[Bug 725860] v4l2src: Fix using v4l2src with Hauppauge HDPVR video capture device

[GStreamer (bugzilla.gnome.org)]

https://bugzilla.gnome.org/show_bug.cgi?id=725860
  GStreamer | gst-plugins-good | 1.2.3

--- Comment #26 from Will Manley <gnome at williammanley.net> 2014-04-01 17:01:25 UTC ---
Right, so this makes sense in the context of Comment 4 and Comment 6:

Tim in Comment 4 said:
> why doesn't the driver return the right size during probing,
> so that we're requesting the right size from the start? (rather than 0x0)

Will in Comment 6 said:
> Ah, the reason is in `gst_v4l2_object_probe_caps_for_format` we see:
>
>   if (pixelformat == GST_MAKE_FOURCC ('M', 'P', 'E', 'G'))
>     return gst_caps_new_empty_simple ("video/mpegts");
>
> and so it never even bothers going through the finding out the size dance.  I
> guess this sort-of makes sense, maybe the mpeg stream contains multiple video
> streams, or they come and go.  Maybe the video stream could change resolution
> half way through.

So the reason it's working is that in 09dabd4b Youness Alaoui removed the code
that was preventing probing.

I've confirmed this theory by reverting 09dabd4b locally.  The failure mode is
different to version 1.2.3 but this confirms that 09dabd4b fixes the issue.

The patch is definitely still valuable as it fixes the GStreamer-CRITICALs
associated with fixating missing parameters in the caps.

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