FFmpeg
gsmdec.c
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1 /*
2  * RAW GSM demuxer
3  * Copyright (c) 2011 Justin Ruggles
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 
23 #include "libavutil/mathematics.h"
24 #include "libavutil/opt.h"
25 #include "avformat.h"
26 #include "internal.h"
27 
28 #define GSM_BLOCK_SIZE 33
29 #define GSM_BLOCK_SAMPLES 160
30 #define GSM_SAMPLE_RATE 8000
31 
32 typedef struct GSMDemuxerContext {
33  AVClass *class;
36 
37 static int gsm_probe(const AVProbeData *p)
38 {
39  int valid = 0, invalid = 0;
40  uint8_t *b = p->buf;
41  while (b < p->buf + p->buf_size - 32) {
42  if ((*b & 0xf0) == 0xd0) {
43  valid++;
44  } else {
45  invalid++;
46  }
47  b += 33;
48  }
49  if (valid >> 5 > invalid)
50  return AVPROBE_SCORE_EXTENSION + 1;
51  return 0;
52 }
53 
55 {
56  int ret, size;
57 
59 
60  pkt->pos = avio_tell(s->pb);
61  pkt->stream_index = 0;
62 
63  ret = av_get_packet(s->pb, pkt, size);
64  if (ret < GSM_BLOCK_SIZE) {
65  return ret < 0 ? ret : AVERROR(EIO);
66  }
67  pkt->duration = 1;
69 
70  return 0;
71 }
72 
74 {
75  GSMDemuxerContext *c = s->priv_data;
77  if (!st)
78  return AVERROR(ENOMEM);
79 
81  st->codecpar->codec_id = s->iformat->raw_codec_id;
82  st->codecpar->channels = 1;
84  st->codecpar->sample_rate = c->sample_rate;
85  st->codecpar->bit_rate = GSM_BLOCK_SIZE * 8 * c->sample_rate / GSM_BLOCK_SAMPLES;
86 
88 
89  return 0;
90 }
91 
92 static const AVOption options[] = {
93  { "sample_rate", "", offsetof(GSMDemuxerContext, sample_rate),
94  AV_OPT_TYPE_INT, {.i64 = GSM_SAMPLE_RATE}, 1, INT_MAX / GSM_BLOCK_SIZE,
96  { NULL },
97 };
98 
99 static const AVClass gsm_class = {
100  .class_name = "gsm demuxer",
101  .item_name = av_default_item_name,
102  .option = options,
103  .version = LIBAVUTIL_VERSION_INT,
104 };
105 
107  .name = "gsm",
108  .long_name = NULL_IF_CONFIG_SMALL("raw GSM"),
109  .priv_data_size = sizeof(GSMDemuxerContext),
114  .extensions = "gsm",
115  .raw_codec_id = AV_CODEC_ID_GSM,
116  .priv_class = &gsm_class,
117 };
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: utils.c:4376
AVCodecParameters::codec_type
enum AVMediaType codec_type
General type of the encoded data.
Definition: codec_par.h:56
options
static const AVOption options[]
Definition: gsmdec.c:92
AV_CH_LAYOUT_MONO
#define AV_CH_LAYOUT_MONO
Definition: channel_layout.h:90
AVOption
AVOption.
Definition: opt.h:248
b
#define b
Definition: input.c:41
AVPacket::duration
int64_t duration
Duration of this packet in AVStream->time_base units, 0 if unknown.
Definition: packet.h:383
mathematics.h
AVProbeData::buf_size
int buf_size
Size of buf except extra allocated bytes.
Definition: avformat.h:449
sample_rate
sample_rate
Definition: ffmpeg_filter.c:156
AVCodecParameters::channels
int channels
Audio only.
Definition: codec_par.h:166
avio_tell
static av_always_inline int64_t avio_tell(AVIOContext *s)
ftell() equivalent for AVIOContext.
Definition: avio.h:538
AVFMT_GENERIC_INDEX
#define AVFMT_GENERIC_INDEX
Use generic index building code.
