Hello everyone, this is my first post...

I am a big fan of MP3gain and have been using it straight after running my CDs though EAC + LAME - before pulling them into my itunes library (and then syncing with my Ipod Touch). I've searched these forums and the web for a definative answer to the following question but i just keep reading conflicting posts/views. The question is in 2 parts:

1) After MP3gaining an MP3 does itunes just see it as a normal MP3 but with a tag added containing the gain value? The reason I ask this is some reports ive read say MP3gain doesnt alter the actual MP3 (the non tag part of the MP3 i.e the music part) in any way - well, it must do right? Itunes doesnt read the tag before playback and alter the volume does it? I thought the tag was purely there so that IF you wanted to undo the gain you made to the file you can do using MP3gain again which reads the tag and undoes the changes. Can someone please give a definative answer on how MP3gain works and how Itunes processes the new MP3. Thank you.

2) My 2nd question is Do you need to turn Souncheck on in itunes/on your ipod to get the benefit of changes you made with MP3gain. I guess the answer to my first question will kind of answer this.

Thank you in advance for your help with this.

John

In MP3Gain, did you click the "Apply" button, or did you just click the "Scan" button? If you applied changes, the audio data would have been modified (in volume only). Then you don't need to do anything about soundcheck. (I'll assume none of the files have been scanned with soundcheck before.)

No, the files havn't been soundchecked before. So, if I load a full album of songs into MP3gain, do an album analysis, then apply the required gain, Itunes wont have a problem with the files and will just treat them like any other MP3? Can you explain the difference between clicking the "Apply" button and the "Scan" button. What, in your opinion is the best approach if using itunes and an ipod. I appreciate your help.

John

MP3Gain does alter the volume of your mp3 data if you apply the gain with the /r option. It does this in a way that can be easily reversed, but, nonetheless, the volume is altered. You might be thinking of other apps (i.e. foobar) that just write tags without altering data.

iTunes doesn't understand replay_gain tags. However, since the volume has been altered in the MP3 data, iTunes will play back you music at the adjusted volume, if soundcheck is off.

What happens if soundcheck is on depends on if you use MP3Gain before or after importing the music into iTunes.

If you MP3Gain prior to iTunes import, then iTunes will think this is a "normal" volume track and apply a minimal amount of soundcheck.

If you import into iTunes first, then soundcheck will be computed based on the original volume. Then, once you modify the volume with MP3Gain, the pre-computed soundcheck is wrong. If you then play back with souncheck on, you will get a double volume adjustment; not what you want.

A good rule of thumb is to use either MP3Gain or Soundcheck, but don't try to use them both at the same time.

Hope that helps...

Dave

the perfect answer (and the one that i wanted), thanks Dave.

One last thing...what is /r and where do I apply it?

Thanks

That is one of the command line options. If you run MP3Gain from the GUI, then it happens when you modify/apply the gain.

If you are interested, there is an easy way to convert the SOUNDCHECK values to replaygain values instead. This is particularly useful if you prefer ALBUM gain rather than TRACK gain (as I do). You'll need MP3TAG to do the job (a very nice program in general). The instructions below assume you have added album and track replaygain tags to your files (using either fb2k or dbpoweramp or mp3gain, etc.).

http://www.mp3tag.de/en/
http://developer.mp3tag.de/

1. First, you'll need the latest development build of mp3tag (ver. m currently).
2. Second, you'll need the action that converts the replaygain album number to the soundcheck (Comment ITuneNorm). You should create a new action with
"format value" formatting the field "COMMENT ITUNENORM" (that is a space between COMMENT and ITUNNORM) with the following format string: $rg2sc(%REPLAYGAIN_ALBUM_GAIN%)

If you want to use replaygain track level simply replace the "ALBUM_GAIN" above with "TRACK_GAIN" (although not worth the effort as track level replaygain and soundcheck values added by itunes are essentially the same). If you want to replace AAC (m4a) files' soundcheck values with the replaygain values all is the same but the field you are formatting is "ITUNNORM" rather than "COMMENT ITUNNORM"

I do this process before importing files into ITUNES. You'll notice that ITUNES no longer takes the time to calculate soundcheck values for each file as it thinks they already exist. If you already have songs in itunes and you want to convert to replaygain values, you can do this too in mp3tag in the same way. The only extra step will be to select (highlight) all songs within ITUNES and then select get info. You won't change anything in the tag boxes simply say OK. This will then cause ITUNES to reread the tags of every file and update its own internal library with the new soundcheck values. I've done this on over 50,000 mp3's in my itunes library and it works great. Obviously, you should set things up and run it on a few files just to confirm your formulas, but all-in-all, a very simple step.