iTunes Sound Check - Big Concerns

Sound Check is the iTunes option that promises to even out volume levels among tracks from many sources.

I was playing around with turning Sound Check on and off the other day, while playing tracks, and noticed something very strange. On relatively louder tracks, Sound Checks *lowers* the volume. In fact, it seems to do this more often than raising the volume of quieter tracks. This has to be happening in the digital domain, because it's passed out from the USB connection to my receiver. Isn't iTunes, in effect, throwing away bits to lower the volume? This can be done, I suppose, by first upsampling the data, but I doubt that kind of sophistication is at work. Raising the peak volume of quiet tracks isn't so bad, but why lower the volume of louder tracks?

I've encoded all my files in Apple Lossless to retain full quality, but it appears that Sound Check is working against me here. I have noticed/imagined that Sound Check has an adverse effect on sound quality; could this be one of the reasons?

BTW, I usually turn it off, and just hope that shuffle doesn't take me from a nice DCC track to, say, the second Travelling Wilburys album.

 

i noticed this a few weeks ago. i'm positive info is being lost. i'm not certain it's in the digital domain though. thought it might be some sort of compression. either which way, the detail lost is very noticeable at my encoding rate of 256kps aac.

quick edit, i haven't noticed sound check effects being passed out the line out usb/fw connection in my car stereo. not the quietest of environs though.

 

I played around with Sound Check briefly, but it did not appear to have much effect (positively or negatively) with anything other than the playback of the items in my library. Since I don't (yet) do any serious listening from my computer, and continue to use Toast for burning copies, I haven't paid much attention to the way that iTunes works -- that will be changing, though, as I eventually intend to archive about 500 CDs for playback through my main audio system, using a high quality external USB DAC (probably Scott Nixon's).

Although it might be a royal PITA, you can use the options in the "Get Info" window to adjust volume levels manually. I just tried this on the tunes in a playlist I just created. This is probably nothing more than a link to your volume control panel, and does not appear to have any effect on the sound quality of the individual files.

I am curious about Apple Lossless versus AIFF. AFAIK, Toast uses either AIFF or MP3, but maybe I need to be thinking about this when I begin the archive project in a few months.

 

http://www.mani.de/en/software/macosx/ivolume/

this may be the answer.

 

apple lossless is not supported by too many other vendors. and itunes doesn't do flac. i suggest aiff if you are archiving and using itunes but want to use those files with other programs in the future.

 

I don't like sound check much. There's noticeable distortion on songs with a lot of dynamics. Some folks here highly recommend iVolume (see post #4). I might look into that.

 

You can use Apple Lossless with Toast.
Souncheck does not do any permanent damage to the files. You can turn it on and off and it does not carry over to burned discs. It does not work very well on most songs so I don't use it anyway.

Pat

 

As an option, Sound Check *can* be applied to burned discs (under Burning in Advanced). But as you say, you can turn it off for both playback and burning. iVolume looks very interesting, but I'm on Windows (no further comment).

Manually adjusting the volume could be a good idea. I'd select an entire album, try to find a decent level, and raise volume only for the entire album, never lower it.

 

Thanks for the info, Pat. What's the advantage of Apple Lossless over AIFF?

 

The process is what is called RMS normalization. The program has a predetermined, or a user determined RMS to adjust all the files to. Or, it determines the files with the highest peaks and adjusts all other files to that one file, which more often than not, means that all others will also go lower in volume. If a song goes up, a limiter is employed to ensure that the files does not exceed FS 0, which could cause audible clipping.

Make no mistake about it, calculations are happening on most or all the files with RMS normalization. And, yes, the sound is potentially degraded, but chances are, if it's done properly, with dither, you probably won't hear it.

Every audio program that uses either peak or RMS normalization handles the data in a slightly different way. This means some programs will make the music sound worse than others.

 

Sound Check doesn't affect the music in the file at all. It tags the file or the database (maybe both) with the information the Ipod and Itunes needs to play it the way it sees as "correct." It then adjusts the volume of playback in the Ipod or Itunes based on that, but it does not alter the actual file itself. If you uncheck the Sound Check option, your music goes back to normal.

And I agree - it stinks! It only seems to bring louder music down in volume. Check out what it does to an album like U2's How to Dismantle an Atomic Bomb! It's quite a shock going between songs from that and other albums! Ultimately I find that the difference in volume much less shocking without Sound Check than with, in general.

 

Now that I think about it, I agree that Sound Check actually worsens the situation.

 

That is exactly one of the many reasons I finally left the world of iTunes/Apple Lossless this week and switched everything over to FLAC. I'm using Foobar2000 for Windows and amaroK on my Linux partition (accessing the same files on another drive). Replaygain is much, much better than Soundcheck. And perhaps I'm imagining it, but I think it sounds better too. I've been listening to random tracks all day, and the volume levels have been more consistent than when using Sound Check.

iVolume looks cool though. Wish it were available for Windows... I'll probaly test it on my work G5 anyway.

