|Originally posted by mavromatis
So there is no rcv1 and rev2 to SAV/EAV ic out there? :) Where do the SAV/EAV codes come from?
The EAV and SAV codes must be generated form H&V sync and inserted into the parallel bit stream. A lot depends here on the phase relationship of the H timing signal. The codes must be inserted at exact pixel locations. As there is no set standard for internal timing signals within a design, the user must make their own logic circuit. Some MPEG decoder chips put EAV/SAV in the data before it leaves the chip. They also probably can enable or disable that via a control registure. There is no video type timing in the MPEG stream. Of course there is sync info but not in a video friendly form. Fast memory used to be expensive. So initially video equipment manufactures did not want to waste bits storing sync info when the whole circuit was synchronous anyway with plenty of places to get timing signals.
Today the best approach is an FPGA. It's not too complex a circuit however the design tools can cost $1000 and up. The logic could also be fabricated from discrete TTL or HC parts but now we get into interconnect timing concerns. A happy medium for the DIY may be GALs which have low cost developement systems. But they cannot do the job alone like an FPGA can. So we would still have an involved wire warp board.
The DirecTivo does not have EAV/SAV. I verified that on a logic analyzer. I too was initially fooled by the bt656 statement on the SAA7120 data sheet. It can also work as CCIR 601 and does in the case of the TiVo
Sony did make a chip that did all the TRS insertion. But it's also a mux designed to intergrate seperate YcBcR data busses. We don't need this function as our data streams are already muxed. I looked into this, actually have some chips, but the glue logic needed to fool the mux into working with an already muxed stream was just about as complex as a fresh design.
If you want to get more info there is a really good book by Keith Jack called "Video Demystified". It is a collection of many standards and papers plus a lot of knowledge by the author who is an video procesing IC designer.