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  1. /*
  2.  * PCM common functions
  3.  * Copyright (c) 2003 Fabrice Bellard
  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/mathematics.h"
  23. #include "avformat.h"
  24. #include "pcm.h"
  25.  
  26. #define RAW_SAMPLES     1024
  27.  
  28. int ff_pcm_read_packet(AVFormatContext *s, AVPacket *pkt)
  29. {
  30.     int ret, size;
  31.  
  32.     size= RAW_SAMPLES*s->streams[0]->codec->block_align;
  33.     if (size <= 0)
  34.         return AVERROR(EINVAL);
  35.  
  36.     ret= av_get_packet(s->pb, pkt, size);
  37.  
  38.     pkt->flags &= ~AV_PKT_FLAG_CORRUPT;
  39.     pkt->stream_index = 0;
  40.     if (ret < 0)
  41.         return ret;
  42.  
  43.     return ret;
  44. }
  45.  
  46. int ff_pcm_read_seek(AVFormatContext *s,
  47.                      int stream_index, int64_t timestamp, int flags)
  48. {
  49.     AVStream *st;
  50.     int block_align, byte_rate;
  51.     int64_t pos, ret;
  52.  
  53.     st = s->streams[0];
  54.  
  55.     block_align = st->codec->block_align ? st->codec->block_align :
  56.         (av_get_bits_per_sample(st->codec->codec_id) * st->codec->channels) >> 3;
  57.     byte_rate = st->codec->bit_rate ? st->codec->bit_rate >> 3 :
  58.         block_align * st->codec->sample_rate;
  59.  
  60.     if (block_align <= 0 || byte_rate <= 0)
  61.         return -1;
  62.     if (timestamp < 0) timestamp = 0;
  63.  
  64.     /* compute the position by aligning it to block_align */
  65.     pos = av_rescale_rnd(timestamp * byte_rate,
  66.                          st->time_base.num,
  67.                          st->time_base.den * (int64_t)block_align,
  68.                          (flags & AVSEEK_FLAG_BACKWARD) ? AV_ROUND_DOWN : AV_ROUND_UP);
  69.     pos *= block_align;
  70.  
  71.     /* recompute exact position */
  72.     st->cur_dts = av_rescale(pos, st->time_base.den, byte_rate * (int64_t)st->time_base.num);
  73.     if ((ret = avio_seek(s->pb, pos + s->data_offset, SEEK_SET)) < 0)
  74.         return ret;
  75.     return 0;
  76. }
  77.