Original commit message from CVS:
* ext/ffmpeg/gstffmpegcodecmap.c: (gst_ffmpeg_caps_to_pixfmt):
Recognize video/x-raw-gray and map to proper pixfmt.
* ext/ffmpeg/gstffmpegenc.c: (gst_ffmpegenc_setcaps),
(gst_ffmpegenc_chain_video):
Fail negotiation if pixfmt cannot be determined from input caps.
Prevent segfault accessing non-existant coded_frame, provide some
warning debug output instead.