FFmpeg: libavdevice

Libavdevice is a complementary library to libavformat. It provides various "special" platform-specific muxers and demuxers, e.g. for grabbing devices, audio capture and playback etc. As a consequence, the (de)muxers in libavdevice are of the AVFMT_NOFILE type (they use their own I/O functions). The filename passed to avformat_open_input() often does not refer to an actually existing file, but has some special device-specific meaning - e.g. for xcbgrab it is the display name.

To use libavdevice, simply call avdevice_register_all() to register all compiled muxers and demuxers. They all use standard libavformat API.

Enumeration Type Documentation

◆ AVAppToDevMessageType

enum AVAppToDevMessageType

Message types used by avdevice_app_to_dev_control_message().

Enumerator
AV_APP_TO_DEV_NONE	Dummy message.
AV_APP_TO_DEV_WINDOW_SIZE	Window size change message. Message is sent to the device every time the application changes the size of the window device renders to. Message should also be sent right after window is created. data: AVDeviceRect: new window size.
AV_APP_TO_DEV_WINDOW_REPAINT	Repaint request message. Message is sent to the device when window has to be repainted. data: AVDeviceRect: area required to be repainted. NULL: whole area is required to be repainted.
AV_APP_TO_DEV_PAUSE	Request pause/play. Application requests pause/unpause playback. Mostly usable with devices that have internal buffer. By default devices are not paused. data: NULL
AV_APP_TO_DEV_PLAY
AV_APP_TO_DEV_TOGGLE_PAUSE
AV_APP_TO_DEV_SET_VOLUME	Volume control message. Set volume level. It may be device-dependent if volume is changed per stream or system wide. Per stream volume change is expected when possible. data: double: new volume with range of 0.0 - 1.0.
AV_APP_TO_DEV_MUTE	Mute control messages. Change mute state. It may be device-dependent if mute status is changed per stream or system wide. Per stream mute status change is expected when possible. data: NULL.
AV_APP_TO_DEV_UNMUTE
AV_APP_TO_DEV_TOGGLE_MUTE
AV_APP_TO_DEV_GET_VOLUME	Get volume/mute messages. Force the device to send AV_DEV_TO_APP_VOLUME_LEVEL_CHANGED or AV_DEV_TO_APP_MUTE_STATE_CHANGED command respectively. data: NULL.
AV_APP_TO_DEV_GET_MUTE

Definition at line 119 of file avdevice.h.

◆ AVDevToAppMessageType

enum AVDevToAppMessageType

Message types used by avdevice_dev_to_app_control_message().

Enumerator
AV_DEV_TO_APP_NONE	Dummy message.
AV_DEV_TO_APP_CREATE_WINDOW_BUFFER	Create window buffer message. Device requests to create a window buffer. Exact meaning is device- and application-dependent. Message is sent before rendering first frame and all one-shot initializations should be done here. Application is allowed to ignore preferred window buffer size. Note : Application is obligated to inform about window buffer size with AV_APP_TO_DEV_WINDOW_SIZE message. data: AVDeviceRect: preferred size of the window buffer. NULL: no preferred size of the window buffer.
AV_DEV_TO_APP_PREPARE_WINDOW_BUFFER	Prepare window buffer message. Device requests to prepare a window buffer for rendering. Exact meaning is device- and application-dependent. Message is sent before rendering of each frame. data: NULL.
AV_DEV_TO_APP_DISPLAY_WINDOW_BUFFER	Display window buffer message. Device requests to display a window buffer. Message is sent when new frame is ready to be displayed. Usually buffers need to be swapped in handler of this message. data: NULL.
AV_DEV_TO_APP_DESTROY_WINDOW_BUFFER	Destroy window buffer message. Device requests to destroy a window buffer. Message is sent when device is about to be destroyed and window buffer is not required anymore. data: NULL.
AV_DEV_TO_APP_BUFFER_OVERFLOW	Buffer fullness status messages. Device signals buffer overflow/underflow. data: NULL.
AV_DEV_TO_APP_BUFFER_UNDERFLOW
AV_DEV_TO_APP_BUFFER_READABLE	Buffer readable/writable. Device informs that buffer is readable/writable. When possible, device informs how many bytes can be read/write. Warning Device may not inform when number of bytes than can be read/write changes. data: int64_t: amount of bytes available to read/write. NULL: amount of bytes available to read/write is not known.
AV_DEV_TO_APP_BUFFER_WRITABLE
AV_DEV_TO_APP_MUTE_STATE_CHANGED	Mute state change message. Device informs that mute state has changed. data: int: 0 for not muted state, non-zero for muted state.
AV_DEV_TO_APP_VOLUME_LEVEL_CHANGED	Volume level change message. Device informs that volume level has changed. data: double: new volume with range of 0.0 - 1.0.

Definition at line 198 of file avdevice.h.

Function Documentation

◆ avdevice_version()

unsigned avdevice_version ( void )

Return the LIBAVDEVICE_VERSION_INT constant.

Definition at line 36 of file avdevice.c.

◆ avdevice_configuration()

const char* avdevice_configuration ( void )

Return the libavdevice build-time configuration.

Definition at line 42 of file avdevice.c.

◆ avdevice_license()

const char* avdevice_license ( void )

Return the libavdevice license.

Definition at line 47 of file avdevice.c.

◆ avdevice_register_all()

void avdevice_register_all ( void )

Initialize libavdevice and register all the input and output devices.

Definition at line 66 of file alldevices.c.

Referenced by main().

◆ av_input_audio_device_next()

AVInputFormat* av_input_audio_device_next ( AVInputFormat * d )

Audio input devices iterator.

