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Fraunhofer Shows HD-AAC at CES

The codec, HD-AAC, offers music encoding "with quality beyond CDs and at the same time, iPod compatibility." The company said the codec is based on the MPEG-4 SLS standard and provides lossless compression of 24-bit quality music content.

Fraunhofer IIS believes its new MPEG audio codec makes CD collections obsolete.

The codec, HD-AAC, offers music encoding “with quality beyond CDs and at the same time, iPod compatibility.” The company said the codec is based on the MPEG-4 SLS standard and provides lossless compression of 24-bit quality music content.

It is the result of a collaboration between Fraunhofer IIS and the Institute for Infocomm Research (I²R). Fraunhofer is offering the software for PC and embedded devices, including microprocessors or DSPs from companies like Analog Devices, Intel and IBM. An HD-AAC logo will identify conforming products.

“Today’s audio CDs store uncompressed music in 16-bit, 44.1 kHz quality, while most music is now produced in the improved 24 bit, 96 kHz format,” the company stated. “HD-AAC is making this new standard efficiently available to consumers, electronic music distribution and the consumer electronics industry.”

In the announcement, Harald Popp, head of the Multimedia Realtime Systems department at Fraunhofer IIS, stated, “Consumers will be able to buy content in online music stores that sounds better than CDs, and preserve their existing CD collection for the future by encoding it in HD-AAC. For casual listening, HD-AAC files conveniently play on existing AAC devices.”

The encoding process preserves the bits in the uncompressed original music track while offering lossless compression rates “comparable or superior to other lossless formats,” Fraunhofer claims.

“Due to its AAC-LC core layer, an HD-AAC file can be directly played on existing music players and millions of mobile phones. For decoding of the fully lossless signal, upcoming devices will be equipped with an HD-AAC decoder.”

In a connected home, it said, “songs stored on media servers in the HD-AAC format can be streamed to multiple devices at varying bitrates. This maximizes the sound quality under difficult network conditions by matching the bitrate to the available bandwidth.”

HD-AAC Is Based on MPEG-4 SLS

Here’s more background on scalable lossless audio coding from Fraunhofer IIS, providing further context for its CES announcement above:

Lossless audio coding schemes offer audio data compression, with the decoded audio data being bit by bit identical to the original audio data.

There is a number of important applications for lossless audio coding schemes, even though their compression ratio is far from that of modern perceptual audio coding schemes. The main application is in archiving speech and music, yet lossless formats also are of high interest as an intermediate in production or broadcast chains to prevent possible tandem-coding artifacts. And during the restoration of old recordings, lossless codecs can save considerable amounts of disk space without running into any risk of generating coding artifacts during later processing of the audio data.

Nevertheless there are numerous application scenarios where there is not enough bandwidth to use a fully lossless audio file – therefore Fraunhofer IIS offers a scalable audio codec that has a fine grain scalability from highest compression to highest lossless quality.

Fraunhofer IIS offers a fully scalable to lossless audio coding solution. On top of MPEG-4 AAC, a scalable extension layer increases the signal-to-noise-ratio, reaching losslessness at data rates comparable to that of current pure lossless audio codecs, that is, at average compression ratios of about 50%. The flexible scalability of the extension makes this combination an ideal coding solution for production environments, where the result is to be transmitted to several recipients through channels of differing bandwidth. Also, for private and professional use in music archives, this enables storing the original music data and transferring highly compressed copies, e.g. to portable devices without time-consuming recoding operations.

The technologies behind HD-AAC are MPEG-4 Advanced Audio Coding (AAC) and MPEG-4 Scalable Lossless Coding (SLS). Both are subparts of the MPEG-4 Audio standard ISO/IEC 14496-3. This open standard guarantees interoperability, reliability, and fair and reasonable licensing terms.