D-VHS Interchange (the REAL issue) - AVS Forum
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post #1 of 19 Old 12-13-2001, 11:06 AM - Thread Starter
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I'd like to follow up with the issue originally brought up by the other thread (which has become "I want a HDTV demo tape thread).

I bought the JVC D-VHS VCR recently, only to found out that it can't play most of my Panasonic-recorded tapes without severe pixalations.

Does anyone know of JVC's solution to the problem? The JVC is basically useless if I can't play back my HDTV library.
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post #2 of 19 Old 12-13-2001, 12:11 PM
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I believe that the 30000U will be unable to live up to its potential until an appropriate STB is engineered to be fully compatible.

Only tapes the JVC records itself playback flawlessly.
Only tapes recorded on the JVC have HD scanning capability.

If 169time can find a way to marry the JVC DVHS VCRs happily to the DTC 100, that would be ideal.

"Dammit Jim, I'm a doctor not an engineer."
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post #3 of 19 Old 12-13-2001, 12:14 PM
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I guess I'm the guy that diverted the other thread. I'll try not to do the same thing here.:)

As I said before, the compatibility problem seems to vary between machines. I'm sure there are members here who have one of each and find them to be completely compatible. Assuming your HD1000 is properly aligned and makes tapes that can be read by other HD1000's, then it should be possible to make slight adjustment to the JVC so that is still within spec and can read your tape library successfully. It might involve recording an analog VHS test tape on your HD1000, and then having a technician align your JVC to that tape.

Another alternative: If tapes made on your JVC play ok on your HD1000, then you could copy your collection to the JVC. The resulting copies would work on either machine, and would offer scan viewing when played on the JVC.

-Roger
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post #4 of 19 Old 12-13-2001, 12:56 PM - Thread Starter
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Yes.. I've made dubs of the Panasonic tapes into the JVC and it played flawlessly... but that's too much work for some 50+ HD tapes I have.

I was planning to take a Panny HD tape to our local service center for adjustment.. now you're saying that it's better to take a analog tape recorded by the Panasonic??

I didn't even know about the scanning 'feature'
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post #5 of 19 Old 12-13-2001, 11:09 PM
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Quote:
Originally posted by jlin
I was planning to take a Panny HD tape to our local service center for adjustment.. now you're saying that it's better to take a analog tape recorded by the Panasonic??
I know... it seems a little odd. The alignment procedure in the HD1000 service manual uses an analog VHS alignment tape to set the tracking. (A very expensive tape BTW.) Auto tracking is turned off and then the A/C head is moved around until the signal (it's just plain RF) from the flying heads is maximum. I guess the assumption is that if tracking is good for the VHS heads it'll be good for DVHS heads. My guess is that JVC techs use the same procedure with the DH30000 and don't have a digital tracking tape (they have one for PG adjustment but that's another matter). Also, with a digital tape it would be possible to align to the wrong track.

If you find a tech that's a little adventurous you could get him to align to an analog tape from the HD1000, and then "fine tune" to a digital tape as well. The problem is that the digital signal is messy looking on a scope, and very expensive scopes are needed to see it at all.

The scan viewing is pretty interesting. I'm not sure how it's done. It almost seems like they'd have to place I-frames at uniform intervals along the tape. However it's done, a tape recorded on the JVC will flash frozen image frames about once a second while scanning on the JVC. Tapes recorded on the HD1000 (and played on the JVC) don't.

-Roger
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post #6 of 19 Old 12-14-2001, 07:26 PM
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Quote:
Yes.. I've made dubs of the Panasonic tapes into the JVC and it played flawlessly... but that's too much work for some 50+ HD tapes I have.
If it's your Panny which is out of spec, it's the only solution you have. Otherwise, the day your Panny breaks, you'll lose your entire collection!
One key advantage of making copies is that the scanning feature will work.
On the other hand, if it's your 30000 which is out of specs, don't do it of course! Only a JVC rep can give you the answer.

Robert
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post #7 of 19 Old 03-04-2002, 08:36 PM
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Back to the top! Having suffered through some tape interchangeability problems, I've learned a thing or two about the PV-HD1000. I have two decks, one that does all the recording, and the other for playback, which I've been trying to make work with my tape collection, but with pretty severe breakups...until now.

Lemme first say that adventurous PV-HD1000 owners should pick up a service manual. There are many things that can cause breakups, pixelization, etc. and this manual can help.
For me, there were two issues which kept my playback machine from working well. First, A/C head azimuth alignment was wrong. I won't bother with the details of performing an alignment since it can be found in the manual and can be done a few different ways.

The key to solving my problem was the following:
The service manual has instructions on how to perform an automatic BER (bit error rate) adjustment. Assuming that your deck is otherwise well-aligned and has been adjusted for correct digital record head current, there is a simple calibration routine which minimizes the BER.

1. Disconnect the 1394 connection from the deck.
2. Connect the deck's composite video output to a monitor.
3. Set the deck to the DTV input, and on HS recording speed.
4. Record a 10 minute segment onto your favorite D-VHS/S-VHS tape stock with no input signal.
5. Rewind and start playback of the 'blank' segment.
6. Press the 'VCR/TV' button on the unit and the '7' button on the remote control simultaneously to enter the BER adjustment mode.
7. A message screen will appear which shows the auto BER adjustment in progress, with "PROCEEDING" on the bottom of the screen.
8. When the calibration is complete, "COMPLETE" will appear on the bottom of the screen. You may also see "TIME OUT" which usually means you didn't record enough of a 'blank' segment for the routine to finish, or, less likely, "EEPROM ERROR", which means your VCR failed to store the new calibration values to the EEPROM, and you've got bigger problems.

