ffmpeg-devices (1)

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NAME

ffmpeg-devices - FFmpeg devices

DESCRIPTION

This document describes the input and output devices provided by the libavdevice library.

DEVICE OPTIONS

The libavdevice library provides the same interface as libavformat. Namely, an input device is considered like a demuxer, and an output device like a muxer, and the interface and generic device options are the same provided by libavformat (see the ffmpeg-formats manual).

In addition each input or output device may support so-called private options, which are specific for that component.

Options may be set by specifying -option value in the FFmpeg tools, or by setting the value explicitly in the device "AVFormatContext" options or using the libavutil/opt.h

for programmatic use.

INPUT DEVICES

Input devices are configured elements in FFmpeg which enable accessing the data coming from a multimedia device attached to your system.

When you configure your FFmpeg build, all the supported input devices are enabled by default. You can list all available ones using the configure option ``--list-indevs''.

You can disable all the input devices using the configure option ``--disable-indevs'', and selectively enable an input device using the option "--enable-indev=

``, or you can disable a particular input device using the option ''--disable-indev=".

The option ``-devices'' of the ff* tools will display the list of supported input devices.

A description of the currently available input devices follows.

alsa

(Advanced Linux Sound Architecture) input device.

To enable this input device during configuration you need libasound installed on your system.

This device allows capturing from an

device. The name of the device to capture has to be an card identifier.

An

identifier has the syntax:

        hw:<CARD>[,<DEV>[,<SUBDEV>]]

where the

and components are optional.

The three arguments (in order:

,,) specify card number or identifier, device number and subdevice number (-1 means any).

To see the list of cards currently recognized by your system check the files /proc/asound/cards and /proc/asound/devices.

For example to capture with ffmpeg from an

device with card id 0, you may run the command:

        ffmpeg -f alsa -i hw:0 alsaout.wav

For more information see: <www.alsa-project.org/alsa-doc/alsa-lib/pcm.html>

Options

sample_rate

Set the sample rate in Hz. Default is 48000.

channels

Set the number of channels. Default is 2.

avfoundation

AVFoundation input device.

AVFoundation is the currently recommended framework by Apple for streamgrabbing on

>= 10.7 as well as on iOS. The older QTKit framework has been marked deprecated since version 10.7.

The input filename has to be given in the following syntax:

        -i "[[VIDEO]:[AUDIO]]"

The first entry selects the video input while the latter selects the audio input. The stream has to be specified by the device name or the device index as shown by the device list. Alternatively, the video and/or audio input device can be chosen by index using the

    B<-video_device_index E<lt>INDEXE<gt>>

and/or

    B<-audio_device_index E<lt>INDEXE<gt>>

, overriding any device name or index given in the input filename.

All available devices can be enumerated by using -list_devices true, listing all device names and corresponding indices.

There are two device name aliases:

default

Select the AVFoundation default device of the corresponding type.

none

Do not record the corresponding media type. This is equivalent to specifying an empty device name or index.

Options

AVFoundation supports the following options:

-list_devices <TRUE|FALSE>

If set to true, a list of all available input devices is given showing all device names and indices.

-video_device_index <

INDEX

>

Specify the video device by its index. Overrides anything given in the input filename.

-audio_device_index <

INDEX

>

Specify the audio device by its index. Overrides anything given in the input filename.

-pixel_format <

FORMAT

>

Request the video device to use a specific pixel format. If the specified format is not supported, a list of available formats is given und the first one in this list is used instead. Available pixel formats are: "monob, rgb555be, rgb555le, rgb565be, rgb565le, rgb24, bgr24, 0rgb, bgr0, 0bgr, rgb0,
 bgr48be, uyvy422, yuva444p, yuva444p16le, yuv444p, yuv422p16, yuv422p10, yuv444p10,
 yuv420p, nv12, yuyv422, gray"

-framerate

Set the grabbing frame rate. Default is "ntsc", corresponding to a frame rate of "30000/1001".

-video_size

Set the video frame size.

-capture_cursor

Capture the mouse pointer. Default is 0.

-capture_mouse_clicks

Capture the screen mouse clicks. Default is 0.

Examples

*

Print the list of AVFoundation supported devices and exit:

        $ ffmpeg -f avfoundation -list_devices true -i ""

*

Record video from video device 0 and audio from audio device 0 into out.avi:

        $ ffmpeg -f avfoundation -i "0:0" out.avi

*

Record video from video device 2 and audio from audio device 1 into out.avi:

        $ ffmpeg -f avfoundation -video_device_index 2 -i ":1" out.avi

*

Record video from the system default video device using the pixel format bgr0 and do not record any audio into out.avi:

        $ ffmpeg -f avfoundation -pixel_format bgr0 -i "default:none" out.avi

bktr

video input device.

Options

framerate

Set the frame rate.

video_size

Set the video frame size. Default is "vga".

standard

Available values are:

pal

ntsc

secam

paln

palm

ntscj

decklink

The decklink input device provides capture capabilities for Blackmagic DeckLink devices.

To enable this input device, you need the Blackmagic DeckLink

and you need to configure with the appropriate "--extra-cflags" and "--extra-ldflags". On Windows, you need to run the files through widl.

DeckLink is very picky about the formats it supports. Pixel format is uyvy422 or v210, framerate and video size must be determined for your device with -list_formats 1. Audio sample rate is always 48 kHz and the number of channels can be 2, 8 or 16.

