Jan 17, 2010

One step forward means two steps backwards

I was thinking to use one of the many commercial encoder for the IP, but most of the "fairly affordable" encoders available, lacks the ProcAmp controls. Reading a little bit about this things, I remember that in the ETC they are using an "Output Amplifier" by Dave Jones. I don't have enough information about this thing but I realize that is very important to have control in the "TV image construction".

I now got an idea because many people building encoders have troubles; especially people using the AD parts (722, 723, 724 and 725), with these parts one can build an encoder easily, but "easy" means you will sacrifice something. On the other hand, I was seeing some professional encoders built around the MC1377 which was reported by DIY people like a bad option. I think this is because people doesn't care about the things like luma-trap, chroma-filter and B-Y/R-Y clamps, and to keep things simple they use the AD724 for that reason (the few external components). And for that reason the commercial grade equipment using MC1377 (in the past, of course) have those big PCB's. And some other companies was using the (ultra rare) MC13077 and others used the MC1378.

As a side comment, I'm reading about the use of other chips like those of Philips and Sony. About the Sony CXA's are reported as very good image quality, especially the CXA2075. Dave Pietromonaco (designer the chip) say is the best encoder built.

The first thing all this chips do, is create the video TV signal translating the RGB to the YUV colourspace, I've learned this is possible to render outside the chip with more modern chips... hmmm I need to follow this path? recreate the function of the encoder chip with submodules for each function?
I need to read more but I remember when I was working in a TV station that they was using something called the ProcAmp, a little of Google takes me to the GVG3241...

Aha! that is what I need... I think the Dave Jones Output Amplifier is something similar to this big box, at least it seems, have it the knobs one could tweak to create a good video signal.

I know all this is going beyond the Sandin IP color encoder module, but in first place the Sony encoder used it's not available, second I think will be better in some aspects (like the way the sync is added at "brute force"), and third counting with the Proc Amp one can build a very good and stable video image.

As I say on the title, all this makes me think if I build the encoder will be very very slow path, for that reason I think this will be the very last module, until I know how to make it. In the meantime, I will use whatever encoder option only to test the other modules. Looking back the whole IP I think the sync and encoder modules is where the fun is.

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