@kitlkatz,
It depends on what you mean by input video. If you mean feeding a composite video signal (like from e.g. a video output of a VCR or another N9/00) then the answer is unquestionable no. A video signal needs a bandwidth of a few MHz while the audio input can only handle a few kHz.

If you mean streaming digital video through the audio port, then sure, as juiceme said, all you need is writing a driver but the bitrate would be fairly small. Do not expect more than about 19 kbps.

Lastly, if you mean copying a video file using the audio port as a serial console then that... a file is a file. This is no different than the original question.