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Some iTunes Sound Quality Questions

post #1 of 11
Thread Starter 
I notice that after converting all of my MP3 files to AIF format using iTunes' built in-encoder, all of them sound indentical when played back from iTunes (no equalization). All MP3 files are 44Khz, and about half are 128kbps with the other half being 160+kbps...the encoding options set were 44 Khz, 16 bit Stereo AIF (what I've always used when importing CD tracks into Peak).

1. According to iTunes (and my own intuition given my experiences with Peak) there should be a noticable sound quality difference when burning the AIF files to CD vs. burning the MP3's to CD. Is this true, given that they sound identical on iTunes? Is there something about iTunes playback / Monsoon Speakers that would hide the differences in sound quality (assuming they're there)?

1a. Any evidence that using an application like Peak to create AIF files from the MP3's would result in a better sounding track?

2. When using iTunes' built-in equalizer, which takes precedent the general equalizer panel where you can change the slider settings, or the Get Info window where you can select any of the presets? It seems like the presets in the Get Info window take a back seat to the former. Whenever I'm tinkering around with the sliders to find optimal settings for a song, it seems like as soon as I settle on a setting and leave it there (close the window), that everything from that point ends up being played in with those settings, regardless of what's saved in the Get Info window.

Bug? Do the songs have to be selected in order for one to take precedent over the other? The way the equalization options are currently accessed and set up is FUBAR IMO.

3. If you assign a preset to an MP3 and then convert it to the AIF format, will the preset colorization end up in the AIF file or will iTunes ignore whatever equalization settings are applied?

4. If someone knows who set up the presets that ship with iTunes, you should tell them to let someone else to it. Most of them are so far off from their genres its ridiculous. Apply "Rock" to most classic rock or pop songs and it sounds like it's being played out of a tin can...lol.

Any help on these issues would be appreciated.
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post #2 of 11
Moogs-

You're misunderstanding the issue of "better sounding CDRs from .aiff files."

What they're saying is that if you extract audio from a CD and save it in .aiff format, and then burn a CDR compilation of all these .aiff files, you will end up with better sound that if you save that extracted audio in .mp3 format and create a CDR from those.mp3 files.

The reason for this is that the mp3 files end up heavily compressed, and in the process of this compression, much quality is lost. Converting an MP3 file back to .aiff does NOT restore the quality that was lost -- that information has already been discarded in the conversion (to mp3) process and cannot be regained.

For the highest-quality compilation CDR, extract the CD audio and save it as .aiff and burn the CDs directly from those. Re-converting your MP3 files to .aiff will not gain you any better quality, and will only waste hard drive space. Even though you're not re-gaining the information discarded through compression, the .aiff format is uncompressed and thus the file size will be at least 5 times larger (probably much more).
post #3 of 11
sizzle is completely correct. There is nothing you can do to regain the lost quality of MP3s.

The built-in speakers on Apples computers (tower, laptops, etc.) aren't good enough for you to notice the difference between CD quality sound (aiff) and MP3s, but as soon as you attach a nice sound system to your computer, the differences become very clear indeed.

I just got a set of Klipsch ProMedia 4.1 computer speakers (VERY high-end speakers for a computer setup), and I now notice all of those little nuances in the music that I was missing before. Music rocks!

-Ender
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If you find yourself sided with the majority, it is time to change your thinking.

-Mark Twain
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post #4 of 11
Thread Starter 
OK guys. Thanks for the tip. You're saving me a bunch of drive space. I had a feeling this was more or less like converting a JPEG into a Photoshop file and expecting better detail of one kind or another. No such luck obviously. Ah well...knowing is half the battle as the super-friends used to say.

Any idea about the iTunes equalizer and how the slider panel works in conjunction with the Song Info presets (which takes precedent, whether there is a bug there when one is set via Info, but changed on the slider panel)? I already submitted feedback to Apple about redesigning the manner in which presets are modified and assigned but as long as I've got your attention....




By the way, if anyone knows which bit rates in AG relate to the various forms of CD, that would be cool to know. The 192 says "Near CD Quality" but what I'm wondering is, can you say with any accuracy that:

AAD CD's = 128 kbps
ADD CD's=160 kbps
DDD / Remastered CD's =192 kbps
HDCD's=320 kbps

Because honestly, I don't understand how if 192 kbps is basically CD quailty, there can be MP3's all over the place that have half again or even twice as high a bit rate, when the source is the same for most intents and purposes.

[ 02-04-2002: Message edited by: Moogs ]</p>
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post #5 of 11
Moogs-

The correspondences between different MP3 bitrates and different kinds of audio masters are, I think, missing the point.

192kbps may be "near CD quality" because 192kbps less compressed than say 128k, so the compression is less audible (closer in fidelity to the CD original).

There is not a linear improvement from AAD to ADD to DDD CDs. Many analog recordings also mastered in the analog domain (AAD) will sound superior to entirely digital recordings. And an AAD CD is absolutely, positively, in every instances, better-sounding than a 128kbps bitrate MP3.

Personally I think people are kidding themselves when they say 192kbps MP3s are "near-CD quality." To me, they're suitable for listening in the car, or on cheap headphones, or on "multimedia" computer speakers. But if you did an A-B comparison between a CD and a 192k MP3 made from that CD, listening on a decent playback system, anybody who wasn't deaf could hear the difference.

To me, 256k is still audibly different from CD audio but you can at least say it's "near CD quality" I guess.

