 : 1152; /* Samples per frame, layer 3 */
149 if(frames)
150 st->duration = av_rescale_q(frames, (AVRational){spf, c.sample_rate},
151 st->time_base);
152 if(size && frames)
153 st->codec->bit_rate = av_rescale(size, 8 * c.sample_rate, frames * (int64_t)spf);
154
155 return 0;
156 }
157
158 static int mp3_read_header(AVFormatContext *s)
159 {
160 AVStream *st;
161 int64_t off;
162
163 st = avformat_new_stream(s, NULL);
164 if (!st)
165 return AVERROR(ENOMEM);
166
167 st->codec->codec_type = AVMEDIA_TYPE_AUDIO;
168 st->codec->codec_id = AV_CODEC_ID_MP3;
169 st->need_parsing = AVSTREAM_PARSE_FULL;
170 st->start_time = 0;
171
172 // lcm of all mp3 sample rates
173 avpriv_set_pts_info(st, 64, 1, 14112000);
174
175 off = avio_tell(s->pb);
176
177 if (!av_dict_get(s->metadata, "", NULL, AV_DICT_IGNORE_SUFFIX))
178 ff_id3v1_read(s);
179
180 if (mp3_parse_vbr_tags(s, st, off) < 0)
181 avio_seek(s->pb, off, SEEK_SET);
182
183 /* the parameters will be extracted from the compressed bitstream */
184 return 0;
185 }
186
187 #define MP3_PACKET_SIZE 1024
188
189 static int mp3_read_packet(AVFormatContext *s, AVPacket *pkt)
190 {
191 int ret;
192
193 ret = av_get_packet(s->pb, pkt, MP3_PACKET_SIZE);
194 if (ret < 0)
195 return ret;
196
197 pkt->stream_index = 0;
198
199 if (ret > ID3v1_TAG_SIZE &&
200 memcmp(&pkt->data[ret - ID3v1_TAG_SIZE], "TAG", 3) == 0)
201 ret -= ID3v1_TAG_SIZE;
202
203 /* note: we need to modify the packet size here to handle the last
204 packet */
205 pkt->size = ret;
206 return ret;
207 }
208
209 AVInputFormat ff_mp3_demuxer = {
210 .name = "mp3",
211 .long_name = NULL_IF_CONFIG_SMALL("MP2/3 (MPEG audio layer 2/3)"),
212 .read_probe = mp3_read_probe,
213 .read_header = mp3_read_header,
214 .read_packet = mp3_read_packet,
215 .flags = AVFMT_GENERIC_INDEX,
216 .extensions = "mp2,mp3,m2a", /* XXX: use probe */
217 };