Questions about detecting video devices (detect.py)

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

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

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?

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

Thanks

Jaap