vgrabbj - grab images from a v4l-compatible webcam
This manual page documents briefly the vgrabbj command.
vgrabbj is a program that will grab images from any v4l-capable device
which supports one of the rgb24, rgb32, yuv420, yuv420p, yuyv, uyvy, or
yuv422 palettes and saves the image as a .jpg, .png, or .pnm file.
Optional, it can timestamp the resulting image, and/or upload it to a
ftp-server. Additionally, a daemon-mode is available to do the above
On startup, the default configuration file /etc/vgrabbj.conf is read
and evaluated. If a configuration file is specified via the -c
parameter (see below), that file is read and parsed. Values which are
present in the default config file keep their values. Finally, the
commandline is evaluated. If an option is presented more than once, the
last in the commandline is taken. If no options given, vgrabbj tries
to open the default v4l-device /dev/video0, grab an image and return it
on /dev/stdout. So be aware.
All options are either numeric values, strings, or booleans. If it is a
boolean switch (e.g. no value/string shown after the switch), it
plainly switches the current setting of that particular option.
Remember, vgrabbj.conf is read first, so any option set to on or off
there will be toggled by the commandline switch.
-h Show summary of options and version number. -c <filename>
Specifies filename as alternative configuration file.
Daemonize & loop with seconds intervals (min. 1).
Daemonize & loop microseconds intervals (min. 1). Same as -l
except you can control it more precisely.
-a Enable vgrabbj's brightness adjustment (default: disabled). To
use vgrabbj's brightness adjustment, RGB24 support of the device
is necessary. You may have to provide it to your device via the
-F parameter (see below). If your device does not support
RGB24, this setting is silently ignored.
Sets the quality of a jpeg output to quality (1-100, default:
Sets the imagesize of input device, where imagesize is one of:
sqcif= 128x96, qsif = 160x120,
qcif = 176x144, sif = 320x240,
cif = 352x288, vga = 640x480,
svga = 800x600, xga = 1024x768,
sxga = 1280x1024, uxga = 1600x1200,
Sets the width of the image to width. Needs -H. The v4l-device
has to support the image width you set with this option.
Sets the height of the image to height. Needs -w. The v4l-
device has to support the image height you set with this option.
Sets the output to format (either jpeg, png, or pnm, default:
Output is written to filename (default: /dev/stdout)
Additional to the output of -f another file is written to the
named path+filename, whereas the whole may be formatted
according to strftime(2). This enables the creation of an
archive of images. Currently, the output is only supported on
the same filesystem as the original output.
Defines how many images shall be read until a copy for the
archive is made. E.g. 1 means each image taken is also put in
the archive. 5 would mean every fifth image taken is put in the
Sets the maximum number of images kept in the archive. If you
defined 5 seconds for daemon mode, archive every image, you
collect 720 images per hour. If you set this switch to 720 you
would keep an hour of images in the archive.
Sets the input device to device (default: /dev/video0)
This flag causes vgrabbj to print the v4l capabilities of
<device> and exit.
-C Causes vgrabbj to open the device only while image data is
grabbed. This is helpful if you need access to the device
besides vgrabbj. It's use is discouraged due to possible
problems with memory fragmentation. Default is to keep the v4l-
device open while vgrabbj is running.
-g Disables setting of the image size (see -i, -H, and -w.
Necessary for certain v4l-devices which do not support to be set
to a particular image size (e.g. IBM-usb-cam, QuickCam). For
these devices you have to specify the size at module load time.
-S Switches colormap from BGR to RGB (or vice versa). Use if you
have odd colors.
-R Swaps left and right of the image like a mirror.
-U Swaps top and bottom of the image like a mirror (e.g. for
upside-down montage of the cam).
-G Turns off use of mmap'ed memory. see vgrabbj.conf(5) for
Sets the loglevel of vgrabbj. Valid for value are 0, 2, 3, 4, 6,
7 (default: 4). 0 means no messages at all, 7 is debug. Don't
use 7 if you are running vgrabbj in daemon mode, it'll surely
fill your syslog. Be aware, that loglevel 7 will also write your
ftp-password (if defined in vgrabbj.conf(5)) in the logfile!