 

Any volume equalizer must attenuate some music. Actually, it must attenuate most music. If you wrote an equalizer that did nothing but boost music, it would sound very, very bad.

 

yuck. Just use flac and convert if you need. AIFF/WAV are horrible ideas because they have no error detection or correction or identifier tags. Dont use ALAC or whatever Apple's is becuase it is vendor specific- never be tied to something like that. Use an open, common, and supported (more devices support flac than the few apples that support alac) format like FLAC.

 

I appreciate everyone's comments about ALE/FLAC/iTunes, and I probably agree with them, but I'm in too deep to turn back right now. I do like iTunes' user interface, and I'm happy enough for now, with Sound Check off. Maybe some day when life gets a little calmer for me, I can make the switch.

Off my own topic: I do think that no-one has really cracked the user interface issue. Wouldn't it be nice to have a voice-activated music browser?

"Computer! John Cale...Paris 1919...-10 dB!"
"Affirmative"

Even a touch screen that lets you flip through your records.

 

heh ya it would be nice to have a better way to play music. Actually, the best way I ever saw was in a phillips demonstration lemme see if i cna find the video. Essentially, the entire wall was a touch monitor... you click "music", and your wall turns into records and you simply touch the record with your hand or whatever and it will play. Ill dig it up.

 

Found it, it was by Panasonic and the video is here:
http://www.akihabaranews.com/review-63-Panasonic's+interactive+TV+wall,+the+demo.html

 

I see! You know, i've never used iTunes for more than downloading and burning backup CD-Rs. So, i'll shut up and know not to use the program for anything else!

 

Well, you've certainly nailed down one of the issues I have with archiving 500 or more CDs onto a single hard drive. While some (at the asylum) are saying that once you've taken the computer sever approach to playing music on a quality audio system you'll never go back, my own iTunes library (most in MP3 format to get ~ 8 hrs music on a single disk) is already getting a little unwieldy with 1412 individual tunes in it.

I'd like some sort of heirarchy where I could have more than one library -- say, one for Jazz another for classical etc -- but this doesn't seem to be possible. Then I thought that it might be useful to create a playlist for each album, but who wants to scroll through as many as 1000 playlists? True, the spotlight function (on a Mac, at least) will let you narrow down the items in your library to a manageable few, but it doesn't look like multiple searches performed simultaneously are possible.

As far as switching away from a Mac is concerned, it ain't gonna happen here.

 

I have about 700 albums on a single disk, all flac, and all organized! The best way to do it, as I have found, is simply use the file system for storing the physical music, and then organizing playlists of sorts later...

The structure is like this:

Artists->Album->Album Version->Disc1 or Disc2
All files are flac, so all files have data in the tags automatically, and each folder has a picture/etc... in them for getting the covers.

I use foobar2000, but you could use anything, that lets me select a playlist which i just drag the folders into or I search for them in foobar (Foobar lets you say "this is my music folder" and it iwll scan it quickly and then becuaes of the filesystem, its really easy to find what you want if you go to artists->album or you can just search.

This system works well

 

Why is that? As I look at some of my files, many tracks are attentuated 8 dB or more by Sound Check. I can see bringing a track down by a tenth of a dB or something, but why by so much? And if this indeed is being done digitally, without upsampling or dithering, then someone smarter than me can figure out how much the resolution is being reduced to achieve that reduction.

The reason I speculate it's all being sone digitally is that I use a USB connection to my receiver; at no point is the signal analog until it is decoded by my receiver, to my knowledge.

IIRC, you can raise the volume of a digital recording without throwing away bits, but how can you lower it without doing that? High-quality digital volume controls do indeed use upsampling to mitigate the impact on the signal.

I don't doubt you, but I'm open to some education here! Thanks.

 

Lowering the volume of most music is far preferable to increasing the volume of most music. If you start to raise the gain of songs to equalize their perceived loudness, you begin to decrease the dynamic range of their peaks.

Here is a link to the Replaygain FAQ, which explains the concept better than I could. http://replaygain.hydrogenaudio.org/faq_quiet.html

PS: and attenuations of 8 db are definitely necessary in some cases to reach the replaygain reference level. Today's maximized, hypercompressed CDs often have a replaygain value of -8 to -11 db. Relatively well mastered current CDs might have a -6 or -7. By comparison, Steve's Bad Co. gold CD is a -3 point something. Very few CDs are quiet enough to need a positive gain adjustment.

 

And by that - at least as far as iTunes is concerned, IIRC - we mean the peaks are clipped hard, which is going to be far more audible than a few lost bits at the bottom. In theory, that is going to be an issue with ANY track whose volume is raised.

 

The files are much smaller using Apple Lossless and they do retain the tagged info. I am not sure what info could be missing that FLAC would have that Apple Lossless does not have. As a Mac user I see no reason to switch to FLAC.

Pat