Options

list_devices

If set to true, print a list of devices and exit. Defaults to false.

list_formats

If set to true, print a list of supported formats and exit. Defaults to false.

bm_v210

If set to 1, video is captured in 10 bit v210 instead of uyvy422. Not all Blackmagic devices support this option.

Examples

*

List input devices:

        ffmpeg -f decklink -list_devices 1 -i dummy

*

List supported formats:

        ffmpeg -f decklink -list_formats 1 -i 'Intensity Pro'

*

Capture video clip at 1080i50 (format 11):

        ffmpeg -f decklink -i 'Intensity Pro@11' -acodec copy -vcodec copy output.avi

*

Capture video clip at 1080i50 10 bit:

        ffmpeg -bm_v210 1 -f decklink -i 'UltraStudio Mini Recorder@11' -acodec copy -vcodec copy output.avi

dshow

Windows DirectShow input device.

DirectShow support is enabled when FFmpeg is built with the mingw-w64 project. Currently only audio and video devices are supported.

Multiple devices may be opened as separate inputs, but they may also be opened on the same input, which should improve synchronism between them.

The input name should be in the format:

        <TYPE>=<NAME>[:<TYPE>=<NAME>]

where

can be either audio or video, and is the device's name or alternative name..

Options

If no options are specified, the device's defaults are used. If the device does not support the requested options, it will fail to open.

video_size

Set the video size in the captured video.

framerate

Set the frame rate in the captured video.

sample_rate

Set the sample rate (in Hz) of the captured audio.

sample_size

Set the sample size (in bits) of the captured audio.

channels

Set the number of channels in the captured audio.

list_devices

If set to true, print a list of devices and exit.

list_options

If set to true, print a list of selected device's options and exit.

video_device_number

Set video device number for devices with the same name (starts at 0, defaults to 0).

audio_device_number

Set audio device number for devices with the same name (starts at 0, defaults to 0).

pixel_format

Select pixel format to be used by DirectShow. This may only be set when the video codec is not set or set to rawvideo.

audio_buffer_size

Set audio device buffer size in milliseconds (which can directly impact latency, depending on the device). Defaults to using the audio device's default buffer size (typically some multiple of 500ms). Setting this value too low can degrade performance. See also <msdn.microsoft.com/en-us/library/windows/desktop/dd377582(v=vs.85).aspx>

video_pin_name

Select video capture pin to use by name or alternative name.

audio_pin_name

Select audio capture pin to use by name or alternative name.

crossbar_video_input_pin_number

Select video input pin number for crossbar device. This will be routed to the crossbar device's Video Decoder output pin. Note that changing this value can affect future invocations (sets a new default) until system reboot occurs.

crossbar_audio_input_pin_number

Select audio input pin number for crossbar device. This will be routed to the crossbar device's Audio Decoder output pin. Note that changing this value can affect future invocations (sets a new default) until system reboot occurs.

show_video_device_dialog

If set to true, before capture starts, popup a display dialog to the end user, allowing them to change video filter properties and configurations manually. Note that for crossbar devices, adjusting values in this dialog may be needed at times to toggle between

PAL

(25 fps) and

NTSC

(29.97) input frame rates, sizes, interlacing, etc. Changing these values can enable different scan rates/frame rates and avoiding green bars at the bottom, flickering scan lines, etc. Note that with some devices, changing these properties can also affect future invocations (sets new defaults) until system reboot occurs.

show_audio_device_dialog

If set to true, before capture starts, popup a display dialog to the end user, allowing them to change audio filter properties and configurations manually.

show_video_crossbar_connection_dialog

If set to true, before capture starts, popup a display dialog to the end user, allowing them to manually modify crossbar pin routings, when it opens a video device.

show_audio_crossbar_connection_dialog

If set to true, before capture starts, popup a display dialog to the end user, allowing them to manually modify crossbar pin routings, when it opens an audio device.

show_analog_tv_tuner_dialog

If set to true, before capture starts, popup a display dialog to the end user, allowing them to manually modify

TV

channels and frequencies.

show_analog_tv_tuner_audio_dialog

If set to true, before capture starts, popup a display dialog to the end user, allowing them to manually modify

TV

audio (like mono vs. stereo, Language A,B or C).

audio_device_load

Load an audio capture filter device from file instead of searching it by name. It may load additional parameters too, if the filter supports the serialization of its properties to. To use this an audio capture source has to be specified, but it can be anything even fake one.

audio_device_save

Save the currently used audio capture filter device and its parameters (if the filter supports it) to a file. If a file with the same name exists it will be overwritten.

video_device_load

Load a video capture filter device from file instead of searching it by name. It may load additional parameters too, if the filter supports the serialization of its properties to. To use this a video capture source has to be specified, but it can be anything even fake one.

video_device_save

Save the currently used video capture filter device and its parameters (if the filter supports it) to a file. If a file with the same name exists it will be overwritten.

