[Bug 702638] New: v4l2: Optimize negotiation by removing the query filter

[GStreamer (bugzilla.gnome.org)]

https://bugzilla.gnome.org/show_bug.cgi?id=702638
  GStreamer | gst-plugins-good | git

           Summary: v4l2:  Optimize negotiation by removing the query
                    filter
    Classification: Platform
           Product: GStreamer
           Version: git
        OS/Version: Linux
            Status: UNCONFIRMED
          Severity: normal
          Priority: Normal
         Component: gst-plugins-good
        AssignedTo: gstreamer-bugs at lists.freedesktop.org
        ReportedBy: sjoerd at luon.net
         QAContact: gstreamer-bugs at lists.freedesktop.org
     GNOME version: ---


Created an attachment (id=247250)
 --> (https://bugzilla.gnome.org/attachment.cgi?id=247250)
proposed patch

As cameras tend to have a quite specific set of capabilities (specific
framerates for each resolution), getting the peer caps filtered by our
probed caps can cause a big increase in the caps size which slows down
things quire a bit.

As for negotiation v4l2 iterates through the caps of the peer to find the
first intersection with the probed caps, getting the fully expanded
intersection of capabilities is not useful.

Using the same testcase as for bug #702632, adding this patch on top of
the patches suggested there speeds up getting the inital frame from
around ~14-15 seconds to around ~3-4 seconds.

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