Video format conversion [??]

Format conversions size change frame rate conversion (de)interlacing

Size change Normally treated as a problem of image resizing; each image is processed separately

Interlaced signal Similar to a spatial quinqunx…

Interlaced signal Similarly, the spectrum of a quinqunx is this:

Interlaced signal Ideal deinterlacing:

Deinterlacing In the areas without motion, the ideal process is temporal interpolation Where there is motion, I can interpolate spatially Or, better (but more difficult), to use motion compensated temporal interpolation (see later)

Deinterlacing A video-temporal (VT) interpolation filter would theoretically solve the problem, if the signal were bandlimited prior to interlacing

Deinterlacing Example of edge-dependent interpolation: con

Deinterlacing Example of VT median filter

Deinterlacing Better: motion compensated temporal interpolation

Frame rate conversion From film (24 fps) to TV (PAL/Secam) - the film is accelerated (24 -> 25 fps) and each image is shown twice -> 50 fps Not in the USA (60 field/s ,actually 29.97x2)-> telecine - 12 field are added every 24 frame -> 60 fps: 2-3 pull-down: - the film is slowed (24 -> 23.976) - the third B is often omitted in DVDs (its equal to the 1st): 480i24 format, and the DVD adds it on-the-fly - similarly, 3-2 pull-down: AAABBCCCDD

Frame rate conversion ... and if we need to return to progressive, 60fps: two ways Weaving takes two successive interlaced fields and reinterleaves them to create a progressive frame - works well - if the original material was progressive, like a film that has undergone the 2:3-pulldown process, and - provided the disc tells the player that it was. Bobbing, the normal process for generating a progressive signal from interlaced video, takes a single field and creates a full progressive frame from it by line doubling or line interpolation

Frame rate conversion If the original material was interlaced video, not 2:3-pulldown film, weaving can cause artifacts More advanced progressive-scan conversion systems combine bobbing and weaving, depending on the content (motion…) of the image. If the monitor is 72 Hz: simply AAABBBCCCDDD…

Scan rate doubling Field repetition: te*=to to*=te Gives loss of resolution Frame repetition te*=te to*=to generates artifacts if motion is present