Examples

*

Print the list of DirectShow supported devices and exit:

        $ ffmpeg -list_devices true -f dshow -i dummy

*

Open video device Camera:

        $ ffmpeg -f dshow -i video="Camera"

*

Open second video device with name Camera:

        $ ffmpeg -f dshow -video_device_number 1 -i video="Camera"

*

Open video device Camera and audio device Microphone:

        $ ffmpeg -f dshow -i video="Camera":audio="Microphone"

*

Print the list of supported options in selected device and exit:

        $ ffmpeg -list_options true -f dshow -i video="Camera"

*

Specify pin names to capture by name or alternative name, specify alternative device name:

        $ ffmpeg -f dshow -audio_pin_name "Audio Out" -video_pin_name 2 -i video=video="@device_pnp_\\?\pci#ven_1a0a&dev_6200&subsys_62021461&rev_01#4&e2c7dd6&0&00e1#{65e8773d-8f56-11d0-a3b9-00a0c9223196}\{ca465100-deb0-4d59-818f-8c477184adf6}":audio="Microphone"

*

Configure a crossbar device, specifying crossbar pins, allow user to adjust video capture properties at startup:

        $ ffmpeg -f dshow -show_video_device_dialog true -crossbar_video_input_pin_number 0
             -crossbar_audio_input_pin_number 3 -i video="AVerMedia BDA Analog Capture":audio="AVerMedia BDA Analog Capture"

dv1394

Linux input device.

Options

framerate

Set the frame rate. Default is 25.

standard

Available values are:

pal

ntsc

Default value is "ntsc".

fbdev

Linux framebuffer input device.

The Linux framebuffer is a graphic hardware-independent abstraction layer to show graphics on a computer monitor, typically on the console. It is accessed through a file device node, usually /dev/fb0.

For more detailed information read the file Documentation/fb/framebuffer.txt included in the Linux source tree.

See also <linux-fbdev.sourceforge.net>, and fbset(1).

To record from the framebuffer device /dev/fb0 with ffmpeg:

        ffmpeg -f fbdev -framerate 10 -i /dev/fb0 out.avi

You can take a single screenshot image with the command:

        ffmpeg -f fbdev -framerate 1 -i /dev/fb0 -frames:v 1 screenshot.jpeg

Options

framerate

Set the frame rate. Default is 25.

gdigrab

Win32 GDI-based screen capture device.

This device allows you to capture a region of the display on Windows.

There are two options for the input filename:

        desktop

or

        title=<window_title>

The first option will capture the entire desktop, or a fixed region of the desktop. The second option will instead capture the contents of a single window, regardless of its position on the screen.

For example, to grab the entire desktop using ffmpeg:

        ffmpeg -f gdigrab -framerate 6 -i desktop out.mpg

Grab a 640x480 region at position "10,20":

        ffmpeg -f gdigrab -framerate 6 -offset_x 10 -offset_y 20 -video_size vga -i desktop out.mpg

Grab the contents of the window named ``Calculator''

        ffmpeg -f gdigrab -framerate 6 -i title=Calculator out.mpg

Options

draw_mouse

Specify whether to draw the mouse pointer. Use the value 0 to not draw the pointer. Default value is 1.

framerate

Set the grabbing frame rate. Default value is "ntsc", corresponding to a frame rate of "30000/1001".

show_region

Show grabbed region on screen.

If show_region is specified with 1, then the grabbing region will be indicated on screen. With this option, it is easy to know what is being grabbed if only a portion of the screen is grabbed.

Note that show_region is incompatible with grabbing the contents of a single window.

For example:

        ffmpeg -f gdigrab -show_region 1 -framerate 6 -video_size cif -offset_x 10 -offset_y 20 -i desktop out.mpg

video_size

Set the video frame size. The default is to capture the full screen if desktop is selected, or the full window size if title=window_title is selected.

offset_x

When capturing a region with video_size, set the distance from the left edge of the screen or desktop.

Note that the offset calculation is from the top left corner of the primary monitor on Windows. If you have a monitor positioned to the left of your primary monitor, you will need to use a negative offset_x value to move the region to that monitor.

offset_y

When capturing a region with video_size, set the distance from the top edge of the screen or desktop.

Note that the offset calculation is from the top left corner of the primary monitor on Windows. If you have a monitor positioned above your primary monitor, you will need to use a negative offset_y value to move the region to that monitor.

iec61883

FireWire input device using libiec61883.

To enable this input device, you need libiec61883, libraw1394 and libavc1394 installed on your system. Use the configure option "--enable-libiec61883" to compile with the device enabled.

The iec61883 capture device supports capturing from a video device connected via

(FireWire), using libiec61883 and the new Linux FireWire stack (juju). This is the default input method in Linux Kernel 2.6.37 and later, since the old FireWire stack was removed.

Specify the FireWire port to be used as input file, or ``auto'' to choose the first port connected.

Options

dvtype

Override autodetection of

DV/HDV.

This should only be used if auto detection does not work, or if usage of a different device type should be prohibited. Treating a

DV

device as

HDV

(or vice versa) will not work and result in undefined behavior. The values auto, dv and hdv are supported.

dvbuffer

Set maximum size of buffer for incoming data, in frames. For

DV,

this is an exact value. For

HDV,

it is not frame exact, since

HDV

does not have a fixed frame size.

dvguid

Select the capture device by specifying it's

GUID.

Capturing will only be performed from the specified device and fails if no device with the given

GUID

is found. This is useful to select the input if multiple devices are connected at the same time. Look at /sys/bus/firewire/devices to find out the GUIDs.

