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Old June 8th, 2004, 12:14 PM   #1
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Loud Intermittent Buzz In Analog Capture

I am getting a loud intermittent buzzing sound when trying to convert some old 8mm video to DV. The buzz drowns everything out and lasts for a second or two and occurs every few minutes. When it happens I can sometimes see something funny going on in a narrow strip at the bottom or top of the preview, although the bottom strip is a defect that is there much of the time, depending on the tape. I don't believe I hear the buzz when viewing the tape on a TV but if this is a critical issue I can test.

Setup: Source tape in Sony deck or camcorder - buzzing happens in same place regardless of source hardware. A-D conversion with passthrough in DVX100A. Capture either to fast Pentium 4 running XP Pro, Premiere Pro and onboard firewire or slower Athlon system running XP Pro, Ulead Video Studio 7 and quality Firewire add-in card.

I'm a newbie. Any suggestions greatly appreciated including how to work around if nothing can be done to eliminate or diminish the capture of the buzz.
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Old June 8th, 2004, 11:50 PM   #2
 
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Do you have access to any other converter card? What you are describing can be a number of things. If it's an intermittent buzz, I'm wondering if you have exceptionally hot audio that is interfering with the video signal, could be other things as well. If it's always at the same place, that's my first best guess though.
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Old June 9th, 2004, 03:47 AM   #3
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Thanks for the ideas. I sorta have access to another A-D converter card. The Athlon has an All-in-Wonder card in it that will do the job but I have never been impressed with either the hardware or codec (it can only make a highly compressed file and do it on the fly so there are lots of compromises for that to be able to happen real time.) I think. The video and audio through the Panasonic are amazingly good except for the bad spots.

I also wondered if the audio might be too hot in the bad places driving the signal into clipping since square waves are very harsh. I don't have a way to attenuate the audio level going into the DVX100A. Say, I ought to look to see if that can be done in the camera with the analog microphone pre-amp level pots before the signal is digitized. Anyone know? (Yes, the audio is not going through the mic inputs.)

Any additional thoughts?
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Old June 9th, 2004, 05:58 AM   #4
 
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If you can see square waves on the file at that point, it's more than likely that the audio distortion is screwing with the picture.
I'd find a way to attenuate. I thought all input on the 100 was controllable? No?
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Old June 12th, 2004, 03:38 PM   #5
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Here is a sample

I really appreciate the suggestions. Alas, so far I cannot see how to limit the audio that comes in through the phono jacks.

I thought it might be useful to hear this problem. Here is what it sounds like (647K)
http://www.sharemation.com/dvwannabe/DV/AnalogCapBuzz.wav

Here is what it looks like: (27K)
http://www.sharemation.com/dvwannabe/DV/AnalogCapBuzz.jpg

Your additional thoughts much appreciated. I'm also going to ask in the DVX100 forum.
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