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Re: Minidisc Mic Input

Subject: Re: Minidisc Mic Input
From: Dan Dugan <>
Date: Sun, 22 Aug 2004 12:54:03 -0700
>  > An interesting point, Rich. High-passing the input reduces the signal
>>  level, and reducing the signal level into ATRAC reduces the need for
>>  data compression.

>This will only work if the signal level is not just reduced, but
>eliminated. The quiet stuff gets compressed along with everything else.
>So you would want to drop the signal by 90+ dB relative to your loudest
>signal I'd assume.

I thought perceptual coders like MP3 and ATRAC work with a "bit 
budget." When the signal has a lower level it needs a smaller 
bandwidth and thus less data compression. Maybe I'm wrong about this.

>I'm also not so sure about eliminating all the low end. That, too, is
>part of the natural ambiance. Even if it's a problem to record and play
>back properly.

I feel the same way, I'd rather preserve all the bandwidth my mics 
can pick up--unless I'm having a problem with something that isn't 
part of what I want, like freeway rumble or wind noise in the mic. I 
often high-pass stuff later, but I want the option.

>It would actually make more sense to eliminate all the
>high end, as most don't really hear that.

ATRAC -does- eliminate the high end, which eliminates a lot of 
bits--I see what appears to be a signal-dependent variable low-pass 
around 16K.

-Dan Dugan


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