Examples

*

Grab and show the input of a FireWire

DV/HDV

device.

        ffplay -f iec61883 -i auto

*

Grab and record the input of a FireWire

DV/HDV

device, using a packet buffer of 100000 packets if the source is

HDV.

        ffmpeg -f iec61883 -i auto -hdvbuffer 100000 out.mpg

jack

input device.

To enable this input device during configuration you need libjack installed on your system.

A

input device creates one or more writable clients, one for each audio channel, with name client_name:input_N, where client_name is the name provided by the application, and N is a number which identifies the channel. Each writable client will send the acquired data to the FFmpeg input device.

Once you have created one or more

readable clients, you need to connect them to one or more writable clients.

To connect or disconnect

clients you can use the jack_connect and jack_disconnect programs, or do it through a graphical interface, for example with qjackctl.

To list the

clients and their properties you can invoke the command jack_lsp.

Follows an example which shows how to capture a

readable client with ffmpeg.

        # Create a JACK writable client with name "ffmpeg".
        $ ffmpeg -f jack -i ffmpeg -y out.wav
        
        # Start the sample jack_metro readable client.
        $ jack_metro -b 120 -d 0.2 -f 4000
        
        # List the current JACK clients.
        $ jack_lsp -c
        system:capture_1
        system:capture_2
        system:playback_1
        system:playback_2
        ffmpeg:input_1
        metro:120_bpm
        
        # Connect metro to the ffmpeg writable client.
        $ jack_connect metro:120_bpm ffmpeg:input_1

For more information read: <jackaudio.org>

Options

channels

Set the number of channels. Default is 2.

lavfi

Libavfilter input virtual device.

This input device reads data from the open output pads of a libavfilter filtergraph.

For each filtergraph open output, the input device will create a corresponding stream which is mapped to the generated output. Currently only video data is supported. The filtergraph is specified through the option graph.

Options

graph

Specify the filtergraph to use as input. Each video open output must be labelled by a unique string of the form "outN", where N is a number starting from 0 corresponding to the mapped input stream generated by the device. The first unlabelled output is automatically assigned to the ``out0'' label, but all the others need to be specified explicitly.

The suffix ``+subcc'' can be appended to the output label to create an extra stream with the closed captions packets attached to that output (experimental; only for

EIA-608 / CEA-708

for now). The subcc streams are created after all the normal streams, in the order of the corresponding stream. For example, if there is ``out19+subcc'', ``out7+subcc'' and up to ``out42'', the stream #43 is subcc for stream #7 and stream #44 is subcc for stream #19.

If not specified defaults to the filename specified for the input device.

graph_file

Set the filename of the filtergraph to be read and sent to the other filters. Syntax of the filtergraph is the same as the one specified by the option graph.

dumpgraph

Dump graph to stderr.

Examples

*

Create a color video stream and play it back with ffplay:

        ffplay -f lavfi -graph "color=c=pink [out0]" dummy

*

As the previous example, but use filename for specifying the graph description, and omit the ``out0'' label:

        ffplay -f lavfi color=c=pink

*

Create three different video test filtered sources and play them:

        ffplay -f lavfi -graph "testsrc [out0]; testsrc,hflip [out1]; testsrc,negate [out2]" test3

*

Read an audio stream from a file using the amovie source and play it back with ffplay:

        ffplay -f lavfi "amovie=test.wav"

*

Read an audio stream and a video stream and play it back with ffplay:

        ffplay -f lavfi "movie=test.avi[out0];amovie=test.wav[out1]"

*

Dump decoded frames to images and closed captions to a file (experimental):

        ffmpeg -f lavfi -i "movie=test.ts[out0+subcc]" -map v frame%08d.png -map s -c copy -f rawvideo subcc.bin

libcdio

Audio-CD input device based on libcdio.

To enable this input device during configuration you need libcdio installed on your system. It requires the configure option "--enable-libcdio".

This device allows playing and grabbing from an Audio-CD.

For example to copy with ffmpeg the entire Audio-CD in /dev/sr0, you may run the command:

        ffmpeg -f libcdio -i /dev/sr0 cd.wav

Options

speed

Set drive reading speed. Default value is 0.

The speed is specified CD-ROM speed units. The speed is set through the libcdio "cdio_cddap_speed_set" function. On many CD-ROM drives, specifying a value too large will result in using the fastest speed.

paranoia_mode

Set paranoia recovery mode flags. It accepts one of the following values:

disable

verify

overlap

neverskip

full

Default value is disable.

For more information about the available recovery modes, consult the paranoia project documentation.

libdc1394

input device, based on libdc1394 and libraw1394.

Requires the configure option "--enable-libdc1394".

openal

The OpenAL input device provides audio capture on all systems with a working OpenAL 1.1 implementation.

To enable this input device during configuration, you need OpenAL headers and libraries installed on your system, and need to configure FFmpeg with "--enable-openal".

OpenAL headers and libraries should be provided as part of your OpenAL implementation, or as an additional download (an

). Depending on your installation you may need to specify additional flags via the "--extra-cflags" and "--extra-ldflags" for allowing the build system to locate the OpenAL headers and libraries.

An incomplete list of OpenAL implementations follows:

Creative

The official Windows implementation, providing hardware acceleration with supported devices and software fallback. See <openal.org>.

