FFmpeg: libavformat/pcm.c Source File

FFmpeg

libavformat

pcm.c

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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 "internal.h"

25 #include "pcm.h"

26

27 #define PCM_DEMUX_TARGET_FPS 10

28

29 int ff_pcm_default_packet_size(AVCodecParameters *par)

30 {

31 int nb_samples, max_samples, bits_per_sample;

32 int64_t bitrate;

33

34 if (par->block_align <= 0)

35 return AVERROR(EINVAL);

36

37 max_samples = INT_MAX / par->block_align;

38 bits_per_sample = av_get_bits_per_sample(par->codec_id);

39 bitrate = par->bit_rate;

40

41 /* Don't trust the codecpar bitrate if we can calculate it ourselves */

42 if (bits_per_sample > 0 && par->sample_rate > 0 && par->ch_layout.nb_channels > 0)

43 if ((int64_t)par->sample_rate * par->ch_layout.nb_channels < INT64_MAX / bits_per_sample)

44 bitrate = bits_per_sample * (int64_t)par->sample_rate * par->ch_layout.nb_channels;

45

46 if (bitrate > 0) {

47 nb_samples = av_clip64(bitrate / 8 / PCM_DEMUX_TARGET_FPS / par->block_align, 1, max_samples);

48 nb_samples = 1 << av_log2(nb_samples);

49 } else {

50 /* Fallback to a size based method for a non-pcm codec with unknown bitrate */

51 nb_samples = av_clip(4096 / par->block_align, 1, max_samples);

52 }

53

54 return par->block_align * nb_samples;

55 }

56

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

58 {

59 int ret, size;

60

61 size = ff_pcm_default_packet_size(s->streams[0]->codecpar);

62 if (size < 0)

63 return size;

64

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

66

67 pkt->flags &= ~AV_PKT_FLAG_CORRUPT;

68 pkt->stream_index = 0;

69

70 return ret;

71 }

72

73 int ff_pcm_read_seek(AVFormatContext *s,

74 int stream_index, int64_t timestamp, int flags)

75 {

76 AVStream *st;

77 int block_align, byte_rate;

78 int64_t pos, ret;

79

80 st = s->streams[0];

81

82 block_align = st->codecpar->block_align ? st->codecpar->block_align :

83 (av_get_bits_per_sample(st->codecpar->codec_id) * st->codecpar->ch_layout.nb_channels) >> 3;

84 byte_rate = st->codecpar->bit_rate ? st->codecpar->bit_rate >> 3 :

85 block_align * st->codecpar->sample_rate;

86

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

88 return -1;

89 if (timestamp < 0) timestamp = 0;

90

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

92 pos = av_rescale_rnd(timestamp * byte_rate,

93 st->time_base.num,

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

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

96 pos *= block_align;

97

98 /* recompute exact position */

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

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

101 return ret;

102 return 0;

103 }

@ AV_ROUND_UP

Round toward +infinity.

Definition: mathematics.h:134

#define av_clip

Definition: common.h:100

Filter the word "frame" indicates either a video frame or a group of audio as stored in an AVFrame structure Format for each input and each output the list of supported formats For video that means pixel format For audio that means channel sample they are references to shared objects When the negotiation mechanism computes the intersection of the formats supported at each end of a all references to both lists are replaced with a reference to the intersection And when a single format is eventually chosen for a link amongst the remaining all references to the list are updated That means that if a filter requires that its input and output have the same format amongst a supported all it has to do is use a reference to the same list of formats query_formats can leave some formats unset and return AVERROR(EAGAIN) to cause the negotiation mechanism toagain later. That can be used by filters with complex requirements to use the format negotiated on one link to set the formats supported on another. Frame references ownership and permissions

AVCodecParameters

This struct describes the properties of an encoded stream.

Definition: codec_par.h:47

ffformatcontext

static av_always_inline FFFormatContext * ffformatcontext(AVFormatContext *s)

Definition: internal.h:188

long long int64_t

Definition: coverity.c:34

AVChannelLayout::nb_channels

int nb_channels

Number of channels in this layout.

