What other protocols besides SSTV can we use to transmit images using audio signals? I don't mean for any practical purpose but just wanted to see how it does when there's a lot of noise. Picture related.
>>55623516
Nothing prevents you from just modulating any binary data and transmitting it. If you want to have error correction you'll have to do your own however, which is easy. Just calculate some BCH codes (look it up, wikipedia) on a small block size (like 8 BCH code bytes for 128 data bytes) and you'll be able to recover a crapload of errors, especially if you write the BCH codes at the end of the frame and using a magic string + parity bits to detect them.
Some audio codecs like opus and aac have error recovery modes, but I wouldn't trust that since you could still easily lose a frame. Error recovery clearly belongs to the lowest level layer. What I described is the most sure way you'll still have a frame to decode.
This is what the SDI protocol uses, except instead of a codec it transmits raw AES/EBU formatted samples at much much higher bitrates.
In fact if I were to design something which transmits compressed audio data, I would take most out of the SDI specs - encode my audio packet, put some 6 or so BCH codes on every 128 bytes, do a Manchester NRTZ encoding on the bitstream (to provide synchronization and some minor error resilience) and finally modulate that onto my carrier frequency with the bandwidth I've been given.
>>55623724
Also forgot to mention you'll need to optimize your BCH code polynomial for the data range you have (for compressed data it's full range with a more or less fully random distribution). Someone has already calculated the perfect CRC polynomials for a wide range of input data and bit widths, they'll match pretty well with the perfect BCH polynomials.
For video I'd do the same but I'd also enable Intra refresh (if using H264 which supports it) since then I'll be guaranteed to have any errors in my reference frames wiped as quickly as possible, at the small cost of a little quality loss.
