MPEG-2 Audio (MPEG-2 AAC)

 
Superior audio coding technology

A powerful audio coding system capable of superior results at stereo bit rates below 128 kb/s.

Advanced Audio Coding, or AAC, is one of several audio coding systems specified in the MPEG-2 standard (ISO/IEC 13818-7).

MPEG-2 AAC is the audio format utilized in the Japanese Digital Broadcast system, known as ISDB (Integrated Services Digital Broadcasting). MPEG-2 AAC is also the basis of the audio coding technology used by Sirius XM Radio, one of two satellite radio services currently operating in the United States.

MPEG-2 AAC has been extended with additional features and capabilities in MPEG-4 AAC. However, companies creating products for the applications described above may not require these additional AAC tools, and for such applications, we offer the MPEG-2 AAC Patent License Agreement.

A copy of the MPEG-2 AAC standard can be purchased from the ISO online store (search for "13818-7").

MPEG-2 Audio (MPEG-2 AAC)

 
Superior audio coding technology

A powerful audio coding system capable of superior results at stereo bit rates below 128 kb/s.

Advanced Audio Coding, or AAC, is one of several audio coding systems specified in the MPEG-2 standard (ISO/IEC 13818-7).

MPEG-2 AAC is the audio format utilized in the Japanese Digital Broadcast system, known as ISDB (Integrated Services Digital Broadcasting). MPEG-2 AAC is also the basis of the audio coding technology used by Sirius XM Radio, one of two satellite radio services currently operating in the United States.

MPEG-2 AAC has been extended with additional features and capabilities in MPEG-4 AAC. However, companies creating products for the applications described above may not require these additional AAC tools, and for such applications, we offer the MPEG-2 AAC Patent License Agreement.

A copy of the MPEG-2 AAC standard can be purchased from the ISO online store (search for "13818-7").

Guaranteed quality


The International Organization for Standardization (ISO) anticipated the importance of compression algorithms for video and audio signals at an early stage and founded the Moving Pictures Expert Group (MPEG) with the intention to develop and standardize these methods. The group´s highly acclaimed achievements are the standards MPEG-1 and MPEG-2. MPEG-2 Advanced Audio Coding (AAC) and was declared international standard by MPEG by the end of April 1997.

The major advantages of data compression are minimum memory requirement and minimum transmission bandwidth required by the compressed signal. This method is of useful service whenever resources are scarce or expensive. Thus digital radio (e.g. Eureka DAB, WorldSpace) and audio transmission in the internet constitute two major domains of application within the field of audio coding.

The driving force to develop AAC was the quest for an efficient coding method for surround signals, like 5-channel signals (left, right, center, left-surround, right-surround); as being used in cinemas today. There have been algorithms for these signals in MPEG-2 for quite a while. Optimum efficiency, however, was not reached due to technical and historical reasons. Therefore, the set aim was a considerable decrease of the necessary bitrate.

What is MPEG-2 AAC?
MPEG-2 AAC is the consequent continuation of the truly successful coding method ISO/MPEG Audio Layer-3. The appropriate incorporation of high coding gain and great flexibility opens up a wide field of applications. With sampling frequencies between 8 kHz and 96 kHz and any number of channels between 1 and 48, the method is well prepared for future developments in the audio sector. Compared to coding methods such as MPEG-2 Layer-2, it is possible to cut the required bitrate by a factor of two with no loss of subjective quality.

Like all perceptual coding schemes, MPEG-2 AAC basically makes use of the signal masking properties of the human ear in order to reduce the amount of data. Doing so, the quantization noise is distributed to frequency bands in such a way that it is masked by the total signal, i.e. it remains inaudible. Even though the basic structure of this coding method hardly differs from its predecessors, a closer look into the details does reveal some new aspects worth paying attention to.

 

Philips licenses its essential patents for MPEG-4 Audio through VIA Licensing. For further details or questions please contact www.via-corp.com

MPEGAudio is an ISO (International Standards Organisation) and IEC (International Electrotechnical Commission) world standard - open to everyone on an equal, non-discriminatory basis.

MPEG Business Applications
MPEG Audio is an ISO (International Standards Organisation) and IEC (International Electrotechnical Commission) world standard, open to everyone on an equal, nondiscriminatory basis. Being a world standard means that all organisations which have contributed to this Standard, will make their MPEG Audio patent rights available against fair, reasonable and nondiscriminatory conditions, thus preventing the influence of vested interests. Investments are future proof, the family approach of MPEG means forward and backwards compatibility, thus perfect audio/video integration. The forward and backward compatibility aspect of MPEG means that new developments will not necessarily make existing equipment and programming obsolete. The existing equipment may not handle additional features of a new standard, but will still operate within the specification of its own standard. MPEG equipped hardware is future-proof. MPEG's compatibility between formats allows for great flexibility. Content providers are free to supply their programs in any format (stereo, multichannel) in the knowledge that excellent audio quality is reproduced at the consumer end, whatever equipment is used. In other words: the supplier has a guarantee of, and control over, the quality of their programming. Efficient implementation of MPEG allows for cost effective consumer equipment prices with high quality and performance.

Patents and agreements

Philips licenses its essential patents for MPEG Audio through Via Licensing. For further details or questions please contact Via Licensing: www.via-corp.com

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