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libavformat
pcm.c
Go to the documentation of this file.
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/*
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* PCM common functions
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* Copyright (c) 2003 Fabrice Bellard
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*
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* This file is part of Libav.
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*
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* Libav is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* Libav is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with Libav; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#include "
libavutil/mathematics.h
"
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#include "
avformat.h
"
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#include "
pcm.h
"
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int
pcm_read_seek
(
AVFormatContext
*s,
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int
stream_index, int64_t timestamp,
int
flags
)
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{
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AVStream
*st;
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int
block_align, byte_rate;
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int64_t pos, ret;
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st = s->
streams
[0];
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block_align = st->
codec
->
block_align
? st->
codec
->
block_align
:
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(
av_get_bits_per_sample
(st->
codec
->
codec_id
) * st->
codec
->
channels
) >> 3;
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byte_rate = st->
codec
->
bit_rate
? st->
codec
->
bit_rate
>> 3 :
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block_align * st->
codec
->
sample_rate
;
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if
(block_align <= 0 || byte_rate <= 0)
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return
-1;
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if
(timestamp < 0) timestamp = 0;
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/* compute the position by aligning it to block_align */
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pos =
av_rescale_rnd
(timestamp * byte_rate,
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st->
time_base
.
num
,
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st->
time_base
.
den
* (int64_t)block_align,
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(flags &
AVSEEK_FLAG_BACKWARD
) ?
AV_ROUND_DOWN
:
AV_ROUND_UP
);
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pos *= block_align;
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/* recompute exact position */
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st->
cur_dts
=
av_rescale
(pos, st->
time_base
.
den
, byte_rate * (int64_t)st->
time_base
.
num
);
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if
((ret =
avio_seek
(s->
pb
, pos + s->
data_offset
, SEEK_SET)) < 0)
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return
ret;
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return
0;
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}