I've used the STV5730A for a couple of years now. Apparently you've run into the problem of its availability--ST wanted to drop it, too many people still wanted it, so they raised its price and kept up production. If you find the right distributor you might still be able to get it in small quantities.

An alternative is the Mitsubishi M3506x. It's a nice chip, in stark contrast to its documentation.

I don't know anything about the Sanyo part. Have you found a datasheet for it?

The STV5730 has two clock inputs. The first is the 14.318 MHz crystal (NTSC) for its video generation, and the second is the clock for its synchronous serial interface...very similar if not identical to SPI. This clock I drove straight from my uC port pin, using bit bashing to drive it and the data line.

Again, I don't know if the Sanyo part has the same interface.

Dennis