AAC vs. OGG vs. MP3

asv108 writes "Yesterday, Apple unveiled their new music service claiming that the AAC format "combines sound quality that rivals CD." Here is a little comparison of lossy music codecs, comparing an Apple ripped AAC file with the commonly used MP3 codec and the increasingly popular OGG codec. Spectrum analysis was used to see which format did the best job of maintaining the shape of the original waveform." Wish they had WMAs in there too. And for the spoilage, it looks like OGG comes out on top.

Hard To Tell Difference

I've got a nice pair of Bose headphones, and I listened to an Apple Store AAC file and an OGG version of the same song. I don't consider myself a real audiophile, but it's damn near impossible to tell the difference between the two; though I can definitely hear the improvement from MP3 to AAC or OGG.

Re:Hard To Tell Difference

You would probably notice the difference if you try the test with certain kinds of classical music...

Even then you would probably have to be selective. Rich orchestral works (say, Janacek, Mahler, Sibelius) won't show an obvious difference, but something more spare (e.g. Debussy string quartet or a good recording of baroque strings) will show a big difference that should be evident even on poorer quality equipment.

Re:Hard To Tell Difference

To do a true test, you need to encode the files, decode them to PCM wav format, then burn to an audio CD.

Then, you have to do a blind test with all of them. You also need to use a variety of source material, because different genres of music compress better under some encoders.

Re:Hard To Tell Difference

To do a true test, you need to encode the files, decode them to PCM wav format, then burn to an audio CD. Then, you have to do a blind test with all of them. You also need to use a variety of source material, because different genres of music compress better under some encoders.

If you have to do all that to tell the difference, doesn't that kinda tell you something?

Re:Hard To Tell Difference

That's there value in ruling out variables when trying to objectively compare things?

Re:Hard To Tell Difference

The problem in your test is that if you know which file you're listening at, you're just not fair in your comparison and by listening several times, your brain just makes you hear stuff that is just not there.

A test was made where people would listen to two WAV file, one supposedely was an MP3 (that was expanded to a WAV). 25% of the people could hear a difference between the two WAV files where they were actually the same...

Re:Hard To Tell Difference

To do a true test, you need to encode the files, decode them to PCM wav format, then burn to an audio CD.

Then, you have to do a blind test with all of them. You also need to use a variety of source material, because different genres of music compress better under some encoders.

Or you could just use ABX [pcavtech.com]. That's actually the de facto standard for comparing audio compression. (See HydrogenAudio [hydrogenaudio.org].)

Re:Hard To Tell Difference

That may be good for you and I, but a true audiophile can tell the difference between a pressed CD and a CD-R... ;-)

Well, I'm off, I have to get some gold cables.

Re:Hard To Tell Difference

Then, you have to do a blind test with all of them. You also need to use a variety of source material, because different genres of music compress better under some encoders.

I don't disagree with you, but I just wanted to throw in my own 2 cents worth of informal experimentation:

I recently discovered the sourceforge cdex ripping software, so I finally had a chance to rip all my music to the superior sounding ogg format instead of mp3. Before doing so, my wife and I ran a couple double blind tests with one another to see where the best encoding was.

The only pair of speakers I had to test this was a pair of old Yamaha YST-M7's. These are Yamaha branded $20 single driver computer speakers that came with some computer I bought a while ago. They are pretty bad speakers. For the test, I selected a reasonable genre swath of music:

Dixie Chicks "There's your Trouble"
Oingo Boingo "On the Outside"
Samuel Barber "Adagio for Strings"
W. A. Mozart "Queen of the Night's Vengeance Aria"
REM "Nightswimming"

Each piece was selected because of particular aspects of song such as use of strings, use of horns, or use of voice. Each song was tried in a variety of encodings in both ogg and mp3, constant and variable bit rate, with the original CD wav file thrown in amongst the samples. The mp3 encoder was Lame v 1.27 engine 3.92 Alpha 1 MMX, the ogg encoder was Ogg Vorbis DLL Encoder v 1.09 enging 1.05.

The results strongly disagreed with conventional wisdom. In every case, across genres, on these low end speakers, 320Kbps mp3's were the only ones that fooled our ears. Low bit rate ogg and mp3 recordings were different, but we didn't take time to notice which was better... they were both unquestionably inferior to the source material. Ogg's 350Kbps encoding was good, but inferior to the smaller 320Kbps mp3 files of the same work.

Reading some of the posts on this article, I am rather shocked how many people find sound reproduction to be anywhere between "very good" and "excellent" on mid end equipment listening to 192Kbps encoded audio.

After running this experiment, I ripped about 30 of my CDs to 320Kbps mp3's and noticed another benefit to CD quality rips: I could listen to the music longer without my ears feeling fatigued. I had always thought that it was pumping sound directly into my head from my headphones that caused my ears to become tired of the music. For whatever reason, it takes much longer now. Perhaps 3 or 4 hours compared to 1 to 1 1/2 before.

Re:Hard To Tell Difference

Well your first problem is your headphones, they are distorting the crap out of any music source, go get some Sennheisers, they start around $60 for a good pair of open cans. Also if you are using anything but Fraunhoffer or better LAME for mp3 its just not fair. Btw, I've found high range problems with OGG that were not present in my Lame mp3's (I did A,B,C blind tests on a variety of samples and found a couple of problems with OGG which I reported with samples). AAC at 128kbit sounds like trash just like every other codec at 128, get around 200kbps VBR or 256 CBR and thats where the differences start to really show up (ok they show up at the very low end like 90kbps too but I don't even want to think about that)

Re:Hard To Tell Difference

I've got a nice pair of Bose headphones, and I listened to an Apple Store AAC file and an OGG version of the same song. I don't consider myself a real audiophile, but it's damn near impossible to tell the difference between the two; though I can definitely hear the improvement from MP3 to AAC or OGG.

