gsmdec.c
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1 /*
2  * RAW GSM demuxer
3  * Copyright (c) 2011 Justin Ruggles
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 
23 #include "libavutil/mathematics.h"
24 #include "libavutil/opt.h"
25 #include "avformat.h"
26 #include "internal.h"
27 
28 #define GSM_BLOCK_SIZE 33
29 #define GSM_BLOCK_SAMPLES 160
30 #define GSM_SAMPLE_RATE 8000
31 
32 typedef struct {
33  AVClass *class;
36 
38 {
39  int ret, size;
40 
41  size = GSM_BLOCK_SIZE;
42 
43  pkt->pos = avio_tell(s->pb);
44  pkt->stream_index = 0;
45 
46  ret = av_get_packet(s->pb, pkt, size);
47  if (ret < GSM_BLOCK_SIZE) {
48  av_free_packet(pkt);
49  return ret < 0 ? ret : AVERROR(EIO);
50  }
51  pkt->size = ret;
52  pkt->duration = 1;
53  pkt->pts = pkt->pos / GSM_BLOCK_SIZE;
54 
55  return 0;
56 }
57 
59 {
62  if (!st)
63  return AVERROR(ENOMEM);
64 
67  st->codec->channels = 1;
69  st->codec->sample_rate = c->sample_rate;
71 
73 
74  return 0;
75 }
76 
77 static const AVOption options[] = {
78  { "sample_rate", "", offsetof(GSMDemuxerContext, sample_rate),
79  AV_OPT_TYPE_INT, {.i64 = GSM_SAMPLE_RATE}, 1, INT_MAX / GSM_BLOCK_SIZE,
81  { NULL },
82 };
83 
84 static const AVClass class = {
85  .class_name = "gsm demuxer",
86  .item_name = av_default_item_name,
87  .option = options,
89 };
90 
92  .name = "gsm",
93  .long_name = NULL_IF_CONFIG_SMALL("raw GSM"),
94  .priv_data_size = sizeof(GSMDemuxerContext),
98  .extensions = "gsm",
99  .raw_codec_id = AV_CODEC_ID_GSM,
100  .priv_class = &class,
101 };