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gsmdec.c
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1 /*
2  * RAW GSM demuxer
3  * Copyright (c) 2011 Justin Ruggles
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 
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->duration = 1;
52  pkt->pts = pkt->pos / GSM_BLOCK_SIZE;
53 
54  return 0;
55 }
56 
58 {
60  AVStream *st = avformat_new_stream(s, NULL);
61  if (!st)
62  return AVERROR(ENOMEM);
63 
66  st->codec->channels = 1;
68  st->codec->sample_rate = c->sample_rate;
70 
72 
73  return 0;
74 }
75 
76 static const AVOption options[] = {
77  { "sample_rate", "", offsetof(GSMDemuxerContext, sample_rate),
78  AV_OPT_TYPE_INT, {.i64 = GSM_SAMPLE_RATE}, 1, INT_MAX / GSM_BLOCK_SIZE,
80  { NULL },
81 };
82 
83 static const AVClass gsm_class = {
84  .class_name = "gsm demuxer",
85  .item_name = av_default_item_name,
86  .option = options,
87  .version = LIBAVUTIL_VERSION_INT,
88 };
89 
91  .name = "gsm",
92  .long_name = NULL_IF_CONFIG_SMALL("raw GSM"),
93  .priv_data_size = sizeof(GSMDemuxerContext),
97  .extensions = "gsm",
98  .raw_codec_id = AV_CODEC_ID_GSM,
99  .priv_class = &gsm_class,
100 };