OpenAL Soft

Portable, open source (

LGPL

) software implementation. Includes backends for the most common sound APIs on the Windows, Linux, Solaris, and

BSD

operating systems. See <kcat.strangesoft.net/openal.html>.

Apple

OpenAL is part of Core Audio, the official Mac

OS X

Audio interface. See <developer.apple.com/technologies/mac/audio-and-video.html>

This device allows one to capture from an audio input device handled through OpenAL.

You need to specify the name of the device to capture in the provided filename. If the empty string is provided, the device will automatically select the default device. You can get the list of the supported devices by using the option list_devices.

Options

channels

Set the number of channels in the captured audio. Only the values 1 (monaural) and 2 (stereo) are currently supported. Defaults to 2.

sample_size

Set the sample size (in bits) of the captured audio. Only the values 8 and 16 are currently supported. Defaults to 16.

sample_rate

Set the sample rate (in Hz) of the captured audio. Defaults to 44.1k.

list_devices

If set to true, print a list of devices and exit. Defaults to false.

Examples

Print the list of OpenAL supported devices and exit:

        $ ffmpeg -list_devices true -f openal -i dummy out.ogg

Capture from the OpenAL device

via PulseAudio:

        $ ffmpeg -f openal -i 'DR-BT101 via PulseAudio' out.ogg

Capture from the default device (note the empty string '' as filename):

        $ ffmpeg -f openal -i '' out.ogg

Capture from two devices simultaneously, writing to two different files, within the same ffmpeg command:

        $ ffmpeg -f openal -i 'DR-BT101 via PulseAudio' out1.ogg -f openal -i 'ALSA Default' out2.ogg

Note: not all OpenAL implementations support multiple simultaneous capture - try the latest OpenAL Soft if the above does not work.

oss

Open Sound System input device.

The filename to provide to the input device is the device node representing the

input device, and is usually set to /dev/dsp.

For example to grab from /dev/dsp using ffmpeg use the command:

        ffmpeg -f oss -i /dev/dsp /tmp/oss.wav

For more information about

see: <manuals.opensound.com/usersguide/dsp.html>

Options

sample_rate

Set the sample rate in Hz. Default is 48000.

channels

Set the number of channels. Default is 2.

pulse

PulseAudio input device.

To enable this output device you need to configure FFmpeg with "--enable-libpulse".

The filename to provide to the input device is a source device or the string ``default''

To list the PulseAudio source devices and their properties you can invoke the command pactl list sources.

More information about PulseAudio can be found on <www.pulseaudio.org>.

Options

server

Connect to a specific PulseAudio server, specified by an

IP

address. Default server is used when not provided.

name

Specify the application name PulseAudio will use when showing active clients, by default it is the "LIBAVFORMAT_IDENT" string.

stream_name

Specify the stream name PulseAudio will use when showing active streams, by default it is ``record''.

sample_rate

Specify the samplerate in Hz, by default 48kHz is used.

channels

Specify the channels in use, by default 2 (stereo) is set.

frame_size

Specify the number of bytes per frame, by default it is set to 1024.

fragment_size

Specify the minimal buffering fragment in PulseAudio, it will affect the audio latency. By default it is unset.

wallclock

Set the initial

PTS

using the current time. Default is 1.

Examples

Record a stream from default device:

        ffmpeg -f pulse -i default /tmp/pulse.wav

qtkit

QTKit input device.

The filename passed as input is parsed to contain either a device name or index. The device index can also be given by using -video_device_index. A given device index will override any given device name. If the desired device consists of numbers only, use -video_device_index to identify it. The default device will be chosen if an empty string or the device name ``default'' is given. The available devices can be enumerated by using -list_devices.

        ffmpeg -f qtkit -i "0" out.mpg

        
        ffmpeg -f qtkit -video_device_index 0 -i "" out.mpg

        
        ffmpeg -f qtkit -i "default" out.mpg

        
        ffmpeg -f qtkit -list_devices true -i ""

Options

frame_rate

Set frame rate. Default is 30.

list_devices

If set to "true", print a list of devices and exit. Default is "false".

video_device_index

Select the video device by index for devices with the same name (starts at 0).

sndio

sndio input device.

To enable this input device during configuration you need libsndio installed on your system.

The filename to provide to the input device is the device node representing the sndio input device, and is usually set to /dev/audio0.

For example to grab from /dev/audio0 using ffmpeg use the command:

        ffmpeg -f sndio -i /dev/audio0 /tmp/oss.wav

Options

sample_rate

Set the sample rate in Hz. Default is 48000.

channels

Set the number of channels. Default is 2.

video4linux2, v4l2

Video4Linux2 input video device.

``v4l2'' can be used as alias for ``video4linux2''.

If FFmpeg is built with v4l-utils support (by using the "--enable-libv4l2" configure option), it is possible to use it with the "-use_libv4l2" input device option.

The name of the device to grab is a file device node, usually Linux systems tend to automatically create such nodes when the device (e.g. an

webcam) is plugged into the system, and has a name of the kind /dev/videoN, where N is a number associated to the device.

Video4Linux2 devices usually support a limited set of widthxheight sizes and frame rates. You can check which are supported using -list_formats all for Video4Linux2 devices. Some devices, like

cards, support one or more standards. It is possible to list all the supported standards using -list_standards all.

