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Has the iTunes AAC encoder changed recently?, specifically between version 7.0.2.16 and the current 7.3.4
STL
post Oct 18 2007, 03:30
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I want to know if the iTunes AAC encoder has changed since 7.0.2.16? If so, are the changes -- overall -- for the good or bad? I don't want to upgrade if the current version of the encoder has some bad tweaks in it.

Moderation: Fixed typo in topic. ACC -> AAC. To help future searches.

This post has been edited by JensRex: Nov 6 2007, 19:47
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skuo
post Oct 18 2007, 18:51
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A new AAC-LC codec is available in the new Mac OS X 10.5 (code named as Leopard) which will be released in Oct. 26. It has some significant sound quality improvement and bitrate mode enhancement. Since iTunes and QT use the AAC codec built natively in the OS X, these enhancements will be reflected in these Apple applications as well (doesn't matter you have upgraded these individual applications or not). You can also use the following commandline tools available in the OS X 10.5 to access the codec:
$> afconvert - perform various audio file conversions, including AAC encoding and decoding.
$> afplay - play back an audio file (compressed or uncompressed).
$> afinfo - display information about an audio file.

This post has been edited by skuo: Nov 14 2007, 23:45
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jarsonic
post Oct 18 2007, 19:12
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i wonder if iTunes will be able to do multiple file conversions at once.
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STL
post Oct 18 2007, 19:13
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QUOTE (skuo @ Oct 18 2007, 12:51) *
doesn't matter you have upgraded these individual applications or not
Acutally since I'm on a PC then I think it does for me, but thanks for the heads-up anyhow!
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goodnews
post Oct 18 2007, 19:14
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Thanks skuo for the info. I just ordered my Leopard (Mac OS X 10.5) OS software for my Mac mini today. I will try out the new commands and AAC encoder/decoder when I receive it.

Are you allowed to report what version of FLAC (if any) comes bundled with the new Mac OS X Leopard yet or do you have to wait until October 26th for the NDA to expire?

Maybe for the original poster (and other Windows users), they will update Quicktime and iTunes for Windows to match the new Leopard audio encoder/decoder AAC (and maybe FLAC) support that will be coming with the new Mac OS due out on October 26th.

This post has been edited by goodnews: Oct 18 2007, 19:19
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skuo
post Oct 18 2007, 19:26
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QUOTE (goodnews @ Oct 18 2007, 11:14) *
Maybe for the original poster (and other Windows users), they will update Quicktime and iTunes for Windows to match the new Leopard audio encoder/decoder AAC


Yup, that's true, and the Windows updates for these Apple applications have not been announced yet.

This post has been edited by skuo: Oct 18 2007, 20:52
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dbAmp
post Oct 20 2007, 03:42
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QUOTE (skuo @ Oct 18 2007, 13:51) *
A new AAC-LC codec is available in the new Mac OS X 1.5 [sic] (code named as Leopard) which will be released in Oct. 26. It has some significant sound quality improvement and bitrate mode enhancement. Since iTunes and QT use the AAC codec built natively in the OS X, these enhancements will be reflected in these Apple applications as well (doesn't matter you have upgraded these individual applications or not). You can also use the following commandline tools available in the OS X 1.5 [sic] to access the codec:
$> afconvert - perform various audio file conversions, including AAC encoding and decoding.
$> afplay - play back an audio file (compressed or uncompressed).
$> afinfo - display information about an audio file.


Are you certain that Apple is planning a major iTunes update and that this is not just rumor?

If you check Apple's Leopard website that purports to list the 300+ features being added in OS X 10.5, neither iTunes nor Core Audio is listed.

See for yourself...

http://www.apple.com/macosx/features/300.html

This post has been edited by dbAmp: Oct 20 2007, 03:42
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Mr VacBob
post Oct 20 2007, 04:25
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iTunes and QuickTime are not on the same release schedule as OS X.

