[mythtv-users] ATI TV-Wonder high Saturation with bttv driver ?

jasonmiller jasonmiller at micron.com
Fri Apr 11 14:44:11 UTC 2003


Quick update.  I installed bttv 0.99 last night, loaded it up, looked pretty much the same.  Then... I realized I hadn't actually loaded the new module :)  I did notice, however, that version 0.7 doesn't seem to set the default saturation or contrast anywhere.  Version 0.9 does, although it is hardcoded, so I should be able to tweak around with it until it is capturing at a decent level.  That should significantly improve the MPEG4 compression since it will reduce the high frequency crappage.

Another minor note for the archives, Mike Wohlgemuth's suggestion got me playing around with my TV-Out settings and I did find that I could make the oversaturated recordings look much better by crankin UP the contrast and turning down the saturation a little less.  All in all I'd say just doing that made the picture a good 50% better.  Hopefully by adjusting the capture side as well I can hit 100% :)

-----Original Message-----
From: Bruce Markey [mailto:bjm at lvcm.com]
Sent: Friday, April 11, 2003 2:34 AM
To: Discussion about mythtv
Subject: Re: [mythtv-users] ATI TV-Wonder high Saturation with bttv
driver?


Mike Wohlgemuth wrote:
> jasonmiller wrote:
> 
>> I'm running an ATI TV-Wonder with the vanilla 2.4.20 kernel which has 
>> the bttv-0.7 drivers built in.  The captured video seems to have a 
>> very high saturation level (ie, too much color.)  I can compensate for 
>> it by reducing my TV-Out saturation to minimum but that causes the 
>> picture to be somewhat washed out.  I see that the bttv-0.9 
>> development drivers mention a fix for saturation and was wondering if 
>> anyone has had the same experience and managed to solve it one way or 
>> another.  If not I may try to patch the development bttv drivers into 
>> my kernel and see what I get.
>>
> Are you sure it's really oversaturated?  I've found (and at least one 
> other person on this list who I got the tip from) that bttv output has 
> way too much contrast.  I compensate for it by lowering the contrast in 
> MythTV (hit j while watching live TV).  I find about 33 works good for 
> most channels.

'Twas I.

Mike Benoit wrote:
 > Does anyone know how or where I can set the contrast/color/brightness
 > levels globally for the TV Out card? (XVideo perhaps?)

The problem is on TV-in during capture from the v4l bttv
driver. This is because the neutral halfway defaults (32768) are
not really line level. Brightness and hue are close to correct
but contrast and color defaults are overdriven which cause
the intensity and color ranges to be distorted. Therefore, if
you try to compensate with Xv, video driver, TV controls, etc.
the ranges will never be right. For contrast, white and near
white at the point of blooming leaves medium intensities drab.
For color, when solids are fully saturated, medium colors are
washed out. These v4l values need to be modified before any other
adjustments in order to get closer to a more life-like picture.

The quickest way to get close is:

mysql> update channel set contrast = 25000;
mysql> update channel set color = 25000;

 From there, go to WatchTV and use the J/j, K/k, and L/l keys
to fine tune per channel. MythTV stores these setting on a
per channel basis.

--  bjm


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