The VideoLAN Forums

Dear Videolan Community,
I would appretiate it very much if you could help me with the following:

I have a Camera (Hover Cam Solo8) hooked up via USB to a Debian (Bullseye) Computer and acces it like so:

vlc --no-autoscale v4l2:///dev/video0:v4l2-width=1920 :v4l2-height=1080 :v4l2-aspect-ratio=16:9 :v4l2-fps=30 :no-v4l2-use-libv4l2

I want to use it to read some Documents on the screen, as a visually very impaired, legally blind person my needs for that require a "inverted black and white" mode, where the font on the document is displayed in white and the paper itself in black. (also I need huge magnification on top of that, but that I manage with other tools (kmag/compiz-ezoom))

I have a very poor solution for this issue with guvcview using this profile:
#V4L2/CTRL/0.0.2
APP{"guvcview 2.0.6"}
# control data
#Brightness
ID{0x00980900};CHK{-128:127:1:0}=VAL{0}
#Contrast
ID{0x00980901};CHK{0:255:1:128}=VAL{0}
#Saturation
ID{0x00980902};CHK{0:255:1:128}=VAL{0}
#White Balance Temperature, Auto
ID{0x0098090c};CHK{0:1:1:1}=VAL{0}

This guvcview solution has the problem, that the paper does not get pure black and the font does not get pure white, they both get a greyish touch.

Any Idea if and how I can accomplush this better with vlc?

Thank you very much for your help

In principle, you can set the V4L2 controls in VLC, but I don't have the syntax on top of my head. It's going to have the exact same limitation as gUVCview, as will any third application, since that's tied to the camera hardware.

You can also try the VLC "invert" video filter. This is hardly used by anyone so it's not optimised however.