If d is NULL, returns the first registered input audio/video device, if d is non-NULL, returns the next registered input audio/video device after d or NULL if d is the last one.

Definition at line 123 of file alldevices.c.

◆ av_input_video_device_next()

AVInputFormat* av_input_video_device_next ( AVInputFormat * d )

Video input devices iterator.

If d is NULL, returns the first registered input audio/video device, if d is non-NULL, returns the next registered input audio/video device after d or NULL if d is the last one.

Definition at line 128 of file alldevices.c.

◆ av_output_audio_device_next()

AVOutputFormat* av_output_audio_device_next ( AVOutputFormat * d )

Audio output devices iterator.

If d is NULL, returns the first registered output audio/video device, if d is non-NULL, returns the next registered output audio/video device after d or NULL if d is the last one.

Definition at line 133 of file alldevices.c.

◆ av_output_video_device_next()

AVOutputFormat* av_output_video_device_next ( AVOutputFormat * d )

Video output devices iterator.

If d is NULL, returns the first registered output audio/video device, if d is non-NULL, returns the next registered output audio/video device after d or NULL if d is the last one.

Definition at line 138 of file alldevices.c.

◆ avdevice_app_to_dev_control_message()

int avdevice_app_to_dev_control_message ( struct AVFormatContext * s,

enum AVAppToDevMessageType type,

void * data,

size_t data_size

)

Send control message from application to device.

Parameters: s device context.

type message type.

data message data. Exact type depends on message type.

data_size size of message data.

Returns: >= 0 on success, negative on error. AVERROR(ENOSYS) when device doesn't implement handler of the message.

Definition at line 53 of file avdevice.c.

◆ avdevice_dev_to_app_control_message()

int avdevice_dev_to_app_control_message ( struct AVFormatContext * s,

enum AVDevToAppMessageType type,

void * data,

size_t data_size

)

Send control message from device to application.

Parameters: s device context.

type message type.

data message data. Can be NULL.

data_size size of message data.

Returns: >= 0 on success, negative on error. AVERROR(ENOSYS) when application doesn't implement handler of the message.

Definition at line 61 of file avdevice.c.

Referenced by opengl_create_window(), opengl_draw(), opengl_release_window(), opengl_resize(), opengl_write_header(), opengl_write_trailer(), pulse_audio_sink_input_cb(), pulse_overflow(), pulse_stream_writable(), pulse_underflow(), and pulse_write_packet().

◆ avdevice_capabilities_create()

attribute_deprecated int avdevice_capabilities_create ( AVDeviceCapabilitiesQuery ** caps,

AVFormatContext * s,

AVDictionary ** device_options

)

Initialize capabilities probing API based on AVOption API.

avdevice_capabilities_free() must be called when query capabilities API is not used anymore.

Parameters: [out] caps Device capabilities data. Pointer to a NULL pointer must be passed.

s Context of the device.

device_options An AVDictionary filled with device-private options. On return this parameter will be destroyed and replaced with a dict containing options that were not found. May be NULL. The same options must be passed later to avformat_write_header() for output devices or avformat_open_input() for input devices, or at any other place that affects device-private options.

Returns: >= 0 on success, negative otherwise.

Definition at line 70 of file avdevice.c.

◆ avdevice_capabilities_free()

attribute_deprecated void avdevice_capabilities_free ( AVDeviceCapabilitiesQuery ** caps,

AVFormatContext * s

)

Free resources created by avdevice_capabilities_create()

Parameters: caps Device capabilities data to be freed.

s Context of the device.

Definition at line 76 of file avdevice.c.

◆ avdevice_list_devices()

int avdevice_list_devices ( struct AVFormatContext * s,

AVDeviceInfoList ** device_list

)

List devices.

Returns available device names and their parameters.

Note: : Some devices may accept system-dependent device names that cannot be autodetected. The list returned by this function cannot be assumed to be always completed.

Parameters: s device context.

[out] device_list list of autodetected devices.

Returns: count of autodetected devices, negative on error.

Definition at line 82 of file avdevice.c.

Referenced by list_devices_for_context().

◆ avdevice_free_list_devices()

void avdevice_free_list_devices ( AVDeviceInfoList ** device_list )

Convenient function to free result of avdevice_list_devices().

Parameters: devices device list to be freed.

Definition at line 145 of file avdevice.c.

Referenced by avdevice_list_devices(), and ff_decklink_list_devices_legacy().

◆ avdevice_list_input_sources()

int avdevice_list_input_sources ( struct AVInputFormat * device,

const char * device_name,

AVDictionary * device_options,

AVDeviceInfoList ** device_list

)

List devices.

Returns available device names and their parameters. These are convinient wrappers for avdevice_list_devices(). Device context is allocated and deallocated internally.

Parameters: device device format. May be NULL if device name is set.

device_name device name. May be NULL if device format is set.

device_options An AVDictionary filled with device-private options. May be NULL. The same options must be passed later to avformat_write_header() for output devices or avformat_open_input() for input devices, or at any other place that affects device-private options.

[out] device_list list of autodetected devices

Returns: count of autodetected devices, negative on error.

Note: device argument takes precedence over device_name when both are set.

Definition at line 123 of file avdevice.c.

◆ avdevice_list_output_sinks()

int avdevice_list_output_sinks ( struct AVOutputFormat * device,

const char * device_name,

AVDictionary * device_options,

AVDeviceInfoList ** device_list

)

Definition at line 134 of file avdevice.c.

Variable Documentation

◆ av_device_capabilities

const attribute_deprecated AVOption av_device_capabilities[]

AVOption table used by devices to implement device capabilities API.

Should not be used by a user.

Definition at line 31 of file avdevice.c.

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