TV Closed Caption CC1 problems

[hmchi]

I use analog VCR to record TV programs nightly. One specific channel, ABC on Channel 7, screws up the CC1 when I play it back to watch. The other channels play back without any problems. If I watch the program live on ABC Channel 7, there is no problem either.

My question is more of curiosity --- What is causing this to happen only on this specific channel ? Could it be a matter of frequency tolerances at this specific channel at the broadcast source ? or something within my VCRs ? I do use 3 different VCRs and the result is consistent among all 3 --- channel 7.

Description of CC1 playback problem --- The words are just illegible, every once in a while a few words may be legible and corresponding to the words spoken .. so it seems that something did not playback correctly that gets misinterpreted by the CC1 processor.

I would like to know what is/are the cause(s) and anything I the user can do to make it better ?

 

[VEBill]

Logically, based on your results with 3 VCRs and many other TV channels, the problem is (at least partly) with ABC 7.

Find their website and drill down to the technical / reception 'Contact Us' page and send them an e-mail.


Also, keep an eye out for hard disk based PVRs / DVRs on sale for $99 (?) to replace at least one of your VCRs.

 

[hmchi]

Hi VE1BLL

[1] There is a matter of which stage of transmission/re-transmission is the culprit. Could it be a problem in the 'local' re-transmission ? I spoke with the local cable company and they of course swear that they did it 110% right Cannot imagine ABC corporate will respond any differently unless we can give them a technical issue to look into .. This is why I came here ..

[2] There is another perspective --- direct viewing ABC 7 without the VCR recording is OK. The problem only comes up after recorded and played back; and only on channel 7. The local cable company of course says it is my VCR's problem.

Like I said, I am more curious intellectually than bothered by this problem. Anybody willing to educate me on how CC1 is superimposed onto the TV signal [bandwidth, etc.] and how a matter of tolerances in VCR recording might have triggered this to happen ?

 

[VEBill]

Basically, just barely off the top of your TV screen, is a scanned line (Line 21) that is used to carry data. You can actually see it sometimes.

Although Wiki cannot always be trusted, it's still a good starting point for non-controversial topics like this.

http://en.wikipedia.org/wiki/Closed_captioning

 

[biff44]

VCR's are funny things. I once tried to distribute VCR tapes to some sports coaches, and found that it is actually pretty hard to get a vcr tape made on one machine to track on another machine! There apparently are all sorts of analog control loops running in the machines trying to synch up what is on the tape to be something like what a TV is expecting.

First, how are you sending the signal from vcr to tv. An analog connection (rca connector or S connector) is much better, especially for words, than remodulating RF and going over an F connector.

Second, how old is your TV? It seems that newer TV's have circuitry to detect letters, where as older tvs just try to draw them as analog shapes. Do not have an actual scientific basis for saying that, just an empiricle basis of having word menus show up on new tvs where they did not show up, from the same recording source, on old tv's.

 

[biff44]

Also, have you tried to manually force VCR tracking? Many VCRs have a +/- switch on the hand held control to manually adjust the tracking.