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 
22 #include "libavutil/mathematics.h"
23 #include "libavutil/opt.h"
24 #include "avformat.h"
25 #include "internal.h"
26 
27 #define GSM_BLOCK_SIZE 33
28 #define GSM_BLOCK_SAMPLES 160
29 #define GSM_SAMPLE_RATE 8000
30 
31 typedef struct {
32  AVClass *class;
35 
37 {
38  int ret, size;
39 
40  size = GSM_BLOCK_SIZE;
41 
42  pkt->pos = avio_tell(s->pb);
43  pkt->stream_index = 0;
44 
45  ret = av_get_packet(s->pb, pkt, size);
46  if (ret < GSM_BLOCK_SIZE) {
47  av_free_packet(pkt);
48  return ret < 0 ? ret : AVERROR(EIO);
49  }
50  pkt->size = ret;
51  pkt->duration = 1;
52  pkt->pts = pkt->pos / GSM_BLOCK_SIZE;
53 
54  return 0;
55 }
56 
58 {
61  if (!st)
62  return AVERROR(ENOMEM);
63 
65  st->codec->codec_id = s->iformat->value;
66  st->codec->channels = 1;
67  st->codec->sample_rate = c->sample_rate;
69 
71 
72  return 0;
73 }
74 
75 static const AVOption options[] = {
76  { "sample_rate", "", offsetof(GSMDemuxerContext, sample_rate),
77  AV_OPT_TYPE_INT, {.dbl = GSM_SAMPLE_RATE}, 1, INT_MAX / GSM_BLOCK_SIZE,
79  { NULL },
80 };
81 
82 static const AVClass class = {
83  .class_name = "gsm demuxer",
84  .item_name = av_default_item_name,
85  .option = options,
87 };
88 
90  .name = "gsm",
91  .long_name = NULL_IF_CONFIG_SMALL("raw GSM"),
92  .priv_data_size = sizeof(GSMDemuxerContext),
96  .extensions = "gsm",
97  .value = CODEC_ID_GSM,
98  .priv_class = &class,
99 };