(Posted as part of my review of number 144, posting here in the interest of completeness)


Auto-normalization for the volume of songs would be nice. This would be a pretty serious software undertaking, but it would be so cool. The unit could peek ahead at the next song (using some free CPU cycles) and decide what relative volume level the next song should be played at.

Here's a transcript of a post I made to the Empeg Mailing list on this issue, in case anyone wants to open a full discussion of this subject.

>Any known utilities to normalize MP3s directly? I see that
>Audio Catalyst will allow you to normalize WAVs but not songs
>in the MP3 format.

I don't think that a direct-MP3-normalizer exists. For a couple of reasons:

First, there's the compression issue. Due to the nature of audio data compression, normalization would require that you decode the MP3 into wave data, normalize the wave data, then re-compress the data back into an MP3. Since MP3 is a lossy compression scheme, this could induce audible artifacts. Re-compressing something that's already been lossy-compressed once is generally a bad idea.

Second, since some people are picky about which MP3 encoders they use (different encoders have different levels of quality and speed), any direct-MP3-normalizer would probably not satisfy all users.

So, for volume normalization, you only have two options: 1) Normalize the source WAV files before encoding them, or 2) Utilize the Version 2 tagging specification to include a relative-volume variable in all your MP3 files (but the Empeg Car does not yet read Version 2 tags as I understand it).

However.. here's an idea...

An AUTO-NORMALIZING PLAYER program is not a farfetched idea. An MP3 player could use some extra CPU cycles to peek ahead at the next song and decide what volume level it should play the next song at.

In theory, all the peek-ahead routine would need to do is to use a single variable to store the maximum peak volume level of the next song. It could decode each frame individually, comparing its maximum volume with the variable. When the routine finished reading through the song, the variable would contain the next track's maximum peak, and could set the playback volume modifier accordingly. It could do this all in the background, while it's playing the current song.

There would be some minor issues, like how do you handle the first song in a playlist? Or if you go back and forth between songs quickly, it might induce a pause as it scans the upcoming song. Still, it could be done.

I wonder if anyone has written a WinAmp plug-in that would do this? If so, then it might be possible to have the Empeg Car do it as well.

Good idea. But I think the volume setting that is needed to normalize a song should be calculated only once (as it would produce the same result everytime it was re-calculated anyway), and that should be done in the Emplode software on the PC. The calculated value could then be stored as a property or attribute of the song in the database. This should make the necessary modifications to the existing player software rather simple, and not eat up any CPU time.

Oh, and to find the volume level, I don't think it's a good idea to just look for the peek level, as also some quiet songs may reach 100% for very brief periods. I'd suggest looking at the energy (RMS) of the wave instead.

Daniel

Empeg is an early-adopter's piece of dream hardware, so far. To stay that way means Empeg's got to stay ahead of the curve and auto-normalization is one way that can be achieved.

Normalization in the Emplode software is one solution -- and not a bad one as it reduces a lot of the technical problems at the expense of even longer load/organization sessions with Emplode. However, normalization on playback would be significantly snazzier as it's transparent to the user and doesn't incur a time cost for the user; just have it toggled on in the player and it happens automagically.

I feel it's a -MUST HAVE- type of feature ... especially as the ability to purchase tunes online increases...

Bleys

"If you would judge, understand." -- Seneca

One thought on this issue is that if you are ripping all your own mp3's.. you could normalize your whole collection during the encoding process. This would assure you of a nice peak setting for all your music.

However there are situations obviously where you will have 3rd party encoded files (mp3 , wma , whatever format becomes the delivery mechanism of the day)

A peek ahead to Db levels at a given volume compares and boost the volume for the next song based on that comparison still sounds processor intensive. Can the EMPEG mark I handle that?

Personally , I would rather just have a analog knob to turn the volume up and down as i needed it. I am used to doing this , and often the computer would probably have me mad. Has anyone seen the volume adjustment on some of the newer cars? (VW jetta and Passat come to mind). Those are annoying and can cause an adjustment right when you DONT want it to the music. It will never be able to actualize a volume level that you feel comfortable with. It will put a gain on poorly recorded music that will distort easily , and lower songs that have a high gain that you purposely want loud because it is "party music". Computers can do a lot of functions digitally , but it can't guess how it warm it will sound to your ears.

Auto-Normalization seems cool from a distance. In reality it would be come a rarely used feature and annoyance to most users. I perfer to have a per song equalization that you can set from EMPLODE. I am for more user definable features that I can set. (such as visulization rotation patterns) than for the computer to take over the control of my music.



Empeg Kicks Ass
S/N 00203
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I think auto-normalization should be toggle-able so-as not to annoy users who prefer to fine-tune by hand. I ripped my entire collection (vinyl, too) some time ago ... as my laptop has a whopping 25GB drive in it (which still doesn't hold enough) and I travel a lot. I did, indeed, normalize the whole lot of them as I went. However, this won't be a workable solution as downloadable MP3s pick up speed and people swap MP3s like they used to swap CD's and tapes...

Bleys

"If you would judge, understand." -- Seneca