@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 @file{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 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

 @file{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 -vframes 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

 @file{jack_connect} and @file{jack_disconnect} programs, or do it
 through a graphical interface, for example with @file{qjackctl}.
 

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

 @file{jack_lsp}.
 

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

 with @file{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 libdc1394
 
 IIDC1394 input device, based on libdc1394 and libraw1394.
 
 @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 @file{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 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 @file{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 @file{dov4l} for Video4Linux
 devices and the command @file{v4l-info} for Video4Linux2 devices.

 
 If the size for the device is set to 0x0, the input device will
 try to autodetect 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.
 
 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, autoadjust size.

 ffplay -f video4linux2 /dev/video0
 

 # Grab and record the input of a video4linux2 device, autoadjust 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
 
 @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
 ommitted, 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 @file{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 @file{ffmpeg}:
 @example
 ffmpeg -f x11grab -r 25 -s cif -i :0.0 out.mpg
 

 # Grab at position 10,20.

 ffmpeg -f x11grab -25 -s cif -i :0.0+10,20 out.mpg
 @end example
 
 @c man end INPUT DEVICES