[Cin] even more OT: time-base correctors

[Andrew Randrianasulu]

I read elsewhere [0] you might want such device for bad quality vhs tapes -
yet they tend to expensive, either in terms of money or skills.

Still, it was pleasure to find some schematic I thought completely lost to
sands of time:

https://web.archive.org/web/20181219122351/http://marcusgun.awardspace.com/
newvidproc.html

https://web.archive.org/web/20051101234823/http://www.astro.uu.se/~marcus/private/tbcsch.jpg

[0]
https://forum.videohelp.com/threads/402960-VHS-recording-advices-would-be-appreciated!/page2

reviews on Amazon tend to be mixed - complex and costly devices do not
works for some, yet work for others (due to condition of device itself?)

"Short Overview: A time-base corrector is essentially a device that
reconstructs a composite video signal scan line by scan line. Composite
video signals (both NTSC and PAL) interlace two fields of lines to
construct a single frame. With NTSC, you are viewing (approximately) 60
fields per second, while PAL uses 50 fields per second. Each line has a
pulse/signal that tells the display device to start the next line. If the
timing is off even slightly for a single field or for a set of scan lines,
the individual scan lines don't align with each other and you get a jagged
effect. A time base corrector tries to correct the timing for the
individual scan lines to improve the picture. This process never works
perfectly, but you can definitely see an improvement on most video material.

A full-frame TBC actually stores the lines to build up a single frame and
then sends them to the video display or monitor. This is preferable to a
unit that just tries to adjust each line as it is processed. An advantage
to the full-frame units is that they normally eliminate the copy protection
signals that are often placed in the unseen scan lines between fields and
frames. They do this because they insert their own synch signals,
discarding the "corrupted" ones that Macrovision and other copy protection
schemes have deliberately inserted. (Yes, I know this is a simplified
description of a complex process.)

The 8710 is one of a series of TBC units that are reasonably priced and do
a pretty good job of correction. The improvement is most noticeable when
you have vertical lines in the picture (telephone poles, lettering, etc.)
The other features on this unit (saturation control, color correction, and
so forth) are secondary. It is a full-frame unit and it builds each frame
using two fields. This allows better alignment of the scan lines and a
better picture."

https://www.amazon.com/AVT-AVT-8710-Time-Base-Corrector/product-reviews/B0015M48RS?pageNumber=2&reviewerType=all_reviews
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