Distorted/Overdrived equalizer in ipod classic

[dieter345]

Some of you might have noticed that the ipod classic equalizer produces an extremely overdrived/distorted signal when applying it to certain music that is already mastered at a high volume level (don't know if older ipod models also suffer from this bad equalizer).
Obviously the equalizer does not reduce the signal before applying the equalizer or it has absolutely no room left in its audio engine to boost the signal (most of the EQ presets on the ipod boost the signal at certain frequencies)
Try e.g. EQ profile "R&B" or "Rock" on such audio files.

I found out that applying replaygain/soundcheck does not help because the ipod's audio-engine obviously first applies the equalizer (which leads to a distorted signal) and AFTERWARDS applies soundcheck value which possibly reduces the gain, resulting in a still distorted but low volume output

I can circumvent the EQ problem however by applying mp3gain to my critical songs as this will lower the gain BEFORE the ipod applies its equalizer, resulting in a "normal" not-distorted sound.
In the wiki I have read that ml_ipods mp3gain feature (to apply mp3gain to all songs on the ipod) is not needed anymore as replaygain can be used instead.
I would like to see however the ability to apply mp3gain to certain songs on my ipod only.
Currently ml_ipod allows to do that only on the whole ipod (which took around 5 hours on my pc/ipod). I would like to apply mp3gain however only to my "problematic" content.

After speaking with the apple hotline a recommended workaround was to apply EQ settings in itunes and have them transmitted to the ipod upon sync. I've no clue where the ipod stores per-song-based EQ settings (obviously not in the mp3 files/id3 tags), but if it would be possible to sync a certain value of the pregain fader found in the itunes eq this could solve the problem too.

Regards,
Dieter

[abu]

Nice idea. Please add this to the feature request list at SF, to insure that it gets tracked. Thanks.

[dieter345]

Thanks for directly providing me with the link to the feature request list at sf
I've added a new feature request for extending the mp3gain support.

Some further information for german readers can be found on a swiss audio magazine. They have an article where they also measured the EQ applied signal and concluded very bad results which match the results I hear
]http://www.avguide.ch/index.cfm/show/page.view/uuid/B909C597-1185-C4B3-5285E5597A15FD81]avguide.ch
(Hmmm, obviously I'm not allowed to post links, so for those too lazy to click reply, here's the link again as text:
"http://www.avguide.ch/index.cfm/show/page.view/uuid/B909C597-1185-C4B3-5285E5597A15FD81")

Sorry, I haven't found a similar article in english.

And last but not least, thanks to the authors for this great and feature-rich plugin. My iPod just became useful

Regards,
Dieter

[abu]

Do you think the Apple guys are talking about this slider:

So if you put that more to the left, the EQ settings wouldn't distort the sound?

If so, try the similar setting in ml_iPod, called "Global volume adjustment" on the "Volume" tab. That has the same effect by writing a special value to the database. Just give it a try and report here, please.

[dieter345]

No, the slider you are referring to is apples soundcheck (practially the same as replaygain but with a different tag name and the tag value is stored in hex format, btw. mp3tag can convert between these two).
I already tried replaygain through ml_ipod and soundcheck through itunes with the effect that the output is still distorted to the same amount as before, but the overall volume is low, thus my assumption, that replaygain/soundcheck is applied by the iPod only AFTER applying the equalizer settings.
If I understand it correctly, then ml_ipod's "Global volume adjustment" is the same thing as having certain replaygain values in my id3 tags, right?

The apple guy said that I could for example bind the eq preset "Linear" to my critical songs and itunes will transfer these eq settings automatically to the iPod.
However I haven't tried if itunes also transfers customized equalizer settings (because you can customize the eq in itunes but not in the iPod).
If itunes would transfer customized settings than the problem of distortion could be solved by transferring a certain value for the pregain value of an eq setting. The respective fader is labeled "Preamp" in itunes (or "Vorverstärker" in the german version) and is the left-most one in the eqalizer window. (Btw. winamp also has a pregain slider on the left side of the eq window).



I'm pretty sure that customizing the preamp value will fix the issue (because that's what I expect from a pregain fader: modifying the gain prior to applying the equalizer).


Regards,
Dieter

[abu]

Ah, I see. Actually, the "Global volume adjustment" has nothing to do with the replay gain values. It is stored in a different field in the database. So, basically, the resulting volume is (roughly speaking)
volume = original volume * replay gain * global volume adjust

Now the question is, when does the iPod apply this database field for the "global adjustment". If it does this as a first step, before applying the EQ, then it would help.

BTW: As far as I know, the iPod does not even support the non-standard EQ settings. iTunes does write them to a file on the iPod, but all the wizards say that this file is not read by the iPod... ???

[dieter345]

Hi, I just finished some experiments:

- Global Volume adjustment:
Unfortunately the iPod treats it the same way as the replay gain: first the eq is applied, which leads to distortion, afterwards, the setting from the glob.vol.adj. is applied which leads to a silent but still distorted sound.
So this won't help

- EQ settings from itunes:
Obviously the factory eq presets are transfered to the iPod while the user-created ones are NOT transfered or the iPod cannot interprete them.
When factory eq presets were defined with itunes for a song, the iPod recognizes it and overrules the eq setting you have done in your iPods extra menu. However when a customized preset is defined for a song, the iPod simply applies what you have configured in your iPods extra menu. Thus the iPod cannot handle customized eq presets.
So this won't help too

So up to now, mp3gain seems to be the only solution to having a nice eq setting without distortion (the other solution would be to use another mp3-player but that's another story )

Regards,
Dieter

[dieter345]

For all interested in trying it out themself, I've uploaded a 20sec sample of a song which is mastered at a high level:
http://stashbox.org/74343/test.mp3

When you here this song with iPods EQ turned off you'll notice that the song itself is not distorted. (while the guitars in it are )
Then try and listen to it with e.g. "R&B" EQ preset on your iPod. You'll surely hear what's this thread about

Btw. the wikipedia article about the iPod already mentions the EQ problem with further citations coming to the same conclusion: use mp3gain:
http://en.wikipedia.org/wiki/Ipod#Equalizer

[abu]

ok, try 3.02p36
And tell that Apple guy about your findings...

[dieter345]

Wowwwww.... that was fast!!!
Works like a charm.
This is exactly what I need.
If I find now another album in my collection that is distorted by the equalizer I can simply apply mp3gain to this album only.
Perfect!
Thank you very much!!!

[dieter345]

After reading the documentation of mp3gain, a further question came into my mind:
How does ml_ipod utilize mp3gain: by using track gain or album gain?

[abu]

mp3gain.exe is called with params /r /c /q /f
That means track gain. It gets called for one file at a time, so we can't use album gain here

[dieter345]

I see, so I guess it's not possible for ml_ipod to e.g. determine which songs from the current selection belong to one album and then call mp3gain on such album sets with album gain?

Not exactly a problem, but would be surely nicer if it worked with album gain.

[abu]

It would be possible. So, if anybody wants to code for that, fine. I don't have the time at the moment

[dieter345]

Btw should I close the respective mp3gain feature request or is this done by you?