PAL Colour Recovery from black-and-white ‘telerecordings’ (2008)

PAL Colour Recovery from black-and-white ‘telerecordings’ (2008)
techmind.org

Maybe adding color did decrease the luma bandwidth and hence the horizontal resolution. I'm not sure about that. I think bw signals just used less bandwidth overall.

But in no way did color decrease the number of lines in the image. Those are defined by the scanning raster and remained the same in color and bw television.

So what does "high frequency luma" mean? it means that the brightness of a signal horizontally along a line goes rapidly from dark to bright and back again - if that happens it stomps on the colour sub carrier and the colour goes wonky.

S-video is just a cable that puts the 2 signals on different wires so this doesn't happen.

So it turns out that the things that are the worst for this are things like checked or p;laid shirts/ties/dresses, tartans, houndstooth jackets etc etc - Think about what happened to fashion in the 70s/80s as colour TV became ubiquitous, people on TV started wearing solid colours, they didn't want to be the person who's whole body was a crawling mess - and people in the rest of the world started wearing the same sorts of styles - all those 50s/early 60s styles with checks and plaids you see on old game shows, all gone, not because of some big change in fashion - but because they could no longer be represented in popular culture.

To comply, stations would strip the colour burst from the TV video sync block before it was broadcast. This infuriated many propeller-head techies and nerds, myself included.

To overcome the problem, the 4.43 MHz colour subcarrier in the broadcast video which wasn't deliberately stripped out was used to reconstitute the colour burst. This was achieved by modifying standard PAL colour TV sets (which weren't that difficult to obtain) with the addition of some subcarrier-extracting filters and appropriate phase-locking/modifying circuitry. This was a bit tricky, as the reference phase was no longer there and the fact that it was a PAL signal (PAL - Phase Alternating Line encoding).

In fact, I recall at the station I was working for at the time we had a modified TV set in the engineering department working in colour from off-air signals (one of my colleagues was a past master at tweaking up sets this way).

Perhaps a bit of broadcasting history trivia but it sure shows the colour recovery technique in this story wasn't the first effort.

Edit: Incidentally, the same trick was used on source material such as quadruplex videotape that already had the burst stripped at other locations.

https://youtu.be/dX649lnKAU0

https://youtu.be/InrDRGTPqnE