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

[Frank Schaefer <fschaefer.oss@googlemail.com>]

Andy Walls schrieb:
> On Tue, 2010-07-06 at 13:27 +0200, Frank Schaefer wrote:
>   
>> 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
>   

Thank you Andy, that really helps a lot !

Regards,
Frank