odd scenario..any way to IVTC this???

[Fullasoul]

Hello,

I've run into a scenario which i've never encountered before...

I'm in the process of converting several VHS films to DVD...the first step I usually take once I've got the initial capture is to IVTC the material (these are all old 80's movies, obviously shot on film). The majority of these when observed in Virtualdub (or something similar) frame by frame is that you'll get 3 progressive frames, then 2 interlaced frames, 3 progressive, 2 interlaced, etc. That's the norm from what I've seen, and that's very easy to accurately IVTC. I HAVE had a few very old titles that were nearly ALL interlaced frames, and obviously i couldn't really IVTC those...I instead used TomsMoComp on them.

Now here's the strange thing...I just recently ran up against one where the source material runs just as follows: 3 progressive, 2 interlaced, 3 progressive, 3 interlaced....and that cycle repeats constantly!! I'm wondering if anyone has any ideas or settings I could use to IVTC this material....I don't really want to have to use TomsMoComp on a source that has so many good progressive frames in it unless I really have no choice. Any suggestions???

[Guest]

First apply Telecide() without Decimate(). Observe the pattern of duplicates. Suppose it is like this (where n is new and d is duplicate):

n n n n d n n n n n d

and this pattern repeats. Now you use multiple Decimate() calls with appropriate cycles to get the end frame rate you desire. For this example, you could do:

Decimate(11)
Decimate(10)

That would remove the duplicates and leave you with 9/11 * input frame rate.

[Mug Funky]

if you have one that's all interlaced, it as probably converted to tape by simply pointing a video camera at a screen.

it's possible that telecide can help for this, but i'd recommend a smart bob and an "unblend" filter, then decimate.

[edit] but after all that, you'll probably have comparable quality to tomsmocomp anyway, seeing as these tapes are so old. but it will help you with those annoying "peculiar blended" frames caused by the transition from one frame to another being caught on one field. (i have the same problem with a PAL clip, and it's quite annoying....)

[Fullasoul]

Thanks for the tip Donald....that worked like a charm...except for one small detail. My file now has a unique framerate of 24.521, which obviously CCE won't touch. I have a feeling that this is probably a simpler question than my original, but unfortunately since I've never done any frame rate conversions other than NTSC to PAL (or "Film"), I have to ask....what's the best way to get this back down to 23.97fps???

Thanks,

Fullasoul

[Wilbert]

Just use AssumeFPS(23.976) and stretch your audio a bit (in an audio editing program).

[Chainmax]

Wouldn't such a change screw up the video (i.é: wierd motion)?

[Boulder]

Originally posted by Chainmax
Wouldn't such a change screw up the video (i.é: wierd motion)?

No, it will only slow down the video since AssumeFPS doesn't add or remove frames;)

[Mug Funky]

if you don't want the bother of using an audio app, just go:

assumefps(23.976, sync_audio=true).resampleaudio(48000)

or if you don't like avisynth's resampler, i think TMPGenc will use SSRC, not sure about CCE. personally, i wouldn't worry about audio resampling quality too much considering a VHS tape isn't going to have many non-noise frequencies above even 10k (most resampling artefacts come from frequencies above the niquist frequency of the audio format, in this case anything above 24k.)