533 lines
15 KiB
Plaintext
533 lines
15 KiB
Plaintext
@chapter Input Devices
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@c man begin INPUT DEVICES
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Input devices are configured elements in FFmpeg which allow to access
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the data coming from a multimedia device attached to your system.
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When you configure your FFmpeg build, all the supported input devices
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are enabled by default. You can list all available ones using the
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configure option "--list-indevs".
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You can disable all the input devices using the configure option
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"--disable-indevs", and selectively enable an input device using the
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option "--enable-indev=@var{INDEV}", or you can disable a particular
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input device using the option "--disable-indev=@var{INDEV}".
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The option "-formats" of the ff* tools will display the list of
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supported input devices (amongst the demuxers).
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A description of the currently available input devices follows.
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@section alsa
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ALSA (Advanced Linux Sound Architecture) input device.
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To enable this input device during configuration you need libasound
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installed on your system.
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This device allows capturing from an ALSA device. The name of the
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device to capture has to be an ALSA card identifier.
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An ALSA identifier has the syntax:
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@example
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hw:@var{CARD}[,@var{DEV}[,@var{SUBDEV}]]
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@end example
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where the @var{DEV} and @var{SUBDEV} components are optional.
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The three arguments (in order: @var{CARD},@var{DEV},@var{SUBDEV})
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specify card number or identifier, device number and subdevice number
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(-1 means any).
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To see the list of cards currently recognized by your system check the
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files @file{/proc/asound/cards} and @file{/proc/asound/devices}.
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For example to capture with @file{ffmpeg} from an ALSA device with
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card id 0, you may run the command:
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@example
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ffmpeg -f alsa -i hw:0 alsaout.wav
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@end example
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For more information see:
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@url{http://www.alsa-project.org/alsa-doc/alsa-lib/pcm.html}
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@section bktr
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BSD video input device.
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@section dshow
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Windows DirectShow input device.
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DirectShow support is enabled when FFmpeg is built with mingw-w64.
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Currently only audio and video devices are supported.
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Multiple devices may be opened as separate inputs, but they may also be
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opened on the same input, which should improve synchronism between them.
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The input name should be in the format:
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@example
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@var{TYPE}=@var{NAME}[:@var{TYPE}=@var{NAME}]
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@end example
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where @var{TYPE} can be either @var{audio} or @var{video},
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and @var{NAME} is the device's name.
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@subsection Options
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If no options are specified, the device's defaults are used.
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If the device does not support the requested options, it will
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fail to open.
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@table @option
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@item video_size
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Set the video size in the captured video.
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@item framerate
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Set the framerate in the captured video.
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@item sample_rate
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Set the sample rate (in Hz) of the captured audio.
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@item sample_size
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Set the sample size (in bits) of the captured audio.
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@item channels
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Set the number of channels in the captured audio.
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@item list_devices
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If set to @option{true}, print a list of devices and exit.
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@item list_options
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If set to @option{true}, print a list of selected device's options
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and exit.
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@end table
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@subsection Examples
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@itemize
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@item
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Print the list of DirectShow supported devices and exit:
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@example
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$ ffmpeg -list_devices true -f dshow -i dummy
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@end example
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@item
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Open video device @var{Camera}:
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@example
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$ ffmpeg -f dshow -i video="Camera"
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@end example
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@item
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Open video device @var{Camera} and audio device @var{Microphone}:
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@example
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$ ffmpeg -f dshow -i video="Camera":audio="Microphone"
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@end example
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@item
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Print the list of supported options in selected device and exit:
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@example
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$ ffmpeg -list_options true -f dshow -i video="Camera"
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@end example
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@end itemize
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@section dv1394
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Linux DV 1394 input device.
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@section fbdev
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Linux framebuffer input device.
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The Linux framebuffer is a graphic hardware-independent abstraction
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layer to show graphics on a computer monitor, typically on the
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console. It is accessed through a file device node, usually
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@file{/dev/fb0}.
