TBC still required for RF capture? (VHS-decode)

[latreche34]

I meant by DOC the drop out compensation when tape loses signal in one or more scan lines. Yeah, the dreaded lack of chroma band on the right edge on most V8/Hi8 camcorders, Not sure if this is PAL specific or all formats, Glad you were able to get rid of that problem and you also managed to reduce the head switch noise.

[Novgorod]

Quote:

Originally Posted by latreche34

I meant by DOC the drop out compensation when tape loses signal in one or more scan lines. Yeah, the dreaded lack of chroma band on the right edge on most V8/Hi8 camcorders, Not sure if this is PAL specific or all formats, Glad you were able to get rid of that problem and you also managed to reduce the head switch noise.

Oh, I wasn't caught up on all the abbreviations .. Dropout handling depends entirely on the field start and line start detection algorithm, so that's (again) up to you since different approaches may perform better or worse depending on the format, player and tape condition. Typically you would scan the luma signal for valid sync pulses (value below and then above a certain threshold for a few microseconds) and then check the time between consecutive sync pulses. If it's outside a certain window to allow for tape flutter (like more than 1.5 times the nominal line time) it's a missed sync pulse due to a dropout and you replace it with an artifical one 64µs (for PAL) after the last valid one (or multiples of that if several consecutive lines are missing). You can still render the bad line, since the dropout may not affect the entire line, or flag it for masking by vertical interpolation. Some care needs to be taken at the head switch position because there is some timing mismatch (the line at the head switch position is too short or too long on alternating fields).

I don't know how well it will perform in extreme cases with lots of flutter (large deviation from the nominal line time) and dropout glitches. This has to be tested case-by-base to improve the algorithm.

[NJRoadfan]

Related, Bob from RetroRGB recently conducted an interview with folks involved in RF capture:

https://www.retrorgb.com/domesday-la...interview.html

I have been keeping an eye on the various developments. Eventually I'll get a hold of an RF capture device and give it a shot. At least some of the VHS decks I own now have documented tap points. No, I don't expect this to replace a standard video capture setup in the near future.

My primary interest in this tech succeeding is that high end TBC/DNR VCRs are eventually going to be impossible to find. When working, this method allows for just about any VCR to produce better output. It also allows better quality from other formats, such as Betamax, that never had high end decks created for it.

Note that RF capture for preservation is NOT a new thing. Over on the vintage computer side of things, flux imaging of floppy disks is now a thing. This allows for 1:1 archiving and preservation of copy protected software from the 1980s, many of which can't be reproduced otherwise.