Framerate conversion (again sorry) 60p to 25p this time

[Panash]

I got a Kodak Zx1 pocket HD camcorder for Christmas, not at all bad for what it is and what it cost.

However switching to PAL leaves the framerate at eitrher 30p or 60p (go figure that one out!) and you may as well whistle in the wind than get Kodak to change that one. Not much good for PAL DVDs, they stutter and jitter all over the place.

Vdub & AVISynth look promising except the pulldowns & decimates don't seem that well optimised for this specific application and I can't write filters for them.

This is how I want a decimating filter to function

Running at 60p and converting to 25p the optimum decimation pattern is

0, 2, 5, 7, 10, which then repeats (as the 12th 60p frame is then synchronous with the 5th 25p frame)

You can bash the calculator like I did and find the error is actually quite low (I'll calculate & post later).

I know the actual frame rate is something like 59.** but I'll deal with warping the sound to fit later when I've got smooth 25p.

PN

and for those who can't do the modulo arithmetic here is the complete sequence for a complete second


60p:- 0, 2, 5, 7, 10, 12, 14, 17, 19, 22, 24, 26, 29, 31,
25p:- 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11

sorry, can't be bothered to do a complete second; you get the idea

[poisondeathray]

There is no "good" way of doing this.

The general approaches are: decimate (juddery) , blend frames (blurry), or motion interpolation (artifacts when generating new frames)

If I had to, I would choose option 3 which would be the smoothest, and put up with the artifacts. You could use mflowfps or mvflowfps in avisynth for example.

[Panash]

blend frames is really good for uncompressed AVI & really, really bad for MPEG as MPEG achieves good (?) compression by exploiting redundancy between frames and a requirement is that each successive frame is similar to the previous one, blended frames destroy all that.

My guess is that mvflowfps generates an intermeadiate frame by motion extraction like I guess the fahouja chips do. Am I correct?

PN

[Panash]

like
Adaptive Motion Interpolation

http://www.videointerchange.com/pal_secam_conversions.htm#Pal%20Conversion%20Quality%2...Considerations

[Panash]

http://avisynth.org.ru/mvtools/mvtools.html

wow!

[poisondeathray]

yes that's what it does: generates intermediate frames

msu has a filter that has similar function, or if you have after effects you can use pixel motion, or 3rd party plugins like twixtor

and in avisynth smoothfps, mvflowfps, mflowfps

the avisynth methods give similar quality to paid programs (i compared the results to AE pixel motion and twixtor), but are usually much faster (like 2-3x faster), and free