FFmpeg: libavformat/pcm.c Source File

FFmpeg

[フレーム]

libavformat

pcm.c

Go to the documentation of this file.

1 /*

2 * PCM common functions

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 */

22 #include "libavutil/mathematics.h"

23 #include "avformat.h"

24 #include "pcm.h"

26 #define RAW_SAMPLES 1024

28 int ff_pcm_read_packet(AVFormatContext *s, AVPacket *pkt)

29 {

30 int ret, size;

32 size= RAW_SAMPLES*s->streams[0]->codec->block_align;

33 if (size <= 0)

34 return AVERROR(EINVAL);

36 ret= av_get_packet(s->pb, pkt, size);

38 pkt->flags &= ~AV_PKT_FLAG_CORRUPT;

39 pkt->stream_index = 0;

40 if (ret < 0)

41 return ret;

43 return ret;

44 }

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;

53 st = s->streams[0];

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;

60 if (block_align <= 0 || byte_rate <= 0)

61 return -1;

62 if (timestamp < 0) timestamp = 0;

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;

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 }

Generated on Wed Jul 10 2013 23:48:03 for FFmpeg by doxygen 1.8.2