Request: TBC

[cj]

I've been scouring the web for a software TBC (or something with similar results), but I've had absolutely no success at all. It's a little surprising, as this seems like a natural for doing with an Avisynth filter. I'm wondering if anyone knows of one, or is willing to take on the challenge of writing one?

Since I only have a handful of tapes that need to be "de-waved", I can't really justify throwing a few hundred $ for a hardware solution.

Thanks

[Guest]

TBC is an analog domain operation performed on the NTSC/PAL analog video signal. Avisynth operates in the digital domain.

[cj]

True enough, but I'm thinking that a reasonable simulation can be effected. E.g.: You've captured an annoying wavy piece of 20-year-old video. On one or the other (or both) side of each frame, you can see the horizontal blanking area. On a clean capture, this is essentially a straight vertical for its entire length. However, on this capture, it is not straight, but wavy... and it's different every frame -- even from one interlaced frame to another. OK. What I'm thinking is that it should be possible to line up every scan line based on the transition from the blank area, and if necessary interpolate out any scan lines that got shortened due to excessive errors. Voila... end result is a video that has re-established horizontal sync for every frame.

The filter would have a parameter for the part of the frame needing correction (increasingly positive for top of frame, increasingly negative for the bottom of frame, zero for full frame) and a (optional?) parameter to give an x-axis position to sync to.

[Mug Funky]

unfortunately it's not that simple... a large number of analog sources will have wavy edges but straight lines in the picture (true!), so any TBC based on the assumption that the left edge will be the right offset will fail on this alone.

also there's the problem of dark scenes. black on the picture and the black in the horizontal blanking area may well be the same (they're not always, and they shouldn't be, but very often they are). if a dark area crosses the bottom half of the frame, a blind TBC filter will cut off a large chunk of your picture...

there's been talk about implementing something like this before, but the technical hurdles don't appear to be worth the gain for a very limited number of sources.

however, lots of consumer DV cameras have a TBC built in. i'm sure you could find one to capture with. i don't know if the results would be much good, but it's certainly cheaper.

hell, there's a good half million worth of equipment where i work, and we still can't get a good VHS capture (it doesn't come up often...).

[mg262]

It's a shame there isn't some way of directly sampling the VHS (composite or S-video) signal...

[Revgen]

Dscaler has a feature called JutterTerminator which kinda acts as a TBC, but you can only use it when feeding your video through your Tv tuner. Dscaler works well well with cheap TV tuners based on the BT8x8 chipset.