One, your headphones suck. Bose sells overpriced junk. People think it is good because it is well marketed. If you compare Bose speakers with equally priced speakers from any quality manufacturer, the difference is amazing.

Bose is a scam, and the fact that they are so popular shows how easy it is to run a massive deception against the American people.

Re:Hard To Tell Difference

I completely agree that Bose isn't all its cracked up to be. However, their mediocre sound quality is a more recent thing -- up until the early 80s, Bose speakers were well-built with excellent sound. I have a set of 601s from 1976 that have the best sound of any speakers I own. They're fantastic, but I wouldn't even consider any other Bose speakers.

I have the Bose headphones as well, and they aren't so bad. They're not $150 good, but they're pretty good for mass-market headphones. They're great for gaming -- comfortable and well-articulated sound, just not audiophile quality for music.

Then again, audiophiles wouldn't be listening to MP3s or AACs or OGGs anyhow :)

Re:Hard To Tell Difference

After spending an hour in the listening room in the Bang & Olufson store in my local mall, I gave up and went to the Bose store. Ten minutes later I walked out with a Lifestyle 25 system.

For the record, the tiny Bose Acoustimass speakers are able to hit both highs and lows that were unreachable with anything in the Bang & Olufson store. People think Bose is good because Bose is good. No, Bose does not produce the best speakers in the world, but neither do they claim to - they claim to provide clear, room-filling sound with a good range. And they do. Oh, and the Bose Tri-Port headphones suck. They're a cheaper (and lower quality) knockoff of Bose's own QuietComfort noise-cancelling headset, which is a great product.

[asbestos underwear]
Don't give me any crap about how the QuietComfort headphones raise the noise floor for listening, either. They are one of the best active noise-cancelling sets on the market, and *no* passive system can beat them. Why? Passive systems can't even *begin* to fight bone conduction. Neither can the Bose, but it can produce limited cancelling frequencies to mute bone conduction. And the headphones sound just *great*. Speaker snobs, flame away...
[/asbestos underwear]

Re:Hard To Tell Difference

After spending an hour in the listening room in the Bang & Olufson store in my local mall, I gave up and went to the Bose store. Ten minutes later I walked out with a Lifestyle 25 system.

Uh... imagine that. You went from possibly the worst, most highly overpriced speaker/electronics line to the second worst... and it was better!

Now go try Paradigm, B&W, PSB, NHT, or any other good but reasonably priced speaker line and you'll see why Bose has such a crappy reputation. Be aware of sound levels too -- the most common trick Bose stores pull is demoing the Bose speakers at one sound level and other speakers at another (lower). The louder system will almost always sound better due to psychology.

Bose isn't inherently shitty... it's just shitty for the price. You can get much better stuff at the same price, or the same quality stuff at about half the price.

To be fair...

Don't forget that Apple's AAC's aren't ripped from 48.8 16-bit AIFF's, but re-mastered directly to AAC.

Ripping from the source a disadvantage? Huh?

Let's see. Given the task of creating a codec de novo and the financial and political means to have access to the original source material rather than a version sent through a horribly non-linear sampling mechanism out of your control and beyond your specification, which would you choose?

I'm sure most Slashdot readers will be familiar with the Nyquist limit and understand the complete inability to represent information above the limit, but how many are familiar with the degradations that occur near the Nyquist limit when you have non-infinite signal lengths? This is why oversampling is so important. In general, if you have a signal at frequency f that you want to accurately capture, you should be sampling (by rule of thumb) at 5f or greater. If you sample at lower frequencies, the distortions in phase and amplitude are difficult to predict and statistically analyze as they tend to have uniform rather than Gaussian distributions.

So again, I re-pose the rhetorical question: given the task of creating a new codec rather than rewriting an old one, wouldn't you want to use the least-filtered signal possible as a source, especially when the extant filtering is non-linear, and be able to select by design which parts to encode and which parts to ignore? I sure would.

Re:To be fair...

CD-DA isn't AIFF. CD-DA contains either 2 or four channels of 16 bit audio, sampled at 44.1 kHz, organized into blocks of 2352 bytes. It's big endian (unlike *.wav).
AIFF is a rather more involved format [swin.edu.au]. One of those formats is 16 bit, 44.1 KHz audio.
The only benefit I could see to encoding directly from masters is that it is possible that the "master" could be less prone to jitter. It is concievable that higher resloution masters would be available (96Khz/24 bit) and the encoding process could take advantage of this extra data somehow.

bleat

Well then that bolsters my original reaction, which is that regardless of the original source of these 'test samples', you'll be hard-pressed to lease the master and rip directly to .ogg or .mp3 like Apple has done with the AAC's available off their service.

That's all very well but

Some decent quality properly blinded listening tests would be more interesting than a graph though.
When VHS established dominance of the video market, there were high barriers to change - your player and media were committed to that format.
There are far less barriers to change in the ripped audio format, although there will still be some inertia, but there is nothing* to stop ogg vorbis becoming the dominant format.

Where's my ogg pod then?

* apart from the silly name.

It's Vorbis, not Ogg.

Ogg is a container format. I could in theory put an ACC audio file into an Ogg container.

The audio format you're babbling about is Vorbis. Usually .ogg because it is inside an Ogg container.

