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Old July 17th, 2012, 11:35 AM   #1
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Choppy "chipmunk" audio problem with MiniDV footage

I am capturing some MiniDV tapes shot ~10 years ago over firewire directly into AVI files on my hard drive so I can edit and then export as MP4. The video was shot on a Sony TRV900 and most of it comes through fine when I play back the AVI. However, some footage was shot with the optional 16-bit audio setting turned on instead of the 12-bit default. The AVI files of with 16-bit audio footage plays back with choppy, high-pitched "chipmunk" audio that runs much faster than the video. This occurs in both VLC and WMP playback. If I convert those AVIs to MP4 with Handbrake, I get the same audio problem. However, if I import those AVIs into Sony Vegas, the audio is normal.

I have tried capturing over firewire with both Sony Vegas and WinDV and get the same results from both. The preview audio/video shown while capturing is fine. The camera plays the tapes back fine if I hook it up to a TV with RCA cables.

Does anyone know how to get 16bit audio MiniDV AVI files to play back correctly on VLC or WMP? Is there a codec I need or something?
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Old July 17th, 2012, 08:49 PM   #2
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Re: Choppy "chipmunk" audio problem with MiniDV footage

Just guessing here ... possibly a 32k sample rate of audio being played back at 48k ... hence a chipmunk effect? Some futzing around in some audio software to correct this hypothetical scenario might reveal if this truly is the problem or not.

Andrew
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Old July 17th, 2012, 10:10 PM   #3
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Re: Choppy "chipmunk" audio problem with MiniDV footage

Try re-sampling your clip. If you don't have audio software, you can download the excellent freeware, Audacity 2.0 for pc or mac here: Audacity: Free Audio Editor and Recorder

Open some of the clips and note the sample rate. If the sample rate of some clips is different from the others, select Tracks > resample and fill in the rate you want. I suspect you have clips at early dv standard (12bit 32 khz) and some at the later, hdv standard (16 bit 48 khz). Probably it is confusing your edit system and you need to conform all the clips to one rate.
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Old July 22nd, 2012, 07:12 PM   #4
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Re: Choppy "chipmunk" audio problem with MiniDV footage

I wonder how Ted went in the end. Sigh ... tourists!

Andrew
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Old July 29th, 2012, 02:11 PM   #5
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Re: Choppy "chipmunk" audio problem with MiniDV footage

Thanks for the tips. Unfortunately Audacity won't open AVI files. Sony Vegas and Handbrake don't like the original AVI files because parts of them are in 12-bit audio and parts are in 16-bit audio. Sony Vegas is ok if you bring each clip in separately. However my tapes have a lot of dropouts on them now so not sure it is even worth messing with. I am going to see if there is software that will extract the audio from my AVIs and handle both audio formats then convert them all to the same thing and re-combine them.
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Old July 29th, 2012, 04:08 PM   #6
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Re: Choppy "chipmunk" audio problem with MiniDV footage

Hi Ted,

If you want, you could always try a 30 day trial of Adobe Audition and see if it does the job for you.

Andrew
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Old July 29th, 2012, 04:28 PM   #7
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Re: Choppy "chipmunk" audio problem with MiniDV footage

Sorry, Ted, I assumed you had extracted the audio, my bad. a program such as mpegStreamclip -- excellent freeware --
(Squared 5 - MPEG Streamclip video converter for Mac and Windows)
can extract the audio --- open the file and select "export audio" and save as, probably, a .wav file. AVI's are wrappers for whatever codec made the video, so this assumes the proper codec is on your computer. There are also a number of freeware or inexpensive shareware programs that can do this also. One that I use is Xilisoft Video Converter (for-pay shareware). (http://www.xilisoft.com/) Another excellent freeware program is SuperC (http://www.erightsoft.com/SUPER.html)

When you have hashed out the synch problems, you then import into your video editing program the corrected files to replace the originals.

Some programs, like Adobe Premiere Pro, will parse audio files not matching the timeline and correct them automatically.
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