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
22 #include "libavutil/channel_layout.h"
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 GSMDemuxerContext {
33 AVClass *class;
34 int sample_rate;
35 } GSMDemuxerContext;
36
gsm_probe(const AVProbeData * p)37 static int gsm_probe(const AVProbeData *p)
38 {
39 int valid = 0, invalid = 0;
40 uint8_t *b = p->buf;
41 while (b < p->buf + p->buf_size - 32) {
42 if ((*b & 0xf0) == 0xd0) {
43 valid++;
44 } else {
45 invalid++;
46 }
47 b += 33;
48 }
49 if (valid >> 5 > invalid)
50 return AVPROBE_SCORE_EXTENSION + 1;
51 return 0;
52 }
53
gsm_read_packet(AVFormatContext * s,AVPacket * pkt)54 static int gsm_read_packet(AVFormatContext *s, AVPacket *pkt)
55 {
56 int ret, size;
57
58 size = GSM_BLOCK_SIZE;
59
60 pkt->pos = avio_tell(s->pb);
61 pkt->stream_index = 0;
62
63 ret = av_get_packet(s->pb, pkt, size);
64 if (ret < GSM_BLOCK_SIZE) {
65 return ret < 0 ? ret : AVERROR(EIO);
66 }
67 pkt->duration = 1;
68 pkt->pts = pkt->pos / GSM_BLOCK_SIZE;
69
70 return 0;
71 }
72
gsm_read_header(AVFormatContext * s)73 static int gsm_read_header(AVFormatContext *s)
74 {
75 GSMDemuxerContext *c = s->priv_data;
76 AVStream *st = avformat_new_stream(s, NULL);
77 if (!st)
78 return AVERROR(ENOMEM);
79
80 st->codecpar->codec_type = AVMEDIA_TYPE_AUDIO;
81 st->codecpar->codec_id = s->iformat->raw_codec_id;
82 st->codecpar->channels = 1;
83 st->codecpar->channel_layout = AV_CH_LAYOUT_MONO;
84 st->codecpar->sample_rate = c->sample_rate;
85 st->codecpar->bit_rate = GSM_BLOCK_SIZE * 8 * c->sample_rate / GSM_BLOCK_SAMPLES;
86
87 avpriv_set_pts_info(st, 64, GSM_BLOCK_SAMPLES, GSM_SAMPLE_RATE);
88
89 return 0;
90 }
91
92 static const AVOption options[] = {
93 { "sample_rate", "", offsetof(GSMDemuxerContext, sample_rate),
94 AV_OPT_TYPE_INT, {.i64 = GSM_SAMPLE_RATE}, 1, INT_MAX / GSM_BLOCK_SIZE,
95 AV_OPT_FLAG_DECODING_PARAM },
96 { NULL },
97 };
98
99 static const AVClass gsm_class = {
100 .class_name = "gsm demuxer",
101 .item_name = av_default_item_name,
102 .option = options,
103 .version = LIBAVUTIL_VERSION_INT,
104 };
105
106 AVInputFormat ff_gsm_demuxer = {
107 .name = "gsm",
108 .long_name = NULL_IF_CONFIG_SMALL("raw GSM"),
109 .priv_data_size = sizeof(GSMDemuxerContext),
110 .read_probe = gsm_probe,
111 .read_header = gsm_read_header,
112 .read_packet = gsm_read_packet,
113 .flags = AVFMT_GENERIC_INDEX,
114 .extensions = "gsm",
115 .raw_codec_id = AV_CODEC_ID_GSM,
116 .priv_class = &gsm_class,
117 };
118