Hell, it's not just a silly name problem, it's an entire naming convention issue.

your ogg pod is here

You can get an ogg pod here [sourceforge.net]. ok, it's a little rough, but it's getting better.

Re:That's all very well but

A few years back, Consumer Reports did an interesting set of listening tests. The usual blinds, of course. But the interesting part was that in addition to random staffers, they had two extra groups: sound engineers and musicians. They reported that these two groups differed radically in their rankings of sound quality. The difference was fairly straightforward: The sound engineers gave a high rank to equipment that produced the sound accurately. The musicians gave a high rank to equipment that made the music clear. These are not at all the same thing. In particular, musicians generally liked "distortions" that removed non-musical information, strengthened the fundamentals, and so on.

From a musician's viewpoint, one of the real frustrations with just about anything published about sound quality is that it's always written from the engineer's viewpoint. But what I want to know is which gadgets do a good job of reproducing the music. They never seem to tell you that.

Re:That's all very well but

If the musicians like it that way, they should record it that way. Sound reproduction equipment should do just that -- reproduce as accurately as possible the sound on the CD (or other source)

If people deliberately want to alter the sound, that should be done by effect processing that can be turned off, but not built in by inherent limitations in the reproduction equipment.

Now, if you are interested in sound production, that is another matter entirely. The sound of a (say) guitar amplifier is as much a part of the musician's instrument as the guitar, though it would still be nice if a lot of that load could be taken off of unreliable power amplifiers and placed on reproducable, removable low level effects processing.

Re:That's all very well but

musicians are legendary for listening on poor equipment and filling in the rest of the music mentally

Yes, of course, but there's a different interpretation of this. It's not unusual for musicians to intentionally use low-quality equipment in order to make the music clearer. They aren't overcoming the limitations of the poor equipment; they are using it as a tool.

As an extreme example, I've known a number of musicians who have recordings of harpsichord music, but don't like the instrument itself. The reason is simple: They have good high-frequency hearing, and a live harpsichord is just a loud high-pitched buzz with barely-audible music in the background. But with a recording, especially on low-quality playback equipment, you can wipe out the high frequencies. This makes the music audible.

There are a fair number of people who have a similar reaction to violins. Although it's not as bad as a harpsichord, a violin has strong high-frequency harmonics that are often badly out of tune. If you clip off everything above 15 kHz or so, you eliminate this distracting noise and the music comes through.

I've made a lot of "very live" recordings of dance bands with a room full of dancers. One of the tricks that I've learned is to use fairly cheap mikes that don't hear the low or high frequencies. Then I don't have to do as much processing to get a good sound.

An interesting thing about this: I've occasionally made two recordings, one with good mikes and one with poor mikes that fall off around 12 or 14 kHz. When I play them for listeners who were there, they inevitably say that the "poor" recording sounds more live than the "good" one. What seems to be going on is that the human brain is fairly good at compensating for the low- and high-frequency noise in such situations. Participants don't hear all the background noise. But in a quiet room with the noise coming from a speaker, people do hear it.

This is similar to the phenomenon that photographers will tell you about: The human eye/brain system is very good at correcting for color cast. Cameras record the true color (within the bounds of the film type and latitude), so the cast is visible in the photo when it wasn't in the original scene. But photographers learn to see the full color and can't ignore a color cast, just a musicians learn to hear all the sound and can't easily ignore background noise.

(Similarly, after playing around with a polarizing filter for a few months, I found that I could "see" polarization. And now I can't turn it off. ;-)

It's all very complicted.

Re:That's all very well but

This is similar to the phenomenon that photographers will tell you about: The human eye/brain system is very good at correcting for color cast. Cameras record the true color (within the bounds of the film type and latitude), so the cast is visible in the photo when it wasn't in the original scene. But photographers learn to see the full color and can't ignore a color cast, just a musicians learn to hear all the sound and can't easily ignore background noise

Well this photographer will tell you differently.

If you use film stock then a very important part of the printing process is setting the filters to give the correct colour balance - either by hand or by bulk scanning the film and normalizing to 18% grey.

On a digital camera or video camera you have to set the white balance so the camera electronics know the reference to record the colour signal against.

Neither film nor CCDs/CMOS sensors have anywhere near the dynamic range of the human eye, so they record a substantially less accurate picture with either the highlights or shadows saturated out.

The only way of accurately scientifically measuring the scene is with a multispectral scanning radiometer - as used in remote sensing.

Speaking as a sound engineer I find it difficult to agree with your stance about this odd entity 'the music' - every stage of the process should be as flat as possible unless it is an artistic decision to change it. So if I'm recording a live event I should use the best mics, with the flatest response, use the recording device with the flatest response on most headroom, and then master the recording. Now at this stage I can play around with the EQ on the recording and make an artistic decision on the timbre and tone of the sound - because I have not predisposed myself one way or the other by colouring the sound I recorded. I don't disagree that a doctored sound might sound better, but it is not more accurate.

In the real world systems aren't perfect, and those that are close cost a lot of money. Now you have to make a decision of what makes the best sense with your budget. Now some mics and recording systems colour the sound in a pleasing and predicateble way - it sounds like the setup you settled on does. A lot of people forget that the post production of a recording or the setup of the PA at live gigs is a very important part of the music creation process, guitars drums and keyboards may be your instruments of choice, but for a sound engineer the instruments of choice are mics gates EQs compressors and sound desks - in producing a recorded work both the musicians and engineers are important - would the Beatles work have been the same if it hadn't been for the creativity of the Abbey Road engineers who broke from the tradition of 'perfect reproduction' and started working with the musicians to create new ways of presenting the sound - probably not.

