[Bug 732326] v4l2: slow UVC webcam startup due to excessive S_FMT

[GStreamer (bugzilla.gnome.org)]

https://bugzilla.gnome.org/show_bug.cgi?id=732326
  GStreamer | gst-plugins-good | git

--- Comment #11 from Nicolas Dufresne <nicolas.dufresne at collabora.co.uk> 2014-07-01 15:52:51 UTC ---
What I'm questioning is why do we need this complex save and restore mechanism
? Reading through the bug let me think that the driver issue was that:

- TRY_FMT leads to internal format change
- later G_FMT return an older format
- GStreamer detect no format change and skips S_FMT

This seems more related to the optimization we do to avoid S_FMT when not
needed (which might be related to previous attempt doing renegotiation). If
driver reports it's internal format wrong, we fail with it. This is very unlike
other implementation, which always set the format.

My conclusion is that we should drop the workaround, drop the save and restore
(as we will S_FMT if drivers reports a format different from what we want).
Then if we face the bug from 2011 again, the proper work around would be to
identify that driver string, and for that driver string enable the
no_initial_format quirk I have added recently (or simply always set the format
and drop the quirk).

Daniel, are you willing to implement this ? I can take care tomorrow otherwise.

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