mp3enc.c
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1 /*
2  * MP3 muxer
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 "avformat.h"
23 #include "avio_internal.h"
24 #include "id3v1.h"
25 #include "id3v2.h"
26 #include "rawenc.h"
27 #include "libavutil/avstring.h"
28 #include "libavcodec/mpegaudio.h"
31 #include "libavutil/intreadwrite.h"
32 #include "libavutil/opt.h"
33 #include "libavutil/dict.h"
34 
35 static int id3v1_set_string(AVFormatContext *s, const char *key,
36  uint8_t *buf, int buf_size)
37 {
39  if ((tag = av_dict_get(s->metadata, key, NULL, 0)))
40  av_strlcpy(buf, tag->value, buf_size);
41  return !!tag;
42 }
43 
44 static int id3v1_create_tag(AVFormatContext *s, uint8_t *buf)
45 {
47  int i, count = 0;
48 
49  memset(buf, 0, ID3v1_TAG_SIZE); /* fail safe */
50  buf[0] = 'T';
51  buf[1] = 'A';
52  buf[2] = 'G';
53  count += id3v1_set_string(s, "TIT2", buf + 3, 30); //title
54  count += id3v1_set_string(s, "TPE1", buf + 33, 30); //author|artist
55  count += id3v1_set_string(s, "TALB", buf + 63, 30); //album
56  count += id3v1_set_string(s, "TDRL", buf + 93, 4); //date
57  count += id3v1_set_string(s, "comment", buf + 97, 30);
58  if ((tag = av_dict_get(s->metadata, "TRCK", NULL, 0))) { //track
59  buf[125] = 0;
60  buf[126] = atoi(tag->value);
61  count++;
62  }
63  buf[127] = 0xFF; /* default to unknown genre */
64  if ((tag = av_dict_get(s->metadata, "TCON", NULL, 0))) { //genre
65  for(i = 0; i <= ID3v1_GENRE_MAX; i++) {
66  if (!av_strcasecmp(tag->value, ff_id3v1_genre_str[i])) {
67  buf[127] = i;
68  count++;
69  break;
70  }
71  }
72  }
73  return count;
74 }
75 
76 typedef struct MP3Context {
77  const AVClass *class;
81 } MP3Context;
82 
83 static int mp3_write_trailer(struct AVFormatContext *s)
84 {
85  uint8_t buf[ID3v1_TAG_SIZE];
86  MP3Context *mp3 = s->priv_data;
87 
88  /* write the id3v1 tag */
89  if (mp3 && mp3->write_id3v1 && id3v1_create_tag(s, buf) > 0) {
90  avio_write(s->pb, buf, ID3v1_TAG_SIZE);
91  }
92 
93  /* write number of frames */
94  if (mp3 && mp3->nb_frames_offset) {
95  avio_seek(s->pb, mp3->nb_frames_offset, SEEK_SET);
96  avio_wb32(s->pb, s->streams[0]->nb_frames);
97  avio_seek(s->pb, 0, SEEK_END);
98  }
99 
100  avio_flush(s->pb);
101 
102  return 0;
103 }
104 
105 #if CONFIG_MP2_MUXER
106 AVOutputFormat ff_mp2_muxer = {
107  .name = "mp2",
108  .long_name = NULL_IF_CONFIG_SMALL("MPEG audio layer 2"),
109  .mime_type = "audio/x-mpeg",
110  .extensions = "mp2,m2a",
111  .audio_codec = CODEC_ID_MP2,
112  .video_codec = CODEC_ID_NONE,
113  .write_packet = ff_raw_write_packet,
114  .write_trailer = mp3_write_trailer,
115 };
116 #endif
117 
118 #if CONFIG_MP3_MUXER
119 
120 static const AVOption options[] = {
121  { "id3v2_version", "Select ID3v2 version to write. Currently 3 and 4 are supported.",
122  offsetof(MP3Context, id3v2_version), AV_OPT_TYPE_INT, {.dbl = 4}, 3, 4, AV_OPT_FLAG_ENCODING_PARAM},
123  { "write_id3v1", "Enable ID3v1 writing. ID3v1 tags are written in UTF-8 which may not be supported by most software.",
124  offsetof(MP3Context, write_id3v1), AV_OPT_TYPE_INT, {.dbl = 0}, 0, 1, AV_OPT_FLAG_ENCODING_PARAM},
125  { NULL },
126 };
127 
128 static const AVClass mp3_muxer_class = {
129  .class_name = "MP3 muxer",
130  .item_name = av_default_item_name,
131  .option = options,
132  .version = LIBAVUTIL_VERSION_INT,
133 };
134 
135 /* insert a dummy frame containing number of frames */
136 static void mp3_write_xing(AVFormatContext *s)
137 {
138  AVCodecContext *codec = s->streams[0]->codec;
139  MP3Context *mp3 = s->priv_data;
140  int bitrate_idx = 1; // 32 kbps
141  int64_t xing_offset = (codec->channels == 2) ? 32 : 17;
142  int32_t header;
143  MPADecodeHeader mpah;
144  int srate_idx, i, channels;
145 
146  for (i = 0; i < FF_ARRAY_ELEMS(avpriv_mpa_freq_tab); i++)
147  if (avpriv_mpa_freq_tab[i] == codec->sample_rate) {
148  srate_idx = i;
149  break;
150  }
152  av_log(s, AV_LOG_ERROR, "Unsupported sample rate.\n");
153  return;
154  }
155 
156  switch (codec->channels) {
157  case 1: channels = MPA_MONO; break;
158  case 2: channels = MPA_STEREO; break;
159  default: av_log(s, AV_LOG_ERROR, "Unsupported number of channels.\n"); return;
160  }
161 
162  /* dummy MPEG audio header */
163  header = 0xff << 24; // sync
164  header |= (0x7 << 5 | 0x3 << 3 | 0x1 << 1 | 0x1) << 16; // sync/mpeg-1/layer 3/no crc*/
165  header |= (bitrate_idx << 4 | srate_idx << 2) << 8;
166  header |= channels << 6;
167  avio_wb32(s->pb, header);
168 
169  avpriv_mpegaudio_decode_header(&mpah, header);
170 
171  ffio_fill(s->pb, 0, xing_offset);
172  ffio_wfourcc(s->pb, "Xing");
173  avio_wb32(s->pb, 0x1); // only number of frames
174  mp3->nb_frames_offset = avio_tell(s->pb);
175  avio_wb32(s->pb, 0);
176 
177  mpah.frame_size -= 4 + xing_offset + 4 + 4 + 4;
178  ffio_fill(s->pb, 0, mpah.frame_size);
179 }
180 
185 static int mp3_write_header(struct AVFormatContext *s)
186 {
187  MP3Context *mp3 = s->priv_data;
188  int ret;
189 
191  if (ret < 0)
192  return ret;
193 
194  if (s->pb->seekable)
195  mp3_write_xing(s);
196 
197  return 0;
198 }
199 
200 AVOutputFormat ff_mp3_muxer = {
201  .name = "mp3",
202  .long_name = NULL_IF_CONFIG_SMALL("MPEG audio layer 3"),
203  .mime_type = "audio/x-mpeg",
204  .extensions = "mp3",
205  .priv_data_size = sizeof(MP3Context),
206  .audio_codec = CODEC_ID_MP3,
207  .video_codec = CODEC_ID_NONE,
208  .write_header = mp3_write_header,
212  .priv_class = &mp3_muxer_class,
213 };
214 #endif