In your example the rolloff at high frequency is a common effect with high volume PAs - at high SPLs your ears get tired and the high frequencies are affected first. Most people can relate to that slightly muted feeling to thier hearing after a particularly good gig - so the slightly muted nature of the mic that you use matches people recollection of live gigs. Interestingly popular mics for live work will not be the same as those for live work - even with the same instrument and musical style.

Re:That's all very well but

A decent, but simplistic article. Unless you're a fussy audiophile, this analysis should be sufficient for you.

[rant] I wish the author would present his graphs in a more readable way. A screen dump of Photoshop in WinXP is not a professional way to show data. It's ironic that while reviewing lossy audio formats he opts to use a lossy image format (JPEG) for the graphs. I had to double their size on my screen just to make some sense out of them. [/rant]

It's not difficult to gain better-than-CD quality. CDs have been around since the early 1980s, and their main drawback is that they have a low sample rate, 44.1KHz. This is why many sound engineers prefer vinyl. because it's an analogue format, vinyl has a potentially infinite sample frequency range (although it's obviously limited by the recording and playback equipment, and by the physics of the media itself). Apple has used original masters (not CDs) to create much of its song library, so all they have to do is encode at a higher frequency than 44.1KHz. At a guess, they're probably using 48KHz, which is on par with DAT and MiniDisc.

I'm not surprised that Apple is using AAC. For one thing, it is clearly better than the decade-old MP3 format in all respects, and the licensing costs are probably the same or better. Technically, it may not be as good as Ogg, but most people don't even know what Ogg is so it doesn't matter. As long as Apple can say "our format is better than MP3 and CD audio" (the two prevailing formats), they will have the attention of consumers. AAC is a more mature format than Ogg (Ogg isn't bad, but AAC is more tried-and-proven), and is probably more compatible with existing DRM technologies. DRM is important to keep the recording companies happy and to ensure that the files will only play on devices that Apple specifies (like on Macs and iPods).

A major stumbling block for Ogg is that until fairly recently it was necessary to use a floating point processor to play the format. In the arena of portable devices, only PDAs have floating point capability, which is why you can play Ogg files on your Zaurus and not on your iPod. AAC is already supported by many devices, so Apple has a larger potential market (although at present only iPods can play the files).

Re:Spectrum analysis is useless

According to this [infoanarchy.org] blind listening test conducted by c't [heise.de] magazine, AAC at 128kbps was ranked the lowest of all codecs sampled at that bitrate (WAV, OGG, WMA, RA, MP3Pro and MP3)... One can always hope that the claims of Apple making their AACs directly from the record masters are true, as this would help the situation some.

Re:Spectrum analysis is useless

How can this parent be +5 insightful? It is wrong and uninformative.

I worked with MPEG4 (AAC) and OGG a lot (for my phd. thesis) and spectral analysis IS very important. Although it is correct that it doesn't show precisely what information is left out because of what our hearing system doesn't register. However, these hearing curves and integration times are already known (although not the same for evry human) and most post-MP3 encoders do this rather correct. Most profit nowadays is in clever signal processing. The spectrum of a decoded signal shows almost all artifacts very well and is therefore something which helps a lot in showing artifacts in a coding scheme.

Of course listening test must also be done. They show that modern encoders make choices (not all our ears are the same, and so isn't all the music) which very often pays of in a certain test.

Theoratically AAC and OGG are rather similar, but AAC has a few nice extra's like the Temporal Noise Shaper. However in practice OGG seems good enough (unless MP3) and is free, while AAC is not that much better and unfree, so my choice is obvious.

I will wait for the OGG hack of the IPod, now it had a better processor.

They chose AAC because it's already in QuickTime

And it's more efficient than MP3.

Their encoder is not particularly good, and AAC is covered by a ton of patents, so there probably are other reasons why they chose it.

For anyone else but Apple I see no reason to use AAC when you can have Ogg Vorbis.

PS: Shameless plug: I wrote a vorbis patch to add SSE support [www.fefe.de] for enhanced encoder and decoder speed. It also contains some 3dnow! optimization for you K6 users, decoder only.

AAC is pretty weak, no marketing can change that.

And it's more efficient than MP3

At low bitrates, AAC is very weak, at 128kbps it was the worst of all:

Study [infoanarchy.org]

I was one of the 3000 participants, btw. And my ranking which I gave (blind, I did not know which sample was which) confirms pretty much the results, at 64kbps, AAC was unbearable, while ogg was not distinguishable (by me anyway) to the original.

The only test where AAC didn't fail miserably was the "expert test" with only 8 listeners.

OGG has beaten all other codecs consitently at all bitrates.

Re:The presentation...

My favorite part of this discussion is where slashdotters believe that they, the open source community and Ogg in particular are foremost in the minds of people like Steve Jobs as he unveils his new music service.

Get a clue already. Apple went with AAC because it's great quality, supports the (fairly mild and necessary to get the RIAA onboard) DRM restrictions for the service, and is a subset of the excellent MPEG4 video codec.

Even if Ogg is better quality at lower bitrate (a point that I am not convinced of, "waveform comparisons" notwithstanding), Apple has legitimate reasons for going AAC that have nothing to do with The Man trying to keep you and the open source community down. Jesus, it's not always about you, mkay?

PhatAudio is on Ogg's dick

Nothing will every beat Ogg in PhatAudio's eyes. They seem to find evidence of Ogg's superiority where there is none. It's like the lovers of vacuum tubes rather than transistors.

"It sounds warmer!"

Sure. And the incandescent lights in my house have a better smell than the fluorescent ones at work.

