January 20, 2004
Comparison of MP3 and AAC

I got my iPod hooked up to my PC last night after installing Win 2000 SP4. ITunes installed nicely and found all my existing mp3s.

Now the real job starts: I've got over 300 CDs back home, and of course they're all going to go on to the iPod over the next months. iTunes proposes to rip in both AAC and MP3 formats, and from before I have a few Ogg Vorbis files, more out of curiousity (and those won't play on the iPod, so that's a goner), and this leaves me with the following question:

Which format should I choose for putting my record collection on to my iPod?

The iPod homepage says:

Designed to give you the best portable digital music experience ever, the iPod delivers the highest sound quality from input to output. iPod supports the most popular audio formats — including MP3 (up to 320 kbps), MP3 Variable Bit Rate (VBR) and WAV — giving you access to a wide range of audio file types. And iPod is the only portable digital music player that supports the AAC format used by the iTunes Music Store for Mac and Windows. AAC features CD-quality audio in smaller file sizes than MP3, so that even more songs fit on your iPod.
Ok; but that's a promotional message. Thankfully the Internet has more information and more detailed analysis and advice: Marc Heijligers' Encoding Observations are extensive and offers good analysis of the different formats and bitrates. From his analysis, a 160 kbps AAC file is similar in quality to a 192 kbps VBR MP3 file (with the AAC file weighing in at less than 90% of the equivalent MP3 file size) and that does seem to support Apple's claims about AAC quality. The participants in this discussion over at iPodLounge seem to agree...

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Comments

Is AAC open, or is just an Apple thing? I kept getting confused when I was looking at it before.. but I might just be stupid. I was hoping there are some free player/encoding libraries for Linux, so that my entire collection is not rendered useless when I reboot to my computer's better half.

Posted by: eliot on January 20, 2004 03:48 PM

Good point, Eliot! I think it's an iTunes thing, hence playable on Win + Mac at the moment. Not sure if it's open and/or if third party rippers/players support it at the moment.

Posted by: Anders on January 20, 2004 03:53 PM

Codec comparisons are difficult as they're often optimal for different types of sound (or different types of music). Thus, the result of a comparison may vary according to the source material.

As a general test, my favourite reference is a recording with Ole Paus and Oslo Kammerkor: Det begynner å bli et liv - det begynner å ligne en bønn (Kirkelig kulturverksted, 1998).

To make a comparison, define a small set of reference music covering a broad range of challenging sounds, both vocal and instrumental.

Posted by: Håkon Styri on January 20, 2004 03:58 PM

Looks like my search was more fruitful this time around. http://www.audiocoding.com/ provides a free MPEG-4 encoding/decoding library. And this [ http://www.foobar2000.org/ ] looks like an interesting player that supports everything under the sun. I think I might start using MPEG-4!

Posted by: eliot on January 20, 2004 04:09 PM

Håkon, FYI the linked codec comparison did just that - sampling a couple of different tracks (classical, pop, etc) in the different codecs and playing it on a top-of-the-line stereo.

I suppose I'll do some testing myself, but feel comforted that others have gone before and done some preparations and given some direction... :-)

Posted by: Anders on January 20, 2004 04:20 PM

For what it's worth, I'm not too thrilled about iTunes' mp3 encoding. Admittedly, AAC isn't bad, but, as noted, for the moment mostly limited to Apple/iTunes/iPod.

I get the best results ripping my cds with ExactAudioCopy and the latest Lame mp3 encoder with the alt-preset standard settings (~192 kbps/VBR).

Always worth to check out the Afterdawn and HydrogenAudio forums for more details.

Links:
http://www.exactaudiocopy.de
http://www.jthz.com/~lame/
http://www.hydrogenaudio.org
http://www.hydrogenaudio.org/index.php?act=ST&f=15&t=203& (for details on alt-presets)
http://www.afterdawn.com/

Posted by: FrankS on January 20, 2004 04:51 PM

a bit off topic but I would NEVER buy music online as long as

1) the format is closed and
2) the format is lossy

FLAC is an open source LOSSLESS compression format that also has hardware support. You get filesizes that are on average ~50-60% of wav so it's really not that bad.

