2015-06-25, 14:11
(2015-06-24, 00:08)noggin Wrote: (But then I've seen high-end broadcast kit get the SD 4:3/16:9 line-width of 702 vs 720 stuff wrong when up/downconverting between 576i and 1080i such that picture width changes were happening for a few frames on BBC One HD in the early days... The technical rule is that an SD 4:3 or 16:9 picture is 702x576 NOT 720x576. The extra 9 samples each side are to avoid clipping transients and mean the 720x576 frame is slightly wider than 16:9 or 4:3. If you scale a 720x576 image to 1920x1080 or 1280x720 it should be the 702x576 portion that is scaled to full screen NOT 720x576. Similarly a 1920x1080 or 1280x720 16:9 image should be scaled to a 702x576 area within a 720x576 frame, not stretched to 720x576 full width)
I thought about the 702 in 720 scale issue some time ago. I think it's less of an issue now the BBC have stopped doing it and like C4 started using 704 for dvb instead.
When they did do 702 in 720 it was quite inefficient for mpeg2 - if you looked closely on some pans you could see artifacts because it made the edges need more bits than full width (or if the black had been 16 wide).
ITV seem to use full 720 no bars, as do DVDs and of course some channels use 536 (IIRC).
I would have liked to test all this new stuff on my baytrail - but I bought it to be a headless router/nas/qos/pvr box and that's its job now and I can't easily reinstate the box it replaced.
After all the issues playing with it as an htpc (all fixed/mitigated now) I thought doing basic stuff would be easy, but I still manage to hit new usb/v4l bugs (need to spin a cpu to avoid usb/v4l occasionally loosing some data from tuner sticks) so my "baytral fun" continues differently :-)
