Re: Questions about detecting video devices (detect.py)

["Jaap A. Haitsma" <jaap haitsma org>]

On Nov 15, 2007 12:57 PM, Patryk Zawadzki <patrys pld-linux org> wrote:
> 2007/11/15, daniel g. siegel <dgsiegel gmail com>:
> > btw: i updated patryks script, which is available on the cheese page
>
> Thanks.
>
> > On Mi, 2007-11-14 at 22:12 +0100, Jaap A. Haitsma wrote:
> > > Patryk,
> > >
> > > Based on you detect.py I made a C implementation that works for me,
> > > but unfortunately not for Daniel.
> > >
> > > I've now discovered what's causing this because I now understand your
> > > detect.py script fully (I think)
> > >
> > >
> > > The problem is that if you ask for the width or height or framerate
> > > gstreamer has multiple ways to tell you this they can be in a GstList
> > > or in a GstFractionRange, GstIntRange or GstDoubleRange.
> > >
> > > My question is do all these types occur for webcams. For instance for
> > > width a GstDoubleRange or GstFractionRange seems pretty lame. My
> > > current thinking is the following
> > >
> > >  width, height
> > > ------------------------------
> > > 1. Just an integer in seprate GstStructures
> > > 2. GstList with ints
> > > 3. GstIntRange
> > >
> > > So no Fractions and doubles
>
> Yes, fractions and doubles are out.
>
> > > Frame rate
> > > ------------------------
> > > 1. a GstList with Fractions
> > > 2. a GstList with ints
> > > 3. a GstList with doubles
> > > 4. a GstFractionRange
> > > 5. a GstDoubleRange
> > >
> > > Do you know if my thinking is correct?
>
> I believe framerate is always a fraction range or a list of fractions.
> Never saw any other entries.
>
> > > Furthermore I see in your code that if width, and height are
> > > GstIntRanges you don't list all the possible values. But just values
> > > that are powers of 2 larger than the minimum or powers of 2 lower than
> > > the maximum.
> > >
> > > Do you do this to limit the number of entries in your fdi file or do
> > > cameras with GstIntRange for width and height not support weird
> > > resolutions such as for instance 349 x 254
>
> My testing shows that no tested camera supported resolutions outsite
> this range. One reason is the sensor has a pre-defined resolution,
> another is it has to keep the aspect ratio. I believe the problem is
> width and height are separate values so there is no way for a driver
> to return a list of working pairs.
>
Are you confirming here that if the width and height are a GstIntRange
that the supported resolutions are indeed powers of 2 larger than the
minimum and powers of 2 smaller than the maximum?

Thanks

Jaap