2020-05-22, 08:45
(2020-05-22, 02:20)olevelo Wrote: Hmm, I guess I'm not smart enough on DVD standards. Not sure why progressive video would get treated as interlaced, when the whole point of progressive is to be...progressive!
DVD is a slightly odd case. AIUI the DVD system is primarily based around interlaced video - but there is scope within the MPEG2 video encoding standard to encode interlaced video that contains progressive sources (i.e. there is no motion between two fields within a frame) as progressive frames, and for 3:2 video (i.e. 23.976p content carried as 59.94i) there is the scope to carry this with a flag to signal which field should be repeated, rather than encoding interlaced video frames with fields from two different film frames (which would have to be encoded interlaced). The underlying system is still based around interlaced video though (and for players to output in either interlaced or progressive 50Hz or 59.94Hz)
The point of progressive in DVD terms was more about compression quality/efficiency (it's more efficient to code interlaced sources carrying native progressive content as progressive rather than interlaced) rather than to be fully progressive standard.
Blu-ray can carry 23.976fps content as native 1080p23.976p. 'NTSC' DVD always carries it as an interlaced i29.97 interlaced signal - though the compression scheme itself allows progressive encoding modes to be used. It may seem like a minor difference - but it's not (as the video compression within a DVD MPEG2 stream can switch between native interlaced, native p29.97 and native p23.976 with pulldown flags at any point I believe - just as would be needed to encode a show with p23.976 sourced inserts and i29.7 studio sequences - and the only way to cope with this is to deinterlace to p59.94 not p29.97).