As far as the comparison between a 320k MP3 and HDCD audio, do you really think that encoding an MP3 at that rate from an audio CD will make the MP3 sound BETTER than the original CD? Even a 320k MP3 is still compressed (thus, by definition, sounds WORSE than the CD it came from).

I would scrap all these comparisons you've come up with and realize one thing: Even the highest bandwidth MP3 file is still a compromised, compressed, altered version of the original CD audio. A lower bitrate means more compressed and worse sound (but a smaller file), and a higher bitrate means less compressed and better sound.... but ANY compression means that it will not sound as good as the original!

Just like I mentioned previously, how you can't make a file sound BETTER by comverting your compressed MP3 into an uncompressed AIFF, you also can't make CD audio sound BETTER than the original CD audio by compressing it at only a 320kbps bitrate.

A higher bitrate equals better sound, yes, but you don't end up with an MP3 that sounds better than its original source just by going up the scale of higher bitrates (less compression). You can't add quality or detail that wasn't there in the first place.
post #6 of 11
Thread Starter 
Thanks Sizzle. I guess I wasn't really expressing my question too well. I understand that if you compress an original CD track, the compressed track will never sound *better* but I just wasn't sure if there *are* bit-rates that corresponded closely to the quality of various uncompressed CD audio types. Apparently it's not even close, regardless of which compression scheme you're talking about.

Honestly, your multimedia or car speaker example might be on the money because even though many of the 128 - 160 kbps songs I've downloaded sound pretty much identical to CD quality on my Mac (and sound almost as good in my car stereo), I've not tried an MP3 to CD disc on my Rotel system. I have a pretty good idea that if I did I'd immediately hear the weakness of any of the compressed-original files.

Just trying to figure out at what point the law of diminishing returns applies to downloaded MP3 files. In other words, assuming the person who made the MP3 didn't color the file with equalization settings or volume over/under-kill, at what point can you no longer tell the difference of Rock or Alternative recordings? I assume 128 kbps is universally liked simply because the sound is OK and the file sizes are pretty small (as you noted)..but all else being equal, on non-hi-fi systems does 192 kbps really sound noticeably better than say 128 or 160? Based on the few files I've listened to, I'd say no.

[ 02-04-2002: Message edited by: Moogs ]</p>
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post #7 of 11
[quote]Originally posted by Moogs :
<strong>Ah well...knowing is half the battle as the super-friends used to say.</strong><hr></blockquote>

<img src="graemlins/bugeye.gif" border="0" alt="[Skeptical]" /> I thought that was a G.I. Joe thing. <img src="confused.gif" border="0">
Living life in glorious 4G HD (with a 2GB data cap).
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post #8 of 11
[quote]Originally posted by sizzle chest:
<strong>Moogs-
...
As far as the comparison between a 320k MP3 and HDCD audio, do you really think that encoding an MP3 at that rate from an audio CD will make the MP3 sound BETTER than the original CD? Even a 320k MP3 is still compressed (thus, by definition, sounds WORSE than the CD it came from).

I would scrap all these comparisons you've come up with and realize one thing: Even the highest bandwidth MP3 file is still a compromised, compressed, altered version of the original CD audio. A lower bitrate means more compressed and worse sound (but a smaller file), and a higher bitrate means less compressed and better sound.... but ANY compression means that it will not sound as good as the original!

...

A higher bitrate equals better sound, yes, but you don't end up with an MP3 that sounds better than its original source just by going up the scale of higher bitrates (less compression). You can't add quality or detail that wasn't there in the first place.</strong><hr></blockquote>

A minor nitpick. The original AIFF could be compressed with a lossless ompression method and still retain its original quality.

As a quick check I just converted a 55.8MB AIFF file to a 39.3MB .sit file with stuffit. I think you will agree that the original file could be recovered with no loss of quality.

I also think that a lossy compression method if lightly applied will be indistinguishable to the ear but still achieve useful compression. Where that level exists will depend on the listener and the playback equipment.

Other than that I completely agree with you.
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post #9 of 11
[quote]Originally posted by Moogs :
<strong>
Just trying to figure out at what point the law of diminishing returns applies to downloaded MP3 files. In other words, assuming the person who made the MP3 didn't color the file with equalization settings or volume over/under-kill, at what point can you no longer tell the difference of Rock or Alternative recordings? I assume 128 kbps is universally liked simply because the sound is OK and the file sizes are pretty small (as you noted)..but all else being equal, on non-hi-fi systems does 192 kbps really sound noticeably better than say 128 or 160? Based on the few files I've listened to, I'd say no.</strong><hr></blockquote>

I havent actually tested the difference between 128kbps and 192 kbps, but what I have found is that people who take the extra time and HD space to convert their CDs to 192 over 128 usually don't have messed up tracks... This is because these people care more about the music then say the people who encode at 128... Of course this is not foolproof... but I've found that it works... Of course, I think that VBR gives the best quality/compression ratio, but that is just me... Personally, I think it is all subjective. If you wanted to, you could be happy with 64 kbps... but I could never be...

-Paul
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post #10 of 11
Thread Starter 
[quote]Originally posted by psantora:
<strong>If you wanted to, you could be happy with 64 kbps... but I could never be...

-Paul</strong><hr></blockquote>


True. Bose invented the Wave Radio for those 64 kbps folks! "Look honey, Hi-Fi stereo sound from a 4" high alarm clock radio system!"

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post #11 of 11
If you really want to find out what settings to use, just rip two or three songs multiple times with different settings, like
AIFF
256
192
160
128
96
VBR
or something, and then burn them all to a cd. Listen to the CD on a nice stereo system and decide what you like.
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