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Old November 30th, 2004, 03:37 PM   #1
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Compression Dropping Out High End Sounds

I have some video footage of a bat (the animal), and on the tape he's making a high-pitch squeaking noise. However, when I export the video to be small enough to put on my website (I'm using Windows Media 9 256K compression), it drops out the high-end sound, and you can't hear the bat at all. I'm using Adobe Premiere to edit the video -- is there an audio effect I can use to change the frequency of the bat's squeal so it is exported under low compression, or something?

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Old November 30th, 2004, 09:24 PM   #2
 
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Not with Premiere, no. Use Vegas or Canopus ProCoder. Premiere has horrible encoding tools.
Keep in mind as well, that even with a good encoder, you'll lose some high end, and low end too. That's part of the problem with lower sample rates and compression.
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Old November 30th, 2004, 09:35 PM   #3
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Well, what is it exactly that I need to do in order to get that particular sound to play on the exported clip?
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Old November 30th, 2004, 10:26 PM   #4
 
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Using a better compressor will fix most of the problem, but if it's a really high freq, you'll need to use a higher bitrate and keep the sample rate high. In theory, the sample rate has got to be at least 22KHz, if the bat is squeaking around 11Khz, and even then, you may run into aliasing and/or loss depending on the encoder/compression. Premiere was never designed for real web-work, so their encoder isn't up to snuff. Even Microsoft's WM encoder (free) is better than the Adobe encoding tools.
You could also try running a tiny bit of compression on that bat, say around 2:1 set to -19dB or so, depending on the level of the original recording.
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Old December 1st, 2004, 12:03 AM   #5
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With Sound Forge saving as WMP9 audio, I noticed there is a low pass filter around 16khz (22khz is kind of the theoretical limit). Any frequencies higher get filtered off.
128kbps, 44.1khz, stereo

So, try using a higher sampling rate like 44.1khz (or 48khz).

*The encoder applies a low pass filter to avoid aliasing. Jay Rose's book Audio Postproduction for Digital Video has a pretty good explanation of this with audio samples.

**Just tried the same thing in WME. Higher bitrates help... and I believe I'm getting different results. Anyways, it's a free download so check it out for yourself.
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