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. You can installed it on GNU/Linux in octave with

 octave> pkg install -forge image-acquisition

If you want to report a bug see Image_acquisition_package#Reporting_bugs

Example session

Lines starting with octave> are executed on the octave prompt.

Load the package and list available hardware

octave> pkg load image-acquisition
octave> imaqhwinfo
ans =

 scalar structure containing the fields:

   driver = uvcvideo
   card = UVC Camera (046d:0825)
   bus_info = usb-0000:00:16.2-2
   version = 3.2.51
   capabilities =  83886081
   device = /dev/video0

Open the v4l2 device and output the result

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
     VideoFrameInterval = 1/30 s (30.0 fps)

Query which properties are available for the used device

The first 6 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] = DeviceCapabilities
 [3,1] = VideoInput
 [4,1] = VideoResolution
 [5,1] = VideoFrameInterval
 [6,1] = VideoFormat
 [7,1] = brightness
 [8,1] = contrast
 [9,1] = saturation
 [10,1] = white_balance_temperature_auto
 [11,1] = gain
 [12,1] = power_line_frequency
 [13,1] = white_balance_temperature
 [14,1] = sharpness
 [15,1] = backlight_compensation
 [16,1] = exposure_auto
 [17,1] = exposure_absolute
 [18,1] = exposure_auto_priority
}

Get device capabilities

octave> get(obj, "DeviceCapabilities")
ans =

 scalar structure containing the fields:

   driver = uvcvideo
   card = UVC Camera (046d:0825)
   bus_info = usb-0000:00:16.2-2
   version = 3.2.51
   capabilities =  83886081

List available video resolutions

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

octave> set(obj, "VideoResolution", [320 240])

Get the current brightness value

octave> get(obj, "brightness")
ans =  100

Query possible range for brightness

octave> set(obj, "brightness")
ans =

 scalar structure containing the fields:

   min = 0
   max =  255
   step =  1
   default =  128

Set a new value for brightness

octave> set(obj, "brightness", 100)

Start preview

octave> preview(obj)

Close it with CTRL+C or with [X] on the preview window

Use higher resolution and start streaming with 2 buffers

octave> set(obj, "VideoResolution", [640 480]);
octave> start(obj, 2)

Get an image from the buffers, view and save it

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 =  19618
   tv_usec =  346553

Stop streaming

octave> stop(obj)

Using v4l2loopback for tests

If you don't have a v4l2 device but test the package you could create a loopback device:

modprobe v4l2loopback
gst-launch-0.10 videotestsrc ! v4l2sink device=/dev/video0

Reporting bugs

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

Consider running the included tests:

octave> test @videoinput/videoinput
octave> test @videoinput/get
octave> test @videoinput/set
octave> test @videoinput/getsnapshot

make check

If you have cloned the hg repo you can run the test scripts to see if all works.

$ cd octave-image-acquisition/devel
$ make check

octave -q run_tests.m
libv4l2: error setting pixformat: Device or resource busy
INFO: this error is expected because /dev/video0 is still streaming
../src/__v4l2_handler__.cc........................ PASS 3/3 
libv4l2: error getting capabilities: Inappropriate ioctl for device
@videoinput/videoinput............................ PASS 3/3 
@videoinput/get................................... PASS 4/4 
@videoinput/set................................... PASS 6/6 
@videoinput/getsnapshot........................... PASS 1/1 
imaqhwinfo........................................ PASS 1/1 

Summary:

  PASS  18
  FAIL   0

The two errors are expected, see test scripts. If there are tests which FAIL, then please have a look at the generated fntest.log and add it to your bug report.

Build src from hg repo

Get the source here [1] and build it yourself. Build dependencies for Debian GNU/Linux are libv4l-dev and libfltk1.3-dev.

$ hg clone http://hg.code.sf.net/p/octave/image-acquisition octave-image-acquisition
$ tar czf image-acquisition.tar.gz octave-image-acquisition
octave:>> pkg install image-acquisition.tar.gz