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For more detailed information read the file
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Documentation/fb/framebuffer.txt included in the Linux source tree.
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To record from the framebuffer device @file{/dev/fb0} with
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@file{ffmpeg}:
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@example
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ffmpeg -f fbdev -r 10 -i /dev/fb0 out.avi
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@end example
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You can take a single screenshot image with the command:
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@example
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ffmpeg -f fbdev -vframes 1 -r 1 -i /dev/fb0 screenshot.jpeg
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@end example
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See also @url{http://linux-fbdev.sourceforge.net/}, and fbset(1).
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@section jack
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JACK input device.
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To enable this input device during configuration you need libjack
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installed on your system.
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A JACK input device creates one or more JACK writable clients, one for
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each audio channel, with name @var{client_name}:input_@var{N}, where
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@var{client_name} is the name provided by the application, and @var{N}
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is a number which identifies the channel.
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Each writable client will send the acquired data to the FFmpeg input
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device.
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Once you have created one or more JACK readable clients, you need to
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connect them to one or more JACK writable clients.
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To connect or disconnect JACK clients you can use the
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@file{jack_connect} and @file{jack_disconnect} programs, or do it
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through a graphical interface, for example with @file{qjackctl}.
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To list the JACK clients and their properties you can invoke the command
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@file{jack_lsp}.
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Follows an example which shows how to capture a JACK readable client
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with @file{ffmpeg}.
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@example
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# Create a JACK writable client with name "ffmpeg".
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$ ffmpeg -f jack -i ffmpeg -y out.wav
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# Start the sample jack_metro readable client.
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$ jack_metro -b 120 -d 0.2 -f 4000
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# List the current JACK clients.
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$ jack_lsp -c
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system:capture_1
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system:capture_2
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system:playback_1
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system:playback_2
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ffmpeg:input_1
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metro:120_bpm
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# Connect metro to the ffmpeg writable client.
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$ jack_connect metro:120_bpm ffmpeg:input_1
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@end example
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For more information read:
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@url{http://jackaudio.org/}
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@section lavfi
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Libavfilter input virtual device.
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This input device reads data from the open output pads of a libavfilter
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filtergraph.
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For each filtergraph open output, the input device will create a
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corresponding stream which is mapped to the generated output. Currently
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only video data is supported. The filtergraph is specified through the
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option @option{graph}.
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To enable this input device, you need to configure your build with
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@code{--enable-libavfilter}.
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@subsection Options
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@table @option
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@item graph
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Specify the filtergraph to use as input. Each video open output must be
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labelled by a unique string of the form "out@var{N}", where @var{N} is a
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number starting from 0 corresponding to the mapped input stream
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generated by the device.
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The first unlabelled output is automatically assigned to the "out0"
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label, but all the others need to be specified explicitely.
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If not specified defaults to the filename specified for the input
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device.
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@end table
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@subsection Examples
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@itemize
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@item
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Create a color video stream and play it back with @file{ffplay}:
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@example
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ffplay -f lavfi -graph "color=pink [out0]" dummy
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@end example
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@item
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As the previous example, but use filename for specifying the graph
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description, and omit the "out0" label:
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@example
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ffplay -f lavfi color=pink
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@end example
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@item
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Create three different video test filtered sources and play them:
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@example
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ffplay -f lavfi -graph "testsrc [out0]; testsrc,hflip [out1]; testsrc,negate [out2]" test3
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@end example
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@item
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Read an audio stream from a file using the amovie source and play it
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back with @file{ffplay}:
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@example
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ffplay -f lavfi "amovie=test.wav"
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@end example
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@item
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Read an audio stream and a video stream and play it back with
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@file{ffplay}:
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@example
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ffplay -f lavfi "movie=test.avi[out0];amovie=test.wav[out1]"
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@end example
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@end itemize
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@section libdc1394
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IIDC1394 input device, based on libdc1394 and libraw1394.
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@section openal
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The OpenAL input device provides audio capture on all systems with a
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working OpenAL 1.1 implementation.
