Are there somewhere listening tests with results for various AAC codecs, like iTunes, Coding Technologies, Nero...? And I would need the most recent ones.

Sound expert did a multi codec (including several aac encoders) at 96 kbit/s around September of last year. Link

If you are on a Mac, use XLD with the TrueVBR aac setting. If you are on Windows/Linux use Nero's aac. Both are of the highest quality

Thank you!

Referring to that link. Can anyone explain their ratings of over 5.0 for these codecs?



What? 5.0 has no audible artifacts at all, but you can rate the codec higher than 5.0 if you wish. Wow Nero AAC is better than 100% transparent at only 96kbps (rating 5.03, where 5.0 is fully transparent).

Check out http://www.hydrogenaudio.org/forums/index....showtopic=70442. Nero and iTunes are compared.

I recommended Nero aac for Windows as it's true VBR (iTunes is only Constrained VBR). Also, to get the full quality of Apple's encoder (including True VBR) you have to use Quicktime Pro, which is a pain. Unfortunately, I don't think there's another solution (like XLD on OS X) for Windows.

Just abx test both against the lossless files, and go with what you're happy with.

?

Bitrate distribution is only one part of codec efficiency.
Good codec with CBR can do better job than other with VBR.

No offense to the person who conducted that listening test but that was one person, it wasn't an open listening. Additionally, they used killer samples for their encoding needs. Killer samples may (and may not) represent real world encoding scenarios. I doubt people have libraries filled with killer samples and that is all they listen to. Killer samples have their place when it comes to reporting possible problems with encoders.



I do see your point. However, past open listening tests have shown that even the constrained VBR settings of iTunes can compete with full VBR encoders such as Lame, OGG vorbis, and Nero AAC. I wouldn't be so quick to dismiss iTunes AAC for Windows use either. It all depends on the audible results produced, not what the encoder looks like on paper. I use Nero AAC but I know many people (who actually conducted blind ABX tests) and were perfectly happy with the iTunes AAC encoder.



So full VBR = full quality? I guess that is why the constrained VBR settings in the iTunes AAC encoder always produced better results than the full VBR FAAC encoder. Oh wait, that isn't what you said. Full VBR does not equal full quality, that is in the ear of the beholder. Some people may want to try out QuickTime's/iTunes' full VBR encoding settings and it is a pain to do that on Windows. However, I wouldn't say that full VBR is full quality as past listening tests have shown that the iTunes AAC encoder (with its constrained VBR setting) produce more than acceptable results even though it isn't true VBR.



This is what should have been said from the get go. I do see what you are saying but disagree with the "full quality" statement. I also wouldn't hold so much merit in a listening test conducted by one person. Yes, it is very informative but your mileage may vary. I would use the information from public listening tests more though. Not that there is anything wrong with sauvage78 or what they did. However, I would lump their listening tests in with other personal and open tests to make a broader judgment. Then conduct my own ABX tests after getting an idea about the bitrate settings that are producing transparent results for other people (ie start at 98-128kbps and work my way up).

Question: if I have QuickTime Pro and rip CDs via iTunes, are those AAC files then VBR?

Or do I have to rip directly through QuickTime?

And what does constrained actually refer to?

True VBR mode gives the encoder more scope when it reaches difficult parts, allowing higher bitrates to be used with lower target bitrates. If you're targetting very high bitrates it's less of an issue.

The quality setting I was referring to is shown in Quicktime's export to mov - acc - audio settings: Image Link. I remember reading somewhere here at HA that someone had proven that iTunes (ripper) doesn't use Quicktime's highest setting, and that ITMS uses the highest quality.

 

I cannot find those Movie Settings anywhere on Windows in QuickTime! Certainly not in Edit > Preferences > Player Preferences / QuickTime Preferences.

Do you know? And do I rip through iTunes when I set those settings?

ITMS is...? Mac iTunes?

iTunes Music Store. But I think he just meant "iTunes."

'She' mean what Apple use to encode their files for the iTunes Music store.

Changing settings in Quicktime Pro will not change settings in iTunes, unfortunately.

Apple's aac encoder IS very good, so do what both I and kornchild2002 suggested. Do an abx test starting at low bitrates and work higher and go with what bitrate you're happy with.

I've just updated iTunes on my Windows partition to 8.1.1. And saw:

in the Release notes

Perhaps they just mean 256 kbit/s (but it could already do that). I think some testing is required.

Where did you read that Nero has 'true' VBR and not ABR-like VBR?
Are you completely sure of your statements?


http://www.hydrogenaudio.org/forums/index....showtopic=66949
http://img205.imageshack.us/img205/7027/resultsfp6.png

So where is your 'truely true' VBR?

Defenately TOS#8

I know, I will ABX. But this is very frustrating! No. 1 - I didn't know QuickTime can rip CDs! 2. - how come even if you have Pro, the iTunes AAC isn't of full quality?

