Re: Chroma gain configuration

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On Tue, 2010-02-23 at 10:33 -0500, Andy Walls wrote:
> On Tue, 2010-02-23 at 15:41 +0100, Hans Verkuil wrote:
> > > On Tue, 2010-02-23 at 08:53 +0100, Hans Verkuil wrote:
> > >> On Monday 22 February 2010 23:00:32 Devin Heitmueller wrote:
> > >> > On Mon, Feb 22, 2010 at 4:54 PM, Hans Verkuil <hverkuil@xxxxxxxxx>
> > >> wrote:
> > >
> > >> > Of course, if you and Mauro wanted to sign off on the creation of a
> > >> > new non-private user control called V4L2_CID_CHROMA_GAIN, that would
> > >> > also resolve my problem.  :-)
> > >>
> > >> Hmm, Mauro is right: the color controls we have now are a bit of a mess.
> > >> Perhaps this is a good moment to try and fix them. Suppose we had no
> > >> color
> > >> controls at all: how would we design them in that case? When we know
> > >> what we
> > >> really need, then we can compare that with what we have and figure out
> > >> what
> > >> we need to do to make things right again.
> 
> > Let me rephrase my question: how would you design the user color controls?
> 
> > E.g., the controls that are exported in GUIs to the average user.
> 
> Look at the knobs on an old TV or look at the menu on more modern
> televisions:
> 
> 1. Hue (or Tint) (at least NTSC TVs have this control)
> 2. Brightness
> 3. Saturation
> 
> These are the three parameters to which the Human Visual System
> sensitive.
> 
> Any other controls are fixing problems that the hardware can't seem to
> get right on it's own - right?

Bah, I forgot contrast.

Regards,
Andy

> 
> >  Most of
> > the controls you mentioned above are meaningless to most users. When we
> > have subdev device nodes, then such controls can become accessible to
> > applications to do fine-tuning, but they do not belong in a GUI in e.g.
> > tvtime or xawtv.
> > 
> > The problem is of course in that grey area between obviously user-level
> > controls like brightness and obviously (to me at least) expert-level
> > controls like chroma coring.
> 
> Right, so an expert can see colors bleeding to the side in portions of
> the image and guess that it's a comb filter problem.  What's my recourse
> at that point, when I see such a clip submitted from user and identify
> it's a comb filter problem?  "Tough, you're not an expert, so I can't
> give you manual control over the comb filter so you can fix your
> problem" ?
> 
> Also, just because a user can't guess what to do, doesn't mean they are
> incapable of "mashing buttons" until they find something that works.  I
> don't quite see the value in restricting controls from users, when the
> only consequence of such restriction is them coming back here asking
> what else they can try to solve a problem.  It's frustrating to have a
> setting on the chip that could fix a user problem and knowing there is
> no control coded up for it.  It just makes the debug cycle longer.
> 
> 
> What is the benefit to us or to end users for denying controls to
> non-expert users?
> 
> 
> OK, I'm done ranting now. :)
> 
> Regards,
> Andy
> 
> 
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