XM Satellite Radio today unveiled its state-of-the-art digital sound technology, featuring customized CT-aacPlus audio encoding with Neural Audio optimization, which provides superior sound quality remarkably close to Compact Disc.
“XM Satellite Radio, Fortune Magazine’s 2001 ‘Product of the Year,’ succeeds because of its superior digital sound technology, unparalleled signal coverage, proven chipset technology and outstanding programming,” said XM Executive Vice President Steve Gavenas at a news briefing today in New York. “The technologies that define XM Satellite Radio sound quality have been auditioned and endorsed by leading audio experts from around the world.”
CT-aacPlus Audio Compression
The superior XM sound quality experience in the car and home begins in XM’s Digital Broadcast Center, where it creates and integrates its 100 state- of-the-art audio channels. The key to XM’s outstanding sound quality is CT- aacPlus, a third-generation audio encoding technology. CT-aacPlus is the combination of Advanced Audio Coding (AAC), a highly efficient global standard combining the work of the world’s foremost experts on perceptual audio encoding – AT&T, Dolby, Fraunhofer, and Sony – with Coding Technologies’ revolutionary Spectral Band Replication (SBR)(TM) technology.
Coding Technologies, a technology leader in perceptual audio compression and inventor of SBR (Spectral Band Replication), which creates additional bitrate efficiency, was formed through a merger between a Swedish group of world-class researchers and experts from the renowned German Fraunhofer Institute, the inventor of MP3.
This combination of AAC and SBR, CT-aacPlus, has been tested by high- profile audio experts from around the world. In a double-blind listening test, AAC alone has historically proven 33% more efficient compared to previous generations of competing algorithms. Double-blind listening tests conducted by the BBC, Deutsche Telekom and Robert Bosch GmbH have established that the CT-aacPlus combination is over 30% more efficient than AAC, thereby providing superior sound quality at satellite radio bit rates compared to any other audio coding technology. Based on superior test results, CT-aacPlus has been adopted by International Digital Radio Mondiale consortium and accepted by MPEG as the “reference model” for the upcoming version of MPEG-4.
The Neural Audio Edge
The XM sound is further optimized with Neural Audio. Neural Audio, a Seattle-based research lab, pioneered future generation audio by merging neural networks with the physics of sound. Neural Audio’s proprietary pre- processing software uses advanced neural network computing techniques to implement algorithms that are based on models of the brain’s perception of sound.
Neural Audio created a customized version of their process, designed to enhance CT-aacPlus results by optimizing temporal and spectral elements prior to encoding, improving soundstage clarity, and increasing intelligibility. The unique combination of CT-aacPlus and Neural Audio algorithms enable XM to deliver a consistent, superior sound experience.
In addition, Neural Audio’s “stereo transcoder” algorithm preserves the imaging and spatiality of stereo and surround-sound content that XM broadcasts. So XM customers with matrix-style surround sound equipment, including Dolby technology, can receive a full surround sound experience.
Unparalleled Signal Coverage
XM’s digitally compressed audio content is then uplinked into outer space. Audio compression is only as effective as the ability to deliver the digital signal to the radio receivers – XM is able to deliver its superior sound quality coast-to-coast by using two of the most powerful commercial satellites ever built, augmented by a nationwide network of more than 800 repeaters in 70 cities, the most extensive SDARS repeater network available.
XM’s two Boeing 702 satellites, “Rock” and “Roll,” deliver more than twice as much total satellite power of any other satellite radio service, thus only two are needed. The satellites are “parked” in geostationary orbits aligned with the east and west coasts of the United States and each broadcasts the full 100-channel service to all XM radios across the country.
Geostationary orbits are used by the majority of communication satellites today. This proven technology offers outstanding signal stability and, with two satellites in geostationary orbits, XM can provide the most consistent “spatial diversity” to ensure reliable reception. Geostationary orbits also allow XM to use shaped-beam broadcasting that focuses the highest power where it’s needed most, in the largest population areas.
Finally, XM devotes bandwidth to error correction and concealment. The result is an extremely reliable delivery system that minimizes momentary signal losses from interfering with the continuous flow of music.
The combination of ultra-high powered satellites, critically important to penetrate foliage in heavily shaded suburban and rural areas, and an extensive ground-based repeater system, providing consistent coverage in cities, provides unparalleled signal coverage for the car and home in urban and rural areas alike.
XM’s Proven Chipset Technology
The third key component of the XM end-to-end system is its acclaimed chipset technology imbedded in XM-capable radios. XM and its technology partners STMicroelectronics and the Faunhofer Institute, world leaders in their field, created two custom integrated circuits that have worked flawlessly. They process the satellite and repeater signals and decode the music, speech and data to ensure an outstanding multimedia experience.
XM’s chipset technology execution and integration into radio production enabled the company to launch nationwide over 45 days in the fall of 2001. Due in large part to its proven chipset technology, XM was the first company to launch its product at electronic retail outlets nationwide, offering products for both the car and home. XM was also the first and is currently the only company to offer satellite radio as a factory-installed option in new cars, which require an extensive chipset validation process. General Motorswas the first automaker to roll out XM in new cars, beginning in 2002 Cadillac Sevilles and Devilles and expanding to twenty-five 2003 models later this year.