There is a Export movie to MPEG-4, but that screenshot and AAC-LC doesn't show up. Only Encoding Quality: Best.  Absolutely uncustomizable, just that option set and impossible to chnage.

I have QuickTime Pro and iTunes 8.1.1. Import Settings offer: High Quality (128 kbps), iTunes Plus, Spoken Podcast and Custom. In Custom you can choose: Stereo Bit Rate, Sample Rate, Channels, Use Variable Bit Rate for Encoding (VBR) tickbox and Optimize for voice.

There are a few personal tests from both iTunes and Nero AAC encoders.

guruboolez did a test to compare codecs that are compatable on the iPod:

http://www.hydrogenaudio.org/forums/index....showtopic=58724

A recent test from IgorC:

http://www.hydrogenaudio.org/forums/index....showtopic=66949

I have also tried out a few killer samples with Nero AAC and Quicktime VBR:

http://www.hydrogenaudio.org/forums/index....st&p=618665

The setting still uses VBR constrained but it also uses QuickTime's "high quality" VBR profile. All other VBR (and CBR settings) in iTunes use QuickTime's "medium quality" settings. I am not sure what the difference is between medium and high quality. Many people had trouble ABXing the iTunes/QuickTime AAC encoder at 192/256kbps before this change so I wouldn't focus on it too much. The iTunes Music store currently uses these settings. I am not sure what Apple (or the record companies) used before as I have seen results that match up with both 256kbps "CBR" and 256kbps VBR constrained.

So, kornchild, a Windows user cannot alter some QuickTime Pro settings to make iTunes use un-constrained AAC?

Apple's un-constrained VBR AAC mode is only on the Mac OS X version of Quicktime.

Thank you, /mnt!

I have just been reading these threads:

http://www.hydrogenaudio.org/forums/index....st&p=616980

http://www.hydrogenaudio.org/forums/index....showtopic=70227

And I'm more confused than ever.



Puzzling, puzzling... If it helps quality, you mean it helps in regards to iTunes CBR and not in regards to true VBR? True VBR would be even better, if such a statement can be made?

I have just encoded fatboy.wav using Windows Quicktime Pro. In File, Export, Quicktime Movie, no video but aac sound, I chose 128 kbit/s. I had choices for quality (eg, normal, best) and 4 modes.

1. Average Bitrate
2 VBR Constrained (128-145 kbits/s)
3 Variable bitrate
3 Constrained Bitrate

File sizes:

'ABR 128 best': 105447 bytes
'VBR Constrained 128-145': 104774 bytes
'Variable Bitrate': 124160 bytes

I also did VBR Constrained 128-146 but changed the Quality to 'normal'. Size: 104618 bytes

I didn't do CBR

I plan to do an abx when I get some time as I believe Nero aac vs Apple aac as I believe both are the most advanced audio music codecs. I love ogg vorbis too, though

Could you make a screenshot of this:



and



this?

I found this screenshot, it sure is old, on Apple's website and there's no Export to AAC:



I've just opened a .wav file and these same options are shown...

Some people are so wise so they don't even bother to read link (gived twice actually) and make the same question about settings.

Oh, I figured it out... Could it be more complicated... So silly.

File > Export > Movie to QuickTime Movie > Options > Un-click Video.

In Sound go to Settings. Then choose AAC and Show Advanced Settings. And that's it.

Movie to Quicktime Movie. There'll be no video of course, so set up the audio with aac. Uncheck streaming.

This will produce an mov file. Open this file and choose Export, Movie to Mpeg-4. Movie tab is blank, choose the audio tab and select AAC Passthrough (which means it's not being re-encoded, only put into another container). You now have an mp4 file.

Sorry I didn't post it before, but I couldn't get to my Windows PC.

I said that true VBR allows for a greater variability in bitrate than the VBR constrained setting. I conducted an ABX comparing VBR constrained to CBR at 128kbps. I had more difficulty picking out the VBR file. So I stand by my statement that enabling VBR encoding in iTunes is better, at least for me, than using the CBR setting.

I don't know if true VBR would be better. It has the potential to be better (just because it allows for a greater flexibility with bitrates) but no one can lay down an iron law and say that QuickTime's true VBR setting is better than the constrained one used in iTunes (hence why I commented about ManekiNeko's statements) unless they have gone through and ABXed every single file in their libraries. I haven't really had any experience regarding the true VBR setting in QuickTime. It takes way too long to get a true VBR file on Windows and I don't think it is worth my time.

I wouldn't worry too much about trying to access QuickTime's true VBR setup as it is really difficult on the Windows platform. Just stick to VBR constrained (in iTunes) and Nero AAC as they seem to be the top two AAC encoders out there (judging from the results of past listening tests as well as my own). My statement that you quoted is still correct though and describes the behavior of the constrained VBR setting. I was also comparing it to the iTunes/QuickTime CBR setting, not the true VBR setting. I explained my reasoning in that statement as well so I didn't violate the TOS here.