(I don't know if it's updated, but if it is, it would be under NDA anyway!)
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Enig123
post Oct 20 2007, 06:48
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I spotted an AAC-LD Codec in the whatsnew list.
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dbAmp
post Oct 20 2007, 07:04
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QUOTE (Enig123 @ Oct 20 2007, 01:48) *
I spotted an AAC-LD Codec in the whatsnew list.


AAC-LD is going to be included in the new version of iChat... because LD stands for low delay... because it's a codec that's tuned for online chat i.e. two-way communications. You're not going to be encoding your music in AAC-LD. tongue.gif
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enry2k
post Oct 22 2007, 22:23
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still no high efficiency aac in Leopard?
Has Apple any plan to include aacplus?
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eofor
post Oct 23 2007, 20:09
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QUOTE (enry2k @ Oct 22 2007, 23:23) *
still no high efficiency aac in Leopard?
Has Apple any plan to include aacplus?


They should have - if they don't then iTunes will be the only music application left that is unable to play HE-AAC webradio.
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kornchild2002
post Oct 23 2007, 22:22
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I thought that a new version of iTunes and QuickTime would be released around the same time as Leopard. It might be built into Leopard (though I thought iTunes was part of iLife) but I am not sure. Last time they did something like this, it took Apple about a week to come out with Windows downloads. That was around the time Panther was released, it took them about a week or so to come out with Windows equivalents.
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chrisgeleven
post Oct 24 2007, 03:04
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QUOTE (kornchild2002 @ Oct 23 2007, 17:22) *
I thought that a new version of iTunes and QuickTime would be released around the same time as Leopard. It might be built into Leopard (though I thought iTunes was part of iLife) but I am not sure. Last time they did something like this, it took Apple about a week to come out with Windows downloads. That was around the time Panther was released, it took them about a week or so to come out with Windows equivalents.


Guarantee there will be a new version of iTunes and QuickTime released in the next week...maybe even by Friday. QuickTime obviously due to the reported encoder updates. iTunes will probably get a minor update just with any last minute Leopard-specific fixes.

Apple always keeps the Mac and Windows versions in sync (unless there is a specific Mac or Windows fix that only applies to 1 platform)...I doubt they will stop now. So expect those who have earlier OS X versions or Windows to get an update as well.

I'll let you guys know when I get Leopard on Friday what version of QuickTime comes with it and see if I can find anything interesting...


--------------------
iTunes 10 - Mac OS X 10.6
256kbps AAC VBR
iPhone 4 32GB
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dbAmp
post Oct 24 2007, 05:20
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QUOTE (chrisgeleven @ Oct 23 2007, 22:04) *
Guarantee there will be a new version of iTunes and QuickTime released in the next week...maybe even by Friday. QuickTime obviously due to the reported encoder updates. iTunes will probably get a minor update just with any last minute Leopard-specific fixes.

Apple always keeps the Mac and Windows versions in sync (unless there is a specific Mac or Windows fix that only applies to 1 platform)...I doubt they will stop now. So expect those who have earlier OS X versions or Windows to get an update as well.

I'll let you guys know when I get Leopard on Friday what version of QuickTime comes with it and see if I can find anything interesting...


While I'll admit that it is very possible iTunes/Quicktime updates are part of the + in the 300+ updates, I haven't been able to find any information on the Apple website that these are pending for next week. Don't get me wrong, I'd love to see updates/improvements to the Apple encoder and, in fact hope I'm wrong on this one... but I think that if these updates were coming, they'd have included them in the feature list... as telling people that iTunes was going to support HE-AAC is sort of a big deal.

