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

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:

     hw:CARD[,DEV[,SUBDEV]]

where the DEV and SUBDEV components are optional.

The three arguments (in order: CARD,DEV,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 /proc/asound/cards and /proc/asound/devices.

For example to capture with ffmpeg from an ALSA device with card id 0, you may run the command:

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

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

bktr
====

BSD video input device.

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 TYPE can be either AUDIO or VIDEO, and NAME is the device's 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 same name (starts at 0, defaults to 0).

audio_device_number
     Set audio device number for devices with 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 http://msdn.microsoft.com/en-us/library/windows/desktop/dd377582(v=vs.85).aspx

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"

dv1394
======

Linux DV 1394 input device.

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.

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

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

You can take a single screenshot image with the command:

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

See also http://linux-fbdev.sourceforge.net/, and fbset(1).

iec61883
========

FireWire DV/HDV 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 IEEE1394 (FireWire), using libiec61883 and the new Linux FireWire stack (juju). This is the default DV/HDV 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 maxiumum 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
====

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

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

Follows an example which shows how to capture a JACK 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: http://jackaudio.org/

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.

     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.

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]"

libdc1394
=========

IIDC1394 input device, based on libdc1394 and libraw1394.

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 SDK). 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 http://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 http://kcat.strangesoft.net/openal.html.

Apple
     OpenAL is part of Core Audio, the official Mac OS X Audio interface. See http://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 DR-BT101 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 OSS 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 OSS see: http://manuals.opensound.com/usersguide/dsp.html

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 http://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.

Examples
--------

Record a stream from default device:

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

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

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 USB 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 TV 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 NTP 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:

  * 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 http://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 WIDTHxHEIGHT 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.

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.

x11grab
=======

X11 video input device.

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 DISPLAY 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 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 :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.

     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.