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

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

[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...

Thanks,
Frank

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

[Andy Walls]

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

> Thanks,
> Frank

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

[Frank Schaefer]

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