mpegvideoparse calculates wrong pixel aspect ratio

Submitted by Matej @Knopp

Link to original bug (#781918)

Description

Created attachment 350679
Patch

If there is no sequence extension or sequence display extension present gst_mpeg_video_finalise_mpeg2_sequence_header will never be called and will not calculate proper aspect ratio.

it's safe to call gst_mpeg_video_finalise_mpeg2_sequence_header without sequence extension, in which case it calculates aspect ratio from sequence header width/height and DAR.

Patch 350679, "Patch":
0001-mpegvideoparse-always-gst_mpeg_video_finalise_mpeg2_.patch