Re:PhatAudio is on Ogg's dick

Tubes and transistors are different though. With Ogg vs whatever, it may be more subjective, who knows. But at least with tubes there is a known difference between how they amplify and how transistors amplify. Tubes produce more even order distortion, which to our ears sounds warm and pleasing. Transistors produce more odd order distortion, which tends to sound harsh and stressing.

Subtle difference? Perhaps, but it's there.

Re:PhatAudio is on Ogg's dick

Umm, no there is a big difference, solid state amps reproduce sounds more exactly but can introduce harsh harmonics, on the other hand tube amps tend to add warm harmonics while distorting. These warm distortions are more pleasing to the ear, of course ideally you would produce zero distortion and get your harmonics from an effects processor =)

Hmmm

What about if I tell someone I'm off to trade some OGGs with my friends, and they think I'm going to throw little plastic discs about?

Maybe in the future...

"the increasingly popular OGG codec."

sadly, I don't think OGG is *currently* known to anybody except nerds or IT pros.

Re:Maybe in the future...

"sadly, I don't think OGG is *currently* known to anybody except nerds or IT pros"

Entering geek-fantasy bizarro world, please wait...

Marketing department hottie: Oh you sexy IT guy! Tell me more how I can get higher quality and higher compression rates on my music files! I want to know ev-ery-thiiinnggg!

Meanwhile, back in reality...

Marketing department hottie: [silence as she passes by, avoiding piercing leer of geek]

Geek: Hmm, I wonder if she noticed me. Doesn't she know the powers of music compression that I possess? (note to reader: she didn't, and she doesn't care)

Re:Maybe in the future...

When you start at zero, anything more than that is "increasingly" :-P

/. effect strikes again

Spectrum analysis was used to see which format did the best job of maintaining the shape of the original waveform.

Furthermore, "ping analysis" was used to see if the webserver survived the /. effect, and tests conclusively show that this is not the case. :^)

Ogg

Most people who use ogg do not use it for it's quality. All that matters in that respect is that Ogg is comaprable to other formats at similar bitrates.

The important aspect of it is that it's free. There are no patents (at least as far as we know of) preventing anyone from using it, and it's made quite clear that the code can be included in open and closed source software without royalty payments.

Re:Vorbis! Not Ogg, Vorbis!

> Is it that difficult to grasp! Ogg is a container file! Vorbis is the audio codec!

IT DOESN'T F'ING MATTER!

Just like Linux isn't an OS, (it's a kernel) no one aside from you and some other geeks (not meant as an insult, I am a geek too, obviously) will ever convince others of the truth.
More importantly it doesn't even matter. The details are subtle and by continuing the geeky "I'm better than the stupid lusers" all you are doing is keeping Vorbis from becoming more popular -- people will become pissed off that they get hassled every time they mention it, and then ignore it in the future.

Unfortunately I'm sticking with MP3

I agree that Ogg is a better format, better quality sound for similar bitrates to MP3, but until the portable devices I use, in-car CD/MP3 players, etc. accept the Ogg format as readily as they do MP3, then I (like most people) are stuck with the MP3 format. At least nowdays storage is cheap, so I whack everything to MP3 at a high bitrate.

Re:pretty lame!

And as all people who have taken advanced math knows: Sound can be described with equal precision in the time-domain and in the frequency-domain.

It's called a Fourier-transform.

And in the frequency-domain you still got phase, in case you wondered. It's covered by the use of imaginary-numbers.

So analysing the signal in the frequency-domain should uncover the same errors as an analysis in the time-domain, if it's extensive enough, that is.

I don't bother going into the theorys behind this, but google for Fourier-transforms and wise up :)

Re:pretty lame!

It's covered by the use of imaginary-numbers.

Yeah, I noticed that a lot of reviews of this type use imaginary numbers.

Anyone seen real specs for Apple's format?

I spent some time last night playing around with the new Music Store feature in iTunes 4. Besides the fact that iTunes crashed on me twice, and 3 never crashed on me, it seems like a very well put together feature.

What kept me from buying the dozen or so tracks I found that I thought were worth a buck a pop was the fact that my Rio Receivers need MP3 or, via "upgraded" software, FLAC, etc... Although the AAC->CD->MP3 route is possible, and I intended to buy a track and see how the quality comes out, has anyone seen anything about how the DRM works on the Apple files?

I'm wondering if there are any libraries out there for decoding them, even within the confines of the DRM... just so I can get them into either a raw data stream or something so I can play them on my Rio Receivers... I'd probably switch to buying all my music (where possible) from them, if thats the case... but if I can't get them into a format I can play using my existing equipment, I'll have to pay the five buck "CD"-tax to get them in a format I can rip to high-bitrate MP3.

Re:Anyone seen real specs for Apple's format?

Although the AAC->CD->MP3 route is possible, and I intended to buy a track and see how the quality comes out, has anyone seen anything about how the DRM works on the Apple files?

Regarding the AAC->CD->MP3, I burned a couple of Music Store tracks to CD, then re-ripped them (using iTunes, no less) using VBR High, and they sounded indistinguishable from the original Music Store files (albeit being significantly higher average bitrates).

Regarding DRM, it appears that your Music Store file is locked to your Apple ID, and you have to Register up to three computers that you want to be able to play songs associated with your Apple ID. If you sell a computer, you have to unregister it before you can register a replacement computer. This appears to be the only restriction on usage -- you can still burn the songs to as many CDs as you want, copy them to as many iPods as you want, and streamthem to as many other Macs (and TiVo) as you want using Rendezvous.

Re:Anyone seen real specs for Apple's format?

