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Old 02-19-2006, 12:52 PM
espron espron is offline
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Default 1 frame offset using TC reader


Hi all.

I am having a peculiar problem here.

Using a sync i/O to convert vitc to mtc I get a consistent 1 frame offset in PTLE 6.4 cs9. On the front panel of the sync i/o I can verify that the vitc is read correctly, but the TC reader in PTLE is always one frame ahead. Has also tried to use a DTP to convert from vitc to mtc and the exact same problem occurs in this setup also.

Has anyone else come across this problem or is it a bug related to 6.4?

Any feedback regarding this issue will be greatly apreciated!


Espen
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Old 02-19-2006, 01:36 PM
Richard Fairbanks Richard Fairbanks is offline
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Default Re: 1 frame offset using TC reader

How are you determining there is a 1 frame difference? I can tell you that you cannot rely on the timecode displays. As I recall, SyncIO displays the frame number of each frame it just finished reading, in other words one frame behind current running timecode. I would expect the timecode counter of LE to show the frame that is currently being played back, and that will be one frame higher than the SyncIO! It seems confusing but this oddity is really just a display thing, not an actual lockup problem. Are you having trouble with out of sync audio playback?
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Old 02-19-2006, 07:29 PM
espron espron is offline
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Default Re: 1 frame offset using TC reader

Hi

The way I am determing that there is a 1 frame difference is that I park the VTR at a specified frame and then look at the incoming TC counter in PTLE. If I park the VTR at e.g 00:00:00:00, the incoming TC counter in PTLE reads 00:00:00:01.

If I use the sync i/o to read vitc with our HD system I do not get this error. It is a bit frustrating when you try to spot something and everything ends up one frame late..

Thank you for responding!


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Old 02-19-2006, 10:14 PM
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TVPostSound TVPostSound is offline
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Default Re: 1 frame offset using TC reader

Only VITC is accurate when parked or crawling, LTC or MTC are only accurate at "play" speeds.

When you convert VITC to LTC or MTC its no longer true VITC

This is normal.
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Old 02-19-2006, 11:41 PM
Scott Wood Scott Wood is offline
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Default Re: 1 frame offset using TC reader

What is the VITC source device?
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Old 02-20-2006, 04:22 AM
espron espron is offline
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Default Re: 1 frame offset using TC reader

The VITC source is a Sony DSR-1500AP. I have tried feeding VITC-MTC into our two HD-systems and they also give an one-frame offset when reading a parked frame.

DiaFXMx:

I understand that only VITC is accurate when parked, but both the sync i/o and the DTP converts parked
VITC correctly to MTC and sends repeated MTC frames which corresponds to the parked VITC frame. When i crawl the VTR the MTC reader in PT follows perfectly, albeit one frame off. The problems seems to be with the MTC reader in PT 6.4.


Thanks everyone for your responses!


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Old 02-20-2006, 05:04 AM
Richard Fairbanks Richard Fairbanks is offline
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Default Re: 1 frame offset using TC reader

Please refer to my previous post! It is not a "bug", even though you are frustrated that one display does not match another.

You can test for proper sync by loading the same session into your HD system and your LE system. Let them both chase the VITC code. If they playback in sync, and they should, then all is well.
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Old 02-20-2006, 09:05 AM
Scott Wood Scott Wood is offline
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Default Re: 1 frame offset using TC reader

On many Sony decks, always check if it's reading VITC on field 1 or field 2. The wrong setting can cause VITC out one frame late.
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Old 02-20-2006, 01:11 PM
Richard Fairbanks Richard Fairbanks is offline
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Default Re: 1 frame offset using TC reader

I spent an hour with two systems today and have verified espron's original complaint, and verified my original post.

I put an identical session on two HD systems. System 1 generated VITC code via SyncIO as I played the session. System 2 ran the same session but was configured to lock to MTC from an amt8. I sent VITC from system 1 to another SyncIO (it was no longer connected to system 2), and took MTC from it into the amt8. When system 1 was playing (and generating code) system 2 locked onto it. Synchronization was perfect. I pulled the MIDI cable just to be certain the lockup was from MTC, and it was. When I stopped system 1 the VITC code would freeze at a particular number. In every instance when I stopped system 1, the two SyncIOs showed the same timecode number, however the incomming timecode window in system 2 always showed 1 frame greater. What I said in my previous post is true. This is expected behavior and allows you to grab an exact timecode number "on the fly", but has the unintended consequence that slowly advancing (or frozen) code may be grabbed one frame greater. That's just the way it is, I'm afraid. Timecode is a linear thing and all systems are designed to work properly with playspeed code. Sometimes the way they work with frozen code is not what you might want.
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