The time base for the timestamps is 1 microsecond. Depending on the kernel version and configuration, the timestamps may be derived from the real time clock (origin at the Unix Epoch) or the monotonic clock (origin usually at boot time, unaffected by

or manual changes to the clock). The -timestamps abs or -ts abs option can be used to force conversion into the real time clock.

Some usage examples of the video4linux2 device with ffmpeg and ffplay:

*

List supported formats for a video4linux2 device:

        ffplay -f video4linux2 -list_formats all /dev/video0

*

Grab and show the input of a video4linux2 device:

        ffplay -f video4linux2 -framerate 30 -video_size hd720 /dev/video0

*

Grab and record the input of a video4linux2 device, leave the frame rate and size as previously set:

        ffmpeg -f video4linux2 -input_format mjpeg -i /dev/video0 out.mpeg

For more information about Video4Linux, check <linuxtv.org>.

Options

standard

Set the standard. Must be the name of a supported standard. To get a list of the supported standards, use the list_standards option.

channel

Set the input channel number. Default to -1, which means using the previously selected channel.

video_size

Set the video frame size. The argument must be a string in the form

WIDTH

x

HEIGHT

or a valid size abbreviation.

pixel_format

Select the pixel format (only valid for raw video input).

input_format

Set the preferred pixel format (for raw video) or a codec name. This option allows one to select the input format, when several are available.

framerate

Set the preferred video frame rate.

list_formats

List available formats (supported pixel formats, codecs, and frame sizes) and exit.

Available values are:

all

Show all available (compressed and non-compressed) formats.

raw

Show only raw video (non-compressed) formats.

compressed

Show only compressed formats.

list_standards

List supported standards and exit.

Available values are:

all

Show all supported standards.

timestamps, ts

Set type of timestamps for grabbed frames.

Available values are:

default

Use timestamps from the kernel.

abs

Use absolute timestamps (wall clock).

mono2abs

Force conversion from monotonic to absolute timestamps.

Default value is "default".

use_libv4l2

Use libv4l2 (v4l-utils) conversion functions. Default is 0.

vfwcap

VfW (Video for Windows) capture input device.

The filename passed as input is the capture driver number, ranging from 0 to 9. You may use ``list'' as filename to print a list of drivers. Any other filename will be interpreted as device number 0.

Options

video_size

Set the video frame size.

framerate

Set the grabbing frame rate. Default value is "ntsc", corresponding to a frame rate of "30000/1001".

x11grab

X11 video input device.

To enable this input device during configuration you need libxcb installed on your system. It will be automatically detected during configuration.

Alternatively, the configure option --enable-x11grab exists for legacy Xlib users.

This device allows one to capture a region of an X11 display.

The filename passed as input has the syntax:

        [<hostname>]:<display_number>.<screen_number>[+<x_offset>,<y_offset>]

hostname:display_number.screen_number specifies the X11 display name of the screen to grab from. hostname can be omitted, and defaults to ``localhost''. The environment variable

contains the default display name.

x_offset and y_offset specify the offsets of the grabbed area with respect to the top-left border of the X11 screen. They default to 0.

Check the X11 documentation (e.g. man X) for more detailed information.

Use the xdpyinfo program for getting basic information about the properties of your X11 display (e.g. grep for ``name'' or ``dimensions'').

For example to grab from :0.0 using ffmpeg:

        ffmpeg -f x11grab -framerate 25 -video_size cif -i :0.0 out.mpg

Grab at position "10,20":

        ffmpeg -f x11grab -framerate 25 -video_size cif -i :0.0+10,20 out.mpg

Options

draw_mouse

Specify whether to draw the mouse pointer. A value of 0 specify not to draw the pointer. Default value is 1.

follow_mouse

Make the grabbed area follow the mouse. The argument can be "centered" or a number of pixels

PIXELS

.

When it is specified with ``centered'', the grabbing region follows the mouse pointer and keeps the pointer at the center of region; otherwise, the region follows only when the mouse pointer reaches within

PIXELS

(greater than zero) to the edge of region.

For example:

        ffmpeg -f x11grab -follow_mouse centered -framerate 25 -video_size cif -i :0.0 out.mpg

To follow only when the mouse pointer reaches within 100 pixels to edge:

        ffmpeg -f x11grab -follow_mouse 100 -framerate 25 -video_size cif -i :0.0 out.mpg

framerate

Set the grabbing frame rate. Default value is "ntsc", corresponding to a frame rate of "30000/1001".

show_region

Show grabbed region on screen.

If show_region is specified with 1, then the grabbing region will be indicated on screen. With this option, it is easy to know what is being grabbed if only a portion of the screen is grabbed.

region_border

Set the region border thickness if -show_region 1 is used. Range is 1 to 128 and default is 3 (XCB-based x11grab only).

For example:

        ffmpeg -f x11grab -show_region 1 -framerate 25 -video_size cif -i :0.0+10,20 out.mpg

With follow_mouse:

        ffmpeg -f x11grab -follow_mouse centered -show_region 1 -framerate 25 -video_size cif -i :0.0 out.mpg

video_size

Set the video frame size. Default value is "vga".

use_shm

Use the MIT-SHM extension for shared memory. Default value is 1. It may be necessary to disable it for remote displays (legacy x11grab only).

grab_x grab_y AVOption

The syntax is:

        -grab_x <x_offset> -grab_y <y_offset>

Set the grabbing region coordinates. They are expressed as offset from the top left corner of the X11 window. The default value is 0.

