Raspberry Pi Pico generated colour composite PAL video demos, early 2023

[@cherrymountains72]

Awesome 3D demos. I’ve just started doing simple 3D stuff in C on my RPi with a LED HAT and this has given me some inspiration. Thanks!

[@youtubasoarus]

Those 3D demos are so cool! I'd lose my mind if I could do that! 😵

[@dimitrisantiago3359]

Great Job! 👍

[@Papinak2]

Regarding the memory limitation, would it help to store in YUV, while reducing chroma resolution and bit depth? Same method was used by video tapes which had limited bandwidth, you can get away with quite a lot of compression on chroma channel with negligible effect on quality. Regarding the signal, are the two fields you are sending truly identical? There are different synchronization pulses between odd and even fields, so that might be the issue. Sorry if the answer is apparent from the code, I can't figure that out with my knowledge :)

[@Aeduo]

Wonder if it'd even be useful to store it as brightness, chroma intensity, chroma phase, so it's already in a format that can be modulated rather than needing RGB to whatever conversion. But yeah I think YUV would be closer to the analog colorspace.

[@jjplano]

really cool man, congrats! have you taken the project any further? I was thinking about the possibilities to build a simple video synthesizer/visualizer using this board (adding an interface for a little bit of control and options to change settings), and your tests show real potential for that. what do you think about implementing the basic of synthesis (oscillators, modulations and such) on the pico? have you come across any project that does something like that (as video or audio). thanks!

[@theguruofthree]

I've been letting the project mature for a bit while I work on other things. There are a couple things I'd like to do with trying to clean up the code some at the very least. I've looked into audio output some as I think that'd be a cool addition and it seems some simple square wave audio output with the PWM looks fairly straight forward. I'm not sure about using the Pico as a more complex synthesizer beyond that. I also love the idea of using this as a display for an audio spectrum visualiser but I'm worried doing the FFT needed for that would take too much CPU to run the display at the same time. Maybe with two Picos working together though.

[@ahsankaukab4651]

The RCA connector is connected with Ground and Green pin of Rpi Pico i.e Pin 19 right ?

[@theguruofthree]

The ground of the RCA is attached to the ground of the Pico. The RCA signal is attached to a DAC made up of resistors attached to pins 1, 2, 4, 5, 6, 7, 9 and 10 (33k, 18k, 10k, 5.6k, 2.2k, 1k, 560 and 270 Ω).

[@denislatushkin9762]

nice job! but is there any way to grab PAL signal?

[@theguruofthree]

I have been thinking how to read a PAL signal some but sadly I haven't figured out a way to do it yet. I think maybe you could get the luminance and record a black and white picture, but getting reading the carrier to get the colour is tricky.

[@matgaw123]

Is pico flash fast enough to out put it on the fly ? Or one frame at the time to memory

[@theguruofthree]

Yes the flash is fast enough to read from directly to screen, as long as what's in flash is already converted to YUV. The Pi Logo and test card are both being read from flash for each frame it's displayed, as well as parts of the badger badger badger.

[@matgaw123]

What kind of dac does it use?

[@matgaw123]

Resistor ladder maybe?

[@matgaw123]

Oooh now I see

[@matgaw123]

Cool video tho

[@theguruofthree]

Regular resistor DAC - not even a resistor ladder. 33k, 18k, 10k, 5.6k, 2.2k, 1k, 560 and 270 Ω resistors each on its own GPIO pin.

[@neuro]

cyan with an s not cyan with a k! 😊

[@theguruofthree]

Ahahaha! Yes absolutely should have been 'sai-an'!