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This one does. You can configure the noise injected into the signal and when it gets too much, it loses sync and the picture starts rolling. It's actually a software NTSC modulator/demodulator, not just an effect to simulate it.

https://github.com/LMP88959/NTSC-CRT

by jmbwell21 hours ago|

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I sincerely appreciate this fidelity to fidelity

by zephen17 hours ago|

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Fidelity to infidelity?

by RgrTheShrubbr19 hours ago|

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These are both amazing projects, but why does NTSC-CRT feel more accurate to how I remember television looking than ntsc-rs?

by doubletwoyou17 hours ago|

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From what I’m seeing ntsc rs “just” emulates VHS and NTSC artifacts, whereas ntsc crt also does all the fun that has to do with CRT rasterizing

by picofarad6 hours ago|

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Finally decided to see why "raster" and it was the Germans, from latin for "rake" ; and it meant scanning-field.

by gregsadetsky22 hours ago|

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I actually posted ntsc-rs as it came up in my research - I'm also looking for something like what you're describing..!

I was also looking into https://codeberg.org/fsphil/hacktv which generates a variety of different analog tv signals (meant to be broadcast using HackRF) - but yes, I want the opposite - an analog-receiver-emulator...? And one that would be "ok" with incorrect signals // fail like an analog TV would... :-)

by picofarad6 hours ago|

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Slow scan and fast scan television encoders and decoders exist, probably the algorithm is public domain, so you can just increase the bandwidth and speed until you get what you're looking for, then you can tamper with IQ .wav files to edit the "signal".

It can't be that hard for someone with skill and determination!

by ErroneousBosh7 hours ago|

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There is, but there isn't one that puts in realistic "teletext sparkles" at the top.

I'd donate heavily to one that would actually let you send decodable teletext pages in the output ;-)

by genewitch5 hours ago|

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like the ones in Holland in the 90s? I don't remember if i noticed it in other countries at that time, but for sure there was like whole text areas on TV channels you could go to, and i think someone at the time told me there was interactive chat through the TV too but they may have been yanking my teenage chain.

by ErroneousBosh2 hours ago|

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There actually were ones that did interactive chat, but that required a modem too.

For teletext it would display 40x25 text with eight colours (the colour control codes took up a character space) and simple block graphics, which was stored in the first 25 lines or so above the top of the screen.

In the UK, the BBC ran Ceefax and ITV ran Teletext, which you could access with a button on your TV remote. These days it's actually possible to recover them from VHS recordings with really careful analysis (the bandwidth wasn't really there for it to work with a naive data slicer). During the day BBC2 ran "Pages from Ceefax" with some library music behind, when it didn't have Test Card F up (making Carole Hersee the most broadcast face on British TV, probably even to this day).