But, uhm, for your question, I don't know :-P

Posted by: Agnar on January 20, 2004 09:18 PM

How to get very good results using EAC:

http://doc.hydrogenaudio.org/wikis/hydrogenaudio/GapSettings

Posted by: Heiko Hebig on January 21, 2004 04:21 AM

Coincidentally I found this today: http://www.digitalnetworksna.com/shop/_templates/item_main_Rio.asp?model=220&cat=53
Rio Karma supports FLAC but I guess it's not as elegant as iPod... you bastard... :)

Posted by: Agnar on January 21, 2004 09:16 PM

http://www.macobserver.com/comments/commentindivdisplay.shtml?id=35315

AAC is an open standard. Thought so. But AAC files bought from the iTunes Music Store have their digital rights managed real good by the FairPlay DRM stuff. Which Apple licences from someone else.

I personally NEVER listen to music unless it's played right in front of me. Admittedly it gets a bit crowded bringing all 28 members of The Polyphonic Spree with me on the tube, but the sound quality is almost indistinguishable from AAC and MP3.

Posted by: Small Paul on April 16, 2004 06:57 PM


For detailed info on AAC and MP3 check out this website (the article is in PDF format)

http://www.aes.org/publications/downloadDocument.cfm?accessID=14703162000122117

For the rest of us.. Read the 'Conclusions' section at or near the last page.. it has told me quite a lot about the two.. seems AAC = MP3 + reduced file size + Digital Rights Protections.

Find out for yourself..

Posted by: Kevin on June 2, 2004 03:56 AM

Hello, if you haven't figured it out - Marc Heijligers is entirely off base. His conclusion happens to match the conventional wisdom - but his approach is ridiculous.

There's not much point in non-blind single user listening tests focusing largely on a single track. Look at some multiple user blind tests that use a variety of music types, like these:
http://www.rjamorim.com/test/

Maybe I need to translate JohnV's overly diplomatic comment - "Thus, it's generally accepted fact that the substraction method is not very accurate especially if you are comparing total noises of different codecs using about same bitrates." What he means is, using graphical representations of frequencies to evaluate codecs is meaningless. Encoding audio is about what humans hear (psychoacoustics), not what they see.

Eg look at the aes.org link posted by Kevin for how comparisons are done.

Posted by: buzzy on June 7, 2004 03:19 PM

Links & download of free audio/video software...
http://mp3.marki-online.net

Posted by: Marki on June 23, 2004 04:17 PM

AAC is Mpeg4, MP3 is Mpeg1.

Psychoacoustic coding has come a long way in the last 10 years. AAC is therefore much better in terms of both perceived quality and file size.

Ben

Posted by: Ben on June 25, 2004 04:15 PM

First off I only have 2 stereo speakers with a subwoofer to listen to music on.

I can't detect much of a difference between .m4a (AAC) and .mp3 (MP3) encoded songs in terms of audio quality.

When ripping from CD at 128 kbps though, the .mp3 files were slightly smaller in my test. I tried ripping "3 Doors Down~The Better Life" and "3 Doors Down~Away From The Sun" using both encoders and here is what I found:

23 Songs Total
128 kbps
44.100 kHz
Stereo Sound

MP3 - 80.0 MB (83,945,455 bytes)
AAC - 80.9 MB (84,879,872 bytes)

As you can see MP3 saves a little bit of space, almost one megabyte for the two CD's. I am working on putting songs on my new 40 Gig Click-Wheel iPod and am trying to figure if it's best to re-encode my collection in AAC format.

If you already have the files on your computer in MP3 or are ripping from CD, the Apple Encoder won't place Digital Rights Management protection codecs on the files (so they're unrestricted). DRM is only for songs downloaded from iTunes.

I used a LAME mp3 encoder through a program called CDex (sorry don't know the web address).