I suppose we'll have to wait and see. Can anyone even point me to an article from somewhere like slashdot, digg, AppleInsider, MacRumors, etc. that implies these updates are coming this week?
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Busemann
post Oct 26 2007, 14:43
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QUOTE (skuo @ Oct 18 2007, 09:51) *
A new AAC-LC codec is available in the new Mac OS X 1.5 (code named as Leopard) which will be released in Oct. 26. It has some significant sound quality improvement and bitrate mode enhancement. Since iTunes and QT use the AAC codec built natively in the OS X, these enhancements will be reflected in these Apple applications as well (doesn't matter you have upgraded these individual applications or not). You can also use the following commandline tools available in the OS X 1.5 to access the codec:
$> afconvert - perform various audio file conversions, including AAC encoding and decoding.
$> afplay - play back an audio file (compressed or uncompressed).
$> afinfo - display information about an audio file.


I just received my copy of 10.5 and a nice new feature is that iTunes lists the actual bitrate of AAC VBR files, albeit only ones encoded in Leopard. The encoder is indeed updated as well since the bitrates are completely different on some test encodes I did compared to the previous version. I haven't had time to do abx tests yet though.

FLAC doesn't seem to be supported.
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ShowsOn
post Oct 26 2007, 17:34
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QUOTE (Busemann @ Oct 26 2007, 22:43) *
I just received my copy of 10.5 and a nice new feature is that iTunes lists the actual bitrate of AAC VBR files, albeit only ones encoded in Leopard. The encoder is indeed updated as well since the bitrates are completely different on some test encodes I did compared to the previous version. I haven't had time to do abx tests yet though.

FLAC doesn't seem to be supported.


Is it now a true VBR mode, or does it still have the bitrate floor? i.e. Other than digital silence, it doesn't encode below the nominal bitrate, only above it.


--------------------
www.petitiononline.com/RHCPWBCD/petition.html
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skuo
post Oct 26 2007, 17:56
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QUOTE (Busemann @ Oct 26 2007, 06:43) *
The encoder is indeed updated as well since the bitrates are completely different on some test encodes I did compared to the previous version. I haven't had time to do abx tests yet though.

You should hear the sound quality improvement as well.

Although Apple applications offer a convenient way to access Apple AAC codecs, for Mac users, the best way to access the full functionality of the codecs is through those af* commandline tools (afconvert, afinfo, afplay). All other applications only use a subset of it. For instance, iTunes only uses ABR and VBR_Constraint encoding modes. QuickTime is better, it accesses most of the feature set, but it can only encodes to a set of pre-determined discrete bitrates (afconvert can encode to any arbitrary bitrate as long as it is within the supported bitrate range).

QUOTE (Busemann @ Oct 26 2007, 06:43) *
FLAC doesn't seem to be supported.

No, it's not in the supported codecs for consumers. It's only supported through SDK.
HE-AAC is not supported yet as many have figured.
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skuo
post Oct 26 2007, 18:08
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QUOTE (ShowsOn @ Oct 26 2007, 09:34) *
Is it now a true VBR mode, or does it still have the bitrate floor?

The newly released Apple AAC encoder offers four encoding modes:
Constant Bit Rate (CBR)
-- Recommended for live streaming --
This mode achieves a constant target bit rate and is completely compliant to the CBR mode specified in the MPEG-4 standard. This mode is suitable for constant-bit-rate network transmission when decoding in real-time with a fixed end-to-end audio delay.

Average Bit Rate (ABR) - Default Mode
-- Recommended for controlling file size --
A target bit rate is achieved over a long term average (typically after the first few seconds of encoding). Unlike CBR mode, this mode does not provide constant delay when using constant bit rate transmission, but this mode provides almost best global quality while still being able to strictly control the resulting file size and with less complexity than the CBR mode.

Variable Bit Rate (VBR)
-- Recommended for controlling the audio quality --
The audio signal is encoded with constant (and settable) quality and virtually no bit rate constraints. This is the best mode to achieve consistent audio quality across many files with the smallest file size to achieve that quality. It also has the lowest complexity of all the encoding modes.

