@chapter Input Devices

 @c man begin INPUT DEVICES
 

 Input devices are configured elements in FFmpeg which allow to access

 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=@var{INDEV}", or you can disable a particular
 input device using the option "--disable-indev=@var{INDEV}".
 
 The option "-formats" of the ff* tools will display the list of
 supported input devices (amongst the demuxers).
 
 A description of the currently available input devices follows.
 
 @section alsa
 
 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 ALSA device. The name of the

 device to capture has to be an ALSA card identifier.
 
 An ALSA identifier has the syntax:
 @example
 hw:@var{CARD}[,@var{DEV}[,@var{SUBDEV}]]
 @end example
 
 where the @var{DEV} and @var{SUBDEV} components are optional.
 
 The three arguments (in order: @var{CARD},@var{DEV},@var{SUBDEV})
 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 @file{/proc/asound/cards} and @file{/proc/asound/devices}.
 

 For example to capture with @command{ffmpeg} from an ALSA device with

 card id 0, you may run the command:
 @example
 ffmpeg -f alsa -i hw:0 alsaout.wav
 @end example
 
 For more information see:
 @url{http://www.alsa-project.org/alsa-doc/alsa-lib/pcm.html}
 
 @section bktr
 
 BSD video input device.
 

 @section dshow
 
 Windows DirectShow input device.
 
 DirectShow support is enabled when FFmpeg is built with mingw-w64.
 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:
 
 @example
 @var{TYPE}=@var{NAME}[:@var{TYPE}=@var{NAME}]
 @end example
 
 where @var{TYPE} can be either @var{audio} or @var{video},
 and @var{NAME} is the device's name.
 
 @subsection 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.
 
 @table @option
 
 @item video_size
 Set the video size in the captured video.
 
 @item framerate
 Set the framerate in the captured video.
 
 @item sample_rate
 Set the sample rate (in Hz) of the captured audio.
 
 @item sample_size
 Set the sample size (in bits) of the captured audio.
 
 @item channels
 Set the number of channels in the captured audio.
 
 @item list_devices
 If set to @option{true}, print a list of devices and exit.
 
 @item list_options
 If set to @option{true}, print a list of selected device's options
 and exit.
 

 @item video_device_number
 Set video device number for devices with same name (starts at 0,
 defaults to 0).
 
 @item audio_device_number
 Set audio device number for devices with same name (starts at 0,
 defaults to 0).
 

 @end table
 
 @subsection Examples
 
 @itemize
 
 @item
 Print the list of DirectShow supported devices and exit:
 @example
 $ ffmpeg -list_devices true -f dshow -i dummy
 @end example
 
 @item
 Open video device @var{Camera}:
 @example
 $ ffmpeg -f dshow -i video="Camera"
 @end example
 
 @item

 Open second video device with name @var{Camera}:
 @example
 $ ffmpeg -f dshow -video_device_number 1 -i video="Camera"
 @end example
 
 @item

 Open video device @var{Camera} and audio device @var{Microphone}:
 @example
 $ ffmpeg -f dshow -i video="Camera":audio="Microphone"
 @end example
 
 @item
 Print the list of supported options in selected device and exit:
 @example
 $ ffmpeg -list_options true -f dshow -i video="Camera"
 @end example
 
 @end itemize
 

 @section dv1394
 
 Linux DV 1394 input device.
 

 @section 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
 @file{/dev/fb0}.
 
 For more detailed information read the file
 Documentation/fb/framebuffer.txt included in the Linux source tree.
 

 To record from the framebuffer device @file{/dev/fb0} with

 @command{ffmpeg}:

 @example
 ffmpeg -f fbdev -r 10 -i /dev/fb0 out.avi
 @end example
 
 You can take a single screenshot image with the command:
 @example

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

 @end example
 
 See also @url{http://linux-fbdev.sourceforge.net/}, and fbset(1).
 

 @section jack
 

 JACK input device.

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

 A JACK input device creates one or more JACK writable clients, one for

 each audio channel, with name @var{client_name}:input_@var{N}, where
 @var{client_name} is the name provided by the application, and @var{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 JACK readable clients, you need to
 connect them to one or more JACK writable clients.

 To connect or disconnect JACK clients you can use the @command{jack_connect}
 and @command{jack_disconnect} programs, or do it through a graphical interface,
 for example with @command{qjackctl}.

 To list the JACK clients and their properties you can invoke the command

 @command{jack_lsp}.

 Follows an example which shows how to capture a JACK readable client

 with @command{ffmpeg}.

 @example

 # 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
 @end example
 
 For more information read:
 @url{http://jackaudio.org/}
 

 @section 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 @option{graph}.
 
 @subsection Options
 
 @table @option
 
 @item graph
 Specify the filtergraph to use as input. Each video open output must be
 labelled by a unique string of the form "out@var{N}", where @var{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.

