xHE-AAC (Extended HE-AAC), the application form of MPEG-D USAC, is the most flexible member of the AAC family. A single codec handles both speech and music seamlessly by switching coding tools per frame, and it scales smoothly across a very wide bitrate range — from roughly 12 kbps up to transparency — which makes it ideal for adaptive streaming where the same content must serve weak and strong connections. It also ships with MPEG-D DRC loudness and dynamic-range metadata, so playback can normalize loudness without re-encoding. Adoption is growing on Android and in streaming, though xHE-AAC still trails plain AAC-LC in universal hardware support.
