Netflix has rolled out a major audio upgrade for users of its Android mobile app.
The company has announced that sound on this platform will now be streamed in the xHE-AAC codec on devices running Android 9 or above.
“With its capability to improve intelligibility in noisy environments, adapt to variable cellular connections, and scale to studio-quality, xHE-AAC will be a sonic delight to members who stream on these devices,” Netflix stated.
The codec allows for higher fidelity audio through enhanced loudness management with the Enhanced HE-AAC codec and MPEG D DRC (Dynamic Range Control).
Netflix explained that these features were necessary for playback scenarios in which the large dynamic range of a TV show or movie is undesirable or even impossible – such as when low-fidelity earbuds or mobile device speakers are used, or users are watching content in noisy environments.
“If the dynamic range of a member’s device and environment is less than the dynamic range of the content, then they will not hear all of the details in the soundtrack,” Netflix stated.
“Or they might frequently adjust the volume during the show, turning up the soft sections, and then turning it back down when things get loud.”
“In extreme cases, they may have difficulty understanding the dialogue, even with the volume turned all the way up,” Netflix said.
DRC employs a sophisticated algorithm and metadata to boost softer sounds according to multiple situation-based profiles or by scaling gains.
Netflix provided two graphs that illustrate how DRC enhances the listening experience in a given environment which contained a large amount of background noise.
The first graph illustrates a situation in which it impossible to hear softer details below -40dBFS even when an elevated output level of -16dBFS is used for dialogue, indicated by the bold black lines.
The second figure shows the impact of adding DRC, which boosts softer sounds without changing the dialogue volume level, making them audible without requiring the user to change the volume.
Adaptive audio bitrate
In addition, xHE-AAC adds adaptive bitrate support to Android mobile devices, a feature which was previously launched on Netflix’s TV-based app.
This allows the audio quality to be automatically adjusted according to the strength of the network that is being used to stream the content.
The result is that buffering is minimised when the connection speed is slow while studio-quality sound can be delivered when the network is strong.