FFmpeg: libavformat/pcm.c Source File

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libavformat

pcm.c

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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 "internal.h"

25 #include "pcm.h"

27 #define RAW_SAMPLES 1024

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

30 {

31 int ret, size;

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

34 if (size <= 0)

35 return AVERROR(EINVAL);

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

39 pkt->flags &= ~AV_PKT_FLAG_CORRUPT;

40 pkt->stream_index = 0;

42 return ret;

43 }

45 int ff_pcm_read_seek(AVFormatContext *s,

46 int stream_index, int64_t timestamp, int flags)

47 {

48 AVStream *st;

49 int block_align, byte_rate;

50 int64_t pos, ret;

52 st = s->streams[0];

54 block_align = st->codec->block_align ? st->codec->block_align :

55 (av_get_bits_per_sample(st->codec->codec_id) * st->codec->channels) >> 3;

56 byte_rate = st->codec->bit_rate ? st->codec->bit_rate >> 3 :

57 block_align * st->codec->sample_rate;

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

60 return -1;

61 if (timestamp < 0) timestamp = 0;

63 /* compute the position by aligning it to block_align */

64 pos = av_rescale_rnd(timestamp * byte_rate,

65 st->time_base.num,

66 st->time_base.den * (int64_t)block_align,

67 (flags & AVSEEK_FLAG_BACKWARD) ? AV_ROUND_DOWN : AV_ROUND_UP);

68 pos *= block_align;

70 /* recompute exact position */

71 st->cur_dts = av_rescale(pos, st->time_base.den, byte_rate * (int64_t)st->time_base.num);

72 if ((ret = avio_seek(s->pb, pos + s->internal->data_offset, SEEK_SET)) < 0)

73 return ret;

74 return 0;

75 }

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