Difference between revisions of "AAC"

From TMB Wiki
Jump to: navigation, search
m (Playback)
(.mp4/.m4a)
 
(8 intermediate revisions by 2 users not shown)
Line 1: Line 1:
'''AAC''' ('''Advanced Audio Coding''') is part of the MPEG-2 and MPEG-4 audio specification and is promoted as the successor to [[MP3]] for audio coding at medium to high bitrates. It is the audio format used by the iTunes Music Store and can be played on iPods.
+
'''AAC''' ('''Advanced Audio Coding''') is part of the MPEG-2 and MPEG-4 audio specification and is promoted as the successor to [[MP3]] for audio coding at medium to high bitrates.
  
 
==File Extensions==
 
==File Extensions==
Line 7: Line 7:
 
===.aac===
 
===.aac===
  
Usually a raw AAC bitstream. Early AAC encoders often produced files like this.
+
Usually a raw AAC bitstream. Early AAC encoders often produced files like this. AAC in its newer AAC+ variant is now increasingly found on the internet as several internet based radio stations use this format to broadcast digital audio streams (raw AAC+ bitstream). To play such raw AAC/AAC+ data it is usually the best to wrap a .mp4/.m4a container around the raw AAC/AAC+ files as most media players have problems with raw AAC/AAC+ data. That can easily be done by using the program "mp4Box".
  
 
===.mp4/.m4a===
 
===.mp4/.m4a===
  
AAC wrapped in an MP4 container. This is how most new AAC encoders produce files. The MP4 container can contain other audio and video formats as well as AAC, so a .mp4 file does not always indicate the presence of AAC (e.g. Apple Lossless is also put in an MP4 container).
+
AAC wrapped in an MP4 container. This is how most new AAC encoders produce files. The MP4 container can contain other audio and video formats as well as AAC, so a .mp4 file does not always indicate the presence of AAC (e.g. Apple Lossless is also put in an MP4 container). Generally however, .m4a files contain just AAC audio.
  
 
In this case there is no difference between the extension (i.e. you can rename .m4a to .mp4 and vice-a-versa).
 
In this case there is no difference between the extension (i.e. you can rename .m4a to .mp4 and vice-a-versa).
Line 33: Line 33:
 
===Hardware===
 
===Hardware===
  
Todo.
+
*[http://www.apple.com/ipod/ iPod]
  
 
==Encoding==
 
==Encoding==
  
Although in theory AAC should outperform MP3 at the same bitrate, early AAC encoders were of a poor quality and would be easily beaten by a decent MP3 encoder like LAME at nearly all bitrates. Below is a list of software with high quality AAC encoders:
+
Although in theory AAC should outperform MP3 at the same bitrate, some early AAC encoders were of a poor quality and were easily beaten by [[LAME]] at medium and high bitrates. Below is a list of free encoders that produce high quality AAC files:
  
 +
*[http://www.nero.com/nerodigital/eng/Nero_Digital_Audio.html Nero Digital Audio]
 
*[http://www.apple.com/itunes/ iTunes]
 
*[http://www.apple.com/itunes/ iTunes]
*[http://www.nero.com/eng/index.html Nero 7]
 
  
  
 
[[Category:Audio Formats]]
 
[[Category:Audio Formats]]

Latest revision as of 17:33, 3 September 2015

AAC (Advanced Audio Coding) is part of the MPEG-2 and MPEG-4 audio specification and is promoted as the successor to MP3 for audio coding at medium to high bitrates.

File Extensions

AAC has a number of common file extensions. Unlike some other media formats, there are differences between the file depending on the extension so you cannot rename from one extension to another.

.aac

Usually a raw AAC bitstream. Early AAC encoders often produced files like this. AAC in its newer AAC+ variant is now increasingly found on the internet as several internet based radio stations use this format to broadcast digital audio streams (raw AAC+ bitstream). To play such raw AAC/AAC+ data it is usually the best to wrap a .mp4/.m4a container around the raw AAC/AAC+ files as most media players have problems with raw AAC/AAC+ data. That can easily be done by using the program "mp4Box".

.mp4/.m4a

AAC wrapped in an MP4 container. This is how most new AAC encoders produce files. The MP4 container can contain other audio and video formats as well as AAC, so a .mp4 file does not always indicate the presence of AAC (e.g. Apple Lossless is also put in an MP4 container). Generally however, .m4a files contain just AAC audio.

In this case there is no difference between the extension (i.e. you can rename .m4a to .mp4 and vice-a-versa).

.m4p

Apple's proprietary copy protected MP4 audio files. No one should be posting these on TMB under any circumstances.

Playback

Software

The following media players will playback AAC files:

Hardware

Encoding

Although in theory AAC should outperform MP3 at the same bitrate, some early AAC encoders were of a poor quality and were easily beaten by LAME at medium and high bitrates. Below is a list of free encoders that produce high quality AAC files: