pcm.c
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1 /*
2  * PCM common functions
3  * Copyright (c) 2003 Fabrice Bellard
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 "avformat.h"
24 #include "pcm.h"
25 
27  int stream_index, int64_t timestamp, int flags)
28 {
29  AVStream *st;
30  int block_align, byte_rate;
31  int64_t pos, ret;
32 
33  st = s->streams[0];
34 
35  block_align = st->codec->block_align ? st->codec->block_align :
37  byte_rate = st->codec->bit_rate ? st->codec->bit_rate >> 3 :
38  block_align * st->codec->sample_rate;
39 
40  if (block_align <= 0 || byte_rate <= 0)
41  return -1;
42  if (timestamp < 0) timestamp = 0;
43 
44  /* compute the position by aligning it to block_align */
45  pos = av_rescale_rnd(timestamp * byte_rate,
46  st->time_base.num,
47  st->time_base.den * (int64_t)block_align,
49  pos *= block_align;
50 
51  /* recompute exact position */
52  st->cur_dts = av_rescale(pos, st->time_base.den, byte_rate * (int64_t)st->time_base.num);
53  if ((ret = avio_seek(s->pb, pos + s->data_offset, SEEK_SET)) < 0)
54  return ret;
55  return 0;
56 }