@chapter Input Devices
@c man begin INPUT DEVICES
-Input devices are configured elements in FFmpeg which allow to access
+Input devices are configured elements in Libav 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 them using the configure option
-"--list-indevs".
+When you configure your Libav 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
To enable this input device during configuration you need libasound
installed on your system.
-This device allows to capture from an ALSA device. The name of the
+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:
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
+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
For more information see:
@url{http://www.alsa-project.org/alsa-doc/alsa-lib/pcm.html}
-@section audio_beos
-
-BeOS audio input device.
-
@section bktr
BSD video input device.
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.
+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
+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
+Each writable client will send the acquired data to the Libav input
device.
-Once you have created one or more jack readable clients, you need to
-connect them to one or more jack writable clients.
+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
+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
+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
+Follows an example which shows how to capture a JACK readable client
with @file{ffmpeg}.
@example
-# create a jack writable client with name "ffmpeg"
+# Create a JACK writable client with name "ffmpeg".
$ ffmpeg -f jack -i ffmpeg -y out.wav
-# start the sample jack_metro readable client
+# Start the sample jack_metro readable client.
$ jack_metro -b 120 -d 0.2 -f 4000
-# list the current jack clients
+# List the current JACK clients.
$ jack_lsp -c
system:capture_1
system:capture_2
ffmpeg:input_1
metro:120_bpm
-# connect metro to the ffmpeg writable client
+# Connect metro to the ffmpeg writable client.
$ jack_connect metro:120_bpm ffmpeg:input_1
@end example
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/}.
+@file{/dev/dsp}.
-For example to grab from @file{/dev/dsp/} using @file{ffmpeg} use the
+For example to grab from @file{/dev/dsp} using @file{ffmpeg} use the
command:
@example
ffmpeg -f oss -i /dev/dsp /tmp/oss.wav
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 to the system, and has a name of the
+(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 using the command @file{dov4l} for Video4Linux
-devices, and the command @file{v4l-info} for Video4Linux2 devices.
+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
-ffplay -s 320x240 -f video4linux /dev/video0
+# Grab and show the input of a video4linux device, frame rate is set
+# to the default of 25/1.
+avplay -s 320x240 -f video4linux /dev/video0
-# grab and show the input of a video4linux2 device, autoadjust size
-ffplay -f video4linux2 /dev/video0
+# Grab and show the input of a video4linux2 device, autoadjust size.
+avplay -f video4linux2 /dev/video0
-# grab and record the input of a video4linux2 device, autoadjust size
+# 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 Window) catpure input device.
+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
This device allows to capture a region of an X11 display.
-The filename passed in input has the syntax:
+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 not
-specified, and defaults to "localhost". The environment variable
+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 image. They
+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 screen (e.g. grep for "name" or
-"dimensions").
+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
+# 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
projects / ffmpeg / blobdiff