I burned a couple of Music Store tracks to CD, then re-ripped them

A coworker recorded a few songs to CD last night. This morning, I ripped them to q7 Ogg Vorbis, and downconverted those Ogg files to MP3 (VBR, 160 to 256 kbps).

Listening to them (on decent speakers, but still computer speakers nonetheless, and also through headphones), they all sound pretty good. I'm listening mostly for "bad artifacts" -- pumping, popping, clicking, phasing/flanging, stereo movement, etc. I can't hear anything of the sort, even on the MP3.

So, we've got WAV -> 128 AAC -> q7 Ogg -> 160+ MP3, and it's still quite listenable. Certainly, it's not studio quality, but for listening at home, on a typical system with typical speakers, it's pretty good, to my ears.

I'm still sort of annoyed, philosophically, at not being able to get a full-bandwidth .WAV file. I mean, you're paying for the track, you should get the exact same data as you can when you purchase the CD outright. But as a "best of evils," this is very good. And, truthfully, I'm not convinced that other similar services (like Listen.com's Rhapsody) don't do essentially the same thing.

Can anyone suggest a good 'test pattern' file? Something with lots of dynamic range, easy-to-identify instruments (especially with lots of layers of detail), variations in note types / waveforms, etc.? Basically, an Indian Head for audio. Because it'd be great to be able to say "download this .wav, and as you decrease the bitrate listen for the flutes at 0:35 to start sounding weird" or somesuch. Just a thought.

Anyway, I'm satisfied with the quality, at least on the minimal sample set I've heard.

Re:Anyone seen real specs for Apple's format?

I'm wondering if there are any libraries out there for decoding them, even within the confines of the DRM...

While I'm not sure, I would say yes.

I noticed last night that the protected AAC files played both in the Finder's preview pane and in Quicktime 6.2 itself. I assume the actual AAC-Protected decoding is done in quicktime, and no modifications were made to the finder to allow it to explicitly play AAC-Protected files. This implies that any program that can use quicktime can also play protected AAC files.

I'd be suprised if may of the other mp3 players on the mac didn't already support playing via Quicktime, and by extension, playing AAC-Protected

But what does it actually sound like???

I don't think graphs are all that useful for comparing lossy sound compression.

Microsoft likes to show how their wma looks better than the other compression methods... it does look beautiful in graphs, but it sounds all tinny and horrible.

I don't care if the compressed frequency response graph looks nothing like the original frequency graph, as long as my ears are unable to tell the difference between the two.

Arggghh!

Will people please stop talking about Ogg as though it were an audio compression scheme. It is not - it is a wrapper format.

I don't care what kind of tests were done, but anything comparing Ogg to a lossy compression scheme is bound to be unfair, as the Ogg family includes a lossless encoding scheme [sf.net]. Not only does Ogg include FLAC and Vorbis, but it also includes Speex, targetted at voice, and Theora, a video codec.

So please, stop trying to compare Ogg to MP3. It's like comparing AVI or Quicktime to MP3.

Converting AAC (".m4p") to MP3?

My portable HD music jukebox, and my car stereo, and tons of other devices out there ONLY play MP3s.

But any new music I buy through Apple is AAC encoded, in an m4p "protected" file.

So here's a purely technical question: What's the shortest path to convert these shiny new "protected" ACC files into plain MP3s so that I can take the music that I've just paid for and listen to it on my Archos MP3 Jukebox? I've already successfully gone from AACs to audio CD, and then re-ripped and re-encoded the album as MP3 but ... ew. There's got to be a better way.

And yes, I know Apple and Big Music and the RIAA and Homeland Security don't want me to be able to do this (easily, or maybe at all) but at this point I'd like to sidestep the politics and focus on a technological solution that works for me- a legit, paying user.

So: what's the closest we can get to "acc2mp3", or better yet "m4p2mp3"?

-Mark

Poem.

There once was a codec named Ogg,
It's name was peculiar and odd,
It replaced MP3,
Because it was free,
Hey, what the fuck is an Ogg?

Two Words

Beta-Max!

Ogg = Too little, too late, overmatched and unknown to the masses. Also, too geeky. No hardware support to speak of. Walk down a street anywhere in the world and ask them what Ogg is, then ask them what MP3 is..... I guarantee you 1000 more people will know what a MP3 is compared to Ogg. It may be smaller, but in the age of 200 Gb harddrives for $200 size is no longer an issue.

MP3 = Widely known, was first on the scene, its everywhere, tons of hardware on the market, good quality, reasonable size ... hell my grandma even knows what it is.... that means Ogg is screwed!

AAC = Already has an installed user base, sounds just as good as Ogg or MP3, plays nicely with the best known\most widely sold MP3 player on the market. Promising, but probably the lesser of the three unless this thing takes off.

You may not like what I have to say, but it is the truth.... and you all know it!

Re:Two Words

Yes, until someone gets sue happy and starts suing MP3 and AAC users. Maybe it will happen, maybe it won't.

Look at GIF, JPEG, and PNG. GIF is used for its quality, JPEG is used for its size, PNG is used by geeks. Unisys started suing webmasters, now the patent holder for JPEG is ruffling feathers, PNG is slowly becoming the accepted format. All it takes is some greedy SOB to make Ogg an attractive format.

Re:Two Words

Can you point out one player? Because I've never seen them.

Yep. The 5GB iPod I bought over a year ago plays AAC encoded files (after installing the v1.3 Firmware Update), as do the other 700,000 iPods out there. Combine that with the new Apple music store, and overnight you've got a whole lot of AAC encoded music out there with hardware support.

