The license states that the library may only be used for purposes as authorized by patent licenses. The license included by Fraunhofer in the FDK library source code allows redistribution in source or binary forms, but does not license patented technologies described by the code. The media frameworks FFmpeg and Libav support audio encoding through libfdk-aac. The code compiles into a shared library, libfdk-aac. Ī cross-platform source distribution is maintained by Martin Storsjö as part of the opencore-amr project under the name fdk-aac. The library allows overriding the low-pass filter setting, and in the highest VBR mode effectively applies no filter at all. In some, not completely rare, combinations the missing high frequencies are noticeable. Higher frequencies are removed so that more bits are available to better describe sounds of lower frequencies, improving the overall quality for most combinations of recordings and listeners. The FDK AAC encoder employs a more aggressive default low-pass filter than is used in other codecs. xHE-AAC also includes MPEG-D DRC mandatory loudness control to playback content at a consistent volume and offers new dynamic range control profiles for listening in noisy situations.

xHE-AAC extends the operating range of the codec from 12 to 300 kb/s for stereo signals and allows seamless switching between bitrates over this range for adaptive bitrate delivery (using standards such as MPEG-DASH or HLS for example). Version 2 of the library, introduced with Android P, also includes support for xHE-AAC and AAC-ELD v2. Those versions of the encoder, however, are not open-source and require a commercial license. Other versions of the Fraunhofer encoder, like the one included in Winamp, are optimized for encoding music on desktop-class processors. The library is currently limited to 16-bit PCM input. The Android-targeted implementation of the Fraunhofer AAC encoder uses fixed-point math and is optimized for encoding on embedded devices/mobile phones. The encoding library supports sample rates up to 96 kHz and up to eight channels (7.1 surround). It supports several Audio Object Types including MPEG-2 and MPEG-4 AAC LC, HE-AAC (AAC LC + SBR), HE-AACv2 (LC + SBR + PS) as well AAC-LD (low delay) and AAC-ELD (enhanced low delay) for real-time communication. Fraunhofer IIS, developed this library for Android 4.1. 'Fraunhofer FDK AAC license' (a free software license without a patent grant) įraunhofer FDK AAC is an open-source library for encoding and decoding digital audio in the Advanced Audio Coding (AAC) format.

Android ffmpeg library