I'd like to start generating (and perhaps also capturing) composite video (PAL) signals from a digital source, eg. FPGA. However, while my digital logic/programming skills are covered, I'm lacking a lot of fundamental analog concepts, and I'm a little lost.
From what I understand, the idea basically boils down to outputting the correct voltage at the correct times from an output pad on my FPGA. I'm thinking that the entire signal (including sync pulses/color carrier modulation/etc) could be generated in the digital domain, and then passed through a DAC. I don't think I'll have much issue figuring these parts out.
The output voltage from the DAC needs to be connected to an output terminal. Already here I'm wondering how this would work - what do I need to worry about? I assume it's not enough to just connect the DAC output pin and ground to the terminal? What kind of current would I need the pin to output/source? What kind of current needs to be on the terminal? Might I need some kind of amplifier/protection circuit in between them? Are these even relevant questions?
From the terminal, the signal would then be transmitted along a composite RCA cable to the receiver on the other end. I know that composite video cables have a characteristic impedance of 75ohms, but I'm not sure what that means beyond knowing I have to match it with my output, which I also don't know how to do. Is this related to my previous questions?
Is there anything else obvious that I'm already overlooking?
I'm also curious about how this might work for audio signals, though I guess it's all the same in theory, just with perhaps some different parameters and maybe some filtering (eg. DC blocking) for the "pure" AC stuff?
Any and all guidance/responses appreciated. Thanks in advance!