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USB audio hiccuping and dropping out

Posted on 2008-10-22
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Last Modified: 2013-11-09
This has been a tough problem, you will likely need to know a lot about USB to crack this one.

I use a video capture component in vb.net and am working with the developer to see if there is an issue with his component, BUT I have used it on other mobo's with no problems, I do not believe this issue lies with the capture component.

So, exact same software, same hardware except the new Asus P5E-VM HDMI motherboards.  The exact same thing is happening on 3 separate computers.
1 USB powered Roland Preamp
1 USB powered Logitech speakers
1 USB mouse
1 Firewire camera (has its own power supply)

I record audio and video from separate sources, audio from USB and video from firewire.  All the latest drivers for the mobo and devices attached.  Video is great, but the audio drops out at seemingly random times and appears to get worse the longer its running and more videos that are captured. By the end of the video the video lags the audio substantially.  After 1 minute the video will lag the audio by about 1 second.  This is no small sync issue.  When the audio drops out it is not replaced with dead air, the lost audio disappears (about .3 seconds worth), and the audio that follows butts right up against the previous audio wave (viewable in sound forge), and the shifting of the audio following is then out of synch by the amount of time lost in the audio drop out.

So the video length and audio wav will look something like this:

----------------------------  Length of Video track at 29.97fps (1 min)
-------------------------      Length of audio wave  (59 sec  or there about)

Initially I thought the problem could be with the power supply, too little and USB powered preamp was not working properly.  I yanked out every card, unplugged every device and stripped it to the bare minimum.  No change.  Power supply ok.

I thought the problem could be a conflict with the onboard HDMI sound system; I disabled it in the BIOS.  No improvement.

NOW heres the tricky part, I changed preamp USB channel (plug) and the problem disappeared.  All great BUT when I put the USB back into the original plug I cant recreate the problem.  This is concerning because the problem could reappear as I never did find out WHY the original problem existed.

I have 2 other machines I will be testing soon and trying to see if the fix is the same, or better yet diagnose WHY this audio drop out is happening.  

Could USB bandwidth be an issue?  Does anyone know why a new board would have USB universal host controller AND a USB2 Enhanced host controller listed in the control panel  I would think USB 1.1 is dead. Do these USB controllers map to individual ports on the motherboard?

Thanks very much all this is driving me nuts. Please keep in mind as you think about this, only the mobo has changed in this scenario.  I have some control over USB in the BIOS but it's pretty stright forward.
http://www.asus.com/products.aspx?modelmenu=1&model=1912&l1=3&l2=11&l3=584&l4=0

Thank you.
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Question by:mbulloch
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by:fredshovel
ID: 22790071
You havent explained why you are "recording" the audio and video seperately. Do you mean recording or capturing?
Is the Roland a Microphone pre-amp and are you doing some sort of podcast or voice over?
If so you should also record a "scratch track" on the video, so you can split and replace the audio later.

 
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by:mbulloch
ID: 22790173
The camera is behind sound insulated glass, the microphones are separate and can't plug into the camera, wish they could.  So, we're capturing both audio and video separately but simultaneously and simply writing it to an avi file.  These avis are put to use right away so we can't do any post editing.

Thanks!
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fredshovel earned 500 total points
ID: 22790930
I would think that the sync problems are because the audio and video have no actual relationship (being independent). In North America NTSC runs at 29.97 fps -- being brought back from 30fps so the video and audio carriers don't cause inteference. But say a PAL system runs at 25 fps -- and film speed is 24 frames per second. So it stands to reason that when cameras are syncing up the audio to the video in any system that they are either stretching or delaying the audio to put it in sync. You need to do this independently. There are a few programmes that will take an AVI and sync the audio -- either by adjusting the stretch or delay of the audio or by adjusting the fps rate (the latter makes me a bit nervous).
You could Google for AVI sync tools. There's AVI sync etc.
There's also this one:
http://www.gromkov.com/faq/faq2004-0064.html
Don't know how to write one though.

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