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To enable this input device during configuration, you need OpenAL
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headers and libraries installed on your system, and need to configure
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FFmpeg with @code{--enable-openal}.
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OpenAL headers and libraries should be provided as part of your OpenAL
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implementation, or as an additional download (an SDK). Depending on your
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installation you may need to specify additional flags via the
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@code{--extra-cflags} and @code{--extra-ldflags} for allowing the build
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system to locate the OpenAL headers and libraries.
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An incomplete list of OpenAL implementations follows:
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@table @strong
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@item Creative
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The official Windows implementation, providing hardware acceleration
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with supported devices and software fallback.
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See @url{http://openal.org/}.
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@item OpenAL Soft
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Portable, open source (LGPL) software implementation. Includes
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backends for the most common sound APIs on the Windows, Linux,
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Solaris, and BSD operating systems.
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See @url{http://kcat.strangesoft.net/openal.html}.
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@item Apple
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OpenAL is part of Core Audio, the official Mac OS X Audio interface.
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See @url{http://developer.apple.com/technologies/mac/audio-and-video.html}
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@end table
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This device allows to capture from an audio input device handled
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through OpenAL.
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You need to specify the name of the device to capture in the provided
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filename. If the empty string is provided, the device will
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automatically select the default device. You can get the list of the
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supported devices by using the option @var{list_devices}.
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@subsection Options
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@table @option
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@item channels
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Set the number of channels in the captured audio. Only the values
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@option{1} (monaural) and @option{2} (stereo) are currently supported.
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Defaults to @option{2}.
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@item sample_size
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Set the sample size (in bits) of the captured audio. Only the values
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@option{8} and @option{16} are currently supported. Defaults to
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@option{16}.
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@item sample_rate
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Set the sample rate (in Hz) of the captured audio.
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Defaults to @option{44.1k}.
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@item list_devices
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If set to @option{true}, print a list of devices and exit.
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Defaults to @option{false}.
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@end table
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@subsection Examples
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Print the list of OpenAL supported devices and exit:
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@example
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$ ffmpeg -list_devices true -f openal -i dummy out.ogg
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@end example
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Capture from the OpenAL device @file{DR-BT101 via PulseAudio}:
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@example
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$ ffmpeg -f openal -i 'DR-BT101 via PulseAudio' out.ogg
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@end example
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Capture from the default device (note the empty string '' as filename):
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@example
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$ ffmpeg -f openal -i '' out.ogg
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@end example
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Capture from two devices simultaneously, writing to two different files,
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within the same @file{ffmpeg} command:
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@example
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$ ffmpeg -f openal -i 'DR-BT101 via PulseAudio' out1.ogg -f openal -i 'ALSA Default' out2.ogg
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@end example
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Note: not all OpenAL implementations support multiple simultaneous capture -
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try the latest OpenAL Soft if the above does not work.
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@section oss
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Open Sound System input device.
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The filename to provide to the input device is the device node
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representing the OSS input device, and is usually set to
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@file{/dev/dsp}.
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For example to grab from @file{/dev/dsp} using @file{ffmpeg} use the
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command:
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@example
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ffmpeg -f oss -i /dev/dsp /tmp/oss.wav
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@end example
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For more information about OSS see:
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@url{http://manuals.opensound.com/usersguide/dsp.html}
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@section sndio
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sndio input device.
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To enable this input device during configuration you need libsndio
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installed on your system.
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The filename to provide to the input device is the device node
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representing the sndio input device, and is usually set to
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@file{/dev/audio0}.
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For example to grab from @file{/dev/audio0} using @file{ffmpeg} use the
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command:
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@example
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ffmpeg -f sndio -i /dev/audio0 /tmp/oss.wav
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@end example
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@section video4linux and video4linux2
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Video4Linux and Video4Linux2 input video devices.
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The name of the device to grab is a file device node, usually Linux
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systems tend to automatically create such nodes when the device
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(e.g. an USB webcam) is plugged into the system, and has a name of the
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kind @file{/dev/video@var{N}}, where @var{N} is a number associated to
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the device.
