I picked up a couple of discounted movie CDs at walmart for a dollar each. One I'm not sure about, but the other for sure had about a one-second mismatch between video and audio all the way through. I know, because at one point, someone was making a repeated noise, and it really became obvious when I watched the person 'make' the noise again, and counted off at least a whole second before the noise came. After that, I pretended I was watching something in a foreign language and dubbed into English, like an old Italian Roman gladiator movie, and manage to mostly ignore it. chizotz-at-mchsi.com |24hoursupport@xxxxxxxxxxxxx| wrote: > > Dale, > > Perhaps audio recorders do not record timing ticks. Audio was never my > specialty. It was my understanding that they did, but I could be mistaken. > Video recorders, on the other hand, do record timing ticks, or they did circa > 1982. Perhaps technology has improved since then to get rid of the timing > ticks, but I don't believe so. > > I can't claim decades of experience in tape recording technology. In fact, my > experience with tape technology is fairly limited. I did write, produce, > direct, and edit a one-season TV series for the local St. Louis market some > years ago. During one editing session, I kept getting bad edits. The picture > would jump and there was distortion. The engineer explained that the editing > machine I was using was malfunctioning by not properly synchronizing the > timing ticks at the edit point. This mis-match of the timing ticks resulted > in > the "glitch" at the edit point. > > That sounded logical and reasonable, but I wasn't sure if it was the truth or > just a line the engineer was handing me. So, as I always do when confronted > with something I want to understand but don't, I self-educated myself. The > engineer was telling me just exactly how it worked. I don't recall the names > of the books I consulted, but I got essentially the same information from > them > that the engineer gave me, plus a lot more. > > Just to be sure I'm not totally mis-remembering things, I found this article > at How Stuff Works http://electronics.howstuffworks.com/vcr.htm It also > explains that there is a control track on VCR tapes, which is what I am > referring to. Basically, you can think of the control track as containing > timing ticks. The VCR reads the control track and synchronizes itself with > the > time ticks. That sets the speed that the tape was recorded at. If at some > point on the tape the timing of the ticks change, there is a glitch at that > point while the VCR re-synchs itself to the tape. That's the effect I was > getting all those years ago when the editing deck I was using was not > synching > the timing ticks between edits. > > As you described, the effect can be easily duplicated with modern VCRs by > recording at one speed, stopping the recording, changing speeds, and > recording > some more, then playing the tape. You're absolutely correct that in those > conditions the VCR will change speeds at the point when you changed recording > speed, and there will be a glitch (what you refer to, correctly, as tracking) > at that point too. It all is based on the difference in spacing of the timing > ticks on the control track at that point changing. > > Ron > > > > > >> >>In a message dated 2/8/2005 1:29:55 P.M. Eastern Standard Time, >>chizotz@xxxxxxxxx writes: >>Magnetic tape has (this is basic so don't hold me to specifics) a stripe down >>one edge that contains timing ticks, and the rest of the tape width is used >>to store the actual analog data, usually sound information. Stereo recorders >>broke that area down into two stripes, one for each channel. >> I've never heard of these timing ticks and I've been dealing with >>recording tape for a good 35 to 40 years now. >> And, I don't recall video tape having them either. I've been dealing >>with that stuff for at least 33 years now, back when it was still only >>available >>on open reels. The video record head spins around at a very fast pace and >>records the picture onto the tape at an angle like this: \\\\\\\\\\\\\\\\\\\\ >> >>Each of those lines is equivalent to one pass of the video head. There are >>actually two heads on the cylinder that spins around. Each of those lines is > > >>probably also equal to one frame, but I'm not absolutely sure about that. As >>far >>as I know, the modern video tape machine doesn't use ticks at all, it just >>very quickly adjusts itself to the correct speed that the tape was recorded >>at. >>That's why the machine has to spend a few seconds tracking when you first pop >>a tape into it. It spends about 1 second adjusting to the correct speed and >>the next few fine tuning to that speed so that the playback will match up >>with >>the record. Record a video tape at one speed for a few minutes, or even a >>few >>seconds, and then stop tape and set it to record at a different speed. When >>you play the tape back from the start, when it get's to the point where you >>switched speeds, you'll hear the sound speed up or slow down dramatically >>within >>about half a second. That's because the machine is adjusting itself to the >>correct speed. It's also going to have to track again to adjust to the new >>playback speed of the tape. >> With audio tape the speed is adjusted by the person operating the >>machine. What good are ticks when you can fine tune the speed (the pitch) >>while >>you >>play or record the tape? >> >> Dale >> >> >> >> >>For a web-based membership management utility and information on list >>policies, >>please see http://nibec.com/24hoursupport/ >> >>To unsubscribe, send a blank email to 24hoursupport-request@xxxxxxxxxxxxx >>with >>"unsubscribe" (without quotes) in the subject. >> >> > > For a web-based membership management utility and information on list > policies, please see http://nibec.com/24hoursupport/ > > To unsubscribe, send a blank email to 24hoursupport-request@xxxxxxxxxxxxx > with "unsubscribe" (without quotes) in the subject. > > > > -- No virus found in this outgoing message. Checked by AVG Anti-Virus. 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