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  #1  
Old 09-18-2008, 03:33 PM
Tom Smith Tom Smith is offline
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Default VTR Jog Response & QC

Hi all,

Been doing a lot of layback to tape lately and have had some tapes rejected by QC for audio sync issues. QC claims 4-5 frames late across the board for the entire 90 minute feature.

Everything looks great when you play at normal speed, but our QC folks don't seem to care about that. They pick a couple of spots and using the VTRs remote controller, jog the tape back and forth frame by frame. When I do it myself, it seems like the slower I jog, the worse the sync.

Is this even a valid test? It seems like the deck would have a tough time keeping up with this in a frame accurate way. These are dubbed language versions so lip sync isn't really a good test so mostly sound effects are checked. To make matters worse, the QC'ers picked some spots where the actual visual event (that creates the sound) isn't even clearly visible!

Any advice on dealing with this? I told them to trust their eyes & ears but was told "this is the way we do it"... Any advice would be greatly appredciated!

Cheers,

Tom
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Old 09-19-2008, 01:17 AM
Petevsi Petevsi is offline
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Default Re: VTR Jog Response & QC

Hi Tom
What tape format are you laying back to?
Pete
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  #3  
Old 09-19-2008, 07:56 AM
Tom Smith Tom Smith is offline
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Default Re: VTR Jog Response & QC

We're laying back to a variety of tape formats: Sony HDCAM SR, Digibeta (on DVW-500 & MVW-2000), D5, NTSC & PAL. Seems like the "problem" tapes are Digibeta, I don't remember having any SRs rejected.

I still feel that, regardless of the tape format or particular deck being used, jogging the deck to a still frame and listening to the audio stutter while the deck tries to play 1 frame of video and 1 frame of audio isn't a valid way to verify sync.

I do think that the variety of tape formats and decks will make that process, however accurate or inaccurate it may be, return inconsistent results. Which, in my mind, makes the test invalid.
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Old 09-20-2008, 05:14 AM
Postman Postman is offline
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Default Re: VTR Jog Response & QC

Those decks are designed to scrub slowly IN SYNC. In other words, when the mode is set for audio to play continuously during scrub, and you scrub very slowly, you can clearly hear which frame an impact sound occurs on. The image will show the same frame as the one you are hearing (looped repeatedly in an annoying way, but you can hear it). This performance can usually be verified where bars/tone have been edited on. The tone will start on precisely the first visual frame. If a count down is included, you can have them check that.
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Old 09-21-2008, 08:39 AM
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Chief Technician Chief Technician is offline
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Question Re: VTR Jog Response & QC

Quote:
Originally Posted by Postman View Post
Those decks are designed to scrub slowly IN SYNC.
If that's true for the SRW-5500 and the AJ-HD3700B, could you share how to configure that? I find scrubbing for purposes of checking sync with the AJ-HD3700B to be extremely difficult.
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Old 09-21-2008, 09:29 AM
Tom Smith Tom Smith is offline
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Default Re: VTR Jog Response & QC

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Originally Posted by Chief Technician View Post
If that's true for the SRW-5500 and the AJ-HD3700B, could you share how to configure that? I find scrubbing for purposes of checking sync with the AJ-HD3700B to be extremely difficult.
I use those decks a lot too & would love to have that info! For the DVW-A500 as well...

I've really begun to mistrust scrubbing tape to confirm audio sync after a couple of recent experiences; In one case, a Digibeta tape was kicked back for a dropped in section at the end being one to two frames late. Later, the same tape was checked again, this time the same section was supposedly 10 frames late. The tape had not been modified! The only difference was the QC tech and that the first test was done on an SRW-5000 and the second on a DVW-A500.

The other case was after I'd layed back a fix for one of these tapes, I was using the remote serial controller that the QC techs use to scrub the tape and check sync. I found that I could fairly easily get the sound to play up to a frame and a half early or late when jogging back and forth and then down to a still frame (with stuttering audio) as the QC techs do.

On top of everything else, the QC techs are using a flat panel (supposedly delay compensated) while I'm using a CRT...

