Rename the chapter Devices -> Input Devices, as the file is about
[libav.git] / doc / indevs.texi
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c32ccf7c 1@chapter Input Devices
4419c8bf
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2@c man begin INPUT DEVICES
3
4Input devices are configured elements in FFmpeg which allow to access
5the data coming from a multimedia device attached to your system.
6
7When you configure your FFmpeg build, all the supported input devices
8are enabled by default. You can list them using the configure option
9"--list-indevs".
10
11You can disable all the input devices using the configure option
12"--disable-indevs", and selectively enable an input device using the
13option "--enable-indev=@var{INDEV}", or you can disable a particular
14input device using the option "--disable-indev=@var{INDEV}".
15
16The option "-formats" of the ff* tools will display the list of
17supported input devices (amongst the demuxers).
18
19A description of the currently available input devices follows.
20
21@section alsa
22
23ALSA (Advanced Linux Sound Architecture) input device.
24
25To enable this input device during configuration you need libasound
26installed on your system.
27
28This device allows to capture from an ALSA device. The name of the
29device to capture has to be an ALSA card identifier.
30
31An ALSA identifier has the syntax:
32@example
33hw:@var{CARD}[,@var{DEV}[,@var{SUBDEV}]]
34@end example
35
36where the @var{DEV} and @var{SUBDEV} components are optional.
37
38The three arguments (in order: @var{CARD},@var{DEV},@var{SUBDEV})
39specify card number or identifier, device number and subdevice number
40(-1 means any).
41
42To see the list of cards currently recognized by your system check the
43files @file{/proc/asound/cards} and @file{/proc/asound/devices}.
44
45For example to capture with @file{ffmpeg} from an alsa device with
46card id 0, you may run the command:
47@example
48ffmpeg -f alsa -i hw:0 alsaout.wav
49@end example
50
51For more information see:
52@url{http://www.alsa-project.org/alsa-doc/alsa-lib/pcm.html}
53
54@section audio_beos
55
56BeOS audio input device.
57
58@section bktr
59
60BSD video input device.
61
62@section dv1394
63
64Linux DV 1394 input device.
65
66@section jack
67
68Jack input device.
69
70To enable this input device during configuration you need libjack
71installed on your system.
72
73A jack input device creates one or more jack writable clients, one for
74each audio channel, with name @var{client_name}:input_@var{N}, where
75@var{client_name} is the name provided by the application, and @var{N}
76is a number which identifies the channel.
77Each writable client will send the acquired data to the FFmpeg input
78device.
79
80Once you have created one or more jack readable clients, you need to
81connect them to one or more jack writable clients.
82
83To connect or disconnect jack clients you can use the
84@file{jack_connect} and @file{jack_disconnect} programs, or do it
85through a graphical interface, for example with @file{qjackctl}.
86
87To list the jack clients and their properties you can invoke the command
88@file{jack_lsp}.
89
90Follows an example which shows how to capture a jack readable client
91with @file{ffmpeg}.
92@example
93# create a jack writable client with name "ffmpeg"
94$ ffmpeg -f jack -i ffmpeg -y out.wav
95
96# start the sample jack_metro readable client
97$ jack_metro -b 120 -d 0.2 -f 4000
98
99# list the current jack clients
100$ jack_lsp -c
101system:capture_1
102system:capture_2
103system:playback_1
104system:playback_2
105ffmpeg:input_1
106metro:120_bpm
107
108# connect metro to the ffmpeg writable client
109$ jack_connect metro:120_bpm ffmpeg:input_1
110@end example
111
112For more information read:
113@url{http://jackaudio.org/}
114
115@section libdc1394
116
117IIDC1394 input device, based on libdc1394 and libraw1394.
118
119@section oss
120
121Open Sound System input device.
122
123The filename to provide to the input device is the device node
124representing the OSS input device, and is usually set to
125@file{/dev/dsp/}.
126
127For example to grab from @file{/dev/dsp/} using @file{ffmpeg} use the
128command:
129@example
130ffmpeg -f oss -i /dev/dsp /tmp/oss.wav
131@end example
132
133For more information about OSS see:
134@url{http://manuals.opensound.com/usersguide/dsp.html}
135
136@section video4linux and video4linux2
137
138Video4Linux and Video4Linux2 input video devices.
139
140The name of the device to grab is a file device node, usually Linux
141systems tend to automatically create such nodes when the device
142(e.g. an USB webcam) is plugged to the system, and has a name of the
143kind @file{/dev/video@var{N}}, where @var{N} is a number associated to
144the device.
145
146Video4Linux and Video4Linux2 devices only support a limited set of
147@var{width}x@var{height} sizes and framerates. You can check which are
148supported for example using the command @file{dov4l} for Video4Linux
149devices, and the command @file{v4l-info} for Video4Linux2 devices.
150
151If the size for the device is set to 0x0, the input device will
152try to autodetect the size to use.
153
154Video4Linux support is deprecated since Linux 2.6.30, and will be
155dropped in later versions.
156
157Follow some usage examples of the video4linux devices with the ff*
158tools.
159@example
160# grab and show the input of a video4linux device
161ffplay -s 320x240 -f video4linux /dev/video0
162
163# grab and show the input of a video4linux2 device, autoadjust size
164ffplay -f video4linux2 /dev/video0
165
166# grab and record the input of a video4linux2 device, autoadjust size
167ffmpeg -f video4linux2 -i /dev/video0 out.mpeg
168@end example
169
170@section vfwcap
171
172VFW (Video For Window) catpure input device.
173
174@section x11grab
175
176X11 video input device.
177
178This device allows to capture a region of an X11 display.
179
180The filename passed in input has the syntax:
181@example
182[@var{hostname}]:@var{display_number}.@var{screen_number}[+@var{x_offset},@var{y_offset}]
183@end example
184
185@var{hostname}:@var{display_number}.@var{screen_number} specifies the
186X11 display name of the screen to grab from. @var{hostname} can be not
187specified, and defaults to "localhost". The environment variable
188@env{DISPLAY} contains the default display name.
189
190@var{x_offset} and @var{y_offset} specify the offsets of the grabbed
191area with respect to the top/left border of the X11 screen image. They
192default to 0.
193
194Check the X11 documentation (e.g. man X) for more detailed information.
195
196Use the @file{dpyinfo} program for getting basic information about the
197properties of your X11 display screen (e.g. grep for "name" or
198"dimensions").
199
200For example to grab from @file{:0.0} using @file{ffmpeg}:
201@example
202ffmpeg -f x11grab -r 25 -s cif -i :0.0 out.mpg
203
204# grab at position 10,20
205ffmpeg -f x11grab -25 -s cif -i :0.0+10,20 out.mpg
206@end example
207
208@c man end INPUT DEVICES