You're not going to do that using any connector normally provided on the radio. You can send the data out of the computer through a serial port but it will need to go directly into the modulator or VFO on the radio. There are special data radios available but most amateur transceivers won't do it. Video is different because of the bandwidth required so you might be better with receiver and transmitter designed for TV use.
I want to read /write data to be broadcast over the RF frequency the radio is set to. I want to intercept the traffic on the computer to run my own protocol, which may be audio/video but encoded into my protocol. I am thinking the answer is reading and writing to the tty may work, or mic input and spk output for audio. But I want data transmission, not audio.My software currently reads/writes to/from a socket. The read side of reading from a tty should probably be buffered, somehow. Something to figure out as I complete my ReedSolomon implementation and fix a few bugs in my protocol software.
Kindly, Robert