About audio compression, CD-MP3 guide

Arguably the best resource for audio compression information can be found at Hydrogen Audio [hydrogenaudio.org]. Visit the various forums, check out the excellent Foobar2000 [hydrogenaudio.org] win32 multiformat audio player, and learn.

I have also written a guide on ripping high-quality MP3s using CDex [iprimus.com.au], aimed towards beginners. If you know people who use Musicmatch, help them switch to a decent, easy-to-use CD ripper [sourceforge.net].

Cheers,
CD

Anybody checked out Neuros?

The Xiph folks have signed up to add Ogg support on the Neuros audio handheld. Its a firmware upgradable handheld which currently supports mp3, but will probably have Ogg support by mid-late summer.

Check out the highlights.

http://www.neurosaudio.com/

Musepack is better at the high-end

MP3 this, OGG that, AAC somewhere in the middle... Sorry, I don't use any of the above. I encode all of my music into Musepack. At high bitrates, it's the best lossy audio codec, period. For more information on Musepack, see <a href="http://www.saunalahti.fi/%7Ecse/mpc/">Case's Musepack Page</a>, or <a href="http://www.hydrogenaudio.org/index.php?act=S T&f=11&t=1927&">List of Recommended Musepack Settings</a>.

Musepack encoders and decoders are available for both Windows and Linux, with Winamp plugins available. The only real downside to Musepack is there is currently no hardware support. But having tried each of the codecs mentioned in this article as well as Musepack at the Quality 8 setting, Musepack is music to my ears each time.

An overlooked key point?

Understandably, most of the discussion here is about the pros & cons of various compression formats. But the first thing that jumped out at me when I clicked on the apple.com link was:

"Preview any song for free, when you find a song you want, buy it for just 99... It's what music lovers have been waiting for: a music store with Apple's legendary ease of use, offering a hassle-free way to preview, buy and download music online quickly and easily."

FINALLY, a business model for downloading music that makes sense! (Now if only I could afford to switch to Apple products.)

Next up...

let's compare video codec image quality by streaming the data thru a hex editor in realtime. :)

I have a better plan

Last night I downloaded a bunch of tracks off of Apple's Music Store Service. I then played them (along with several tracks I already had in OGG and mp3) through my computers $9.95 speakers while holding my portable cassette recorder very, very close to the speaker (For the technical out there I was holding it close to the LEFT speaker and even turned the TV down some to get the best possible sound) and then replayed them all back on the same portable cassette recorder.

My conclusion is that all three sound like complete shit.

Useless Comparison

AAC/MP3/OGG are all based on psychoacoustic models. Comparing their decoded spectrums is pointless. The spectrum isn't supposed to be faithfully reproduced. Frequencies that your brain wouldn't fully hear aren't fully stored.

The only value I can see in a spectrum comparison would be to find obvious errors in the encoder or decoder. Like the 16kHz spike in the Xing encoder. But how likely is that going to be these days?

The only proper comparison involves a good hi-fi, a sensibly furnished room, and a comfortable chair. It is called "golden ear" testing and it's the ONLY way to compare psychoacoustic models.

Or at least it's the only way until the research scientists work out how the human brain works.

Spectum analysis in invalid

Learn why you shouldn't use spectral analysis to determine lossy codecs' quality [hydrogenaudio.org].

The most respected technique is double-blind testing using an ABX tool such as PC ABX [pcabx.com], WinABX [arrakis.es] or ABC/HR [ff123.net].

More info on conducting blind tests can be found at the PC ABX site [pcabx.com].

Spectral analysis != psychoacoustic model...

Modern compressions schemes are supposed to make sound that sounds as much like the original as possible, not looks like the original on an FFT.

The only way to test this is to use double-blind listening tests. The spectral analysis stuff is absolutely useless for finding out how good the music actually sounds.

all 15 ogg listeners...

all 15 ogg listeners are getting together to 'rally' at apple trying to get them to support ogg. they have each committed to buy at least 5 ipods each if ogg is implemented, so then apple would sell at least 15*5 ipods, and it will definately be worth the effort to port ogg to ipod.

fools. its a 'mass-market' device. no one in the mass market even knows what ogg is. (do you use ogg? yeah i like em over-easy.)

CD is the problem, not wma, mp3 or ogg

CDs have flat sound to begin with when compared to analog masters. So in order to get "better than CD" quality you would have to rip from the master tape. Also, file size would have to be less than 60mb per song. (size of a 5 minute uncompressed song from a CD)
While most master-to-CD transfers sound fine, classical music tends to lose its "warmth." I am no audiophile but I noticed a big difference when I listened to Crux Shadows live and on CD. Speaking of audiophiles, by the time they can afford to buy their must-have equipment, they've already lost their hearing. Give them 128kps mp3 file stamped on vinyl and will swear it sounds better than your original CD :)

Re:CD is the problem, not wma, mp3 or ogg

Are you sure that the problem isn't in the mastering engineers, not the CD format? Almost all pop music is dynamically compressed within an inch of its life to make it sould louder on cheap equipment. I am told that this is much less of a problem with classical music, but classical music also tends to have a much higher crest factor than pop, and is therefore more sensitive to compression as well.

The noise floor and dynamic range of a CD with a high quality DAC should be better than almost anybody's ears, if correctly mastered. DVD-Audio should be even better than CD, with multi-channel to boot, and also gives recording engineers a lot of headroom in the ultrasonic to avoid aliasing while using low order filters that are in principle somewhat gentler on the sound. SACD on the other hand is a travesty, superbly wasteful of bandwidth, while having less resolution and more noise in the highest octave of the audio range and much, much more noise in the ultrasonic, which is inaudiable, but can have negative effects on the audible spectrum because of effects in the tweeter.

