[gst-devel] Problems setting brightness value to a v4l2 stream

[Steffen Liebscher]

Hi guys,

I'm recently having a project running, concerning an application that 
aquires images from a video4linux2 source. First of all, I tried both of 
following commands:

gst-launch-0.10 videotestsrc ! xvimagesink hue=1000 saturation=1000 
brightness=1000
gst-launch-0.10 videotestsrc ! xvimagesink

Here's the URL I took the example from:
http://www.gstreamer.net/data/doc/gstreamer/head/gst-plugins-base-plugins/html/gst-plugins-base-plugins-xvimagesink.html#gst-plugins-base-plugins-xvimagesink.synopsis 


Both images show the exact same image. I tried different values for hue, 
saturation and brightness but none of the values I set had any effect to 
the output image. Am I getting something wrong here?
Corresponding to these results, any changes concerning hue, saturation 
and brightness to my v4l2 parameters, using the gst-launch tool, had any 
effect. I also tried both versions, gst-launch and gst-launch-0.10.

Another question I like to ask is: How do I change the brightness value 
of my v4l2 stream in my source code? As I understand the gstreamer 
pipeline structure, I need an imagesink to aquire an 
GstColorBalanceChannel. But if I do so, only my output on screen will be 
changed, not my frame object that I can access using my playbin which I 
use for further image processing in my application. Is there a way to 
set up my video grabber using v4l2 with my desired brightness values? 
I've been searching for examples and reading the API reference for the 
past two days but I couldn't find any suitable result.

Thanks in advance,

Steffen