Q: Bob deinterlace DV and output (un)cropped frame to H.264
I have lots of old interlaced DV files, some converted from VHS. I currently have most of them converted to deinterlaced H.264 so I can view them on a progressive computer monitor.
I'm re-editing some of that old footage. I wonder if I should “bob” deinterlace (*) so I don't throw away 50% of the footage in the process. And maybe also include all image area of the DV frame (**).
(*) The usual deinterlacing throws away top or bottom field. One the other hand, “bob” deinterlacing preserves both fields and doubles the frame rate making the movementes smoother.
Bob deinterlacing makes a progressive frame of each interlaced field. PAL is 25 frames per second but also 50 fields per second (NTSC is 30/1.001 frames per second and 60/1.001 fields per second).
(**) With old analog VHS converted to DV there is image content only in the square pixel PAL 768x576 or NTSC 640x480 area because the extra width is used for analog horizontal blanking (***). On the other hand, in DV there is information in the whole square pixel PAL 788x576 or NTSC 656x480 image area.
So I now wonder if I should export the DV footage to output all fields and the whole square pixel PAL 788x576 or NTSC 656x480 frame instead of the usual PAL 768x576 or NTSC 640x480 cropped frame. On the other hand it might be best to crop to the standard 4:3 PAL 768x576 or NTSC 640x480.
I experimented a little with FCP and it is possible to convert all interlaced fields and the whole DV frame with this workflow:
a) the whole DV PAL 788x576 or NTSC 656x480 frame
b) the standard 4:3 PAL 768x576 or NTSC 640x480 frame
In Final Cut:
a) File > New... > Project > Custom 788x576 50p (PAL) or 656x480 59.94p (NTSC)
b) File > New... > Project > Custom 768x576 50p (PAL) or 640x480 59.94p (NTSC), then crop L10+R10 pixels (PAL) or L8+R8 pixels (NTSC)
Then share:
a) File > Share > Apple Devices 720p/1080p > Format: Computer, Resolution: 788 x 576 (PAL 50 fps) or 656 x 480 (NTSC 59.94 fps)
b) File > Share > Apple Devices 720p/1080p > Format: Computer, Resolution: 768 x 576 (PAL 50 fps) or 640 x 480 (NTSC 59.94 fps)
Seems to work OK and the movements are smoother and un-film-like.
p.s. (***) PAL rectangular pixel actual active picture size 702x576 corresponds 768x576 square pixels. NTSC rectangular pixel actual active picture size 710.85x486 corresponds 648x486 square pixels. Those are the actual active picture square pixel 4:3 ratios. The sampling matrix of standard definition NTSC DV is 720x480. Notice that inside (and outside!) of it the actual active picture size is 710.85x486. Weird but true.
Posted on Apr 27, 2016 1:44 PM