Fraunhofer Institute for Integrated Circuits IIS


xHE-AAC - bridging the gap

  • Speech and Audio Coding at 16 kbit/s (stereo)
  • Mandatory Codec for DRM
  • Codec of Choice for Low Bit Rate Streaming

xHE-AAC (Extended HE-AAC), the latest upgrade to the MPEG AAC codec family, is the audio codec of choice for digital radio and low bit rate streaming applications. Selected as the mandatory audio codec for DRM (Digital Radio Mondiale), xHE-AAC bridges the gap between speech and audio coding, and provides consistent high quality audio for all signal types, such as talk radio, a music program or a jingle.

Another important feature is the codec’s coding efficiency. Starting at 8 kbit/s mono, xHE-AAC allows the transmission of good audio quality and, in addition, the delivery of more audio programs. xHE AAC therefore enables new services even on bit rate constrained networks.

Composition and compatability of xHE-AAC

xHE-AAC profile decoders are capable of decoding all AAC versions including AAC-LC, HE-AAC and HE-AACv2. xHE-AAC streams can easily be integrated into existing encoding workflows by supplementing legacy higher bit rate streams.


Its special features make xHE-AAC the ideal codec for digital radio and low bit rate streaming.


DRM is a typical application scenario for xHE-AAC. The digital radio standard adopted xHE-AAC as mandatory audio codec in 2013. xHE-AAC is a superset of the MPEG HE‑AAC codec used for all DRM transmissions to date. Of course, HE‑AAC remains available as part of the DRM standard to retain compatibility with existing systems. DRM broadcasters benefit from a simplified codec configuration process: All quality relevant parameters are automatically optimized internally by the encoder, and the need to change configuration settings depending on the type of audio content being broadcast is eliminated.

xHE-AAC for audio streaming applications

Further application scenarios include streaming on 2G, 3G and 4G networks as well as on WiFi. xHE-AAC improves reliability as it permits the transmission of good audio quality starting at bit rates as low as 6 kbit/s per channel, even over congested networks. In addition, low bit rate streaming carries the potential of significant cost savings for service providers as well as listeners. The latter will also have more streaming time available before reaching their data plan limit.


Codec implementations of xHE-AAC for use in DRM and streaming applications are available for the following hardware platforms:

  • PC (Windows/Mac OS X/Linux)
  • ARM (decoder only)
  • MIPS (decoder only)
  • Texas Instruments C6x, DaVinci, OMAP (decoder only)
  • Analog Devices Blackfin (decoder only)
  • Apple iOS® SDK (decoder only)
  • Android™

DRM broadcast encoder solutions based on Fraunhofer’s ContentServer technology, as well as third-party implementations, already support xHE-AAC. All DRM receiver chipsets belonging to the initial mass-market generation include xHE-AAC from market launch.

Patent licensing:

Via Licensing has issued a call for essential patents for the USAC Baseline Profile to enable a patent pool license for xHE-AAC which is expected to be available in 2015.

Please contact us for an individual license to the related Fraunhofer patents.

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