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There are people who recover teletext from VHS tapes, for example: http://www.uniquecodeanddata.co.uk/teletext76/bbc1_1983-06-23/ http://www.uniquecodeanddata.c
by ahoka 8y ago
There are people who recover teletext from VHS tapes, for example: http://www.uniquecodeanddata.co.uk/teletext76/bbc1_1983-06-23/ http://www.uniquecodeanddata.co.uk/teletext76/bbc1_1983-06-2...
- LeoPanthera 8y agoI've actually done this. Recovery from VHS tapes is at least technically possible, but not reliable, and relies on pages being sent multiple times. (And often a bit of guesswork.) It's much more reliable from S-VHS recordings, though those are understandably much rarer.
- dylan604 8y agoIs there an FFMPEG type of filter that can translate information recorded in the vertical interval space like CCs or even VITC? All of the equipment I ever used expected an incoming video signal for processing. For archival processing, it would be an interesting approach when finding the proper video based equipment would/could be difficult.
- LeoPanthera 8y agoSpecifically for teletext (so, in general, PAL territories only), you can use this: https://github.com/ali1234/vhs-teletext https://github.com/ali1234/vhs-teletext
- mzs 8y ago$ ffmpeg -f lavfi -i "movie=test.ts[out0+subcc]" -map s output.srt https://stackoverflow.com/a/27780366/7106583 https://stackoverflow.com/a/27780366/7106583
- dylan604 8y agoI love FFMPEG and everyone that contributes to it. For the really old farts (of digital media), I also loved the old AVISynth contributors. I've noticed a lot of the old plugins for that are now available as FFMPEG filters.
- dylan604 8y agoFinally had a chance to look into this further. The filter you found requires an MPEG2 Transport Stream. That tells me that this filter is just extracting the CC data within the MPEG stream. We've had tools to do that since MPEG2 was a thing. I'm specifically talking about a full raster SD video capture at 720x486 NTSC with the VBI information visible. Is there a filter that will read the white dashes in the VBI and do some sort of optical translation of the dashes into something like an SCC file. A long time ago in a galaxy far far away, I used to actually be able to decode the VITC in my head by reading the dashes. It started out as a joke while bored working 3rd shift where we'd offset the H/V delay on a monitor. It actually became a useful skill when we started digitizing the full raster video image but the time code was not captured/saved in the resulting digital media. Reading the white dashes allowed me to then reset the time code of the digital file. For those wondering, there were 2 types of time code in video tapes. LTC (linear time code) was an encoded audio signal that would sound like a series of tones that would be decoded into time. VITC (vertical interval time code) was visibly encoded into part of the video signal that consumer televisions would not display. Normally, the player would "listen" to the LTC while playing and fast scan/rewind. While a player was paused onto a video frame, it could no longer "hear" the LTC. It would instead then switch to decoding the VITC. The VITC was also not able to be decoded at fast speeds since it went by too quickly. When the VITC and LTC did not match, all sorts of interesting things would happen in an edit bay.