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Normalizing ALAC to avoid sound clipping in iPod with EQ on
R1sky
post Oct 6 2011, 09:54
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I've ripped my whole CD collection with dBpoweramp to ALAC, but as soon as I use some "bass heavier" EQ on my iPod classic (6th gen), I can hear quite loud sound clipping (in more bassy sections of tracks) instead of deeper bass. I was searching for solution to fix this and the answer was to lower the gain of songs (using iTunNORM tag). The only way to do this is by using iVolume, because mp3gain (also AACGain) and all other utilities doesn't support ALAC. This could be fine, but the problem is, that iPod firstly applies the EQ (which distorts the sound) and after that applies the iTunNORM tag to decrease the gain -> the result is just distorted quieter sound.

I was also looking on WaveGain (CD -> wave -> WaveGain -> ALAC), but it looks like, there's fairly a lot of bit loss - which means WaveGain-ed ALAC files aren't lossless anymore. I wanted to ask, if there is any lossless way to play my ALAC files on iPod without distortion with EQ on? = do you have any idea how to lower the gain of tracks without losing quality?

Thanks.
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DVDdoug
post Oct 6 2011, 19:27
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If you can't EQ without distortion, that sounds like a bug in the iPod (assuming you are listening at reasonable levels).

Maybe another solution would be headphones/earphones with more bass. Or, maybe you can "permanently" EQ your iPod-targeted files with an audio editor. (Of course, you'll still have to reduce the volume to accommodate the bass boost without clipping.)

QUOTE
was also looking on WaveGain (CD -> wave -> WaveGain -> ALAC), but it looks like, there's fairly a lot of bit loss - which means WaveGain-ed ALAC files aren't lossless anymore.
Why do you say there's loss??? It's just a volume change, and as you've diagnosed & described the problem, volume reduction before EQ is the only solution! You need to reduce the volume by at least the amount of bass boost to ensure there is no clipping on any song. If you are using lots of bass boost, you need lots of volume reduction.

OK... technically almost any analog or digital volume change is lossy (the data is altered and it's not always 100% reversible). But, volume adjustments are done all throughout the music production process and it's generally not considered lossy. And, it doesn't alter the data as drastically as EQ.... I'd consider EQ to be more lossy than volume change.

Are you using the default WaveGain settings? You probably need to use extra volume reduction, since you want to re-boost with EQ. (I don't use WaveGain and I don't know how to do that... But, any audio editor can reduce the volume.)

This post has been edited by DVDdoug: Oct 6 2011, 19:33
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R1sky
post Oct 6 2011, 22:46
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Thank you for your explanation, it really helped me a lot. I was just thinking, that you're losing bits, when you're lowering the volume, because the modified track is smaller than original (eg. 26 MB modified track vs 30 MB original file) - this leads to theory, that when you set the output level to 0 dB, you'll get an empty file = 100% data loss. And that's the reason, why I thought it's so lossy.

QUOTE (DVDdoug @ Oct 6 2011, 20:27) *
If you can't EQ without distortion, that sounds like a bug in the iPod (assuming you are listening at reasonable levels).


It isn't bug just in my iPod at all. It's a well known issue of (probably) most iPods, they have poorly engineered EQ. Few weeks ago, I was looking at some tests on another webpage. The results were exellent, when playing without EQ, but as soon as they put some more bassy EQ on, the sound was terribly distorted. It doesn't matter if you're playing it at lowest or highest volume, the result is everytime the same - firstly the EQ is applied (sound distorted) and after that this distorted sound goes through volume adjustement - so as you can see, the only way to add more bass is (maybe) to lower the volume of the file itself.

Btw my earphones are fine, not one of the cheap ones. They play flawlessly on any other music device. The only issue here is poor iPod firmware.
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Dr_Colossus
post Oct 6 2011, 22:58
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Turn on Soundcheck on your iPod then set all your files to a certain negative dB, you may have to test a number. I'm not sure how easy that's done in iTunes because I haven't used it in ages. I'm not sure if you can batch set the Soundcheck level.
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kornchild2002
post Oct 7 2011, 10:44
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Soundchek and adjusting the volume of a track in iTunes are two completely different things. Soundcheck is Apple's way of trying to make it so all of the files in a library play at the same volume. Honestly, it is a rather bad implementation as I can hear volume fluctuations quite easily. Instead the best thing to do for normalization such as this is turn Soundcheck on, let iTunes scan the library, and then use a program to scan the track, use ReplayGain to normalize them, and then convert the ReplayGain values to something Soundcheck can read. Being on a Mac, my options were limited so I ended up purchasing iVolume. There is also iVolume for Windows but I understand that foobar2000 can do this for free though you have to jump through some hoops. Either way, I believe that this is the best route for trying to volume normalize tracks in iTunes. iVolume work with mp3, non-DRM AAC, WAV, AIFF, and ALAC tracks. I am not sure what foobar2000's compatibility is.

