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Old January 25th, 2006, 12:11 PM   #1
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Digitizing issues with Avid (not rs422)

I'm working with footage shot on the JVC GY-HD100, and have been capturing from the camera and the BR-HD50 deck with this same problem:

When digitizing some HDV shots into Avid Xpress Pro HD 5.2.2, there seems to be some disconnect between the video and audio. The video captures fine, but the audio stutters ocasionally, throwing it farther and farther behind the video. It is actually captured this way to the hard drives, and nothing I have found so far will fix this problem. I think it's important to note that most shots capture fine, it's just with a few (usually darker) shots that I have this problem. I have 3gb ram on a xw4100 with dual P4 2.8 GHZ, and task manager shows no "spikes" on either the cpu or RAM when capturing media.

Any ideas or similar problems out there?

Last edited by Brian Busher; January 25th, 2006 at 12:57 PM.
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Old January 25th, 2006, 01:27 PM   #2
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Brian,

I work with Avid, but not HD or HDV. When I have a question, I generally take it to the Avid board at www.avid.com you might have better luck there.
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Old January 25th, 2006, 01:35 PM   #3
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don't worry, it's there too! I'm just trying to cover all of the bases.
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Old January 25th, 2006, 05:23 PM   #4
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Quote:
Originally Posted by Brian Busher
don't worry, it's there too! I'm just trying to cover all of the bases.
Can you try to capture on a non Avid system.

We all know what drop-outs look like in the image. Perhaps these are DO in only the audio.

However, I have often wondered if the HDV codec uses "concealment" to cover-up some errors in the MPEG-2 stream. Concealment has been used for decades to cover DOs in analog video.

But, I doubt there is such a thing for audio. Thus the PCM stream simply doesn't get audio for a few mS and COULD fall further behind.

Which makes me wonder if there is a difference between AVI and QT in how audio is stored with video. If a system forces sync -- perhaps by time stamps -- then there will be audio gaps but no increasing loss of sync. If there is no forced sync -- then increased delays will occur.

I've never seen this in FCP.
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Old January 26th, 2006, 01:59 PM   #5
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Thanks Steve, but no-can-do on a non avid. We have three Avids here that do the same thing, and I need to fix them.

I don't think it's an issue with audio drop outs. I don't lose frames and then continue. It actually stops capturing audio for a few frames, and then picks up exactly where it left off, but now its a few frames behind, then a few more, and a few more, and so on. It seems like it can't keep up with processing both streams simultaneously, and so it holds on to video at audio's expense.
Does anybody have an HDV Avid Xpress Pro HD that works 100% of the time? If so, what are your specs? I'd love to compare with a system that works.
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Old January 27th, 2006, 09:46 AM   #6
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Quote:
Originally Posted by Brian Busher
Thanks Steve, but no-can-do on a non avid. We have three Avids here that do the same thing, and I need to fix them.

I don't think it's an issue with audio drop outs. I don't lose frames and then continue. It actually stops capturing audio for a few frames, and then picks up exactly where it left off, but now its a few frames behind, then a few more, and a few more, and so on. It seems like it can't keep up with processing both streams simultaneously, and so it holds on to video at audio's expense.
Does anybody have an HDV Avid Xpress Pro HD that works 100% of the time? If so, what are your specs? I'd love to compare with a system that works.
That's strange because the audio must be buffering in RAM to actually do this (obviously the audio can't get out of sync from the tape itself). Things to check would be make sure your project is set to the correct sample rate (48KHz), suspect your sound card, but the MOST likely thing is some other background program (like iTunes) is intermittently using resources required for audio. Could the dark scenes thing be just a coincidence? Does the same thing happen if you try digitising directly off the camera?

I believe the recommended chipset for Xpress Pro was higher end than the one you have, but I doubt that's the problem. What video card do you have (Quadro980XGL absolute minimum, FX1100 and FX1400 recommended)?
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Old January 29th, 2006, 12:16 PM   #7
 
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Have you verified that your editing system captures audio and video in sync using a regular DV based device?

Quote:
Originally Posted by Brian Busher
I'm working with footage shot on the JVC GY-HD100, and have been capturing from the camera and the BR-HD50 deck with this same problem:

When digitizing some HDV shots into Avid Xpress Pro HD 5.2.2, there seems to be some disconnect between the video and audio. The video captures fine, but the audio stutters ocasionally, throwing it farther and farther behind the video. It is actually captured this way to the hard drives, and nothing I have found so far will fix this problem. I think it's important to note that most shots capture fine, it's just with a few (usually darker) shots that I have this problem. I have 3gb ram on a xw4100 with dual P4 2.8 GHZ, and task manager shows no "spikes" on either the cpu or RAM when capturing media.

Any ideas or similar problems out there?
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