AAC works for me...

I bought about 10 songs from Apple's music service yesterday, and they all sound great. When I got home, I ripped Would? from Alice in Chains's Dirt and compared it to the 182kbps VBR MP3 I already had. The AAC sounded about the same as the MP3. It didn't sound worse, and I was running this through my iMac G4's audio system and then a pair of Polk bookshelf speakers I have on my desk (and a Pioneer receiver/amp). I'll stick with AAC, and I'll stick with the iTunes Music Store. For my money, it's a good deal.

Under-reported but VERY important distinction:

from macslash:

AAC comes with a significantly lower number of b*tching [\.] users than ogg

How to convert from MP3 to AAC with iTunes 4?

In my workflow, I want to keep a big bunch of high data rate files on the home server (about 140 GB of 320 Kbps MP3 files), and then recompress to more portable formats to carry around on the PowerBook or whatever. This used to work fine. I'd use the Import feature of iTunes, and would convert from the 320 Kbps master file to ~150 Kbps VBR MP3 files for the road. While the lower data rates wouldn't work on my home Paradigm speakers, they were fine for listening to on airplanes.

However, this doesn't seem to work in iTunes 4. I see the Import option, but all the MP3 files in my current library are grayed out. Is this operator error, or does this not work anymore? If not, what is the Import function for?

Obviously I'd like to switch to 128 Kbps AAC-LC for my mobile music. But heck, I'd live with being able to make my old MP3 files!

-Ben

Spectrum analysis :-

Spectrum analysis was used to see which format did the best job of maintaining the shape of the original waveform

Will people ever stop doing that. It's complete bullshit and certainly not the way to evaluate a codec. These codecs use perceptual weighting of the noise. That means that the idea is to distort the signal as much as possible in any region of the spectrum where it won't be heard at a certain time. That means that you see a big distortion in the spectrum and think the codec is worse than the others when in fact it's better because it realized that it doesn't matter.

The only way to correctly evaluate a codec is to listen to it. I write codecs (see sig), so I know a bit what I'm talking about. I use spectral analysis sometimes, but only to identify problems which I've already heard before, not to say that my codec is good.

As a aside, I'd say it probably wouldn't be hard to write a codec that does better than any other on those spectrum analysis. They would sound like crap because their psycho-acoustic model would be all wrong.

found an OGG vs. MP3 vs. WMA vs. RA comparison

While googling for the name of a magazine I haven't picked up in years in order to refer to it in my previous posting, I ran into this comaprison of OGG vs. MP3 vs. WMA vs. RA [ekei.com]. I thought it seemed relevant an might be interesting to some of you guys.

Re:MP3 Pro is better than OGG in some cases

The point is you don't see the same kind of bias when it comes to sorting algorithms that you do when it comes to OGG and other audio formats.

Re:Gotta pick something...

"It's too tough to figure out which one is best, so let's back OGG blindly." That's a pretty weak argument. Looks like you are the one trolling.

Re:MP3 Pro is better than OGG in some cases

A $10,000 stereo set up in a listening room at your local audiophile shop sounds better than a $500 Sony in your living room, while we're at it. I don't know many people who'd pay for the $10,000 setup just to listen to some music though.

Ogg may not sound as good as MP3 Pro[1] but so what? Open Source is better overall simply because it is both Free and free. On top of that you even point out yourself that MP3 Pro is only sometimes better than Ogg. So why pay for something that will only sometimes be better if you can get as damn near with a Free format anyway?

[1]: Sometimes.

Re:I'm an audio analyst...

Any explanation on *why* it's better? Better compression / algorhythms?

I've found that 64khz OGG (3MB) ~= 128khz WMP (3MB) ~= 128khz MP3 (4MB). Admittedly the WMP is *slightly* better, but I thought that's only because of the extra sampling rate...

Also for some reason when ripping from CD to ogg there's very little difference between 64khz and 128khz, but then 44khz is utterly unlistenable.

> If someone would like to come up with a different format that can actually compete, I'd be happen to lend you my expertise and objectively analyze it for you.

Why not just help improve ogg? Are there any major problems that would need a total rewrite to get past them?

I'm The Archangel Gabriel

...and I gotta tell you, having played that trumpet and serving as Music Director for the Celestial Choir since the Dawn of Time, I know Audio, and MP3 is the way to go. I've analyzed OGG, WMV, AAC, and this cute l'il analog thing which that wack job Orpheus put together Back in the Day, and I must say, nothing beats MP3, in your or anyone else's universe.

Of course, I'm logging in here under a pseudonym, so you'll just have to trust me. But hey, would a member of the Heavenly Host lie to you?

Re:I'm an audio analyst...

son, if you were an audio expert, you wouldn't be working for Real.

Re:Ok, here goes...

Sure he's flamebait, but he's right. When I decided to rip all of my CDs and store them on my computer, I tried various formats. MP3, MP3pro, WMA, and yes OGG. In all honesty I could not hear the difference between any of them whether I played them via headphones or through my Sony STR-DE475.

Thus the choice was easy because only one factor remained: ubiquitousness.

Will it work with any portable player I buy, or will my hardware choices be limited?

Will I be able to share them with friends without having to explain how to play them?

Will it work with programs such as Nero without decoding the files to a different format first?

One format fit that criterion and it was MP3. Sure it's proprietary. But so is my car. I'm not going to stop using something that works merely because its proprietary. Computers are tools, not a religion!