3 * Copyright (c) 2011 Justin Ruggles
5 * This file is part of Libav.
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.
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.
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
22 #include "libavutil/mathematics.h"
23 #include "libavutil/opt.h"
26 #define GSM_BLOCK_SIZE 33
27 #define GSM_BLOCK_SAMPLES 160
28 #define GSM_SAMPLE_RATE 8000
35 static int gsm_read_packet(AVFormatContext *s, AVPacket *pkt)
39 size = GSM_BLOCK_SIZE * 32;
41 pkt->pos = avio_tell(s->pb);
42 pkt->stream_index = 0;
44 ret = av_get_packet(s->pb, pkt, size);
45 if (ret < GSM_BLOCK_SIZE) {
47 return ret < 0 ? ret : AVERROR(EIO);
50 pkt->duration = ret / GSM_BLOCK_SIZE;
51 pkt->pts = pkt->pos / GSM_BLOCK_SIZE;
56 static int gsm_read_header(AVFormatContext *s, AVFormatParameters *ap)
58 GSMDemuxerContext *c = s->priv_data;
59 AVStream *st = avformat_new_stream(s, NULL);
61 return AVERROR(ENOMEM);
63 st->codec->codec_type = AVMEDIA_TYPE_AUDIO;
64 st->codec->codec_id = s->iformat->value;
65 st->codec->channels = 1;
66 st->codec->sample_rate = c->sample_rate;
67 st->codec->block_align = GSM_BLOCK_SIZE;
68 st->codec->bit_rate = GSM_BLOCK_SIZE * 8 * c->sample_rate / GSM_BLOCK_SAMPLES;
70 av_set_pts_info(st, 64, GSM_BLOCK_SAMPLES, GSM_SAMPLE_RATE);
75 static int gsm_read_seek2(AVFormatContext *s, int stream_index, int64_t min_ts,
76 int64_t ts, int64_t max_ts, int flags)
78 GSMDemuxerContext *c = s->priv_data;
80 /* convert timestamps to file positions */
81 if (!(flags & AVSEEK_FLAG_BYTE)) {
82 if (stream_index < 0) {
83 AVRational bitrate_q = { GSM_BLOCK_SAMPLES, c->sample_rate * GSM_BLOCK_SIZE };
84 ts = av_rescale_q(ts, AV_TIME_BASE_Q, bitrate_q);
85 min_ts = av_rescale_q(min_ts, AV_TIME_BASE_Q, bitrate_q);
86 max_ts = av_rescale_q(max_ts, AV_TIME_BASE_Q, bitrate_q);
89 min_ts *= GSM_BLOCK_SIZE;
90 max_ts *= GSM_BLOCK_SIZE;
93 /* round to nearest block boundary */
94 ts = (ts + GSM_BLOCK_SIZE / 2) / GSM_BLOCK_SIZE * GSM_BLOCK_SIZE;
101 ts -= GSM_BLOCK_SIZE;
102 if (ts < min_ts || ts > max_ts)
105 return avio_seek(s->pb, ts, SEEK_SET);
108 static const AVOption options[] = {
109 { "sample_rate", "", offsetof(GSMDemuxerContext, sample_rate),
110 AV_OPT_TYPE_INT, {.dbl = GSM_SAMPLE_RATE}, 1, INT_MAX / GSM_BLOCK_SIZE,
111 AV_OPT_FLAG_DECODING_PARAM },
115 static const AVClass class = {
116 .class_name = "gsm demuxer",
117 .item_name = av_default_item_name,
119 .version = LIBAVUTIL_VERSION_INT,
122 AVInputFormat ff_gsm_demuxer = {
124 .long_name = NULL_IF_CONFIG_SMALL("raw GSM"),
125 .priv_data_size = sizeof(GSMDemuxerContext),
126 .read_header = gsm_read_header,
127 .read_packet = gsm_read_packet,
128 .read_seek2 = gsm_read_seek2,
130 .value = CODEC_ID_GSM,
131 .priv_class = &class,