path: root/libavformat/gsmdec.c (plain)
blob: 1627106a22e78250f94a612acc44d24975c96322

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
37	static int gsm_probe(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
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	av_packet_unref(pkt);
66	return ret < 0 ? ret : AVERROR(EIO);
67	}
68	pkt->duration = 1;
69	pkt->pts = pkt->pos / GSM_BLOCK_SIZE;
70
71	return 0;
72	}
73
74	static int gsm_read_header(AVFormatContext *s)
75	{
76	GSMDemuxerContext *c = s->priv_data;
77	AVStream *st = avformat_new_stream(s, NULL);
78	if (!st)
79	return AVERROR(ENOMEM);
80
81	st->codecpar->codec_type = AVMEDIA_TYPE_AUDIO;
82	st->codecpar->codec_id = s->iformat->raw_codec_id;
83	st->codecpar->channels = 1;
84	st->codecpar->channel_layout = AV_CH_LAYOUT_MONO;
85	st->codecpar->sample_rate = c->sample_rate;
86	st->codecpar->bit_rate = GSM_BLOCK_SIZE * 8 * c->sample_rate / GSM_BLOCK_SAMPLES;
87
88	avpriv_set_pts_info(st, 64, GSM_BLOCK_SAMPLES, GSM_SAMPLE_RATE);
89
90	return 0;
91	}
92
93	static const AVOption options[] = {
94	{ "sample_rate", "", offsetof(GSMDemuxerContext, sample_rate),
95	AV_OPT_TYPE_INT, {.i64 = GSM_SAMPLE_RATE}, 1, INT_MAX / GSM_BLOCK_SIZE,
96	AV_OPT_FLAG_DECODING_PARAM },
97	{ NULL },
98	};
99
100	static const AVClass gsm_class = {
101	.class_name = "gsm demuxer",
102	.item_name = av_default_item_name,
103	.option = options,
104	.version = LIBAVUTIL_VERSION_INT,
105	};
106
107	AVInputFormat ff_gsm_demuxer = {
108	.name = "gsm",
109	.long_name = NULL_IF_CONFIG_SMALL("raw GSM"),
110	.priv_data_size = sizeof(GSMDemuxerContext),
111	.read_probe = gsm_probe,
112	.read_header = gsm_read_header,
113	.read_packet = gsm_read_packet,
114	.flags = AVFMT_GENERIC_INDEX,
115	.extensions = "gsm",
116	.raw_codec_id = AV_CODEC_ID_GSM,
117	.priv_class = &gsm_class,
118	};
119