Definition: avformat.h:468
GSM_BLOCK_SIZE
#define GSM_BLOCK_SIZE
Definition: gsmdec.c:28
pkt
AVPacket * pkt
Definition: movenc.c:59
AVInputFormat
Definition: avformat.h:621
gsm_class
static const AVClass gsm_class
Definition: gsmdec.c:99
s
#define s(width, name)
Definition: cbs_vp9.c:257
gsm_probe
static int gsm_probe(const AVProbeData *p)
Definition: gsmdec.c:37
AVInputFormat::name
const char * name
A comma separated list of short names for the format.
Definition: avformat.h:626
AVProbeData::buf
unsigned char * buf
Buffer must have AVPROBE_PADDING_SIZE of extra allocated bytes filled with zero.
Definition: avformat.h:448
AVMEDIA_TYPE_AUDIO
@ AVMEDIA_TYPE_AUDIO
Definition: avutil.h:202
AVFormatContext
Format I/O context.
Definition: avformat.h:1097
internal.h
AVStream::codecpar
AVCodecParameters * codecpar
Codec parameters associated with this stream.
Definition: avformat.h:984
LIBAVUTIL_VERSION_INT
#define LIBAVUTIL_VERSION_INT
Definition: version.h:85
read_header
static int read_header(FFV1Context *f)
Definition: ffv1dec.c:527
AVClass
Describe the class of an AVClass context structure.
Definition: log.h:67
ff_gsm_demuxer
const AVInputFormat ff_gsm_demuxer
Definition: gsmdec.c:106
NULL
#define NULL
Definition: coverity.c:32
read_probe
static int read_probe(const AVProbeData *pd)
Definition: jvdec.c:55
av_default_item_name
const char * av_default_item_name(void *ptr)
Return the context name.
Definition: log.c:235
AVProbeData
This structure contains the data a format has to probe a file.
Definition: avformat.h:446
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
AVPROBE_SCORE_EXTENSION
#define AVPROBE_SCORE_EXTENSION
score for file extension
Definition: avformat.h:456
AVCodecParameters::sample_rate
int sample_rate
Audio only.
Definition: codec_par.h:170
AV_CODEC_ID_GSM
@ AV_CODEC_ID_GSM
as in Berlin toast format
Definition: codec_id.h:440
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
avpriv_set_pts_info
void avpriv_set_pts_info(AVStream *s, int pts_wrap_bits, unsigned int pts_num, unsigned int pts_den)
Set the time base and wrapping info for a given stream.
Definition: utils.c:4801
size
int size
Definition: twinvq_data.h:10344
GSM_SAMPLE_RATE
#define GSM_SAMPLE_RATE
Definition: gsmdec.c:30
gsm_read_header
static int gsm_read_header(AVFormatContext *s)
Definition: gsmdec.c:73
AVPacket::pts
int64_t pts
Presentation timestamp in AVStream->time_base units; the time at which the decompressed packet will b...
Definition: packet.h:358
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:279
GSM_BLOCK_SAMPLES
#define GSM_BLOCK_SAMPLES
Definition: gsmdec.c:29
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:280
GSMDemuxerContext
Definition: gsmdec.c:32
ret
ret
Definition: filter_design.txt:187
read_packet
static int read_packet(void *opaque, uint8_t *buf, int buf_size)
Definition: avio_reading.c:42
AVStream
Stream structure.
Definition: avformat.h:837
gsm_read_packet
static int gsm_read_packet(AVFormatContext *s, AVPacket *pkt)
Definition: gsmdec.c:54
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:72
avformat.h
channel_layout.h
AV_OPT_TYPE_INT
@ AV_OPT_TYPE_INT
Definition: opt.h:225
AVPacket::stream_index
int stream_index
Definition: packet.h:367
AVCodecParameters::codec_id
enum AVCodecID codec_id
Specific type of the encoded data (the codec used).
Definition: codec_par.h:60
AVPacket
This structure stores compressed data.
Definition: packet.h:342
GSMDemuxerContext::sample_rate
int sample_rate
Definition: gsmdec.c:34
AVPacket::pos
int64_t pos
byte position in stream, -1 if unknown
Definition: packet.h:385
AVCodecParameters::channel_layout
uint64_t channel_layout
Audio only.
Definition: codec_par.h:162
flags
#define flags(name, subs,...)
Definition: cbs_av1.c:561
AVCodecParameters::bit_rate
int64_t bit_rate
The average bitrate of the encoded data (in bits per second).
Definition: codec_par.h:89