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In my dabblings with SDR, playing around with analog video was one of the highlights. Something about this technology that was such a prominent yet opaque featu
by mrgriscom 4y ago
In my dabblings with SDR, playing around with analog video was one of the highlights. Something about this technology that was such a prominent yet opaque feature of my youth and now being able to control it from the inside out felt extremely empowering.
I wrote my own decoder in python (nowhere near realtime) because at the time I couldn't find one that handled color. The deep dive on the design tradeoffs and signal processing hacks for NTSC was fascinating.
A few of my exploits below:
Full-frame decode of VHS w/ closed captioning: https://mrgris.com/a/ntsc-cc.mp4 https://mrgris.com/a/ntsc-cc.mp4
Faithful reproduction of analog artifacts: https://mrgris.com/a/colorbars_slow.gif https://mrgris.com/a/colorbars_slow.gif
Analog scrambling: https://www.youtube.com/watch?v=qceZgxSBHwo https://www.youtube.com/watch?v=qceZgxSBHwo
Inject custom captions (it supports color!): https://mrgris.com/a/thanks.mp4 https://mrgris.com/a/thanks.mp4
Sad that these signals are gone now... would have loved to play around with SAP/MTS, teletext, C-band...
- anyfoo 4y agoI can see just by the artifacts gif that you've definitely been down the same rabbit hole. Kudos for actually pulling through on also adding some scrambling, I only read about that (and since I don't have any descrambling hardware, I would have had to do that part, too). I share the sadness about those signals being effectively gone. How fun it would have been to work with real live broadcast ones at their heyday. There still are a few ones, but they're mostly pretty basic now.
- pajko 4y agoYou might find this interesting: https://github.com/ali1234/vhs-teletext https://github.com/ali1234/vhs-teletext