vtdec: Frames will not be ordered correctly if no PTS present
As noticed in a review for !5163 (comment 2038221) - currently vtdec will not be able to output correctly ordered frames if PTS is missing. Quote @slomo:
The solution here would be to actually parse the H264 bitstream to correctly reorder frames and calculate the PTS from the DTS.
There's code for that in the libgstcodecs library (for the stateless codecs), but that's probably not directly re-usable.
There's also such code in the h264timestamper element.