Question about BTTV-video controls "whitecrush upper/lower"

Hi,

there are two video controls in the Bttv-driver called "whitecrush upper" and "whitecrush lower".
But what does "whitecrush" mean ? Is it the same as "white noise" ? The german KDE translators are currently trying to translate these strings...

Thanks,
Frank

Quoted 8 lines · Frank Schaefer

Hi,

there are two video controls in the Bttv-driver called "whitecrush upper" and "whitecrush lower".
But what does "whitecrush" mean ? Is it the same as "white noise" ? The german KDE translators are currently trying to translate these strings...

"White Crush" is Conexant's term for adapting to nonstandard or varying Sync to White level voltage differences of the incoming video signal. It's basically an adaptive AGC to prevent "blooming" of the video signal due to very high Luminance levels.

The public BT878A datasheet has terse descriptions of what the registers settings do: they are basically upper and lower thresholds to determine when to adapt the automatic gain control.

The public CX25840 datasheet gives a better written description of white crush in section 3.4.9:

http://dl.ivtvdriver.org/datasheets/video/cx25840.pdf

I'm actually surprised the bttv driver has those presented as user controls at all.

Regards,
Andy