Apple AAC: Difference between revisions

From Hydrogenaudio Knowledgebase
No edit summary
No edit summary
Line 2: Line 2:
[[AAC]] encoders and is also another commercial AAC implementation. The current version of Quicktime supports [[Multichannel]] encoding up to 8 channels, and HE-AAC v1 with [[SBR]].
[[AAC]] encoders and is also another commercial AAC implementation. The current version of Quicktime supports [[Multichannel]] encoding up to 8 channels, and HE-AAC v1 with [[SBR]].


Although this is a comercial implementation and part of the QuickTime Pro package, VBR and CBR modes (with a maximum [[sampling rate]] of 44.1khz for iTunes 10+ and 48khz for iTunes 9-) are available for free
Although this part of the commercial QuickTime Proe, VBR and CBR modes are available for free
through [http://www.apple.com/itunes/ iTunes ]
through [http://www.apple.com/itunes/ iTunes] (with a maximum [[sampling rate]] of 44.1khz for iTunes 10+ and 48khz for [http://www.oldapps.com/itunes.php?old_itunes=61 iTunes 9-])


Free Third-party interfaces such as [http://sites.google.com/site/qaacpage/ qAAC] expose more modes such as TVBR (equivalent to quality modes in other encoders) and CVBR ("constrained VBR")
Free Third-party CLI interfaces such as [http://sites.google.com/site/qaacpage/ qAAC] expose more modes such as TVBR (equivalent to quality modes in other encoders) and CVBR ("constrained VBR")


Multichannel channel mapping is buggy but can be remedied by installing an older version of Quicktime (7.68-)
In recent tests for [http://listening-tests.hydrogenaudio.org/igorc/results.html 64kbps HE-AAC] and [http://listening-tests.hydrogenaudio.org/igorc/aac-96-a/results.html 96kbps LC-AAC] Quicktime has consistently come out near the top. This also applies to higher bitrates such as 128kbps and is likely to apply to higher bitrates such as 160kbps and beyond.
 
In recent tests for [http://listening-tests.hydrogenaudio.org/igorc/results.html 64kbps HE-AAC] and [http://listening-tests.hydrogenaudio.org/igorc/aac-96-a/results.html 96kbps LC-AAC] Quicktime has consistently come out near the top.


In 2009, the core AAC encoding algorithm was updated with "higher fidelity". The bitrate distribution algorithm was also changed.
In 2009, the core AAC encoding algorithm was updated with "higher fidelity". The bitrate distribution algorithm was also changed.


More information can be found at the [http://www.apple.com/quicktime Apple Quicktime Website]
==External links==
*[http://www.apple.com/quicktime Apple's Quicktime Website]


{{stub}}
{{stub}}

Revision as of 07:41, 17 September 2011

QuickTime AAC is known to be one of the highest quality medium-bitrate CBR and VBR LC AAC encoders and is also another commercial AAC implementation. The current version of Quicktime supports Multichannel encoding up to 8 channels, and HE-AAC v1 with SBR.

Although this part of the commercial QuickTime Proe, VBR and CBR modes are available for free through iTunes (with a maximum sampling rate of 44.1khz for iTunes 10+ and 48khz for iTunes 9-)

Free Third-party CLI interfaces such as qAAC expose more modes such as TVBR (equivalent to quality modes in other encoders) and CVBR ("constrained VBR")

In recent tests for 64kbps HE-AAC and 96kbps LC-AAC Quicktime has consistently come out near the top. This also applies to higher bitrates such as 128kbps and is likely to apply to higher bitrates such as 160kbps and beyond.

In 2009, the core AAC encoding algorithm was updated with "higher fidelity". The bitrate distribution algorithm was also changed.

External links