This IS the Avid L2: Re: [Avid-L2] OT: Sony BVU 800 series TBCs color direct vs. color process?

Friday, October 10, 2014

Re: [Avid-L2] OT: Sony BVU 800 series TBCs color direct vs. color process?

Here's how "subcarrier feedback" worked:

The TBC analyzed the time-base error of the composite signal and created a "jittered 3.58" signal with matching time-base error. When fed back to the deck, this jittered 3.58 forced the playback chroma (3.58, heterodyned back up from the 688 color-under signal) to have identical time-base error with the composite signal. Thus the composite video signal was coherent (chroma and luma with fixed phase relative to each other) albeit with time-base error. This coherent-but-jittering signal could then be processed in "direct" mode to remove the time-base error from the composite signal, just as could be done with "direct" recorders such as Quad. No chroma-luma separation (with attendant losses) was necessary.

This is NOT the same technique used in TBCs with Y-688 inputs or Y/C ("S-VHS") inputs.

Can we move on now? :-)

On Fri, Oct 10, 2014 at 1:18 PM, bigfish@pacbell.net [Avid-L2] <Avid-L2@yahoogroups.com> wrote:

It's the how it worked I'm trying to remember. The subcarrier feed back to the deck somehow neutralized the time base error of the chroma decode or some such thing. If you can fill in the blanks in my memory maybe I can let this go.

---In avid-l2@yahoogroups.com, <DennyD1@...> wrote :

On Oct 9, 2014, at 12:26 PM, bigfish@... wrote:

> Mr. Dennis,
> The color direct mode was a switch on the front of the BVU TBC inside the flap cover IIRC. The choices were "direct" which required the TBC cable or perhaps a bnc cable could also be used to feed a SC subcarrier signal back to the deck from the TBC, and the other choice was color process. When wired up with the sony TBC cable the direct mode was better for the picture quality so I was told and still believe to be true.

I say:

I didn't recall it actually saying 'direct' on the TBC, but I believe you. I'll have to check that for my own sanity once I get behind my Sony TBC for a look-see.
I do know how it worked, I only thought they didn't call it 'direct'.

Dennis Degan, Video Editor-Consultant-Knowledge Bank
NBC Today Show, New York