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I've got an NEC S-VHS deck that I believe is from the late 80s that has digital TBC. It averages frames with 3 different settings and can be bothered by motion or 3-2 pull down from film if set to the most aggressive setting.
An appreciable percentage of non-pro VHS decks didn't start getting TBCs much until DVD recorder combos came out (needed it for dubbing). In the consumer space it was typically only higher end S-VHS decks that got TBCs in the 80s and 90s, because it was an expensive feature that typically you would only go to after (or along with) the move to S-VHS. The people who bought S-VHS were the only ones who cared enough about picture quality to spend the extra on a TBC, and the number of S-VHS decks without TBC speaks to how many of the S-VHS buyers thought it wasn't necessary/worth the cost. S-VHS decks can record and play in VHS mode too (S-VHS-ET decks can even record S-VHS signal to the cheaper VHS tapes which is a feature I loved when I was archiving to tape). Personally if I had to start from scratch I'd look for a DVD-recorder/VHS combo with SQPB, and HDMI like my Toshiba. Then I'd have everything from RF output to HDMI for capture to digital...Like I do now.
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Tom C. Zenith: The quality stays in EVEN after the name falls off! What I want. --> http://www.videokarma.org/showpost.p...62&postcount=4 |
#2
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#3
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Pioneer sold its first Laser Disc player with digital video memory in 1988-89, the CLD-3030. That machine only stored one field of NTSC video, so that is an indication of the cost of memory at that time. It also may be that just storing frames/fields of video is a lot simpler than actually manipulating that memory as needed for time-base correction. That level of information is beyond my knowledge.
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Chris Quote from another forum: "(Antique TV collecting) always seemed to me to be a fringe hobby that only weirdos did." |
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__________________
Tom C. Zenith: The quality stays in EVEN after the name falls off! What I want. --> http://www.videokarma.org/showpost.p...62&postcount=4 |
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After about mid-1981 or so, probably 99% or more of Laser Discs were Extended Play (CLV), so that feature was a real treat to have.
__________________
Chris Quote from another forum: "(Antique TV collecting) always seemed to me to be a fringe hobby that only weirdos did." |
Audiokarma |
#6
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Flagging/skewing/hooking is a defect that can originate from mechanical issues, but this is exactly what TBC should be able to fix. This is from 1985. One would expect if not late 1980s then 1990s models to take advantage of digital processing. OTOH, it looks that memory price was decreasing slowly and only dropped significantly by mid-late 1990s. |
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The whole history of VTRs is a battle against mechanical imperfections.
Quadruplex, with its small drum, could, under ideal conditions, keep the jitter down to 100ns or so, good enough for synchronous monochrome replay. It wasn't easy to avoid banding and other visible errors. The first TBC was Amtec, an analogue delay line with varicaps instead of fixed capacitors. Correction range less than 1uS (I think) but it was enough. Followed by Colortec to get good enough stability for direct NTSC playback. The frequency spectrum of timing errors on helical scan VTRs was very different. Much more low frequency stuff due to the big drum. Hence hooking. Still all sorts of other errors caused by tape flutter and heaven knows what else. If the errors are bad you get velocity errors along a line which aren't easy to correct. Colour under was a brilliant kludge to record colour on low-cost VTRs, at the expense of wrecking the delicate relationship between colour subcarrier and H. Didn't matter in domestic environment. General purpose TBCs had a tough job following all these errors on all sorts of VTRs and tapes. When memory was expensive enough that you only afford a few lines of storage a few early TBCs had a feedback output to drive the capstan motor of the VTR via a power amplifier in order to get true synchronous replay. No idea if this was used very much in practice. I once did it manually with an audio oscillator, public address amplifer with 100V output and a step-up transformer. I could just about keep an Ampex 7003 1" VTR within the correction window of an early CVS517 TBC. But not for very long. From the early 1990s I designed framestore TBCs for a small company called G2 Systems in the UK. They also did standards conversion, though not to full professional quality. The first versions used dedicated framestore FIFO chips. Later I used first generation SDRAM with an FPGA to give multiport video framestore memory. There were great "get out of jail" boxes in their time. You could stick just about any SD video signal into them (including S video, SDI and in some cases analogue component) on PAL/SECAM/NTSC (and oddballs like NTSC443, PAL-M, PAL-N) and have the output perfectly timed into your vision mixer. |
#8
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Which is why it seems to me that it made sense to build a TBC into VCRs themselves, at least into expensive top level models, as manufacturers shoudl have known better what sorts of errors their machine produced. Ah, well.
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