OUTPUT DEVICES

Output devices are configured elements in FFmpeg that can write multimedia data to an output device attached to your system.

When you configure your FFmpeg build, all the supported output devices are enabled by default. You can list all available ones using the configure option ``--list-outdevs''.

You can disable all the output devices using the configure option ``--disable-outdevs'', and selectively enable an output device using the option "--enable-outdev=

``, or you can disable a particular input device using the option ''--disable-outdev=".

The option ``-devices'' of the ff* tools will display the list of enabled output devices.

A description of the currently available output devices follows.

alsa

(Advanced Linux Sound Architecture) output device.

Examples

*

Play a file on default

ALSA

device:

        ffmpeg -i INPUT -f alsa default

*

Play a file on soundcard 1, audio device 7:

        ffmpeg -i INPUT -f alsa hw:1,7

caca

output device.

This output device allows one to show a video stream in

window. Only one window is allowed per application, so you can have only one instance of this output device in an application.

To enable this output device you need to configure FFmpeg with "--enable-libcaca". libcaca is a graphics library that outputs text instead of pixels.

For more information about libcaca, check: <caca.zoy.org/wiki/libcaca>

Options

window_title

Set the

CACA

window title, if not specified default to the filename specified for the output device.

window_size

Set the

CACA

window size, can be a string of the form widthxheight or a video size abbreviation. If not specified it defaults to the size of the input video.

driver

Set display driver.

algorithm

Set dithering algorithm. Dithering is necessary because the picture being rendered has usually far more colours than the available palette. The accepted values are listed with "-list_dither algorithms".

antialias

Set antialias method. Antialiasing smoothens the rendered image and avoids the commonly seen staircase effect. The accepted values are listed with "-list_dither antialiases".

charset

Set which characters are going to be used when rendering text. The accepted values are listed with "-list_dither charsets".

color

Set color to be used when rendering text. The accepted values are listed with "-list_dither colors".

list_drivers

If set to true, print a list of available drivers and exit.

list_dither

List available dither options related to the argument. The argument must be one of "algorithms", "antialiases", "charsets", "colors".

Examples

*

The following command shows the ffmpeg output is an

CACA

window, forcing its size to 80x25:

        ffmpeg -i INPUT -vcodec rawvideo -pix_fmt rgb24 -window_size 80x25 -f caca -

*

Show the list of available drivers and exit:

        ffmpeg -i INPUT -pix_fmt rgb24 -f caca -list_drivers true -

*

Show the list of available dither colors and exit:

        ffmpeg -i INPUT -pix_fmt rgb24 -f caca -list_dither colors -

decklink

The decklink output device provides playback capabilities for Blackmagic DeckLink devices.

To enable this output device, you need the Blackmagic DeckLink

and you need to configure with the appropriate "--extra-cflags" and "--extra-ldflags". On Windows, you need to run the files through widl.

DeckLink is very picky about the formats it supports. Pixel format is always uyvy422, framerate and video size must be determined for your device with -list_formats 1. Audio sample rate is always 48 kHz.

Options

list_devices

If set to true, print a list of devices and exit. Defaults to false.

list_formats

If set to true, print a list of supported formats and exit. Defaults to false.

preroll

Amount of time to preroll video in seconds. Defaults to 0.5.

Examples

*

List output devices:

        ffmpeg -i test.avi -f decklink -list_devices 1 dummy

*

List supported formats:

        ffmpeg -i test.avi -f decklink -list_formats 1 'DeckLink Mini Monitor'

*

Play video clip:

        ffmpeg -i test.avi -f decklink -pix_fmt uyvy422 'DeckLink Mini Monitor'

*

Play video clip with non-standard framerate or video size:

        ffmpeg -i test.avi -f decklink -pix_fmt uyvy422 -s 720x486 -r 24000/1001 'DeckLink Mini Monitor'

fbdev

Linux framebuffer output device.

The Linux framebuffer is a graphic hardware-independent abstraction layer to show graphics on a computer monitor, typically on the console. It is accessed through a file device node, usually /dev/fb0.

For more detailed information read the file Documentation/fb/framebuffer.txt included in the Linux source tree.

Options

xoffset

yoffset

Set x/y coordinate of top left corner. Default is 0.

Examples

Play a file on framebuffer device /dev/fb0. Required pixel format depends on current framebuffer settings.

        ffmpeg -re -i INPUT -vcodec rawvideo -pix_fmt bgra -f fbdev /dev/fb0

See also <linux-fbdev.sourceforge.net>, and fbset(1).

opengl

OpenGL output device.

To enable this output device you need to configure FFmpeg with "--enable-opengl".

This output device allows one to render to OpenGL context. Context may be provided by application or default

window is created.

When device renders to external context, application must implement handlers for following messages: "AV_DEV_TO_APP_CREATE_WINDOW_BUFFER" - create OpenGL context on current thread. "AV_DEV_TO_APP_PREPARE_WINDOW_BUFFER" - make OpenGL context current. "AV_DEV_TO_APP_DISPLAY_WINDOW_BUFFER" - swap buffers. "AV_DEV_TO_APP_DESTROY_WINDOW_BUFFER" - destroy OpenGL context. Application is also required to inform a device about current resolution by sending "AV_APP_TO_DEV_WINDOW_SIZE" message.