Hope that helped someone. Thanks.

Posted by: Brendan on August 11, 2004 11:59 PM

Hi Buzzy. On my pages I mention my observations are personal and based on more than one track.

Can you explain why I'm "entirely off-base", and why my approach is ridiculous?


Marc

Posted by: Marc Heijligers on September 2, 2004 01:08 AM

Whoah..
Busted.

And by Marc himself.

Posted by: on October 8, 2004 06:17 AM

Found this blog via Googling for an iTunes comparison...

Just in case nobody's figured it out yet, AAC is not an Apple-branded format. It was developed by Dolby.

FairPlay is the digital rights management used by Apple on its music store files.

They are not one and the same. It's even possible for FairPlay DRM to be attached to mp3 files.

Lastly, the FairPlay terms are the same for every file bought through iTunes.

Simple enough? Good.

Posted by: Leland Jordon on October 30, 2004 07:24 PM

I just encoded 20 of my brother's cd's as MP3 320 kB via iTunes ; they sounded great on my powerbook g4 (gig ethernet) ; took a walk with my iPod ... NO NO NO NO NO to anything subtle (Glenn Gould, Bach French Suites, Lyle Lovett Fat Babies off of I Love Everybody). Checked the PowerBook files again, they sound OK... Does my iPod (5 gig wheel version 1.4 -- no upgrades available) need better decoding software ?

I tested (blind) mp3 320 kB, aac 320 kB, apple lossless, aif, and the only two acceptable were aif (duh) and the aac.

That's all my ears tell me, and since I'm listening on the go, it's got to be aac.

Posted by: Nicolas R. Troff on November 9, 2004 01:36 AM

Can anybody explain to me the following:
I have some MP3 ripped CD´s which I wanted the convert to AAC and put in my iPod. The size of the files however are much bigger after converting at 128 kb.
How come so many people are writing that the AAC is smaller in size?

Posted by: Mickey on November 9, 2004 12:51 PM

AAC is definatly better then MP3 (mp3 pro is something completely different)

MPEG-AAC Compression Format Explained, it is definatly beter then MP3 - (MP3pro is comletely different to MP3)
To start to understand why Apple choose AAC over the many other available formats on the market I will need to explain who created it, when it was created and why it the sounds quality is better than the MP3 File Format.

AAC was created by the MPEG group that includes Dolby, Fraunhofer (FhG), AT&T, Sony, and Nokia, companies that have also been involved in the development of audio codec’s such AC3 (also known as Dolby Digital). MP3 was also created by the MPEG Group but I believe that the MP3’s time is now up from once being the most popular codec for storing and transferring music and that AAC’s time has just started.

The MP3 file codec was created over 10 years ago, I was never a big fan of MP3’s sound quality one of the reasons that this may have been because was that it employed a "lossy" compression system which removes some data leading to the loss frequencies, judged to be essentially inaudible. Listeners believed to think that MP3 managed to deliver near-CD sound quality in a file that's only about a tenth or twelfth the size of a corresponding uncompressed WAV file, the size maybe true but I strongly disagree that it was near CD quality and would rather listen to tape. When creating an MP3 file, various amounts of compression can be selected, depending on the desired file size and sound quality a lot of the times I found these files to be over compressed resulting in a thin sound with loss off bass and definition within certain frequencies.

The original MP3 codec in now being replaced with MP3 Pro, which I have just recently found out. Its combined with MPEG4 which also includes AAC allowing small, low-bit rate files to contain much more high-frequency detail than standard MP3 files encoded at similar low bit rates.) The high-frequency portion of the audio signal is handled by an advanced and extremely efficient coding process known as Spectral Band Replication (SBR), while the rest of the signal is encoded using the same process as in regular MP3. This enables older MP3 "player" software applications to play files encoded in MP3. I am not going to do in to the depths of MP3Pro as it contains AAC, but I would say that they are each other’s competition.

