[mythtv] [PATCH] V4L picture controls use same interface as Xv

[Bruce Markey]

Joseph A. Caputo wrote:
> bobnvic at everestkc.net wrote:
>>Would it be possible to have separate V4L settings for each
>>encoder?  I have a PVR-250 and a bttv card.  The bttv card needs
>>the contrast set much differently than the PVR-250.  From what
>>I've read on the mailing list, this sounds like a fairly common
>>situation.  Will V4L allow each encoder to be used at the same time
>>with different settings?  If it does, would anyone be interested in
>>coding it?

> Hmmm... the V4L settings are stored on a per-channel basis.
> IIRC (I don't have access to my DB atm), if you're sharing
> a video source between more than one card, then they'll also
> share the V4L settings for the channels.

Correct. The solution for this situation is that there would
need to be global setting per cardtype. If so, the channel
settings should default to 50% (32768) so that the value could
be determined by hue = cardtype-hue + channel-hue - 32758.
If bttv contrast is 26000 and ivtv contrast is 31000, changing
channel 8 to 52% would increase the contrast for both types
of cards when recording that channel.

I've hacked the source for my test machine to use different
setting for the different types of cards but haven't bothered
following through because I still don't want to use my PVR-250
in my production pool. To do this right there should probably
be sliders on the recording profiles page which lists the four
profile names for each cardtype but I've never attempted to
add that.

In any case, what you are doing with the per-channel control
keys is the right thing and is separate from the card type
settings issue.

> However, in your case I think it's a moot point, as the V4L
> picture controls don't affect the PVR-250 (AFAIK), since it's
> not a V4L card.  Somebody please chime in if I'm wrong.

Ding-ding-ding =). The ivtv driver uses the V4L interface and
the per-channel settings are used to set the picture controls
for these cards.

--  bjm