So, I'm at my grandparents for winter break and I found this old tv in their basement. I also found a 3.5 mm stereo jack to AV style cable converter. So I put the two and two together and hooked the audio from a computer to the video input on the TV and got a cool oscilloscope effect shown in this video:
I want to know, though, if I can use this newfound knowledge to make pictures on the screen. Basically giving a video input it would normally be receiving but from an audio source. What do you think? It beats reading old books
I have figured out that the TV's refresh rate can fluctuate. If I give it a strong click before I play what I want it to show then it uses that click as the top of the screen every time. Also if I play the sine wave loud enough it also works and the lines on the screen don't move. Pretty exciting! I still haven't figured out pictures though or if they're even possible.
I want to know, though, if I can use this newfound knowledge to make pictures on the screen. Basically giving a video input it would normally be receiving but from an audio source. What do you think? It beats reading old books
Probably not. Looks like you're feeding it a composite input, with what I assume is an NTSC TV. Consequently the expected input is NTSC without any RF component, which means a signal with components in the range approx. (-1.25,4.75) MHz. Given that scale, any audio signal you might be able to generate it basically rounds off to being DC (up to about 20 kHz). You'd have some control over luminance around DC, but not much resolution.
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I have figured out that the TV's refresh rate can fluctuate. If I give it a strong click before I play what I want it to show then it uses that click as the top of the screen every time. Also if I play the sine wave loud enough it also works and the lines on the screen don't move.
It might be (mis)detecting some part of the signal as vsync I guess. You might be clipping, which could be seen as a delimiter of some kind within the signal. Demodulation at the TV is almost certainly a set of filters which could be confused by particularly broken signals.
Ha! You know what? I was going to test it but I didn't have a calculator with mobiletunes on it and I'm no longer at my grandparents house. But it would work the same. I was playing youtube videos and watching the screen and it was pretty cool so you're right, it would work.
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I still haven't figured out pictures though or if they're even possible. 
