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ffmpeg / libavformat / pcm.c @ f59d8ff8

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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 FFmpeg.
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 *
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 * FFmpeg 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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 * FFmpeg 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 FFmpeg; 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 "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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}