Similar to h264parse, this patch enhances the element to parse LCEVC enhancement
data from SEI, and attach it to output buffers as GstLcevcMeta. The 'lcevc'
field in the output caps is also set to TRUE or FALSE depending on whether LCEVC
data is present or not.
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/9335>
The framerate should only be replaced (and corrected for alternating field)
when it is parsed from the bitstream. Otherwise, the upstream framerate
from caps should be trusted and assumed correct.
Related to gst-plugins-bad!2020
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/4259>