Anyway, I used a slight variant of these instructions to solve my tape compatibility problem. After recording the 'blank' segment on my workhorse recording VCR, I put the tape in my playback VCR and did the BER adjustment. In essence, this optimizes the playback deck to my recording deck. And now I get flawless playback on both machines. Obviously this procedure isn't for everyone, and I strongly suggest picking up a service manual before diving into this type of adjustment.

Hope this helps.
-D

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post #8 of 19 Old 03-05-2002, 01:58 PM
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From my own experience with a JVC HM-DH30000U and reports from others, it appears that this deck has an MPEG decoder defect that causes random audio dropouts and video freezes (dropouts which freeze the last complete image on screen for a second or so). This happens with its own demo tape!!! as well as more often with HD1000 tapes that playback perfectly on multiple HD1000 VCRs.

The only people claiming perfect playback are running the deck's firewire output into a 169time modofied DTC 100 and using that STB's MPEG decoder.

No one at JVC seems to have picked up the ball and responded to this serious problem.

joel@HI-REZ
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post #9 of 19 Old 03-05-2002, 02:12 PM
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Quote:
Originally posted by joelco
From my own experience with a JVC HM-DH30000U and reports from others, it appears that this deck has an MPEG decoder defect that causes random audio dropouts and video freezes (dropouts which freeze the last complete image on screen for a second or so). This happens with its own demo tape!!! as well as more often with HD1000 tapes that playback perfectly on multiple HD1000 VCRs.

The only people claiming perfect playback are running the deck's firewire output into a 169time modofied DTC 100 and using that STB's MPEG decoder.
Is that also true if you use a DST50 for playback?

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post #10 of 19 Old 03-05-2002, 02:13 PM - Thread Starter
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Maybe not enough of us is complaining loudly to JVC about this?
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post #11 of 19 Old 03-05-2002, 02:47 PM
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So far using tapes recorded on the JVC, I dont remember getting audio drop outs. I sure did with DH1000 tapes. So has anyone had issues with a tape that was made ON the jvc?

dave
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post #12 of 19 Old 03-05-2002, 08:45 PM
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Yes, a tape which has been copied onto a 30000 or 35000 has similar audio drops as the original tape.

If you rewind and play again, the drops do not happen at the same place, so the problem is not located on the recorded material, but on the decoding hardware.

The severity of the drops depends on the original source: Braveheart has a drop every 2 minutes, and most CBS OTA shows have less than a drop every hour.

Robert
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post #13 of 19 Old 03-06-2002, 08:51 AM
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I have not tried playback from the JVC through the DST-50. One reason being that the DST-50 seams to have a softer image than the JVC's own decoder or the DTC-100. I also do not have a 169time modified DTC-100, so the JVC is gathering dust while we try to get JVC intetrested in the problem. has anyone found an interested party at JVC?

joel@HI-REZ
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post #14 of 19 Old 03-06-2002, 12:06 PM
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Quote:
Originally posted by joelco
I have not tried playback from the JVC through the DST-50.
I don't believe anyone here has succeeded in doing so more than a few times, probably because of 5C.

-Roger
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post #15 of 19 Old 03-06-2002, 12:15 PM
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Has anyone purchased the 30000U lately. Has JVC fixed the freezing problem or audio dropout probem yet?

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post #16 of 19 Old 03-06-2002, 03:26 PM
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I've recorded 124 hours of the Winter Olympics without any freeze or dropout problems. My JVC is performing perfectly (with the 169time modified DTC 100).

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post #17 of 19 Old 03-06-2002, 05:16 PM
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Quote:
Originally posted by dneily
I've recorded 124 hours of the Winter Olympics without any freeze or dropout problems. My JVC is performing perfectly (with the 169time modified DTC 100).
If you use the DTC 100 then you are not using the JVC decoder and you will not have problems, unless you tried to play back a D-Theater tape which will not work at all on the DTC100.

I am trying to find out if JVC fixed their decoder problem. Could you try playing back using the JVC decoder directly to see if you get the problems?


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post #18 of 19 Old 03-06-2002, 06:19 PM
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I don't understand
Quote:
If you use the DTC 100 then you are not using the JVC decoder and you will not have problems, unless you tried to play back a D-Theater tape which will not work at all on the DTC100.
It appears to me that your message is a "double" non-sequitur. I use the DTC-100 as a device for input into the JVC. The JVC provides the only (HD) output to my TV. Playing the D-Theater tape (e.g., the demo tape that came with the JVC, or any of my Winter Olympic recordings) does not involve the DTC-100. What am I missing?

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post #19 of 19 Old 03-06-2002, 06:31 PM
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Quote:
Originally posted by dneily
I don't understand

It appears to me that your message is a "double" non-sequitur. I use the DTC-100 as a device for input into the JVC. The JVC provides the only (HD) output to my TV. Playing the D-Theater tape (e.g., the demo tape that came with the JVC, or any of my Winter Olympic recordings) does not involve the DTC-100. What am I missing?
Yes I understand that now. I thought you were also using the DTC100's analog output to go to your projector or display.

In any case it appears that the freezing and audio dropout problem does not occur with tapes recorded by the JVC, but have you used your VCR to play a tape originally recorded on the Panasonic HD-1000? If you don't have any such tape I would be happy to send you one (for testing purposes of course). Just contact me by private message with your email address.

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