FFmpeg: libavformat/g726.c Source File

FFmpeg
g726.c
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1 /*
2  * G.726 raw demuxer
3  * Copyright 2017 Carl Eugen Hoyos
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 "config_components.h"
23 
24 #include "avformat.h"
25 #include "internal.h"
26 #include "libavutil/opt.h"
27 
28 typedef struct G726Context {
29  AVClass *class;
30  int code_size;
31   int sample_rate;
32 } G726Context;
33 
34  static int g726_read_header(AVFormatContext *s)
35 {
36  G726Context *c = s->priv_data;
37  AVStream *st = avformat_new_stream(s, NULL);
38  if (!st)
39  return AVERROR(ENOMEM);
40 
41  st->codecpar->codec_type = AVMEDIA_TYPE_AUDIO;
42  st->codecpar->codec_id = s->iformat->raw_codec_id;
43 
44  st->codecpar->sample_rate = c->sample_rate;
45  st->codecpar->bits_per_coded_sample = c->code_size;
46  st->codecpar->bit_rate = ((int[]){ 16000, 24000, 32000, 40000 })[c->code_size - 2];
47  st->codecpar->ch_layout.nb_channels = 1;
48 
49  return 0;
50 }
51 
52  static int g726_read_packet(AVFormatContext *s, AVPacket *pkt)
53 {
54  int res;
55  res = av_get_packet(s->pb, pkt, 1020); // a size similar to RAW_PACKET_SIZE divisible by all code_size values
56  if (res < 0)
57  return res;
58  return 0;
59 }
60 
61  #define OFFSET(x) offsetof(G726Context, x)
62  static const AVOption options[] = {
63  { "code_size", "Bits per G.726 code",
64  OFFSET(code_size), AV_OPT_TYPE_INT, {.i64 = 4}, 2, 5, AV_OPT_FLAG_DECODING_PARAM },
65  { "sample_rate", "",
66  OFFSET(sample_rate), AV_OPT_TYPE_INT, {.i64 = 8000}, 0, INT_MAX, AV_OPT_FLAG_DECODING_PARAM },
67  { NULL },
68 };
69 
70  static const AVClass g726_demuxer_class = {
71  .class_name = "G.726 demuxer",
72  .item_name = av_default_item_name,
73  .option = options,
74  .version = LIBAVUTIL_VERSION_INT,
75 };
76 
77 #if CONFIG_G726_DEMUXER
78 const AVInputFormat ff_g726_demuxer = {
79  .name = "g726",
80  .long_name = NULL_IF_CONFIG_SMALL("raw big-endian G.726 (\"left aligned\")"),
81  .read_header = g726_read_header,
82  .read_packet = g726_read_packet,
83  .priv_data_size = sizeof(G726Context),
84  .priv_class = &g726_demuxer_class,
85  .raw_codec_id = AV_CODEC_ID_ADPCM_G726,
86 };
87 #endif
88 
89 #if CONFIG_G726LE_DEMUXER
90 const AVInputFormat ff_g726le_demuxer = {
91  .name = "g726le",
92  .long_name = NULL_IF_CONFIG_SMALL("raw little-endian G.726 (\"right aligned\")"),
93  .read_header = g726_read_header,
94  .read_packet = g726_read_packet,
95  .priv_data_size = sizeof(G726Context),
96  .priv_class = &g726_demuxer_class,
97  .raw_codec_id = AV_CODEC_ID_ADPCM_G726LE,
98 };
99 #endif
100 
G726Context
Definition: g726.c:82
AVERROR
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
opt.h
avformat_new_stream
AVStream * avformat_new_stream(AVFormatContext *s, const AVCodec *c)
Add a new stream to a media file.
Definition: options.c:237
AVCodecParameters::codec_type
enum AVMediaType codec_type
General type of the encoded data.
Definition: codec_par.h:57
G726Context::sample_rate
int sample_rate
Definition: g726.c:31
AVOption
AVOption.
Definition: opt.h:251
AVChannelLayout::nb_channels
int nb_channels
Number of channels in this layout.
