xHE-AAC^®

xHE-AAC, the combination of Extended HE-AAC and MPEG-D DRC and the latest addition to the MPEG AAC codec family, bridges the gap between speech and audio coding. It provides consistently high quality audio for all signal types, such as speech, music or mixed content, at all bit rates – starting as low as 6 kbit/s for mono and 12 kbit/s for stereo services, up to 320 kbit/s and above. This makes xHE-AAC the audio codec of choice for digital radio and adaptive streaming applications. It is a mandatory audio codec in Digital Radio Mondiale (DRM), Google's Android operating systems, and Apple´s iOS.

Adaptive Streaming

xHE-AAC was inherently designed for adaptive streaming: its bit rate flexibility enables MPEG-DASH or HLS streaming apps and streaming radio players to switch to very low bit rate streams and offer continuous playback even under challenging network conditions. When network connectivity recovers, the xHE-AAC player will adapt to a higher bit rate and seamlessly switch over the full range of bit rates, up to transparent quality. Additionally, the outstanding coding efficiency of xHE-AAC means the bit rate saving can be invested in improving the video quality of mobile video streaming.

Loudness and Dynamic Range Control

MPEG-D DRC – Loudness and Dynamic Range Control – provides mandatory loudness control for xHE-AAC to play back content at a consistent volume and offers dynamic range control processing to provide the best possible user experience for listening on any platform and in any environment.

Compatibility of xHE-AAC

xHE-AAC profile decoders are capable of decoding all AAC versions including AAC-LC, HE-AAC and HE-AACv2. It is easy to integrate xHE-AAC streams into existing encoding workflows by supplementing legacy higher bit rate streams.

With its special features, xHE-AAC effortlessly meets the requirements of digital radio, audio messaging, and mobile audio as well as video streaming applications, where various audio content types need to be transmitted at very low bit rates.

Streaming  

xHE-AAC stands for state-of-the-art audio coding with bit rates from 6 kbit/s mono to excellent stereo quality. Metadata-based loudness management and DRC enable the production and transmission of one audio stream for all devices and target loudness levels. Low bit rates reduce running CDN cost. The codec makes it possible to reach billions of users in emerging markets where 2G/3G networks still exist in significant numbers and wherever heavily congested 4G/5G networks in major cities or heavy traffic are common. 

Live Programs

For the encoding of live streaming programs (such as concerts, sports events, and news streams) with xHE-AAC, the encoder is equipped with the Live Automatic Loudness feature. This offers a fully automated, unattended loudness control for live signals, while preserving much of the signal’s dynamic range and loudness transients. Live content is played by an xHE-AAC decoder at a loudness level consistent with other xHE-AAC content. As the feature is completely integrated with the xHE-AAC encoder, users do not need to make any adjustments.

Digital Radio Mondiale (DRM)

DRM is the first digital radio standard to adopt xHE-AAC (mandatory since 2013) and benefit from its features. As xHE-AAC is a superset of the MPEG HE‑AAC codec used for all DRM transmissions to date, HE‑AAC remains available as part of the DRM standard to retain compatibility with existing systems. With xHE-AAC, DRM broadcasters can now use the same codec for all types of content and benefit from a simplified codec configuration process: The encoder automatically optimizes all quality-relevant parameters, eliminating the need to change configuration settings depending on the type of audio content being broadcast. In addition, the reduced bit demand of the codec allows the delivery of a broader range of audio programs.

Audio Messaging

As part of the RCS 3.1 standard by GSMA, xHE-AAC enables the highly efficient encoding and decoding of shared audio content. This enhances the quality both of speech and non-speech applications significantly. Whether users are sending voice notes, ambient sound clips, or business messaging content such as advertisements, they can now expect clearer, more natural playback. In China RCS is known as 5G Messaging.

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

• Windows (x86 and ARM)
• Linux (x86 and ARM)
• macOS/Darwin (Universal)

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.

Further information about our development and design kits can be found on our "Platforms" page.

Fraunhofer Software Implementations

If you are interested in licensing software from us, please fill out the request form below.

Third Party Software Providers

xHE-AAC encoders and decoders are not only available directly through Fraunhofer. Examples of products that integrate the Fraunhofer xHE-AAC codec libraries are:

• MainConcept(R) AAC family SDK and FFmpeg Plugin
• Poikosoft xHE-AAC Encoder as part of the EZ CD Audio Converter, a Windows stand-alone application
• Sonnox Fraunhofer Pro-Codec real-time codec auditioning plugin for digital audio workstations

Patent Licensing

xHE-AAC is part of the AAC patent pool licensing program administered by Via Licensing Alliance. Please visit https://www.via-la.com/ for more information or contact contracts@via-la.com.

xHE-AAC is a registered trademark of Fraunhofer in Germany, the United States and other countries.