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xHE-AAC Audio Streaming

1 post · Jan 2021

What this trail covers

Netflix is evolving its audio streaming capabilities by implementing Extended HE-AAC with MPEG-D DRC (xHE-AAC) for compatible Android mobile devices. This technology improves intelligibility in noisy environments, adapts to variable cellular connections, and scales to studio-quality audio. The system leverages MPEG-D DRC metadata for loudness management, ensuring consistent dialogue levels across all content, and for dynamic range control, optimizing the audio experience for various devices and environments. This builds upon previous efforts in adaptive bitrate audio and Dolby Atmos.

All Netflix trails
  1. Optimizing the Aural Experience on Android Devices with xHE-AACThis post introduces the implementation of xHE-AAC on Android devices. It details the technical aspects of MPEG-D DRC, including its use for loudness management by normalizing dialogue levels using anchorLoudness metadata and decoder-side gain. It also explains dynamic range control (DRC) using the uniDRC payload to adapt audio to different playback environments and devices, reducing dynamic range where necessary without affecting dialogue. The post highlights the use of Android's MediaFormat APIs and specific keys like KEY_AAC_DRC_TARGET_REFERENCE_LEVEL.