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363 lines
9.8 KiB
Plaintext
363 lines
9.8 KiB
Plaintext
@chapter Input Devices
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@c man begin INPUT DEVICES
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Input devices are configured elements in Libav 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 Libav 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 av* 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 @command{avconv} 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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avconv -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 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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@command{avconv}:
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@example
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avconv -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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avconv -f fbdev -frames:v 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 Libav 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 @command{avconv}.
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@example
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# Create a JACK writable client with name "libav".
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$ avconv -f jack -i libav -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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libav:input_1
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metro:120_bpm
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# Connect metro to the avconv writable client.
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$ jack_connect metro:120_bpm libav: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 libdc1394
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IIDC1394 input device, based on libdc1394 and libraw1394.
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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 @command{avconv} use the
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command:
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@example
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avconv -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 pulse
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pulseaudio input device.
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To enable this input device during configuration you need libpulse-simple
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installed in your system.
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The filename to provide to the input device is a source device or the
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string "default"
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To list the pulse source devices and their properties you can invoke
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the command @file{pactl list sources}.
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@example
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avconv -f pulse -i default /tmp/pulse.wav
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@end example
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@subsection @var{server} AVOption
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The syntax is:
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@example
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-server @var{server name}
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@end example
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Connects to a specific server.
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@subsection @var{name} AVOption
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The syntax is:
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@example
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-name @var{application name}
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@end example
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Specify the application name pulse will use when showing active clients,
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by default it is "libav"
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@subsection @var{stream_name} AVOption
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The syntax is:
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@example
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-stream_name @var{stream name}
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@end example
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Specify the stream name pulse will use when showing active streams,
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by default it is "record"
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@subsection @var{sample_rate} AVOption
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The syntax is:
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@example
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-sample_rate @var{samplerate}
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@end example
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Specify the samplerate in Hz, by default 48kHz is used.
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@subsection @var{channels} AVOption
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The syntax is:
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@example
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-channels @var{N}
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@end example
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Specify the channels in use, by default 2 (stereo) is set.
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@subsection @var{frame_size} AVOption
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The syntax is:
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@example
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-frame_size @var{bytes}
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@end example
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Specify the number of byte per frame, by default it is set to 1024.
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@subsection @var{fragment_size} AVOption
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The syntax is:
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@example
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-fragment_size @var{bytes}
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@end example
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Specify the minimal buffering fragment in pulseaudio, it will affect the
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audio latency. By default it is unset.
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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 @command{avconv} use the
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command:
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@example
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avconv -f sndio -i /dev/audio0 /tmp/oss.wav
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@end example
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@section video4linux2
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Video4Linux2 input video device.
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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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Video4Linux2 devices usually 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 using @command{-list_formats all} for Video4Linux2 devices.
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Some usage examples of the video4linux2 devices with avconv and avplay:
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@example
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# Grab and show the input of a video4linux2 device.
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avplay -f video4linux2 -framerate 30 -video_size hd720 /dev/video0
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# Grab and record the input of a video4linux2 device, leave the
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framerate and size as previously set.
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avconv -f video4linux2 -input_format mjpeg -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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omitted, 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 @command{avconv}:
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@example
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avconv -f x11grab -r 25 -s cif -i :0.0 out.mpg
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# Grab at position 10,20.
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avconv -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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avconv -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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avconv -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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avconv -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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avconv -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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