Interlaced MJPEG is a big hack. Most of the streams we've found are from old
AVID tools. There are two methods to detect interlaced stream: the container
offers a height bigger (or double) than the image's height in SOF. The other
is from a APP0 marker.
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/5838>
Now it uses the JPEG parser in libgstcodecparsers, while the whole
code is simplified by relying more in baseparser class for tag
handling.
The element now signals chroma-format and default framerate is 0/1,
which is for still-images.
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/1473>