Image acquisition package
The image-acquisition package is part of the Octave Forge project.
Build dependencies for Debian GNU/Linux are libv4l-dev and libfltk1.3-dev or libfltk1.1-dev. You can install it on GNU/Linux in octave with
octave> pkg install -forge image-acquisition
If you see complains about a missing mkoctfile: FAQ#I_cannot_install_a_package._Octave_complains_about_a_missing_mkoctfile.
If you want to report a bug: Image_acquisition_package#Reporting_bugs
image-acquisition will not work on Windows as far as there is not port of v4l2 (standing for Video for Linux 2)
Example session[edit]
Lines starting with "octave:>" are executed on the octave prompt.
Load the package and list available hardware[edit]
octave:> pkg load image-acquisition octave:> imaqhwinfo ans = scalar structure containing the fields: driver = uvcvideo card = UVC Camera (046d:0825) bus_info = usb-0000:00:12.2-4 version = 3.16.7 capabilities = 2.2314e+09 device = /dev/video0
Open the v4l2 device and output the result[edit]
octave:> obj = videoinput("v4l2", "/dev/video0")
obj = videoinput for v4l2
device = /dev/video0
driver = uvcvideo
card = UVC Camera (046d:0825)
VideoInput = 0
VideoResolution = 320 x 240 px
VideoFormat = YUYV
Query which properties are available for the used device[edit]
The first 8 ones, starting with an upper letter are fixed, the other specific to the used v4l2 device.
octave:> get(obj)
ans =
{
[1,1] = SelectedSourceName
[2,1] = ReturnedColorSpace
[3,1] = BayerSensorAlignment
[4,1] = DeviceCapabilities
[5,1] = VideoInput
[6,1] = VideoResolution
[7,1] = VideoFrameInterval
[8,1] = VideoFormat
[9,1] = brightness
[10,1] = contrast
[11,1] = saturation
[12,1] = white_balance_temperature_auto
[13,1] = gain
[14,1] = power_line_frequency
[15,1] = white_balance_temperature
[16,1] = sharpness
[17,1] = backlight_compensation
[18,1] = exposure_auto
[19,1] = exposure_absolute
[20,1] = exposure_auto_priority
}
Set VideoFormat to RGB3 aka RGB24[edit]
octave:> set(obj, "VideoFormat", "RGB3");
List available video resolutions[edit]
octave:> set(obj, "VideoResolution") ans = 640 480 160 120 176 144 320 176 320 240 352 288 432 240 544 288 640 360 752 416 800 448 800 600 864 480 960 544 960 720 1024 576 1184 656 1280 720 1280 960
Set the video resolution to 320x240px[edit]
octave:> set(obj, "VideoResolution", [320 240])
Get the current brightness value[edit]
octave:> get(obj, "brightness") ans = 100
Query possible range for brightness[edit]
octave:> set(obj, "brightness") ans = scalar structure containing the fields: min = 0 max = 255 step = 1 default = 128
Set a new value for brightness[edit]
octave:> set(obj, "brightness", 100)
Start preview[edit]
octave:> preview(obj)
Close it with CTRL+C or with [X] on the preview window
Use higher resolution and start streaming with 2 buffers[edit]
octave:> set(obj, "VideoResolution", [640 480]); octave:> start(obj, 2)
Get an image from the buffers, view and save it[edit]
octave:> img = getsnapshot(obj); octave:> image(img) octave:> imwrite(img, "ex1_a.png") octave:> [img, seq, t] = getsnapshot(obj); octave:> seq seq = 1 octave:> t t = scalar structure containing the fields: tv_sec = 10281 tv_usec = 779303
Stop streaming[edit]
octave:> stop(obj)
Using v4l2loopback for tests[edit]
If you don't have a v4l2 device but want to test the package you could create a loopback device:
modprobe v4l2loopback gst-launch-0.10 videotestsrc ! v4l2sink device=/dev/video0
Reporting bugs[edit]
Please install v4l2-ctl (for example from Debian package v4l-utils), run the following commands and attach the output.
$ v4l2-ctl -w --list-devices $ v4l2-ctl -w -D $ v4l2-ctl -w -L $ v4l2-ctl -w -n $ v4l2-ctl -w --list-formats
Enable libv4l2 logging:
$ export LIBV4L2_LOG_FILENAME=libv4l2_debug.log
Start octave and execute your commands/scripts which show the problem.
Please include the whole octave session beginning with the start of octave. There might be some warnings like "warning: function xyz shadows a built-in function" at start.
Exit octave and add libv4l2_debug.log to your bug report. The logfile libv4l2_debug.log is overwritten between open/close so you have to rename it if you run different scripts.
Consider running the included tests:
octave> test @videoinput/videoinput octave> test @videoinput/get octave> test @videoinput/set octave> test @videoinput/getsnapshot
Run the compliance check (perhaps also with -s)
v4l2-compliance -d /dev/video0
Build source from mercurial repository[edit]
Warning: You really should use the <pkg install -forge> method described above if you are not sure what you are doing here.
Get the source and build it yourself. The build dependencies for Debian GNU/Linux jessie are libv4l-dev and libfltk1.3-dev or libfltk1.1-dev. You also need the GNU autotools to generate the configure script.
$ hg clone http://hg.code.sf.net/p/octave/image-acquisition octave-image-acquisition $ cd octave-image-acquisition/ $ make install
make check[edit]
If you have cloned the hg repo you can also run the test scripts to see if all works.
$ cd octave-image-acquisition/devel $ make check octave -q run_tests.m ../src/__v4l2_handler__.cc........................ PASS 3/3 @videoinput/videoinput............................ PASS 1/1 @videoinput/get................................... PASS 4/4 @videoinput/set................................... PASS 7/7 @videoinput/getsnapshot........................... PASS 4/4 imaqhwinfo........................................ PASS 1/1 Summary: PASS 20 FAIL 0
If there are tests which FAIL, then please have a look at the generated fntest.log and add it to your bug report.