Den 28.09.2021 18:36, skrev Andrew Randrianasulu via Cin:
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/pr...
[0] https://forum.videohelp.com/threads/402960-VHS-recording-advices-would-be-ap...
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."
I want to confirm from my own experience the importance of using a good TBC at the End of the analog workflow from tape source playback, just in front of A/D converting and recording. Especial early generation Hi8 recordings, in the first nineties with Sony CCD-TR805 & TR808 camcorders, got unacceptable images with jitter, flagging and even dropouts. If this was due to unstable tape operation with slippery Hi8 Pro tapes, I don't know. The footages became fine and stable with upgrade/replacement to Sony TR-2000 camcorder, still functional as Hi8 VCR player). * A simple Line based TBC for normal playback were built-in in good, reference VCR decks, like my Panasonic FS-200EC S-VHS VCR and Sony EV-S880E Hi8 VCR. * A full frame or Dual Field TBC was built-in in my Videonics MX-1 digital videomixer, which resulted in wonderful clear and steady analog video images. As Videonics also published a Digital Video Primer that explained the Time Base problems in an easy and useful way, I have scanned and attached these 4 pages to this post. And for further references and reading this old stuff, follow some related urls which are still active: What is a TBC? Time Base Correction for Videotapes www.digitalfaq.com/forum/video-restore/2251-tbc-time-base.html What is a TBC* and why would I need one? https://www.questronix.com.au/tbc.htm Videomaker https://www.videomaker.com/article/f3/641-a-tbc-tale https://www.videomaker.com/article/1210-edit-suite-tbc-trivia Videonics MX-1 videomixer https://www.southernadvantage.com/products/videonics-mx-1-4-input-synchroniz... https://www.amazon.com/Videonics-MX-1-Video-Mixer-MX1/dp/B000ZS88N8 Terje J. H
