[Bug 726194] New: 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

           Summary: v4l2src does not cope well when a capture card is
                    sometimes interlaced, sometimes progressive at the
                    same resolution
    Classification: Platform
           Product: GStreamer
           Version: git
        OS/Version: Linux
            Status: UNCONFIRMED
          Severity: minor
          Priority: Normal
         Component: gst-plugins-good
        AssignedTo: gstreamer-bugs at lists.freedesktop.org
        ReportedBy: simon.farnsworth at onelan.co.uk
         QAContact: gstreamer-bugs at lists.freedesktop.org
     GNOME version: ---


v4l2src currently sets its caps wrongly if a capture card can handle the same
resolution in both progressive and interlaced form; it indicates
"interlace-mode=progressive", when this is not true. Compounding this,
V4L2_FIELD_ANY (which is the same as "interlace-mode=mixed") was treated as
progressive, too.

The long term answer is to redo v4l2src's caps handling, so that interlace-mode
is mixed for V4L2_FIELD_ANY, progressive for V4L2_FIELD_NONE and interleaved
for the three V4L2_FIELD_INTERLACED options. In the short term, however, the
patch I'm about to attach makes us try interlaced first - this works for me,
and sets "interlace-mode" to "mixed" correctly for sizes that can be either
progressive or interlaced, while still setting it to "progressive" for
progressive-only capture sizes

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