If it plays fine in videolan, try using videolan to remux to another
format (i.e. mkv) before transcoding or whatever you want to do.
VLC > Media > Convert/Save > Add the .sdp, click Convert/Save
Now, in "settings" section, create a new profile, call it something
like "Video - MKV Passthru", choose the following
Encapsulation: mkv
Video Codec: video, keep original video track
Audio Codec: audio, keep original audio track
if it doesn't have subs you can ignore subs
Now save and choose that profile from the drop-down list
Now choose the destination file and you should be ready to go
I did not test this as I don't have any sdp files, but mkv can handle
pretty much everything.