 
 If not specified defaults to the filename specified for the input
 device.
 @end table
 
 @subsection Examples
 
 @itemize
 @item

 Create a color video stream and play it back with @command{ffplay}:

 @example
 ffplay -f lavfi -graph "color=pink [out0]" dummy
 @end example
 
 @item
 As the previous example, but use filename for specifying the graph
 description, and omit the "out0" label:
 @example
 ffplay -f lavfi color=pink
 @end example
 
 @item
 Create three different video test filtered sources and play them:
 @example
 ffplay -f lavfi -graph "testsrc [out0]; testsrc,hflip [out1]; testsrc,negate [out2]" test3
 @end example

 
 @item
 Read an audio stream from a file using the amovie source and play it

 back with @command{ffplay}:

 @example
 ffplay -f lavfi "amovie=test.wav"
 @end example
 
 @item
 Read an audio stream and a video stream and play it back with

 @command{ffplay}:

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

 @end itemize
 

 @section libdc1394
 
 IIDC1394 input device, based on libdc1394 and libraw1394.
 

 @section 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 @code{--enable-openal}.
 
 OpenAL headers and libraries should be provided as part of your OpenAL
 implementation, or as an additional download (an SDK). Depending on your
 installation you may need to specify additional flags via the
 @code{--extra-cflags} and @code{--extra-ldflags} for allowing the build
 system to locate the OpenAL headers and libraries.
 
 An incomplete list of OpenAL implementations follows:
 
 @table @strong
 @item Creative
 The official Windows implementation, providing hardware acceleration
 with supported devices and software fallback.
 See @url{http://openal.org/}.
 @item 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 @url{http://kcat.strangesoft.net/openal.html}.
 @item Apple
 OpenAL is part of Core Audio, the official Mac OS X Audio interface.
 See @url{http://developer.apple.com/technologies/mac/audio-and-video.html}
 @end table
 
 This device allows 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 @var{list_devices}.
 
 @subsection Options
 
 @table @option
 
 @item channels
 Set the number of channels in the captured audio. Only the values
 @option{1} (monaural) and @option{2} (stereo) are currently supported.
 Defaults to @option{2}.
 
 @item sample_size
 Set the sample size (in bits) of the captured audio. Only the values
 @option{8} and @option{16} are currently supported. Defaults to
 @option{16}.
 
 @item sample_rate
 Set the sample rate (in Hz) of the captured audio.
 Defaults to @option{44.1k}.
 
 @item list_devices
 If set to @option{true}, print a list of devices and exit.
 Defaults to @option{false}.
 
 @end table
 
 @subsection Examples
 
 Print the list of OpenAL supported devices and exit:
 @example
 $ ffmpeg -list_devices true -f openal -i dummy out.ogg
 @end example
 
 Capture from the OpenAL device @file{DR-BT101 via PulseAudio}:
 @example
 $ ffmpeg -f openal -i 'DR-BT101 via PulseAudio' out.ogg
 @end example
 
 Capture from the default device (note the empty string '' as filename):
 @example
 $ ffmpeg -f openal -i '' out.ogg
 @end example
 
 Capture from two devices simultaneously, writing to two different files,

 within the same @command{ffmpeg} command:

 @example
 $ ffmpeg -f openal -i 'DR-BT101 via PulseAudio' out1.ogg -f openal -i 'ALSA Default' out2.ogg
 @end example
 Note: not all OpenAL implementations support multiple simultaneous capture -
 try the latest OpenAL Soft if the above does not work.
 

 @section oss
 
 Open Sound System input device.
 
 The filename to provide to the input device is the device node
 representing the OSS input device, and is usually set to

 @file{/dev/dsp}.

 For example to grab from @file{/dev/dsp} using @command{ffmpeg} use the

 command:
 @example
 ffmpeg -f oss -i /dev/dsp /tmp/oss.wav
 @end example
 
 For more information about OSS see:
 @url{http://manuals.opensound.com/usersguide/dsp.html}
 

 @section pulse
 
 pulseaudio input device.
 
 To enable this input device during configuration you need libpulse-simple
 installed in your system.
 
 The filename to provide to the input device is a source device or the
 string "default"
 
 To list the pulse source devices and their properties you can invoke

 the command @command{pactl list sources}.

 
 @example

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

 @end example
 
 @subsection @var{server} AVOption
 
 The syntax is:
 @example
 -server @var{server name}
 @end example
 
 Connects to a specific server.
 
 @subsection @var{name} AVOption
 
 The syntax is:
 @example
 -name @var{application name}
 @end example
 
 Specify the application name pulse will use when showing active clients,

 by default it is the LIBAVFORMAT_IDENT string

 
 @subsection @var{stream_name} AVOption
 
 The syntax is:
 @example
 -stream_name @var{stream name}
 @end example
 
 Specify the stream name pulse will use when showing active streams,
 by default it is "record"
 
 @subsection @var{sample_rate} AVOption
 
 The syntax is:
 @example
 -sample_rate @var{samplerate}
 @end example
 
 Specify the samplerate in Hz, by default 48kHz is used.
 