Due to the popularity and development of the internet over the last few years, most people downloading music (via MP3 format), have relised that the quality compared to newer formats such as MPEG-4, 3GPP, and 3GPP2 is not nearly as good as it should be. This is due to the fact that the MP3 is over a decade old; within in this time lots advances in audio coding and compression have been achieved. AAC combines many of these advances; we can now use lower data rates whilst gaining a higher quality output, this has opened a doorway to the future of how we listen to music. The first encounter of AAC even for those of us that don’t have an I-pod will be via digital broadcasting, mobile multimedia, and Internet services.

The AAC codec builds upon new, state-of-the art signal processing technology from Dolby Laboratories and brings true variable bit rate (VBR) audio encoding. Bit rates are a measure of how many bits describe each sound in an audio file. A low bit rate means lower quality and a smaller file size, while a high bit rate means better quality and larger files. The standard bit rate is 128 kbps. True variable bit rate is a type of compression wherein certain audio sections are encoded at different bit rates so that complex sounds are encoded at a higher rate while simple sounds are encoded at a lower rate, as opposed to Standard bit rate encoding where the type of compression wherein an entire audio file is encoded at the same bit rate. This means you get the best sound possible for a certain amount of disk space. There is a disadvantage of this which is that certain players occasionally have problems decoding VBR audio files.

Getting Technical

Although I have been only referring to AAC as the one and only file type, advances have been made and will going as I write this essay. AAC can really stand for two things: either MPEG-2 Advanced Audio Coding or MPEG-4 Advanced Audio Coding and as its full name suggests, it is either an MPEG-2 or MPEG-4-based audio format.

The MPEG-2 version of the format is also often called as MPEG-2 NBC as in Non-backwards compatible, but the correct name that should be used, is the AAC. The NBC name comes from the fact that unlike older MPEG audio encoding methods, it is not backwards compatible (for example, MP3 is backwards compatible to MP2) to older MPEG audio formats.

When coming to music we are mainly concerned with MPEG-4 AAC as it produces better quality and smaller files than MPEG-2 AAC. This again can be broken to MPEG-4 AAC Low Complexity (LC) and MPEG-4 Spectral Band Replication (SBR) to MPEG-4/HE-AAC.

HE AAC stands for High Efficiency Advanced Audio Coding, it was created from a combination of MPEG-4 AAC (LC) and MPEG-4 (SBR). Quoted and proven from MPEG it can deliver “coding gains of more than 40 percent compared to MPEG-4 AAC LC.” It also has an ultra low bit rate coding, as low as 32 Kb/s Stereo (45:1 compression!) HE AAC is able to achieve superior audio quality, without losing treble sound or collapsing of the stereo image. According to the formal listening tests done by leading broadcast unions, HE AAC clearly outperforms competition at 48 and 64 Kb/s.

Advantades of AAC over MP3

Improved compression provides higher-quality results with smaller file sizes this could be put to the test be listening to of the same songs with the same file size via MP3 and AAC and hearing the the Aac file was defiantly a lot better in quality..

Support for multichannel audio, providing up to 48 full frequency channels

Higher resolution audio, yielding sampling rates up to 96 kHz rather then the MP3 which only goes to 48 kHz.

Improved decoding efficiency, requiring less processing power for decode

Posted by: Mojo on November 10, 2004 01:23 AM

I noticed you said your few Ogg Vorbis files are a "goner" but there are programs out there that will allow you to recode those Ogg Vorbis files to MP3 or AAC or whatever you want.
Something like dBpowerAMP should do the trick!(http://www.dbpoweramp.com/dmc.htm).

- Hope this helps!

Posted by: Mikey on February 24, 2005 10:12 PM

May you find my comparison interesting. The url is:

http://www.telefonica.net/web2/audioformats/

Posted by: Pablo on April 2, 2005 09:55 PM

For best converting mp3 to aac and aac to mp3 use Total Audio Converter for www.CoolUtils.com/TotalAudioConverter

Posted by: Alex on December 6, 2005 09:57 AM
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