Problems with recording using a lavalier microphone

[Anonymous]

I have a canon elura 90 camcorder and am recording using a Shure MX 183BP external lavalier microphone with battery-powered amplifier. I am having problems with distortion and extremely low sound volume when I export the video to quicktime or windows media. It gets even worse when the file is uploaded to a video site. I have been trying to diagnose the problem but am mystified. Here is what I have found:

1. When I listen to the recorded audio by plugging headphones into the camcorder everything sounds fine.
2. On the computer the audio in the avi file sounds fine.
3. When I use the camcorder’s internal microphone I have no problems with the audio in quicktime or in windows media.
4. Looking at the waveforms the audio recorded with the lavalier microphone seems to have a greater amplitude than that using the camcorder’s microphone, showing some clipping.

Has anyone had similar experiences or have suggestions for fixing the problem?

Sean

[Anonymous]

The clipping is pretty minor, but I thought that it indicated that volume in the recording wasn’t too low. Most of the sound is below -6 db. The recording is purely vocal. Here is an image of the waveform:

I’m using Adobe Premiere elements as an NLE. I’ve also exported the avi directly to Quicktime using MPEG Stream. I encounter problems with both systems. I even tried Microsoft Movie maker on a separate system and had the same issues which was what was leading me to believe there was something about the recording that was causing a problem not the NLE. I have managed to clean up the distortion in both mov and wmv by increasing the audio to 128 kbs from 64 kbs, but the audio is still lacking in volume and once the files are uploaded to youtube it is heavily muted and distorted. Normalizing the audio has little or no effect.

Sean

[Anonymous]

Sorry. I’ve adjusted the size of the image. 😀

The camcorder is recording in 16-bit mode. I was thinking that if encoders were the problem, wouldn’t it occur with both microphones? I’m pretty sure that the encoders are fairly up to date since I just upgraded to Premiere Elements 3 a couple of weeks ago.

Sean

[Anonymous]

I finally discovered what appears the be the problem and found a work around. When converting the audio from stereo to mono in Audition I noticed a dramatic drop off in amplitude, similar to what was being produced by Youtube. The fix was to only sample one channel when converting from stereo to mono, and then use that audio. The video with this new mono audio track works fine on Youtube.

Sean

P.S. It appears the problem was due to a polarity inversion (sometimes called phase inversion). I was also able to fix it using fill left or fill right in the NLE

[Author]

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