 @subsection @var{channels} AVOption
 
 The syntax is:
 @example
 -channels @var{N}
 @end example
 
 Specify the channels in use, by default 2 (stereo) is set.
 
 @subsection @var{frame_size} AVOption
 
 The syntax is:
 @example
 -frame_size @var{bytes}
 @end example
 
 Specify the number of byte per frame, by default it is set to 1024.
 
 @subsection @var{fragment_size} AVOption
 
 The syntax is:
 @example
 -fragment_size @var{bytes}
 @end example
 
 Specify the minimal buffering fragment in pulseaudio, it will affect the
 audio latency. By default it is unset.
 

 @section 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
 @file{/dev/audio0}.
 

 For example to grab from @file{/dev/audio0} using @command{ffmpeg} use the

 command:
 @example
 ffmpeg -f sndio -i /dev/audio0 /tmp/oss.wav
 @end example
 

 @section video4linux and video4linux2
 
 Video4Linux and Video4Linux2 input video devices.
 
 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 USB webcam) is plugged into the system, and has a name of the

 kind @file{/dev/video@var{N}}, where @var{N} is a number associated to
 the device.
 
 Video4Linux and Video4Linux2 devices only support a limited set of
 @var{width}x@var{height} sizes and framerates. You can check which are

 supported for example with the command @command{dov4l} for Video4Linux

 devices and using @command{-list_formats all} for Video4Linux2 devices.

 
 If the size for the device is set to 0x0, the input device will

 try to auto-detect the size to use.

 Only for the video4linux2 device, if the frame rate is set to 0/0 the
 input device will use the frame rate value already set in the driver.

 
 Video4Linux support is deprecated since Linux 2.6.30, and will be
 dropped in later versions.
 

 Note that if FFmpeg is build with v4l-utils support ("--enable-libv4l2"
 option), it will always be used.
 

 Follow some usage examples of the video4linux devices with the ff*
 tools.
 @example

 # Grab and show the input of a video4linux device, frame rate is set
 # to the default of 25/1.

 ffplay -s 320x240 -f video4linux /dev/video0
 

 # Grab and show the input of a video4linux2 device, auto-adjust size.

 ffplay -f video4linux2 /dev/video0
 

 # Grab and record the input of a video4linux2 device, auto-adjust size,

 # frame rate value defaults to 0/0 so it is read from the video4linux2
 # driver.

 ffmpeg -f video4linux2 -i /dev/video0 out.mpeg
 @end example
 

 "v4l" and "v4l2" can be used as aliases for the respective "video4linux" and

 "video4linux2".
 

 @section 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.
 

 @section x11grab
 
 X11 video input device.
 
 This device allows to capture a region of an X11 display.
 

 The filename passed as input has the syntax:

 @example
 [@var{hostname}]:@var{display_number}.@var{screen_number}[+@var{x_offset},@var{y_offset}]
 @end example
 
 @var{hostname}:@var{display_number}.@var{screen_number} specifies the

 X11 display name of the screen to grab from. @var{hostname} can be

 omitted, and defaults to "localhost". The environment variable

 @env{DISPLAY} contains the default display name.
 
 @var{x_offset} and @var{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 @command{dpyinfo} program for getting basic information about the

 properties of your X11 display (e.g. grep for "name" or "dimensions").

 For example to grab from @file{:0.0} using @command{ffmpeg}:

 @example
 ffmpeg -f x11grab -r 25 -s cif -i :0.0 out.mpg
 

 # Grab at position 10,20.

 ffmpeg -f x11grab -r 25 -s cif -i :0.0+10,20 out.mpg
 @end example
 
 @subsection @var{follow_mouse} AVOption
 
 The syntax is:
 @example
 -follow_mouse centered|@var{PIXELS}
 @end example
 
 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 @var{PIXELS} (greater than
 zero) to the edge of region.
 
 For example:
 @example
 ffmpeg -f x11grab -follow_mouse centered -r 25 -s cif -i :0.0 out.mpg
 
 # Follows only when the mouse pointer reaches within 100 pixels to edge
 ffmpeg -f x11grab -follow_mouse 100 -r 25 -s cif -i :0.0 out.mpg

 @end example
 

 @subsection @var{show_region} AVOption
 
 The syntax is:
 @example
 -show_region 1
 @end example
 
 If @var{show_region} AVOption is specified with @var{1}, then the grabbing
 region will be indicated on screen. With this option, it's easy to know what is
 being grabbed if only a portion of the screen is grabbed.
 
 For example:
 @example
 ffmpeg -f x11grab -show_region 1 -r 25 -s cif -i :0.0+10,20 out.mpg
 
 # With follow_mouse
 ffmpeg -f x11grab -follow_mouse centered -show_region 1  -r 25 -s cif -i :0.0 out.mpg

 @end example
 
 @c man end INPUT DEVICES