FFmpeg  2.1.1
amr.c
Go to the documentation of this file.
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 */
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');
95  st->codec->sample_rate = 16000;
96  } else {
97  st->codec->codec_tag = MKTAG('s', 'a', 'm', 'r');
99  st->codec->sample_rate = 8000;
100  }
101  st->codec->channels = 1;
104  avpriv_set_pts_info(st, 64, 1, st->codec->sample_rate);
105 
106  return 0;
107 }
108 
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  }
136 
137  if (!size || av_new_packet(pkt, size))
138  return AVERROR(EIO);
139 
140  /* Both AMR formats have 50 frames per second */
141  s->streams[0]->codec->bit_rate = size*8*50;
142 
143  pkt->stream_index = 0;
144  pkt->pos = pos;
145  pkt->data[0] = toc;
146  pkt->duration = enc->codec_id == AV_CODEC_ID_AMR_NB ? 160 : 320;
147  read = avio_read(s->pb, pkt->data + 1, size - 1);
148 
149  if (read != size - 1) {
150  av_free_packet(pkt);
151  return AVERROR(EIO);
152  }
153 
154  return 0;
155 }
156 
157 #if CONFIG_AMR_DEMUXER
158 AVInputFormat ff_amr_demuxer = {
159  .name = "amr",
160  .long_name = NULL_IF_CONFIG_SMALL("3GPP AMR"),
161  .read_probe = amr_probe,
162  .read_header = amr_read_header,
163  .read_packet = amr_read_packet,
164  .flags = AVFMT_GENERIC_INDEX,
165 };
166 #endif
167 
168 #if CONFIG_AMR_MUXER
169 AVOutputFormat ff_amr_muxer = {
170  .name = "amr",
171  .long_name = NULL_IF_CONFIG_SMALL("3GPP AMR"),
172  .mime_type = "audio/amr",
173  .extensions = "amr",
174  .audio_codec = AV_CODEC_ID_AMR_NB,
175  .video_codec = AV_CODEC_ID_NONE,
176  .write_header = amr_write_header,
177  .write_packet = amr_write_packet,
178 };
179 #endif
const char * s
Definition: avisynth_c.h:668
Bytestream IO Context.
Definition: avio.h:68
int size
void av_free_packet(AVPacket *pkt)
Free a packet.
Definition: avpacket.c:279
const char * name
A comma separated list of short names for the format.
Definition: avformat.h:478
int64_t pos
byte position in stream, -1 if unknown
Definition: avcodec.h:1092
void avpriv_set_pts_info(AVStream *s, int pts_wrap_bits, unsigned int pts_num, unsigned int pts_den)
Set the time base and wrapping info for a given stream.
Definition: utils.c:3922
AVCodecContext * codec
Codec context associated with this stream.
Definition: avformat.h:686
static int amr_read_header(AVFormatContext *s)
Definition: amr.c:76
int size
Definition: avcodec.h:1064
void avio_write(AVIOContext *s, const unsigned char *buf, int size)
Definition: aviobuf.c:173
int void avio_flush(AVIOContext *s)
Force flushing of buffered data to the output s.
Definition: aviobuf.c:193
static const char AMR_header[]
Definition: amr.c:34
int avio_r8(AVIOContext *s)
Definition: aviobuf.c:471
Format I/O context.
Definition: avformat.h:968
uint8_t
mode
Definition: f_perms.c:27
unsigned char * buf
Buffer must have AVPROBE_PADDING_SIZE of extra allocated bytes filled with zero.
Definition: avformat.h:336
static av_always_inline int64_t avio_tell(AVIOContext *s)
ftell() equivalent for AVIOContext.
Definition: avio.h:248
static const char AMRWB_header[]
Definition: amr.c:35
AVStream * avformat_new_stream(AVFormatContext *s, const AVCodec *c)
Add a new stream to a media file.
Definition: utils.c:3348
int duration
Duration of this packet in AVStream->time_base units, 0 if unknown.
Definition: avcodec.h:1085
int av_new_packet(AVPacket *pkt, int size)
Allocate the payload of a packet and initialize its fields with default values.
Definition: avpacket.c:83
void * priv_data
Format private data.
Definition: avformat.h:988
#define NULL_IF_CONFIG_SMALL(x)
Return NULL if CONFIG_SMALL is true, otherwise the argument without modification. ...
Definition: internal.h:151
static int amr_probe(AVProbeData *p)
Definition: amr.c:63
#define AVFMT_GENERIC_INDEX
Use generic index building code.
Definition: avformat.h:355
uint64_t channel_layout
Audio channel layout.
Definition: avcodec.h:1934
int bit_rate
the average bitrate
Definition: avcodec.h:1204
AVStream ** streams
Definition: avformat.h:1016
const char * name
Definition: avformat.h:395
Stream structure.
Definition: avformat.h:667
enum AVMediaType codec_type
Definition: avcodec.h:1154
enum AVCodecID codec_id
Definition: avcodec.h:1157
int sample_rate
samples per second
Definition: avcodec.h:1873
main external API structure.
Definition: avcodec.h:1146
unsigned int codec_tag
fourcc (LSB first, so "ABCD" -> ('D'<<24) + ('C'<<16) + ('B'<<8) + 'A').
Definition: avcodec.h:1172
AVIOContext * pb
I/O context.
Definition: avformat.h:1001
#define MKTAG(a, b, c, d)
uint8_t * data
Definition: avcodec.h:1063
This structure contains the data a format has to probe a file.
Definition: avformat.h:334
static int amr_read_packet(AVFormatContext *s, AVPacket *pkt)
Definition: amr.c:109
#define AVPROBE_SCORE_MAX
maximum score
Definition: avformat.h:342
int avio_read(AVIOContext *s, unsigned char *buf, int size)
Read size bytes from AVIOContext into buf.
Definition: aviobuf.c:480
int url_feof(AVIOContext *s)
feof() equivalent for AVIOContext.
Definition: aviobuf.c:280
Main libavformat public API header.
int channels
number of audio channels
Definition: avcodec.h:1874
#define AVERROR(e)
static AVPacket pkt
Definition: demuxing.c:52
int stream_index
Definition: avcodec.h:1065
#define AV_CH_LAYOUT_MONO
This structure stores compressed data.
Definition: avcodec.h:1040