Re: [GnomeMeeting-list] video failure with ovfx2

[Dan Egnor <egnor ofb net>]

> > By default, when I start gnomemeeting (0.98) it claims at start that
> > it cannot set the video frame size.  After debugging the code (the
> > PTLib/OpenH323 makefiles sure are icky!), I found that if I swap the
> > order of initialization so that it sets the frame size after setting
> > e.g. the color conversion, that gets past that error.  This is such a
> > simple and obvious error that I presume it's been fixed in CVS by now.

> That's a bug of the driver, not of GnomeMeeting or pwlib... However,
> 0.98 has a different order of initialisation, I'll revert it to the old
> order in CVS, but again, you are running a buggy driver.

PVideoDevice::SetFrameSizeConverter() includes the following code, near
the top:

  if (!converter)
    converter = PColourConverter::Create(colourFormat, colourFormat, width, heig
ht);
  if (!converter) {
    PTRACE(1, "PVidDev\tSetFrameSizeConverter Colour converter creation failed")
;
    return FALSE;
  }

If the color format has not been initialized at that point -- which it 
hasn't, in the gnomemeeting code -- then colourFormat will be an empty
string, and PColourConverter::Create() will attempt to look up a conversion
from "" to "", and since it has no such conversion registered, it will
return NULL.

What I wonder is: how can that order of initialization work with any
driver?  It seems guaranteed to fail in libpt before even touching the
driver, but surely it doesn't.  Why did you change the order of 
initialization at all?  And why not just use PVideoInput::OpenFull(),
which initializes everything at once in the correct order?

> Other apps are not using the same size, color palettes and such. If your
> driver has been tested with xawtv only, it is highly possible it only
> works with applications based on xawtv's code.
> Given the fact that pwlib works with other cameras and drivers, I would
> suggest you to report them bugs so that they can fix the driver.

GnomeMeeting author: "GM works with other cameras, it must be a driver bug"
Driver author: "Driver works with other apps, it must be a GM bug"
Me: "I don't care, I'll fix the bug myself, I just want it to work"

If you can think of another app that's not Xawtv-based, I'll be happy to
try it.  So far I've been unable to find a v4l app besides GM that doesn't
work.  Maybe another app that uses pwlib for video grabbing?  Know any?

The driver only supports a single size and colour palette, anyway, as far
as I know; anything else is done by conversion (in GM's case, in the pwlib
layer).  Anyway, I guess I'll dig into the pwlib capture code.

Dan Egnor