FFmpeg: libavformat/amr.c Source File

FFmpeg
amr.c
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1 /*
2  * amr file format
3  * Copyright (c) 2001 ffmpeg project
4  *
5  * This file is part of FFmpeg.
6  *
7  * FFmpeg 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  * FFmpeg 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 FFmpeg; if not, write to the Free Software
19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20  */
21 
22 /*
23 Write and read amr data according to RFC3267, http://www.ietf.org/rfc/rfc3267.txt?number=3267
24 
25 Only mono files are supported.
26 
27 */
28 
29 #include "libavutil/avassert.h"
30 #include "libavutil/channel_layout.h"
31 #include "avformat.h"
32 #include "internal.h"
33 
34  static const char AMR_header[] = "#!AMR\n";
35  static const char AMRWB_header[] = "#!AMR-WB\n";
36 
37 #if CONFIG_AMR_MUXER
38 static int amr_write_header(AVFormatContext *s)
39 {
40  AVIOContext *pb = s->pb;
41  AVCodecContext *enc = s->streams[0]->codec;
42 
43  s->priv_data = NULL;
44 
45  if (enc->codec_id == AV_CODEC_ID_AMR_NB) {
46  avio_write(pb, AMR_header, sizeof(AMR_header) - 1); /* magic number */
47  } else if (enc->codec_id == AV_CODEC_ID_AMR_WB) {
48  avio_write(pb, AMRWB_header, sizeof(AMRWB_header) - 1); /* magic number */
49  } else {
50  return -1;
51  }
52  avio_flush(pb);
53  return 0;
54 }
55 
56 static int amr_write_packet(AVFormatContext *s, AVPacket *pkt)
57 {
58  avio_write(s->pb, pkt->data, pkt->size);
59  return 0;
60 }
61 #endif /* CONFIG_AMR_MUXER */
62 
63  static int amr_probe(AVProbeData *p)
64 {
65  // Only check for "#!AMR" which could be amr-wb, amr-nb.
66  // This will also trigger multichannel files: "#!AMR_MC1.0\n" and
67  // "#!AMR-WB_MC1.0\n" (not supported)
68 
69  if (!memcmp(p->buf, AMR_header, 5))
70  return AVPROBE_SCORE_MAX;
71  else
72  return 0;
73 }
74 
75 /* amr input */
76  static int amr_read_header(AVFormatContext *s)
77 {
78  AVIOContext *pb = s->pb;
79  AVStream *st;
80  uint8_t header[9];
81 
82  avio_read(pb, header, 6);
83 
84  st = avformat_new_stream(s, NULL);
85  if (!st)
86  return AVERROR(ENOMEM);
87  if (memcmp(header, AMR_header, 6)) {
88  avio_read(pb, header + 6, 3);
89  if (memcmp(header, AMRWB_header, 9)) {
90  return -1;
91  }
92 
93  st->codec->codec_tag = MKTAG('s', 'a', 'w', 'b');
94  st->codec->codec_id = AV_CODEC_ID_AMR_WB;
95  st->codec->sample_rate = 16000;
96  } else {
97  st->codec->codec_tag = MKTAG('s', 'a', 'm', 'r');
98  st->codec->codec_id = AV_CODEC_ID_AMR_NB;
99  st->codec->sample_rate = 8000;
100  }
101  st->codec->channels = 1;
102  st->codec->channel_layout = AV_CH_LAYOUT_MONO;
103  st->codec->codec_type = AVMEDIA_TYPE_AUDIO;
104  avpriv_set_pts_info(st, 64, 1, st->codec->sample_rate);
105 
106  return 0;
107 }
108 
109  static int amr_read_packet(AVFormatContext *s, AVPacket *pkt)
110 {
111  AVCodecContext *enc = s->streams[0]->codec;
112  int read, size = 0, toc, mode;
113  int64_t pos = avio_tell(s->pb);
114 
115  if (url_feof(s->pb)) {
116  return AVERROR(EIO);
117  }
118 
119  // FIXME this is wrong, this should rather be in a AVParset
120  toc = avio_r8(s->pb);
121  mode = (toc >> 3) & 0x0F;
122 
123  if (enc->codec_id == AV_CODEC_ID_AMR_NB) {
124  static const uint8_t packed_size[16] = {
125  12, 13, 15, 17, 19, 20, 26, 31, 5, 0, 0, 0, 0, 0, 0, 0
126  };
127 
128  size = packed_size[mode] + 1;
129  } else if (enc->codec_id == AV_CODEC_ID_AMR_WB) {
130  static const uint8_t packed_size[16] = {
131  18, 24, 33, 37, 41, 47, 51, 59, 61, 6, 6, 0, 0, 0, 1, 1
132  };
133 
134  size = packed_size[mode];
135  } else {
136  av_assert0(0);
137  }
138 
139  if (!size || av_new_packet(pkt, size))
140  return AVERROR(EIO);
141 
142  /* Both AMR formats have 50 frames per second */
143  s->streams[0]->codec->bit_rate = size*8*50;
144 
145  pkt->stream_index = 0;
146  pkt->pos = pos;
147  pkt->data[0] = toc;
148  pkt->duration = enc->codec_id == AV_CODEC_ID_AMR_NB ? 160 : 320;
149  read = avio_read(s->pb, pkt->data + 1, size - 1);
150 
151  if (read != size - 1) {
152  av_free_packet(pkt);
153  return AVERROR(EIO);
154  }
155 
156  return 0;
157 }
158 
159 #if CONFIG_AMR_DEMUXER
160 AVInputFormat ff_amr_demuxer = {
161  .name = "amr",
162  .long_name = NULL_IF_CONFIG_SMALL("3GPP AMR"),
163  .read_probe = amr_probe,
164  .read_header = amr_read_header,
165  .read_packet = amr_read_packet,
166  .flags = AVFMT_GENERIC_INDEX,
167 };
168 #endif
169 
170 #if CONFIG_AMR_MUXER
171 AVOutputFormat ff_amr_muxer = {
172  .name = "amr",
173  .long_name = NULL_IF_CONFIG_SMALL("3GPP AMR"),
174  .mime_type = "audio/amr",
175  .extensions = "amr",
176  .audio_codec = AV_CODEC_ID_AMR_NB,
177  .video_codec = AV_CODEC_ID_NONE,
178  .write_header = amr_write_header,
179  .write_packet = amr_write_packet,
180 };
181 #endif
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