Definition: channel_layout.h:321

static av_always_inline FFStream * ffstream(AVStream *st)

Definition: internal.h:419

AVRational::num

int num

Numerator.

Definition: rational.h:59

#define av_clip64

Definition: common.h:103

av_get_bits_per_sample

int av_get_bits_per_sample(enum AVCodecID codec_id)

Return codec bits per sample.

Definition: utils.c:550

AVPacket * pkt

Definition: movenc.c:60

AV_PKT_FLAG_CORRUPT

#define AV_PKT_FLAG_CORRUPT

The packet content is corrupted.

Definition: packet.h:595

s

#define s(width, name)

Definition: cbs_vp9.c:198

int64_t bitrate

Definition: av1_levels.c:47

if(ret)

Definition: filter_design.txt:179

AVFormatContext

Format I/O context.

Definition: avformat.h:1287

AVStream::codecpar

AVCodecParameters * codecpar

Codec parameters associated with this stream.

Definition: avformat.h:771

AVSEEK_FLAG_BACKWARD

#define AVSEEK_FLAG_BACKWARD

Definition: avformat.h:2477

AVStream::time_base

AVRational time_base

This is the fundamental unit of time (in seconds) in terms of which frame timestamps are represented.

Definition: avformat.h:787

ff_pcm_default_packet_size

int ff_pcm_default_packet_size(AVCodecParameters *par)

Definition: pcm.c:29

AVCodecParameters::ch_layout

AVChannelLayout ch_layout

Audio only.

Definition: codec_par.h:180

AVCodecParameters::sample_rate

int sample_rate

Audio only.

Definition: codec_par.h:184

@ AV_ROUND_DOWN

Round toward -infinity.

Definition: mathematics.h:133

int64_t av_rescale_rnd(int64_t a, int64_t b, int64_t c, enum AVRounding rnd)

Rescale a 64-bit integer with specified rounding.

Definition: mathematics.c:58

int size

Definition: twinvq_data.h:10344

AVPacket::flags

int flags

A combination of AV_PKT_FLAG values.

Definition: packet.h:545

AVCodecParameters::block_align

int block_align

Audio only.

Definition: codec_par.h:191

ff_pcm_read_packet

int ff_pcm_read_packet(AVFormatContext *s, AVPacket *pkt)

Definition: pcm.c:57

int64_t av_rescale(int64_t a, int64_t b, int64_t c)

Rescale a 64-bit integer with rounding to nearest.

Definition: mathematics.c:129

int av_get_packet(AVIOContext *s, AVPacket *pkt, int size)

Allocate and read the payload of a packet and initialize its fields with default values.

Definition: utils.c:91

ret

Definition: filter_design.txt:187

Stream structure.

Definition: avformat.h:748

int64_t avio_seek(AVIOContext *s, int64_t offset, int whence)

fseek() equivalent for AVIOContext.

Definition: aviobuf.c:231

ff_pcm_read_seek

int ff_pcm_read_seek(AVFormatContext *s, int stream_index, int64_t timestamp, int flags)

Definition: pcm.c:73

PCM_DEMUX_TARGET_FPS

#define PCM_DEMUX_TARGET_FPS

Definition: pcm.c:27

unsigned int pos

Definition: spdifenc.c:414

AVRational::den

int den

Denominator.

Definition: rational.h:60

AVPacket::stream_index

int stream_index

Definition: packet.h:541

AVCodecParameters::codec_id

enum AVCodecID codec_id

Specific type of the encoded data (the codec used).

Definition: codec_par.h:55

This structure stores compressed data.

Definition: packet.h:516

FFStream::cur_dts

int64_t cur_dts

Definition: internal.h:410

#define flags(name, subs,...)

Definition: cbs_av1.c:482

AVCodecParameters::bit_rate

int64_t bit_rate

The average bitrate of the encoded data (in bits per second).

Definition: codec_par.h:97

int av_log2(unsigned v)

Definition: intmath.c:26

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