FFmpeg
utils.c
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1 /*
2  * This file is part of FFmpeg.
3  *
4  * FFmpeg is free software; you can redistribute it and/or
5  * modify it under the terms of the GNU Lesser General Public
6  * License as published by the Free Software Foundation; either
7  * version 2.1 of the License, or (at your option) any later version.
8  *
9  * FFmpeg is distributed in the hope that it will be useful,
10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12  * Lesser General Public License for more details.
13  *
14  * You should have received a copy of the GNU Lesser General Public
15  * License along with FFmpeg; if not, write to the Free Software
16  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
17  */
18 
19 #include "internal.h"
20 #include "libavutil/opt.h"
21 #include "libavformat/avformat.h"
22 
24 {
26  int ret = 0;
27 
28  *avctx = NULL;
29  if (!iformat && !format)
30  return AVERROR(EINVAL);
31  if (!(s = avformat_alloc_context()))
32  return AVERROR(ENOMEM);
33 
34  if (!iformat)
35  iformat = av_find_input_format(format);
36  if (!iformat || !iformat->priv_class || !AV_IS_INPUT_DEVICE(iformat->priv_class->category)) {
37  ret = AVERROR(EINVAL);
38  goto error;
39  }
40  s->iformat = iformat;
41  if (s->iformat->priv_data_size > 0) {
43  if (!s->priv_data) {
44  ret = AVERROR(ENOMEM);
45  goto error;
46  }
47  if (s->iformat->priv_class) {
48  *(const AVClass**)s->priv_data= s->iformat->priv_class;
50  }
51  } else
52  s->priv_data = NULL;
53 
54  *avctx = s;
55  return 0;
56  error:
58  return ret;
59 }
#define NULL
Definition: coverity.c:32
int ff_alloc_input_device_context(AVFormatContext **avctx, AVInputFormat *iformat, const char *format)
Definition: utils.c:23
void av_opt_set_defaults(void *s)
Set the values of all AVOption fields to their default values.
Definition: opt.c:1305
void * av_mallocz(size_t size)
Allocate a memory block with alignment suitable for all memory accesses (including vectors if availab...
Definition: mem.c:236
int priv_data_size
Size of private data so that it can be allocated in the wrapper.
Definition: avformat.h:705
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 format(the sample packing is implied by the sample format) and sample rate.The lists are not just lists
Format I/O context.
Definition: avformat.h:1358
AVOptions.
#define AV_IS_INPUT_DEVICE(category)
Definition: log.h:50
AVFormatContext * avformat_alloc_context(void)
Allocate an AVFormatContext.
Definition: options.c:144
const AVClass * priv_class
AVClass for the private context.
Definition: avformat.h:679
ff_const59 struct AVInputFormat * iformat
The input container format.
Definition: avformat.h:1370
ff_const59 AVInputFormat * av_find_input_format(const char *short_name)
Find AVInputFormat based on the short name of the input format.
Definition: format.c:118
AVClassCategory category
Category used for visualization (like color) This is only set if the category is equal for all object...
Definition: log.h:130
#define s(width, name)
Definition: cbs_vp9.c:257
static void error(const char *err)
static AVInputFormat * iformat
Definition: ffprobe.c:257
Describe the class of an AVClass context structure.
Definition: log.h:67
void avformat_free_context(AVFormatContext *s)
Free an AVFormatContext and all its streams.
Definition: utils.c:4399
Main libavformat public API header.
void * priv_data
Format private data.
Definition: avformat.h:1386
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