[Bug 726194] v4l2src does not cope well when a capture card is sometimes interlaced, sometimes progressive at the same resolution

[GStreamer (bugzilla.gnome.org)]

https://bugzilla.gnome.org/show_bug.cgi?id=726194
  GStreamer | gst-plugins-good | git

--- Comment #11 from Nicolas Dufresne (stormer) <nicolas.dufresne at collabora.co.uk> 2014-10-31 13:14:44 UTC ---
I've asked Hans if drivers returning ANY from TRY_FMT are doing it wrong,
answer was quite direct:

<hverkuil> 04:23:45> stormer: that's correct, drivers should never return
FIELD_ANY.

The reason is that ANY only exist for requesting something, basically when the
application don't care. It's not an interlaced mode. Reading attentively the
quote you have brought, the specification is actually correct. Any is for a
"request" when "V4L2_FIELD_NONE,
V4L2_FIELD_TOP, V4L2_FIELD_BOTTOM, or V4L2_FIELD_INTERLACED is acceptable". I'm
sure next release of Hans driver validation will check this ;-P.

Note, it's just one case, everything else seems right in your patch. What
trigger my concern is that "mixed" was present all over your test results.
Where mixed is something that should be very rare.

If you don't have time, don't worry about the rest, I can take over from here.
About checking both min and max, I'll think about it, I still think it's not
really needed. Keep in mind that this code was written a long time ago, where
literally none of the drivers where implementing the spec the same way. The
situation is much better now and I'm pushing forward cleaning up some
"workaround" code when possible.

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