Audio Codec Implementations

Fraunhofer IIS has been working on audio coding for more than 35 years and remains the worldwide respected authority in low bitrate high quality audio coding. Since 2012, the Fraunhofer IIS software implementations of the open ISO MPEG audio codecs AAC, HE-AAC, HE-AACv2 and AAC-ELD have been part of Android and the Android Open Source Project with the FDK AAC Codec Library. In 2018, the new version FDK2 was launched, and brings several new technologies to Android OEMs, service providers and developers, including xHE-AAC, MPEG-D DRC dynamic range control and AAC-ELDv2. Android users benefit from the high audio quality of the Fraunhofer FDK.

The Fraunhofer FDK2 AAC Codec Library for Android is a low resource implementation of AAC encoders and decoders available for Android on ARM and x86 processors and is available from the Android source code tree.

Fraunhofer continues to offer the CDK commercial libraries (see above), available for all major processors and operating systems, including iOS and Android under its standard commercial license. The Fraunhofer CDK software is also available for other MPEG audio standards.

AAC is an open MPEG standard and many companies and organizations participated in the technical development and standardization process. A patent licensing program is administered by Via Licensing Alliance. There are currently more than 10 billion licensed devices. Please contact VIA on https://www.via-la.com/ for information on whether your application is already covered by an existing license.

xHE-AAC extends the usable stereo bitrate range of AAC: from as low as 12 kbit/s up to 500 kbit/s, enabling subscription video on demand (SVOD) and streaming music distributors to globally offer an improved, more reliable consumer experience over congested networks and particularly in regions where consumers still rely on 2G or 3G connections. In addition, MPEG-D DRC will provide mandatory loudness control for xHE-AAC to playback content at a consistent volume and offers new dynamic range control profiles for listening in noisy situations.

AAC-ELD and AAC-ELDv2 provide up to CD-comparable audio quality for communications applications. They avoid many of the problems typically found in speech codecs used today for real-time communications applications such as audio and/or video chat and VoIP. These problems are caused by, for example, background noise, multiple talkers, children’s voices, ring-back tones, music on hold, and music in general. AAC-ELD and AAC-ELDv2 enable new Android communication apps and services to transform everyday communications into an emotional, state-of-the-art rich-media experience.

HE-AACv2 and HE-AAC Multichannel for high quality 5.1 surround sound are used in TV, radio and streaming services worldwide.

AAC-LC is the high-performance audio codec for excellent audio quality. First used by the Japanese digital broadcasting system ISDB and for music download and mobile music playback, today AAC is used in all state-of-the-art consumer electronics devices.

Fraunhofer IIS has been working on audio coding for more than 35 years and remains the worldwide respected authority in low bitrate, high-quality audio coding. Since 2012, the Fraunhofer IIS software implementations of the open ISO MPEG audio codecs AAC, HE-AAC, HE-AACv2 and AAC-ELD have been part of Android and the Android Open Source Project with the FDK AAC Codec Library. In 2018, Fraunhofer FDK2 was launched in Android AOSP which added AAC-ELDv2 encoding and decoding as well as xHE-AAC decoding with mandatory support for MPEG-D DRC dynamic range control and loudness metadata.The Fraunhofer FDK Extended High Efficiency AAC Encoder Software for Android was launched with Android 17 in 2026. For the first time, Android developers can now encode xHE-AAC directly on the device.

With the publication of GSMA's Rich Communication Services (RCS) Universal Profile v3.1 and 4.0, xHE-AAC has become the recommended codec for audio messaging and high-quality media sharing over RCS and the mandatory default on devices that support the codec for encoding and decoding. The Fraunhofer FDK Extended High Efficiency AAC Encoder provides a high quality, high efficiency, low bit rate encoder for use in RCS. Other Android applications for audio recording, audio and video editing as well as user-generated content (UGC), can also benefit from the superior auditory experience offered by xHE-AAC.

The Fraunhofer FDK Extended High Efficiency AAC Encoder Library for Android is an implementation of an MPEG-D USAC encoder with mandatory MPEG-D DRC available for Android on ARM and x86 processors and is available from the Android source code tree.

Fraunhofer IIS continues to offer professional xHE-AAC audio encoder libraries, available for all major processors and operating systems, including macOS, Windows, Linux, iOS, and Android under its standard commercial license. The professional Fraunhofer IIS encoder offers extended features and expert support. In addition, Fraunhofer offers a specifically tailored version of the professional audio encoder libraries implementing the advanced components and functionalities required for digital radio broadcasting services, such as DRM (Digital Radio Mondiale) and similar standards.

The AAC family of codecs is published as a series of open MPEG standards and many companies and organizations participated in the technical development and standardization process. A patent licensing program is administered by Via Licensing Alliance. Please contact VIA on https://www.via-la.com/ for information on whether your application is already covered by an existing license.

Extended High Efficiency AAC has been built for efficiency and quality. The codec supports adaptive streaming from 12 to over 320 kbit/s, includes mandatory loudness and dynamic range control, and improves both speech clarity and stereo imaging. For mobile network operators deploying RCS, this marks a major step forward in delivering high-quality audio messaging to users – right within their native messaging apps. That means clearer voice notes, better intelligibility, stereo audio, and a more consistent listening experience – even in challenging network conditions.

xHE-AAC is the combination of Extended High Efficiency AAC with MPEG-D DRC. xHE-AAC and its associated logo are registered trademarks of Fraunhofer in Germany, the United States and other countries. Fraunhofer offers a free, web-based xHE-AAC codec test service at https://test.xhe-aac.com/ as a requirement to obtain an xHE-AAC trademark license. You can find more details on the xHE-AAC Trademark Program here.