Thank you, kornchild!

No one is mentioning Coding Technologies? I think they use only CBR, which isn't "true" CBR: if you check the bitrate in foobar2000, it varies.

Coding Technologies (CT) AAC encoder has only CBR mode. You can see bitrate fluctuation in foobar because AAC format is variable by itself. AAC's CBR is short window ABR (some sort of temporal restriction).
http://www.hydrogenaudio.org/forums/index....showtopic=55253

You can start from here
http://en.wikipedia.org/wiki/Advanced_Audio_Coding
http://wiki.hydrogenaudio.org/index.php?title=AAC
http://www.mp3-tech.org/

Thank you, Igor!

Could you, or anyone, make any kind of statement as to how does CT’s encoder compare with the others (Nero’s, iTunes...)?

Most of the hydrogenaudio forums says that aac VBR>160 provide transparent sound and aac lc is better than other codec like HE-AAC. Though it have more complexity but it do not provide transparent sound. As u are convarting to lossy codec so it is better for u to use abr bitrate mode because in a Lossy format if u use high bitrate the sound will hear good. The true vbr is good but if u want quality use abr mode.

Excessive generalization here. At high bitrates above roughly 128 kbps, HE-AAC does not offer any advantage over AAC LC, yes, because it is more complex, because enough bits are available even for coding with AAC LC, and because in principle (because of SBR), it cannot provide transparency for some items, even non-killer ones. Still, HE could be slightly better than LC for some items. For low bitrates around 64 kbps, HE-AAC is significantly better than AAC LC on most items, because not enough bits are available for coding a sufficient bandwidth artefact-free with AAC LC.

The thing with the "if you want quality": If you want quality, use a sufficient bitrate. Period. Doesn't really matter what flavor of ABR or CBR or VBR you use.


I don't know, but Winamp has the CT encoder built-in, so try for yourself. In the free full version, it says you can rip CDs to AAC 8 times.

Chris

So, roughly above 12 kbps, but definitely above 192 kbps, AAC-LC is definitely better than aacPlus? aacPlus should only be used for lower, > 128 kbps bitrates?

Could you explain on how SBR interferes with transparency?

SBR reconstructs higher frequencies using lower frequencies. See here. Since the high-frequency content never really matches the low-frequency part in terms of spectral shape and harmonics, SBR can never perfectly reconstruct the upper part of the spectrum. AAC LC can, because it encodes the upper-frequency part as it is, without reconstructing it from lower frequencies. But to do that, AAC LC needs a sufficiently high bitrate, because coding the high-frequency part is much more "expensive" than reconstructing it via SBR. 192 kbps for stereo (or 96 kbps for mono) is definitely enough for AAC LC. In fact, Fraunhofer's (and maybe Coding Technologies') AAC encoder does not even allow using SBR for bitrates higher than 128 kbps.

Chris

And does any piece of software use Fraunhofer's AAC?

Well, this statement goes against popular trend. Encoders that offer VBR use a constant quality method. For example, the Nero AAC encoder has different quality settings. -q0.5, -q-0.4, -q0.65, etc. This means that regardless of bitrate, a -q setting is going to provide the same quality for your music. Some songs may need a lower overall bitrate while others need a higher one. VBR encoding allows for this type of procedure. People should use VBR when they want a constant quality that may lead to unknown resulting overall bitrates. People should use ABR if they want a known bitrate. The general consensus is that VBR > ABR > CBR when it comes to overall quality. VBR allows for an encoder to drop the bitrate when needed and to drastically increase it as well. ABR forces the encoder to focus on a given bitrate "range" so that the resulting files have an overall bitrate close to the setting.


Sylph, I am not sure which software uses the FhG (Fraunhofer) AAC encoder. I don't know if I would worry about it too much. The Nero AAC and iTunes/QuickTime AAC encoders are the two that are most heavily tested here on HA. I conducted a quick search and couldn't really find anything regarding the FhG AAC encoder. You can try contacting FhG directly to see if they will provide you with a binary/encoder for testing purposes.

Thank you very much, kornchild! Do you think they would allow for someone to test it?

Apparently, it has already been implemented in these two programs.

Unfortunately, Fraunhofer does not offer an evaluation encoder to individual persons, only to companies interested in purchasing it (i.e. potential customers).

Chris

Is it true that the highest bitrate their AAC offers is 256 kbps?

No, it's 320 kbps for stereo.

Chris

That's what I thought would be logica, but Magix program offers only 256. Perhaps it's because it's the demo version?

Chris, you wouldn't know any other program that has Fraunhofer's AAC?

Apparently, that's not true.

http://www.iis.fraunhofer.de/bf/amm/products/aaclc.jsp

256 kbit/s per channel, for stereo that's even more then 320 kbps