This still may not fix the issue when it comes to playing back the content with the EQ on since the EQ's used both in iTunes and on iPods, iPhones, and iPads are pretty bad to begin with. You won't have any issues going the ReplayGain + Soundcheck route without relying on the EQ but things change once you throw that in there. I would ignore the EQ and just try to normalize the tracks anyway unless you like constantly having to adjust the volume.
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mixminus1
post Oct 7 2011, 14:54
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@OP: Try some different headphones...really. wink.gif


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saratoga
post Oct 7 2011, 19:45
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You might be interested in rockbox down the road. The port for your player isn't all that stable yet, but is improving. Once its solid, there is a parametric EQ with precut, so its pretty simply to boost bass without clipping/distortion.
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R1sky
post Oct 7 2011, 22:24
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Thank you guys for your advices. I already tried to use both ReplayGain and iVolume (Soundcheck ability)... the normalization itself was great, but as i already said, it didn't solve the problem with EQ (because all of these methods are using the principles with tag reading, which is applied after the EQ, not before).

QUOTE (saratoga @ Oct 7 2011, 20:45) *
You might be interested in rockbox down the road. The port for your player isn't all that stable yet, but is improving. Once its solid, there is a parametric EQ with precut, so its pretty simply to boost bass without clipping/distortion.

Yes, this is the best solution to all of these issues so far, but I'd rather wait for stable release, that is why I'm looking for some fix to help me with waiting for it wink.gif Btw is there any difference in battery consumption playing ALAC with default iPod firmware against ALAC or FLAC playback through Rockbox?

QUOTE (mixminus1 @ Oct 7 2011, 15:54) *
@OP: Try some different headphones...really. wink.gif

This is another thing I was thinking of besides modifying the tracks. My current earphones aren't that bad, but buying some new can be another sound improvement smile.gif Do you know about any (earphones, not headphones), that should produce the best sound? I mean as clean as possible, but also with fairly deep bass. The price isn't a problem.
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kornchild2002
post Oct 8 2011, 21:40
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What is it about the EQ that you absolutely must use it? I have owned iPods starting in 2003 and not once have I ever used their EQ simply because it has always been a sub-par experience (at best, the one in my 3G iPod was a mess). Are you having bass/treble issues with your headphones? Is something wrong with the audio coming out of the iPod as-is with just the normalizations applied that you need to also use an EQ?

Edit: I realize that my above statement could be seen as abrasive. That was not my intent as I am simply curious as to why you want/need an EQ on a system whose EQ's have always been bad dating back to the first iPod released in 2001.

This post has been edited by kornchild2002: Oct 8 2011, 21:41
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greynol
post Oct 8 2011, 22:09
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FWIW, my encoding process is to pre-scale my tracks to RG album gain +3dB before converting to MP3. I still use a 3G iPod and when listening with the stock ear buds I turn on the bass boost.

Am I pre-scaling in order to avoid clipping due to the bass boost? No.

Do I notice any issues with clipping because of the bass boost? No.

Do I know if there would have otherwise been audible clipping because of the bass boost if I had not pre-scaled? No.

This post has been edited by greynol: Oct 8 2011, 22:58


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metalboy
post Nov 1 2011, 19:10
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I use foobar2000 to manage my files, convert from FLAC to ALAC and even play most of the time. I use iTunes to manage the library for my iPhone. So, I scan ALAC files with replaygain in Foobar2000 then I use MP3tag to apply these values to a soundcheck values. The result is very good. Soundcheck in itunes is only a Track gain but with the method I use you can do either Track or Album. You do wind up using basically three programs (mp3tag, foobar2000 and iTunes) but best method I have found so far. Also, this works for all files (mp3, AAC) you might want to put on the iPod/iPhone.

Link to Mp3tag forum http://forums.mp3tag.de/index.php?showtopi...p;hl=soundcheck
That explains and gives you an Action to apply your soundcheck from replaygain.
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andy o
post Nov 5 2011, 07:12
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As the OP has said, EQ is applied digitally before Sound Check is, so Sound Check doesn't fix it. And FWIW (not much to the OP since it's an iPod Classic, unless they've released a FW update for it), this has been fixed at least since the iPod Touch 4, probably with iOS4, so maybe older Touches/iOS devices as well (Touch 4 for sure, I have it). With it, when applying EQ the whole gain lowers accordingly and prevents clipping.
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Synchronated
post Mar 8 2012, 11:16
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"@OP: Try some different headphones...really."

It's not the headphones; most of the EQ settings on an ipod classic introduce clearly audible clipping in the signal regardless of the headphones (seems to be because it boosts frequencies at a stage where there is no headroom... rather than attenuating the unwanted frequencies as it should do if there's no headroom).

I'm going to test newer firmware on this point this week but it's definitely true of version 2.0.2 and earlier.

The only way around it seems to be to use a headphone amp for your EQ needs. Having quieter files by maybe 6dB might do it, and sound check/replaygain will sort the volume anyway, but that involves re-ripping/acquiring everything unless you still have lossless copies.
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evereux
post Mar 8 2012, 13:45
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I think the different headphone suggestion was so the OP could avoid having to EQ altogether. I second that idea.


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Synchronated
post Mar 12 2012, 11:18
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Yes that's fair, if you look at it like that.

Doesn't really excuse an EQ that doesn't work when applied to practically anything (even stuff that is not loud and is mastered 'properly' will not have the 6dB or more clear headroom throughout that it would need for this EQ to work), especially in such a widely-used product that has storage space, gapless playback and replaygain support (if you use Foobar) over its rivals.

I tested an ipod classic running 2.0.4 and it still clips horribly unless you're using the ones that only subtract frequencies. Unfortunately for me there is no 'subtract mids' preset so all the smiley-face-esque EQs that I would actually want to use cause distortion.
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