# 128 kbps stereo AAC audio "indistinguishable" from original uncompressed audio?!?!



## simX (Jun 19, 2002)

Holy cats!

I was reading up on the new MPEG 4 technology included in the QuickTime 6 Public Preview, and I saw this quote on this page of Apple's website:



> AAC compressed audio at 128 kbps (stereo) has been judged by expert listeners to be indistinguishable from the original uncompressed audio source.*



The asterisk just says, "See the AAC website for reference."

That floors me.  If everything that I read on Apple's site is true, MPEG4 technology will certainly overhaul the digital music sector again, just like MP3 did.  Much better quality, smaller file sizes, less CPU power to decode  everything seems great.

I'm just thinking about it: what if soon after QuickTime 6 is released, Apple releases iTunes 2.1 which is compatible with AAC audio and can encode it, and then Apple releases a firmware update to the iPod to allow it to handle AAC audio.  That would probably transform my iPod into a music player that can hold, say, maybe 1500 audio files instead of 1000!  That would be sooo awesome.

I just hope the rest of the world (*ahem*Windozepeeps*ahem*) realize that MPEG4 technology is beneficial and will adopt it as quickly as Mac users undoubtedly will.  I would hate to be toting around my iPod with AAC audio in it while all those suckers are out there encoding in MP3 audio still.  While I could still control my music, file sharing services might still offer only MP3-encoded songs, which would be bad. 

I can't wait for QuickTime 6 and Jaguar.  At most, what, three months?


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## rharder (Jun 19, 2002)

Using only the Quicktime 6 Preview version of MPEG-4, I've been appalled at the terrible video quality. I hope it's just me.

-Rob


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## MacLone (Jun 19, 2002)

As far as i know, more compression means less quality.
Maybe they did a great job and MPG4 is more compressed but with the same audio quality. I really don't beleive they can compress it more and have superior sound quality than a less compressed file.


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## wdw_ (Jun 19, 2002)

When I used that QT6 beta that came with Jaguar the Mpeg-4 video quality was terrible, but when I used the free beta from Apple's site the video quality was awsome.


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## wdw_ (Jun 19, 2002)

Wait a sec. If AAC audio encoded at 128 kbps is undistinguishable from its original audio source, then why is there even the option to encode it up to 256 kbps in QT6?


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## Pascal (Jun 19, 2002)

> _Originally posted by wdw_ _
> *Wait a sec. If AAC audio encoded at 128 kbps is undistinguishable from its original audio source, then why is there even the option to encode it up to 256 kbps in QT6? *


Why ? Simply so that the music will sound _better_ of course !


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## wdw_ (Jun 20, 2002)

But if at 128 kbps the sound is indistinguishable from the original source, then how could it get any better?


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## Shifting (Jun 20, 2002)

> _Originally posted by wdw_ _
> *Wait a sec. If AAC audio encoded at 128 kbps is undistinguishable from its original audio source, then why is there even the option to encode it up to 256 kbps in QT6?*



the sound is indistinguishable _according_ to a panel of experts.  obviously, not everyone is going to agree with these experts.  we should be able to encode at whatever bit-rate we want...experts be damned.  if 128kbps really is cd-quality, then i'm sure few will encode any higher then that, but it's good to have the option to encode at higher bit-rates if we want to, right?  more options are good, less options are bad.

:edit: used the wrong quote.  oops.


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## popey.marin (Jun 20, 2002)

You may be a windoz guy to think it would be better to limite the quality .
Seriously, the sound can be undistinguishable, but it does not mean it has the same quality. If you are going to manipulate this sound track, you will loose quality at each step of your manipulation (for example, compressing, resampling, amplifying ...). So, it is quite important to minimize the lose of quality in each step, even if this mean larger files ...


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## fryke (Jun 20, 2002)

Also, CD quality isn't the highest possible quality. Analogue is the highest possible quality, which, of course, isn't achievable digitally. So if DVD Audio starts to kick in - or yet another 'standard', we'll see higher quality sources for our AAC files.


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## ladavacm (Jun 21, 2002)

> _Originally posted by fryke _
> *Also, CD quality isn't the highest possible quality. Analogue is the highest possible quality, which, of course, isn't achievable digitally. *



Unfortunately, it is not achievable in the analog domain, either (at least, assuming we are talking about _recording_ here.

It is possible to achieve this in the amplifier domain, but eventually you have to put it on media, high-speed magnetic tape being still the best for analog recordings.

Analog equivalent of CD quality requires metal particle tape running at 38 cps at least. Higher speed (76 cps) is used in order to reduce wow and flutter.

To get the equivalent of 24bit, it is possible to use multiple heads recording the same signal out of phase in order further to suppress the tape hiss and rumble (hiss being random, it tends to cancel out regardless of the phase addition; some types of rumble come from macroscopic irregularities in tape coating, so that they cancel out when added together with inverted phase).  But then, we are talking about 16 channel reel-to-reel decks with tape running at .76 meter per second just to get you 2 audio channels comparable to something you get out of any budget hard-disk recording systems; no wonder analog recording is practically dead.

And please, don't get me started on analog fader hiss and scratching.


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## vanguard (Jun 22, 2002)

> _Originally posted by wdw_ _
> *Wait a sec. If AAC audio encoded at 128 kbps is undistinguishable from its original audio source, then why is there even the option to encode it up to 256 kbps in QT6? *



Well duh, it's for non-humans.  Sure, our experts can't tell the difference but what about cats and dogs?  I heard that horses have pretty good hearing and that they love Barry White.

256 kbps recording is for bardyard romance. 

Vanguard


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