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Subject: Re: mp3 features
From: Neon John (johngd_at_bellsouth.net)
Date: 2003-09-11


On Wed, 10 Sep 2003 17:40:18 -0500, LoveLearn <LoveLearn_at_iw.net> wrote:

>The current automatic volume alteration discussion raised questions.
>MusicMatch JukeBox includes a volume leveling option. Select which mp3
>files to process. Processed files are replaced by slightly larger
>volume leveled copies. On MusicMatch playback formerly frustratingly
>quiet files seem normally loud. Is this processing equivelant or
>identical to the volume leveling proposed RockBox?
>MusicMatch volume leveling processing appears CPU intensive on PCs.
>Similar processing might be very slow on Archos hardware.

I don't know how MusicMatch does it (being adverse to huge programs that mess
with everything) but MP3 Gain does it by altering the appropriate header bits
in each MP3 packet. The actual sound data is not affected and the process is
completely reversible. If you use a program that will CRC the sound data, you
see that it remains the same.

IMNSHO, MP3 Gain is the best thing that has happened to MP3 music since its
invention. Everything that goes on my hard drive gets normalized. MP3 Gain
reports how much overall correction is applied to each file and whether the
file clips or not. It's amazing just how overdriven some CD material is!

MP3 Gain uses a psycho-acoustic model that attempts to keep the perceived
level the same across a wide range of material. It does that quite nicely.

It would seem like a tremendous waste of power, effort and memory to try to do
this on-the-fly in a Jukebox when it can be done once on the PC and then
forgotten about. MP3 Gain is not terribly slow, taking perhaps 10 minutes to
crunch a whole CD full of audio book sound. The GUI can follow a whole
directory tree so if all your music is under ./mp3 then you can unleash the
program on ./mp3 and fix everything at once. My music is kept on an almost
full 80 gig drive and my 2 gig laptop did the whole drive overnight while
talking over an ethernet LAN.

John

---
John De Armond
johngdDONTYOUDARE_at_bellsouth.net
http://bellsouthpwp.net/j/o/johngd/
Cleveland, Occupied TN



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