Does iTunes' "sound check" actually change your files?

[ebow]

Just wondering if, when you check the Sound Check option in iTunes' preferences, does iTunes go and mess around with the actual encoding of each file? Or does it just adjust the volume slider for each file, and save that adjustment somewhere (e.g. the iTunes database, file headers, resource fork, etc.)?

My guess is that it just tweaks the sliders and stores that info, meaning that if I check it, and don't like the results, I can uncheck it and get my current sounds back.

Thanks for any quick thoughts on this. I did a search here and in the Help Viewer pages (yuck) and couldn't figure it out.

:confused:

[skymaXimus]

Originally posted by ebow
Just wondering if, when you check the Sound Check option in iTunes' preferences, does iTunes go and mess around with the actual encoding of each file? Or does it just adjust the volume slider for each file, and save that adjustment somewhere (e.g. the iTunes database, file headers, resource fork, etc.)?

My guess is that it just tweaks the sliders and stores that info, meaning that if I check it, and don't like the results, I can uncheck it and get my current sounds back.

Thanks for any quick thoughts on this. I did a search here and in the Help Viewer pages (yuck) and couldn't figure it out.

:confused:

I'm sure it "normalizes" on the fly. I seriously doubt it actually changes all the files in your iTunes db...that would probably require a few min of processing power, like when you "convert selection to mp3" And you would notice.

[AmbitiousLemon]

it doesnt do it 'on the fly' and it does take several minutes processing.

it changes the tags. so the audio file itself is left untouched and you can adjust or undo any of the changes.

[ebow]

Thanks for the info. Knowing that it can be undone I'll let iTunes chug away at it over night...

p.s What does it take to move out of "newbie" status here? I guessed it would change at post 20 or 25. I know that 26, now 27 posts isn't a lot for almost 2 years, but still...

[AmbitiousLemon]

i believe it is 30 if i remember correctly.

soemtimes it does seem like forum age is more important than post count. dont know if there are any vbulletin hacks for that. if there are i might do it on my forums.

[moss84]

Actually the changes may be stored in the iTunes Music Library database. If you're interested in the details, they can be found in Article 61655 (http://docs.info.apple.com/article.html?artnum=61655) of the Apple Knowledge Base. In either case, though, the changes are not made to the audio file.

[AmbitiousLemon]

thansk for that moss (i fixed your link)

here is the info for those who find it hard to click outside links (you know who you are)


Sound Check is a feature introduced in iTunes 3 that allows you to hear all of your songs at approximately the same volume. You can turn Sound Check on and off in the Effects pane of iTunes preferences.

How it works

When Sound Check is on, iTunes scans the songs in your library and computes characteristics of their playback volume. As new songs are added, iTunes computes this information in the background. This data is stored in either the "normalization information" ID3 tag or the iTunes Music Library database. The audio data in your music files is never changed. If you encode or "rip" a song with iTunes, the sound check level is stored in the song's ID3 tags. For songs that were encoded with iTunes 1 or iTunes 2, or another application, the sound check levels are stored in the iTunes Music Library database.

When Sound Check is off

If you turn Sound Check off, the Sound Check data stored for each song is ignored, but not removed from the iTunes Music Library or the ID3 tags.

Notes
1. Sound Check works with .mp3, .wav, and .aiff file types. It does not work with other file types that iTunes 3 can play.
2. Any boosts in playback volume are protected against clipping by iTunes' built-in limiter.