FFmpeg  2.1.1
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 "pcm.h"
25 
26 #define RAW_SAMPLES 1024
27 
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 
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 :
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,
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 }
const char * s
Definition: avisynth_c.h:668
int size
int64_t av_rescale_rnd(int64_t a, int64_t b, int64_t c, enum AVRounding) av_const
Rescale a 64-bit integer with specified rounding.
Definition: mathematics.c:60
AVCodecContext * codec
Codec context associated with this stream.
Definition: avformat.h:686
int num
numerator
Definition: rational.h:44
int64_t data_offset
offset of the first packet
Definition: avformat.h:1287
int block_align
number of bytes per packet if constant and known or 0 Used by some WAV based audio codecs...
Definition: avcodec.h:1910
Format I/O context.
Definition: avformat.h:968
int64_t cur_dts
Definition: avformat.h:796
Round toward +infinity.
Definition: mathematics.h:71
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:200
int av_get_bits_per_sample(enum AVCodecID codec_id)
Return codec bits per sample.
Definition: utils.c:2928
int flags
A combination of AV_PKT_FLAG values.
Definition: avcodec.h:1069
int bit_rate
the average bitrate
Definition: avcodec.h:1204
int64_t av_rescale(int64_t a, int64_t b, int64_t c) av_const
Rescale a 64-bit integer with rounding to nearest.
Definition: mathematics.c:118
ret
Definition: avfilter.c:961
AVStream ** streams
Definition: avformat.h:1016
int64_t avio_seek(AVIOContext *s, int64_t offset, int whence)
fseek() equivalent for AVIOContext.
Definition: aviobuf.c:199
int ff_pcm_read_seek(AVFormatContext *s, int stream_index, int64_t timestamp, int flags)
Definition: pcm.c:46
Stream structure.
Definition: avformat.h:667
int ff_pcm_read_packet(AVFormatContext *s, AVPacket *pkt)
Definition: pcm.c:28
enum AVCodecID codec_id
Definition: avcodec.h:1157
int sample_rate
samples per second
Definition: avcodec.h:1873
AVIOContext * pb
I/O context.
Definition: avformat.h:1001
#define AVSEEK_FLAG_BACKWARD
Definition: avformat.h:1838
Round toward -infinity.
Definition: mathematics.h:70
static int flags
Definition: cpu.c:45
Main libavformat public API header.
int den
denominator
Definition: rational.h:45
#define AV_PKT_FLAG_CORRUPT
The packet content is corrupted.
Definition: avcodec.h:1114
int channels
number of audio channels
Definition: avcodec.h:1874
#define AVERROR(e)
static AVPacket pkt
Definition: demuxing.c:52
int stream_index
Definition: avcodec.h:1065
AVRational time_base
This is the fundamental unit of time (in seconds) in terms of which frame timestamps are represented...
Definition: avformat.h:703
This structure stores compressed data.
Definition: avcodec.h:1040
#define RAW_SAMPLES
Definition: pcm.c:26