Cheers,

Tom
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Old 09-21-2008, 10:17 AM
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Lightbulb Re: VTR Jog Response & QC

Quote:
Originally Posted by Tom Smith View Post
I use those decks a lot too & would love to have that info! For the DVW-A500 as well...
Tom,

Ping me outside of the DUC with what the menu settings are on the DVW-A500 you are using. We have never had a problem with checking audio sync using the jog wheel on a DVW-A500.
Quote:
I've really begun to mistrust scrubbing tape to confirm audio sync after a couple of recent experiences;
I don't trust it on the AJ-HD3700B or the SRW-5500 at the moment.
Quote:
In one case, a Digibeta tape was kicked back for a dropped in section at the end being one to two frames late. Later, the same tape was checked again, this time the same section was supposedly 10 frames late. The tape had not been modified!
Are you only inserting audio? I suspect the answer is yes, but I have to ask.
Quote:
The only difference was the QC tech and that the first test was done on an SRW-5000 and the second on a DVW-A500.
Well, I think that difference (read - failure) falls on the QC department. They should be performing QC on whatever deck will ultimately be used for playback. I understand that the SRW-5500 will playback a Digital Betacam tape if you have an option card in it, but playback and operation may not be the same, as we're discussing now. We use a SRW-5500 to playback Digital Betacam, but we're not performing QC on our laybacks or clones with that deck. We do that work on a DVW-A500.
Quote:
The other case was after I'd layed back a fix for one of these tapes, I was using the remote serial controller that the QC techs use to scrub the tape and check sync. I found that I could fairly easily get the sound to play up to a frame and a half early or late when jogging back and forth and then down to a still frame (with stuttering audio) as the QC techs do.
I don't recall getting the stuttering audio, but on the AJ-HD3700B I can absolutely get the sync error to be 2-3 frames by jogging slowly.
Quote:
On top of everything else, the QC techs are using a flat panel (supposedly delay compensated) while I'm using a CRT...
You may want to find out if those QC techs are going to AES, and if so, tell them to attend this session.
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Old 09-23-2008, 05:33 AM
Postman Postman is offline
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Default Re: VTR Jog Response & QC

Quote:
Originally Posted by Tom Smith View Post
We're laying back to a variety of tape formats: Sony HDCAM SR, Digibeta (on DVW-500 & MVW-2000), D5, NTSC & PAL. Seems like the "problem" tapes are Digibeta,
Quote:
Originally Posted by Chief Technician View Post
If that's true for the SRW-5500 and the AJ-HD3700B, could you share how to configure that
I should have been more specific, I'm sorry. Every Sony Digibeta deck, PAL or NTSC, I have ever owned and/or used has been capable of near-perfect slo-mo scrub. Those are what I was thinking of when I wrote "those decks". I have also had good slomo scrub experience with HDW-F500. D5 I haven't touched in several years, and that Panasonic deck Chief mentioned I have no experience with.

added: The timecode reader display may not always be perfect. When I say near-perfect scrub, I mean that when scrubbing across a hard cut, like from black to first frame of bars/tone, there is no uncertainty that audio and video are scrubbing on the same frame at the same time.

Last edited by Postman; 09-23-2008 at 05:53 AM. Reason: added thought
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Old 09-23-2008, 04:54 PM
Tom Smith Tom Smith is offline
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Talking Re: VTR Jog Response & QC

Quote:
Originally Posted by Postman View Post
I should have been more specific, I'm sorry. Every Sony Digibeta deck, PAL or NTSC, I have ever owned and/or used has been capable of near-perfect slo-mo scrub. Those are what I was thinking of when I wrote "those decks". I have also had good slomo scrub experience with HDW-F500. D5 I haven't touched in several years, and that Panasonic deck Chief mentioned I have no experience with.

added: The timecode reader display may not always be perfect. When I say near-perfect scrub, I mean that when scrubbing across a hard cut, like from black to first frame of bars/tone, there is no uncertainty that audio and video are scrubbing on the same frame at the same time.
I've found that I get what I believe to be more accurate results when scrubbing slowly. Results that seem to go along with what my PT session is telling me. I think the problem is when the scrub speed goes to zero and the deck is displaying a still frame. This is what the QC tech do, listening to the audio stutter for a few seconds until the deck stops so it wont burn a hole in the tape.

Anyway, like it or not, I've got to learn to deal with this since I'm sure the QC group will continue to do things the same way...
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