Audio dropout during capture

Posted by Dove*Sterling 
G4 dual 867 with 1.5 RAM, OS 10.3.7. FCPro HD 4.5. Sony TRV 900 camera as deck capturing to an external 80GB Firewire Drive (400) Indigita with about 13 GB free. Disk Warrior rebuilt directory. Restarted. Dumped preferences. Recaptured to internal drive. Still I get small area of audio dropout scattered thruout the captured footage. Often occurs in same place but tends to get worse when recaptured. I recently accidently trashed my whole 46 GB project and rebuilt it from the project file and only a few of the tapes had this problem, and no video dropout. I rerecorded the voice over on a new preblacked tape and some was ok, and some dropped out. Have collected pristine audio from other, older tapes since this problem started. Listening to the audio it is always pristine, tho occasionally, during capture, I can hear a soft whisper, but doesn't always correlate with dropout. I just need a few more (less than 3 minutes) of audio and I can finish this project. About ready to trash my system, but thought I would post here instead. Much appreciate any ideas.
Is the problematic sound sync sound with image, or audio-only recorded onto tape?

Have you cleaned your camera? Or tried a DV deck instead?

I'm just wondering whether, since you're so close to finishing the project, it might be good to implement a "pagan solution" just to get the project done, before you attempt to locate the source of the problem. For example, making dupe master clips of the problematic clips, labelling them "audio only", then seeing if the capture works better. (This allows you to modify the Media In and Out points as well, which has a chance of improving the capture)

Or capturing the missing remaining audio in very small chunks, possibly even by using Capture Now, to reduce the chances of the glitch.
Greg Kozikowski
Re: Audio dropout during capture
May 28, 2005 05:45PM

Especially if you can play older tapes OK, change the deck. You didn't say whether or not the tape was Extended Play or not, but if it is, you may need to get the original CamCorder to play it back.

Extended Play tapes are brittle and highly not recommended.

Hook up the speaker out of the DV Deck, not the Mac. See if that helps.

Dear Eric, Greg, and Gunner,

So grateful to get some new ideas. I'm using the original camcorder as the deck, and the audio out of the camera is pristine when played, and glitchy when the captured clip is played. It happens with audio alone capture, either stereo or 1 +2, and with video plus audio either stereo or 1 + 2 channels. It is never out of sync with the video. I never listen to my project audio out of the Mac or the hooked in TV, usually headphones or speakers attached to the camera/deck. I never use extended play to record or playback. I did use a head cleaner for the camcorder.

Longer (up to about a minute) are as good (or bad) as shorter, 6-8 sec. clips when captured, and later clips in a series of captured clips can be pristine as well.

The odd thing is that once a glitch develops in a clip, the same spot over and over again is glitchy and the clips, even when relogged and relabeled after trashing all the info and scratch on the first log, continue to glitch on that same point and then find new glitches. But the original always plays pristine.

Haven't tried the "pagan solutions" with master dupes and capture now, but sounds like worth a try

Thanks, reassuring to get everyone's feedback. Maybe I won't have to give up Ghost (my G4's nickname). Dove*
> The odd thing is that once a glitch develops in a clip, the same spot
> over and over again is glitchy and the clips, even when relogged and
> relabeled

This is key information...if the problems do occur with 100 per cent consistency, then chances are it's not a hardware problem like your FireWire cable or camera head. "Perfectly repeating" glitches tend to be a combination of footage, hardware and software. It's also, often, a flaw in the tape which causes the capture process to come up with the exactly same glitch every time.

And just because a tape plays back in the device without problems doesn't mean it will capture without incident. Also, some tapes just don't like certain playback devices, and often for not-so-apparent reasons -- two tapes of exactly the same brand shot on the exact same camera may not play back with the same quality. (If one tape baked in the sun for two hours and the other didn't, of course, that would also cause differences in response.)

I strongly suggest you find another capture device, and not a camera. If your problems occur 100 per cent of the time, at the same spots and with the same results, you'll probably continue to get those glitches until you change a major piece of the puzzle. Or, redub one of your problem clips from your camera, using FireWire out onto another recording device. Now capture from the dub and see if the problem still exists.

One more thing: If your capture preset has the wrong sample rate (eg. 44.1 kHz for 48kHz footage), you often get perfectly consistent problems. I know I had consistent audio glitches whenever I tried to use the Voice Over tool with my Tascam US-122 audio interface using a 48kHz sample rate. I had huge blank spaces of lost audio on the recorded take, while 44.1kHz was perfectly fine. This might explain why the tape's audio might play fine but your clips don't. Try changing your audio settings one at a time and see if your clips out out different.
Re: Audio dropout during capture
May 29, 2005 08:03AM
This is probably not your problem, but I just thought I'd throw it in on the off chance it helps spark some other line of enquiry. Is the audio very loud in the drop-out areas? Some digital cameras can't handle loud noise and just pretend it never happened, which means blank spaces in the audio track.

We recently got a small throw-away mini-dv camera which we install in places where a possible total loss could occur, like the inside of drag racing cars, which has a nice tiny security cam and mike attached.

The audio was coming back distorted and empty in places (not surprising to anyone who has been near a top-fuel drag racer), so I dragged out the manual to figure out how to knock down the input levels, and it basically said "If the noise you are recording is too loud it will cause distortions and audio drop-outs. To solve this, shoot from further away." Hmm.
Greg Kozikowski
Re: Audio dropout during capture
May 29, 2005 01:26PM

<<<drag racing cars>>>

This doesn't happen any more, but we used to lose picture on the cameras around the track because the "audio" was so loud it would shake the optics and the electronics enougn to temporarily fail.

I'd drop out, too.

Built-in mics are almost always electret style because they can be cheap and small. They have a loud limit above which they just stop delivering electricity. You might be able to get a cheap Dynamic microphone (say Radio Shack) and try that in the external microphone connection (if any).

They work by moving a small coil of wire inside a robust chamber. You need a thermo-chemical event to make them overload.

Thanks for everyone's input, I've been out of town for the holiday.

I don't think it's the tapes, different tapes have the same problem. And I use a wireless Sennheiser lavalier mic with the levels set using the level meter and the dropouts seem to have nothing to do with loudness. Also, my camera and FCPro HD are both set at 48mHz.

Changing FW cables and eliminating everything else (FW hub with other devices) so that I go directly into the computer with camera and FW drive didn't change things.

Now I have borrowed a friend's camera to switch out my old reliable (but 7 yo TRV-900). I don't have access to a DV deck without major effort, money. And I'm copying the project onto a larger internal harddrive so I should have about 40GB unused and not have to go via FW.

Will keep you posted, will figure this out. Thanks, Dove*
Well, I rented a TRV 950, and it still had the same dropout problem with audio as my older TRV 900, so I don't think that it is the camera. I have captured to an empty internal drive (not the boot drive) on a new project, same problem. Upgraded to 10.3.9, no change. Changed FW cables, captured to an external FW with more room and a different brand. Still, no better.

There is a firmware update for G4 audio:


Think that would make any difference??? And what about wiping the boot drive and reinstalling FC Pro 4.5. I'm running out of ideas here, guys. Dove*
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