Advanced Audio Coding
The Rockbox Open source firmware (available for multiple portable players) also offers support for AAC to varying degrees, depending on the model of player and the AAC profile.
Optional iPod Support (playback of unprotected AAC files) for the Xbox 360 is available as a free download from Xbox Live.[11]
[
Other software media players
Almost all current computer media players include built-in decoders for AAC, or can utilize a library to decode it. On Microsoft Windows, DirectShow can be utilized this way with the corresponding filters to enable AAC playback in any DirectShow based player. Software player applications of particular note include:
- Easy CD-DA Extractor for Windows, CD Ripper and audio converter, which includes an AAC encoder that supports LC and HE AAC.
- ffdshow is a free open source DirectShow filter for Microsoft Windows operating systems that uses FAAD2 to support AAC decoding.
- foobar2000 is a freeware audio player for Windows that supports LC and HE AAC.
- Jetaudio is a free media player for Microsoft Windows that plays a large array of formats, including AAC.
- The KMPlayer also supports AAC.
- KSP Sound Player also supports AAC.
- Media Player Classic
- MPlayer or xine are often used as AAC decoders on Linux.
- RealPlayer includes RealNetworks’s RealAudio 10 AAC encoder.
- Songbird (software) for Windows, Linux and Apple Macintosh supports AAC, including the DRM rights management encoding used for purchased music from the iTunes Store, with a plug-in.
- Sony SonicStage also support AAC.
- VLC media player supports playback of MP4 and AAC files.
- Winamp for Windows, which includes an AAC encoder that supports LC and HE AAC;
- Another Real product, Rhapsody supports the RealAudio AAC codec, in addition to offering subscription tracks encoded with AAC.
- XBMC (XBox Media Center) supports both AAC (LC and HE) on modified Xbox game-consoles.
- XMMS supports mp4 playback using a plugin provided by the faad2 library.
- ConvertDirect.com serves AAC Files using Youtube Video conversion. It converts Youtube video to AACs.
Some of these players (e.g., foobar2000, Winamp, and VLC) also support the decoding of raw or MP4-contained AAC streamed over HTTP using the SHOUTcast protocol. Plug-ins for Winamp and foobar2000 enable the creation of such streams.
[
Nero Digital Audio
In May 2006, Nero AG released an AAC encoding tool free of charge, Nero Digital Audio [2], which is capable of encoding LC, HE and HEv2 AAC streams. The tool is a Command Line Interface tool only, and a separate utility is included to decode to PCM WAV.
Various tools including the foobar2000 audio player and MeGUI can provide a GUI for the encoder.
[
FAAC and FAAD2
FAAC and FAAD2 stand for Freeware Advanced Audio Coder and Decoder 2 respectively, collectively make up an open source implementation of AAC.
[
Extensions and improvements
Some extensions have been added to the original AAC standard:
- Perceptual Noise Substitution (PNS) – added in MPEG-4. It allows the coding of noise as pseudorandom data;
- MPEG-4 Scalable To Lossless (SLS) – can supplement an AAC stream to provide a lossless decoding option, such as in Fraunhofer IIS's "HD-AAC" product;
- High Efficiency AAC (HE-AAC), a.k.a. aacPlus v1 or AAC+ – the combination of SBR (Spectral Band Replication) and AAC; used for low bitrates;
- HE-AAC v2, a.k.a. aacPlus v2 or eAAC+ – the combination of Parametric Stereo (PS) and HE-AAC; used for even lower bitrates;
- Long Term Predictor (LTP) – added in MPEG-4.
[
See also
[
Notes
- ^ Johnston, J. D. and Ferreira, A. J., “Sum-difference stereo transform coding,” ICASSP '92, March, 1992, pp. II-569-572.
- ^ Sinha, D. and Johnston, J. D., “Audio compression at low bit rates using a signal adaptive switched filterbank,” IEEE ASSP, 1996, pp. 1053-1057.
- ^ Johnston, J. D., Sinha, D., Dorward, S. and Quackenbush, S., “AT&T perceptual audio coder (PAC)” in Collected Papers on Digital Audio Bit-Rate Reduction, Gilchrist, N. and Grewin, C. (Ed.), Audio Engineering Society, 1996.
- ^ Herre, J. and Johnston, J. D., “Enhancing the performance of perceptual audio coders by using temporal noise shaping,” AES 101st Convention, no. preprint 4384, 1996
- ^ a b http://www.codingtechnologies.com/products/assets/CT_aacPlus_whitepaper.pdf
- ^ ISO/IEC 14496-3:2005/Amd.2 [1]
- ^ Apple - QuickTime - Technologies - AAC Audio
- ^ Via Licensing. MPEG-4 Audio Licensing FAQ Q6.
- ^ Via Licensing. MPEG-4 AAC License Fees.
- ^ | Nintendo - Customer Service | Wii - Photo Channel
- ^ Xbox.com | System Use - Use an Apple iPod with Xbox 360
[
External links
- Apple's page on MPEG-4 AAC
- Fraunhofer MPEG-2 AAC Information
- AudioCoding.com - home of FAAC and FAAD2
|
|||||||||||||||||||||||||||||||||||||||||||
|
||||||||||||||||||||||||||
For more information review our copyright contact and privacy policy.