Re: [GnomeMeeting-list] how to support another capture card? (WAS: experience with the V4L1 compatibility of V4L2)

[Damien Sandras <dsandras seconix com>]

On Thu, Apr 18, 2002 at 09:46:25AM -0700, Guilhem Tardy wrote:
> I added grabber->SetFrameSize(width, height) in videograbber.cpp, and got to
> the bottom of this:

You shouldn't have added that method, but used SetFrameSizeConverter
and add a HINT in video4linux.cxx for your card to force the size.
That way, VerifyHardwareFrameSize will ignore the problem and it will work.

> 
> Since the Videum card doesn't support 352x288 (but still advertises 640x288 as
> maximum frame size), it fall backs on 352x240 (same behavious with 'vctrl'),
> and VideoInputDevice::VerifyHardwareFrameSize() doesn't like it at all.
> 
> I am a bit confused with the logic here, because
> VideoInputDevice::SetFrameSize() first sets the size internally, then verifies
> hardware that returns FALSE (at this point, the card is set with 352x240, and
> internally to PWLib with 352x288, no converter is configured).
> 
> So now, my question is: does the PWLib library behave so by design? Should we
> address this in PWLib or work around it in the application (e.g. GnomeMeeting)?

You have to add a HINT in PWLib. That works this way because all Video4Linux 
drivers do not respect the API. So you set a HINT, to force the required size for your specific driver, and then it will work.
> 
> Guilhem.
> 
> --- Guilhem Tardy <guilhem_tardy yahoo com> wrote:
> > Hi,
> > 
> > As I found out yesterday, the palette is not an issue. The problem lies in
> > the
> > VideoInputDevice::Open() function, which gets the device capabilities, sets
> > the
> > height and width internal values to the maximum values  (i.e. 640x240), and
> > mutes the audio.
> > 
> > In effect, the WinNov video frame size is changed from whatever I set it to
> > before (e.g. 352x240x24, via the 'vctrl' utility) to 640x240x8. This is also
> > reflected by the 'vctrl' utility after the facts.
> > 
> > Guilhem.
> > 
> > --- Damien Sandras <dsandras seconix com> wrote:
> > > On Wed, Apr 17, 2002 at 03:45:25PM -0700, Guilhem Tardy wrote:
> > > > I found that the problem is actually not the palette, but a subversive
> > > change
> > > > of frame size (640x288) when you Open() a VideoInputDevice.
> > > > Then, the SetFrameColourConverter() calls SetFrameColour(), which calls
> > > > SetFrameSizeConverter(), and returns FALSE (640x288 is definitely
> > > > non-standard).
> > > > Do you know why VideoInputDevice::Open() resets the frame size?
> > > > 
> > > 
> > > I'm not sure I understand what you mean.
> > > PWLib only tries sizes CIF (352x288) and QCIF (176x144).
> > 
> > 
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