Definition: channel_layout.h:300
sample_rate
sample_rate
Definition: ffmpeg_filter.c:153
OFFSET
#define OFFSET(x)
Definition: g726.c:61
pkt
AVPacket * pkt
Definition: movenc.c:59
AVInputFormat
Definition: avformat.h:656
ff_g726le_demuxer
const AVInputFormat ff_g726le_demuxer
AV_CODEC_ID_ADPCM_G726
@ AV_CODEC_ID_ADPCM_G726
Definition: codec_id.h:368
s
#define s(width, name)
Definition: cbs_vp9.c:256
AVInputFormat::name
const char * name
A comma separated list of short names for the format.
Definition: avformat.h:661
AVMEDIA_TYPE_AUDIO
@ AVMEDIA_TYPE_AUDIO
Definition: avutil.h:202
g726_demuxer_class
static const AVClass g726_demuxer_class
Definition: g726.c:70
AVFormatContext
Format I/O context.
Definition: avformat.h:1213
internal.h
AVStream::codecpar
AVCodecParameters * codecpar
Codec parameters associated with this stream.
Definition: avformat.h:1108
LIBAVUTIL_VERSION_INT
#define LIBAVUTIL_VERSION_INT
Definition: version.h:85
AVClass
Describe the class of an AVClass context structure.
Definition: log.h:66
NULL
#define NULL
Definition: coverity.c:32
av_default_item_name
const char * av_default_item_name(void *ptr)
Return the context name.
Definition: log.c:237
AVCodecParameters::ch_layout
AVChannelLayout ch_layout
Audio only.
Definition: codec_par.h:212
c
Undefined Behavior In the C some operations are like signed integer dereferencing freed accessing outside allocated Undefined Behavior must not occur in a C it is not safe even if the output of undefined operations is unused The unsafety may seem nit picking but Optimizing compilers have in fact optimized code on the assumption that no undefined Behavior occurs Optimizing code based on wrong assumptions can and has in some cases lead to effects beyond the output of computations The signed integer overflow problem in speed critical code Code which is highly optimized and works with signed integers sometimes has the problem that often the output of the computation does not c
Definition: undefined.txt:32
AVCodecParameters::sample_rate
int sample_rate
Audio only.
Definition: codec_par.h:177
NULL_IF_CONFIG_SMALL
#define NULL_IF_CONFIG_SMALL(x)
Return NULL if CONFIG_SMALL is true, otherwise the argument without modification.
Definition: internal.h:117
G726Context::code_size
int code_size
Definition: g726.c:102
AV_OPT_FLAG_DECODING_PARAM
#define AV_OPT_FLAG_DECODING_PARAM
a generic parameter which can be set by the user for demuxing or decoding
Definition: opt.h:282
g726_read_packet
static int g726_read_packet(AVFormatContext *s, AVPacket *pkt)
Definition: g726.c:52
av_get_packet
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:102
AVStream
Stream structure.
Definition: avformat.h:948
ff_g726_demuxer
const AVInputFormat ff_g726_demuxer
AVClass::class_name
const char * class_name
The name of the class; usually it is the same name as the context structure type to which the AVClass...
Definition: log.h:71
avformat.h
g726_read_header
static int g726_read_header(AVFormatContext *s)
Definition: g726.c:34
AV_CODEC_ID_ADPCM_G726LE
@ AV_CODEC_ID_ADPCM_G726LE
Definition: codec_id.h:392
AV_OPT_TYPE_INT
@ AV_OPT_TYPE_INT
Definition: opt.h:225
AVCodecParameters::bits_per_coded_sample
int bits_per_coded_sample
The number of bits per sample in the codedwords.
Definition: codec_par.h:103
options
static const AVOption options[]
Definition: g726.c:62
AVCodecParameters::codec_id
enum AVCodecID codec_id
Specific type of the encoded data (the codec used).
Definition: codec_par.h:61
AVPacket
This structure stores compressed data.
Definition: packet.h:351
AVCodecParameters::bit_rate
int64_t bit_rate
The average bitrate of the encoded data (in bits per second).
Definition: codec_par.h:90
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