Original commit message from CVS:
* ext/ffmpeg/gstffmpegdec.c: (gst_ffmpegdec_frame):
So, stupid ffmpeg.... Not all [en|de]coders set AVFrame->type.
This should handle the case where AVFrame->reference is set to 1 (which
is the equivalent of a keyframe).
Also fixes #323286.
I tried a truckload of other files with this modification and it didn't seem
to break playback.