Image acquisition package

The image_acquisition package is part of the Octave Forge project.

There is not release package yet but if you can get the source here [1]

Example session

Lines starting with $ are commands executed on the octave prompt.

Load the package and list available hardware

$ pkg load image-acquisition
$ 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

$ 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.

$ 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

$ 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

$ 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

$ set(obj, "VideoResolution", [320 240])

Get the current brightness value

$ get(obj, "brightness")
ans =  100

Query possible range for brightness

$ set(obj, "brightness")
ans =

 scalar structure containing the fields:

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

Set a new value for brightness

$ set(obj, "brightness", 100)
$ 

Start preview

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

$ preview(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:

test @videoinput/videoinput
test @videoinput/get
test @videoinput/set
test @videoinput/getsnapshot