Variable Bit Rate But Constrained (VBR_Constrained)
-- Recommended as a compromise between VBR and ABR --
This mode is similar to VBR but limits the average bit rate variation. The lower limit is the user-selected bit rate. Higher bit rate is adapted for difficult tracks and can generate up to 10% larger files than the ABR mode.

Note that QuickTime and the commandline tools on Mac can access all these four encoding modes. However, iTunes can only access ABR and VBR_Constrained.

This post has been edited by skuo: Oct 26 2007, 19:32
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skuo
post Oct 26 2007, 18:26
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QUOTE (dbAmp @ Oct 19 2007, 23:04) *
AAC-LD is going to be included in the new version of iChat... because LD stands for low delay... because it's a codec that's tuned for online chat i.e. two-way communications.

Yup, I believe people will be very pleased by the significant sound quality improvement in iChat (especially for music) when both parties are running on Leopard (Mac OS X 10.5).

This post has been edited by skuo: Oct 26 2007, 18:29
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goodnews
post Oct 26 2007, 18:59
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Anyone know what version of FLAC is being supported for developers on Mac Leopard (OS X 10.5) in the SDK? We should get more Apple Mac FLAC supporting apps right?
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kornchild2002
post Oct 26 2007, 19:19
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It is nice to hear that a new AAC encoder is being implemented in iTunes/QuickTime. I wonder when Windows users and older Mac OS X users will get this update. I am glad that they are implementing a true VBR encoding mode now as that has always been a major gripe against iTunes in that it used a constrained VBR encoding mode.
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Busemann
post Oct 26 2007, 19:51
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QUOTE (skuo @ Oct 26 2007, 08:56) *
Although Apple applications offer a convenient way to access Apple AAC codecs, for Mac users, the best way to access the full functionality of the codecs is through those af* commandline tools (afconvert, afinfo, afplay). All other applications only use a subset of it. For instance, iTunes only uses ABR and VBR_Constraint encoding modes. QuickTime is better, it accesses most of the feature set, but it can only encodes to a set of pre-determined discrete bitrates (afconvert can encode to any arbitrary bitrate as long as it is within the supported bitrate range).


I played around with the command line to access the true VBR mode in order to get high quality VBR files, but I'm not sure if I got it right;

afconvert -f m4af -d aac -s 3 -q 127

This setting produced vbr files with a fairly low bitrate (80-140kbps), and the bitrate option (-b) didn't make any difference.. Is there a way to make the true vbr mode aim for transparency and higher bitrate files?
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dbAmp
post Oct 26 2007, 22:19
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Correct me if I'm wrong... but wasn't it stated above that iTunes still only uses VBR_constrained? I'm not sure much as changed. I was under the impression that full VBR was always available in Tiger through command line or CoreAudio, which is what programs such as Maxx use to encode AAC.
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skuo
post Oct 27 2007, 01:43
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QUOTE (Busemann @ Oct 26 2007, 11:51) *
Is there a way to make the true vbr mode aim for transparency and higher bitrate files?

The command line for the true VBR mode is as follows:

afconvert -f m4af -d aac -s 3 -u vbrq 127

In VBR mode (-s 3), bitrate option (-b) is ignored because the mode is configured by sound quality which is set by "-u vbrq <sound_quality>" where <sound_quality>: 0-127. Note that the ABR and VBR modes are new features supported in Leopard. CBR and VBR_Constrained modes were in previous Mac OS X.

QUOTE (goodnews @ Oct 26 2007, 10:59) *
Anyone know what version of FLAC is being supported for developers on Mac Leopard (OS X 10.5) in the SDK?

FLAC 1.2.0 is the version that the SDK is tested against, however, it should work just fine with any other FLAC versions.

In fact, it's pretty easy for people to build FLAC codec from the SDK provided in Leopard install DVD. Once you have installed those developer tools, all you have to do is to follow the steps given in /Developer/Examples/CoreAudio/AudioCodecs/Codecs/FLAC/README.txt to build and install the FLAC codec to the system to make it accessible via af* command line tools.
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