-n Disable the use of the temporary outputfile and write directly
to the output-file specified with -f. Output to /dev/stdout is
always written directly without the use of a temporary file.
If a filename different from /dev/stdout was given with the -f
parameter, vgrabbj defaults to use a temporary file called
filename.tmp to write the image. This file is then renamed to
filename to shorten the time period corrupt data may be read
Ask vgrabbj to launch an external program. May be used to pass
the picture through ImageMagick or others filters. The first
'%s' instance in the command line will be replaced with
filename. If UseTmpOut is On, 'commands' will be run before the
file is renamed.
Force the usage of the specified palette. If palette is not
supported by either vgrabbj or the v4l-device, fallback to a
palette supported by both is provided. If no common denominator
is available, vgrabbj exits. See DESCRIPTION for details on
palettes supported by vgrabbj. Possible values are (copy from
1 VIDEO_PALETTE_GREY Linear greyscale
2 VIDEO_PALETTE_HI240 High 240 cube (BT848)
3 VIDEO_PALETTE_RGB565 565 16 bit RGB
4 VIDEO_PALETTE_RGB24 24bit RGB
5 VIDEO_PALETTE_RGB32 32bit RGB
6 VIDEO_PALETTE_RGB555 555 15bit RGB
7 VIDEO_PALETTE_YUV422 YUV422 capture
10 VIDEO_PALETTE_YUV411 YUV411 capture
11 VIDEO_PALETTE_RAW RAW capture (BT848)
12 VIDEO_PALETTE_YUV422P YUV 4:2:2 Planar
13 VIDEO_PALETTE_YUV411P YUV 4:1:1 Planar
14 VIDEO_PALETTE_YUV420P YUV 4:2:0 Planar
15 VIDEO_PALETTE_YUV410P YUV 4:1:0 Planar
(no default, depends on v4l-device)
value images are grabbed and immediately discarded. Only the
last image is written to the output. This might be helpful if
your v4l-device needs to take a couple of images to auto-adjust
to the current light.
-X Does not fork daemon process and keeps vgrabbj in daemon mode in
foreground, attached to the terminal. Useful for debugging
purpose. Not available in config file.
HARDWARE CONTROL OPTIONS
With the following options you can control the hardware settings of
your cam - if it is supported by your cam. Be aware that these options
might break your hardware, as there is no check on what values are
available, allowed, and supported by your hardware.
The following options are available only if vgrabbj was compiled with
the freetype library available. If you set any one of these options on
the commandline timestamp will be enabled with default values for all
-e Switches timestamp to be used or not. Default is off, but may be
overridden by config-file, so just try to enable this switch if
there is no timestamp in the resulting image.
The TrueType font to be used for the timestamp (default
Set the fontsize to size for timestamp (3-100, default: 12).
Defines the timestamp. format-str can be plain text or any
strftime format and has to be enclosed with '""' (default: "%a,
%e. %B %Y - %T" - see strftime(3) for details)
Alignment of the timestamp in the image. Possible value:
0 = upper left, 1 = upper right,
2 = lower left, 3 = lower right,
4 = upper center, 5 = lower center
Defines the blend between font background and image (1-100,
value pixels will be used as border around the timestamp string
(1-255, default: 2).
There are no options for ftp-upload on the command line. This is due to
the need to provide a password which would be visible via the ps(1)
command. See vgrabbj.conf for details on how to set-up the ftp-upload
option. Additionally, vgrabbj has to be compiled with libftp support.
%F in the archive time-string (year with century) causes memory
corruption at a pentium-machine running vgrabbj (not validated). No
further bugs are known at this time.
vgrabbj.conf(4), strftime(3), ps(1)
This manual page was originally written by Michael Janssen
<email@example.com>, for the Debian GNU/Linux system and enhanced by
Jens Gecius <firstname.lastname@example.org>.
February 24, 2002 VGRABBJ(1)