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Video4Linux and Video4Linux2 devices only support a limited set of
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@var{width}x@var{height} sizes and framerates. You can check which are
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supported for example with the command @file{dov4l} for Video4Linux
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devices and the command @file{v4l-info} for Video4Linux2 devices.
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If the size for the device is set to 0x0, the input device will
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try to autodetect the size to use.
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Only for the video4linux2 device, if the frame rate is set to 0/0 the
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input device will use the frame rate value already set in the driver.
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Video4Linux support is deprecated since Linux 2.6.30, and will be
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dropped in later versions.
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Follow some usage examples of the video4linux devices with the ff*
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tools.
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@example
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# Grab and show the input of a video4linux device, frame rate is set
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# to the default of 25/1.
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ffplay -s 320x240 -f video4linux /dev/video0
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# Grab and show the input of a video4linux2 device, autoadjust size.
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ffplay -f video4linux2 /dev/video0
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# Grab and record the input of a video4linux2 device, autoadjust size,
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# frame rate value defaults to 0/0 so it is read from the video4linux2
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# driver.
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ffmpeg -f video4linux2 -i /dev/video0 out.mpeg
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@end example
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@section vfwcap
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VfW (Video for Windows) capture input device.
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The filename passed as input is the capture driver number, ranging from
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0 to 9. You may use "list" as filename to print a list of drivers. Any
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other filename will be interpreted as device number 0.
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@section x11grab
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X11 video input device.
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This device allows to capture a region of an X11 display.
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The filename passed as input has the syntax:
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@example
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[@var{hostname}]:@var{display_number}.@var{screen_number}[+@var{x_offset},@var{y_offset}]
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@end example
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@var{hostname}:@var{display_number}.@var{screen_number} specifies the
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X11 display name of the screen to grab from. @var{hostname} can be
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ommitted, and defaults to "localhost". The environment variable
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@env{DISPLAY} contains the default display name.
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@var{x_offset} and @var{y_offset} specify the offsets of the grabbed
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area with respect to the top-left border of the X11 screen. They
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default to 0.
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Check the X11 documentation (e.g. man X) for more detailed information.
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Use the @file{dpyinfo} program for getting basic information about the
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properties of your X11 display (e.g. grep for "name" or "dimensions").
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For example to grab from @file{:0.0} using @file{ffmpeg}:
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@example
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ffmpeg -f x11grab -r 25 -s cif -i :0.0 out.mpg
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# Grab at position 10,20.
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ffmpeg -f x11grab -r 25 -s cif -i :0.0+10,20 out.mpg
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@end example
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@subsection @var{follow_mouse} AVOption
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The syntax is:
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@example
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-follow_mouse centered|@var{PIXELS}
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@end example
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When it is specified with "centered", the grabbing region follows the mouse
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pointer and keeps the pointer at the center of region; otherwise, the region
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follows only when the mouse pointer reaches within @var{PIXELS} (greater than
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zero) to the edge of region.
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For example:
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@example
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ffmpeg -f x11grab -follow_mouse centered -r 25 -s cif -i :0.0 out.mpg
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# Follows only when the mouse pointer reaches within 100 pixels to edge
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ffmpeg -f x11grab -follow_mouse 100 -r 25 -s cif -i :0.0 out.mpg
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@end example
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@subsection @var{show_region} AVOption
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The syntax is:
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@example
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-show_region 1
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@end example
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If @var{show_region} AVOption is specified with @var{1}, then the grabbing
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region will be indicated on screen. With this option, it's easy to know what is
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being grabbed if only a portion of the screen is grabbed.
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For example:
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@example
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ffmpeg -f x11grab -show_region 1 -r 25 -s cif -i :0.0+10,20 out.mpg
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# With follow_mouse
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ffmpeg -f x11grab -follow_mouse centered -show_region 1 -r 25 -s cif -i :0.0 out.mpg
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@end example
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@c man end INPUT DEVICES
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