The AAC family of audio codecs comprises some of the most efficient audio coding technologies available today. Standardized by ISO MPEG, it is designed to provide high quality audio at lower bit-rates than previous MPEG audio coding formats.
The original MPEG-2 AAC codec was further reﬁned through the MPEG-4 standardization process and has subsequently been enhanced with bandwidth extension technology yielding HE-AAC (High Efficiency AAC), and with the addition of parametric stereo, resulting in HE-AAC v2.
Most recently, MPEG standardized the latest AAC enhancement xHE-AAC (Extended HE-AAC). xHE-AAC adds an optimized speech coding approach to the AAC family of codecs, resulting in a single audio coding system capable of maintaining exceptional quality starting at very low bit-rates with any type of program content, whether speech, music, or ambient sounds.
Via Licensing administers a joint patent license which provides a convenient and cost-effective way to acquire the rights to practice the essential AAC patents from a set of licensors. The AAC patent licensing program provides coverage for all the AAC technologies identiﬁed in the following diagram.
The core of this AAC family is a set of backwards-compatible audio coding technologies. For example, MPEG-4 AAC-LC (Low Complexity) decoders can playback MPEG-2 AAC-LC bit-streams, MPEG-4 HE-AAC (High Efficiency) decoders can playback both MPEG-4 and MPEG-2 AAC-LC bit-streams, etc.
In this way the AAC family with its latest enhancement, xHE-AAC can support a wide variety of applications ranging from extremely low bit-rates required for reliable speech and music delivery over 2G cellular phone networks, to “transparent” quality (indistinguishable from the original source material) for the most discriminating listeners.
Additional AAC technologies covered by the patent license include AAC-LD (Low Delay), AAC-ELD (Enhanced Low Delay) and AAC-ELD v2, which enable high quality audio for videoconferencing or other communications applications where low-latency performance is critical.
For additional information about Via’s AAC patent licensing program, please see our FAQ (Frequently Asked Questions) page. AAC FAQ>>
Via Licensing also offers joint patent licenses for two technologies that are complimentary to AAC, the MPEG Surround license and the MPEG-4 SLS license (as used in HD-AAC).