Options

background

Set background color. Black is a default.

no_window

Disables default

SDL

window when set to non-zero value. Application must provide OpenGL context and both "window_size_cb" and "window_swap_buffers_cb" callbacks when set.

window_title

Set the

SDL

window title, if not specified default to the filename specified for the output device. Ignored when no_window is set.

window_size

Set preferred window size, can be a string of the form widthxheight or a video size abbreviation. If not specified it defaults to the size of the input video, downscaled according to the aspect ratio. Mostly usable when no_window is not set.

Examples

Play a file on

window using OpenGL rendering:

        ffmpeg  -i INPUT -f opengl "window title"

oss

(Open Sound System) output device.

pulse

PulseAudio output device.

To enable this output device you need to configure FFmpeg with "--enable-libpulse".

More information about PulseAudio can be found on <www.pulseaudio.org>

Options

server

Connect to a specific PulseAudio server, specified by an

IP

address. Default server is used when not provided.

name

Specify the application name PulseAudio will use when showing active clients, by default it is the "LIBAVFORMAT_IDENT" string.

stream_name

Specify the stream name PulseAudio will use when showing active streams, by default it is set to the specified output name.

device

Specify the device to use. Default device is used when not provided. List of output devices can be obtained with command pactl list sinks.

buffer_size

buffer_duration

Control the size and duration of the PulseAudio buffer. A small buffer gives more control, but requires more frequent updates.

buffer_size specifies size in bytes while buffer_duration specifies duration in milliseconds.

When both options are provided then the highest value is used (duration is recalculated to bytes using stream parameters). If they are set to 0 (which is default), the device will use the default PulseAudio duration value. By default PulseAudio set buffer duration to around 2 seconds.

prebuf

Specify pre-buffering size in bytes. The server does not start with playback before at least prebuf bytes are available in the buffer. By default this option is initialized to the same value as buffer_size or buffer_duration (whichever is bigger).

minreq

Specify minimum request size in bytes. The server does not request less than minreq bytes from the client, instead waits until the buffer is free enough to request more bytes at once. It is recommended to not set this option, which will initialize this to a value that is deemed sensible by the server.

Examples

Play a file on default device on default server:

        ffmpeg  -i INPUT -f pulse "stream name"

sdl

(Simple DirectMedia Layer) output device.

This output device allows one to show a video stream in an

window. Only one window is allowed per application, so you can have only one instance of this output device in an application.

To enable this output device you need libsdl installed on your system when configuring your build.

For more information about

check: <www.libsdl.org>

Options

window_title

Set the

SDL

window title, if not specified default to the filename specified for the output device.

icon_title

Set the name of the iconified

SDL

window, if not specified it is set to the same value of window_title.

window_size

Set the

SDL

window size, can be a string of the form widthxheight or a video size abbreviation. If not specified it defaults to the size of the input video, downscaled according to the aspect ratio.

window_fullscreen

Set fullscreen mode when non-zero value is provided. Default value is zero.

Interactive commands

The window created by the device can be controlled through the following interactive commands.

q,

ESC

Quit the device immediately.

Examples

The following command shows the ffmpeg output is an

window, forcing its size to the qcif format:

        ffmpeg -i INPUT -vcodec rawvideo -pix_fmt yuv420p -window_size qcif -f sdl "SDL output"

sndio

sndio audio output device.

xv

(XVideo) output device.

This output device allows one to show a video stream in a X Window System window.

Options

display_name

Specify the hardware display name, which determines the display and communications domain to be used.

The display name or

DISPLAY

environment variable can be a string in the format hostname[:number[.screen_number]].

hostname specifies the name of the host machine on which the display is physically attached. number specifies the number of the display server on that host machine. screen_number specifies the screen to be used on that server.

If unspecified, it defaults to the value of the

DISPLAY

environment variable.

For example, "dual-headed:0.1" would specify screen 1 of display 0 on the machine named ``dual-headed''.

Check the X11 specification for more detailed information about the display name format.

window_id

When set to non-zero value then device doesn't create new window, but uses existing one with provided window_id. By default this options is set to zero and device creates its own window.

window_size

Set the created window size, can be a string of the form widthxheight or a video size abbreviation. If not specified it defaults to the size of the input video. Ignored when window_id is set.

window_x

window_y

Set the X and Y window offsets for the created window. They are both set to 0 by default. The values may be ignored by the window manager. Ignored when window_id is set.

window_title

Set the window title, if not specified default to the filename specified for the output device. Ignored when window_id is set.

For more information about XVideo see <www.x.org>.

Examples

*

Decode, display and encode video input with ffmpeg at the same time:

        ffmpeg -i INPUT OUTPUT -f xv display

*

Decode and display the input video to multiple X11 windows:

        ffmpeg -i INPUT -f xv normal -vf negate -f xv negated

SEE ALSO

ffmpeg(1), ffplay(1), ffprobe(1), ffserver(1), libavdevice(3)

AUTHORS

The FFmpeg developers.

For details about the authorship, see the Git history of the project (git://source.ffmpeg.org/ffmpeg e.g. by typing the command git log in the FFmpeg source directory, or browsing the online repository at <source.ffmpeg.org>.

Maintainers for the specific components are listed in the file

in the source code tree.