Following API allows user to probe device capabilities (supported codecs, pixel formats, sample formats, resolutions, channel counts, etc). More...

#include <avdevice.h>

Public Attributes
const AVClass *	av_class

AVFormatContext *	device_context

enum AVCodecID	codec

enum AVSampleFormat	sample_format

enum AVPixelFormat	pixel_format

int	sample_rate

int	channels

int64_t	channel_layout

int	window_width

int	window_height

int	frame_width

int	frame_height

AVRational	fps

Detailed Description

Following API allows user to probe device capabilities (supported codecs, pixel formats, sample formats, resolutions, channel counts, etc).

It is build on top op AVOption API. Queried capabilities make it possible to set up converters of video or audio parameters that fit to the device.

List of capabilities that can be queried:

Capabilities valid for both audio and video devices:
- codec: supported audio/video codecs. type: AV_OPT_TYPE_INT (AVCodecID value)
Capabilities valid for audio devices:
- sample_format: supported sample formats. type: AV_OPT_TYPE_INT (AVSampleFormat value)
- sample_rate: supported sample rates. type: AV_OPT_TYPE_INT
- channels: supported number of channels. type: AV_OPT_TYPE_INT
- channel_layout: supported channel layouts. type: AV_OPT_TYPE_INT64
Capabilities valid for video devices:
- pixel_format: supported pixel formats. type: AV_OPT_TYPE_INT (AVPixelFormat value)
- window_size: supported window sizes (describes size of the window size presented to the user). type: AV_OPT_TYPE_IMAGE_SIZE
- frame_size: supported frame sizes (describes size of provided video frames). type: AV_OPT_TYPE_IMAGE_SIZE
- fps: supported fps values type: AV_OPT_TYPE_RATIONAL

Value of the capability may be set by user using av_opt_set() function and AVDeviceCapabilitiesQuery object. Following queries will limit results to the values matching already set capabilities. For example, setting a codec may impact number of formats or fps values returned during next query. Setting invalid value may limit results to zero.

Example of the usage basing on opengl output device:

 AVFormatContext *oc = NULL;
 AVDeviceCapabilitiesQuery *caps = NULL;
 AVOptionRanges *ranges;
 int ret;
 if ((ret = avformat_alloc_output_context2(&oc, NULL, "opengl", NULL)) < 0)
     goto fail;
 if (avdevice_capabilities_create(&caps, oc, NULL) < 0)
     goto fail;
 //query codecs
 if (av_opt_query_ranges(&ranges, caps, "codec", AV_OPT_MULTI_COMPONENT_RANGE)) < 0)
     goto fail;
 //pick codec here and set it
 av_opt_set(caps, "codec", AV_CODEC_ID_RAWVIDEO, 0);
 //query format
 if (av_opt_query_ranges(&ranges, caps, "pixel_format", AV_OPT_MULTI_COMPONENT_RANGE)) < 0)
     goto fail;
 //pick format here and set it
 av_opt_set(caps, "pixel_format", AV_PIX_FMT_YUV420P, 0);
 //query and set more capabilities
fail:
 //clean up code
 avdevice_capabilities_free(&query, oc);
 avformat_free_context(oc);

Structure describes device capabilities.

It is used by devices in conjunction with av_device_capabilities AVOption table to implement capabilities probing API based on AVOption API. Should not be used directly.

The documentation for this struct was generated from the following file:

libavdevice/avdevice.h

Public Attributes

Detailed Description