Oh well, there goes my theory! I keep telling my clients things were easier when you had 2 choices, film or BVU!
Nick H
From: "Dave Hogan mactvman@yahoo.com [Avid-L2]" <Avid-L2@yahoogroups.com>
To: "Avid-L2@yahoogroups.com" <Avid-L2@yahoogroups.com>
Sent: Wednesday, October 8, 2014 6:53 PM
Subject: Re: [Avid-L2] OT: Sony BVU 800 series TBCs color direct vs. color process?
I don't have a tentelometer, but here goes...
To record on 3/4", a composite signal with a 3.58mHz color signal superimposed onto a luminance signal was first split into it's separate chrominance and luminance signals. As 3.58Mhz is a difficult frequency to record onto slower 3/4" u-matic tape/head speeds, it is first heterodyned down to 688 kHz to record on it's separate chrominance channel. This was done to different frequencies by all helical scan recording systems. (beta, vhs and 1").
On playback, the signal was heterodyned back up to 3.58mHz, and re-imposed onto the luminance signal. The heterodyne process introduced some signal degradation, so 3/4" umatic decks allowed direct output of the separate luminance and heterodyned signals to another deck for cleaner dubs, and to TBCs for cleaner color processing.
IIRC there were direct camera to U-matic recorders that recorded higher quality initially, due to the fact that the luminance channel and chrominance channels were generated directly from the RGB signals of the camera, and therefore never suffered the degradation of an initial compositing of the luminance and chrominance. The precursor to YUV signals of betacam and digital betacam, which recorded two separate color difference signals sampled at half the bandwidth of luminance.
U-matic direct color was the precursor to what also became S-video in consumer equipment, where luminance and chrominance are transmitted separately, to provide higher quality and eliminate artifacts like chroma crawl.
Dave Hogan
Burbank, CA
On Wednesday, October 8, 2014 3:16 PM, "John Moore bigfish@pacbell.net [Avid-L2]" <Avid-L2@yahoogroups.com> wrote:
Just trying to recall some of the specifics of the Sony BVU-800 series 3/4 inch machines with the external TBCs. There was a function that worked with the Sony TBC interconnect cable that involved the TBC sending the deck a dithered subcarrier signal that allowed for better chroma performance. The subcarrier signal was sent to the deck to allow for color direct vs. color processing. My hazy recollection was the subcarrier signal fed back to the deck had shifted in frequency to somehow reflect elements of the time base error that the TBC had detected. It all made sense when it was explained to me in 1982 but I'm pretty fuzzy on what was going on exactly. Anybody with a tentelometer want to set me straight?
John Moore
Barking Trout Productions
Studio City, CA
bigfish@pacbell.net
Barking Trout Productions
Studio City, CA
bigfish@pacbell.net
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Posted by: Nick Hrycyk <bigblueav@yahoo.com>
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