Why xHE-AAC is being embraced at Meta
- We’re sharing how Meta delivers high-quality audio at scale with the xHE-AAC audio codec.
- xHE-AAC has already been deployed on Fb and Instagram to supply enhanced audio for options like Reels and Tales.
At Meta, we serve each media use case possible for billions of individuals the world over — from short-form, user-generated content material, corresponding to Reels, to premium video on demand (VOD) and live broadcasts. Given this, we’d like a next-generation audio codec that helps a variety of working factors with glorious compression effectivity and fashionable, system-level audio options.
To deal with these wants now and into the long run, Meta has embraced xHE-AAC because the automobile for delivering high-quality audio at scale.
The advantages of xHE-AAC
xHE-AAC is the most recent member of the MPEG AAC audio codec household. The Fraunhofer Institute for Integrated Circuits IIS performed a considerable function within the growth of xHE-AAC and the MPEG-D DRC commonplace.
At present, xHE-AAC is already offering a superior audio expertise on Fb and Instagram — together with on Reels and Stories — and has a lot of precious options.
Loudness administration
With hundreds of millions of uploads per day across Facebook and Instagram, we obtain audio tracks with loudness ranges starting from silence to full scale, and all the pieces in between.
When folks play these movies sequentially, they will understand some audio as being too loud or too quiet. This creates listener fatigue from having to continuously regulate the quantity.
xHE-AAC’s built-in loudness administration system solves for loudness inconsistency whereas meticulously preserving creator intent by bringing the common loudness of all periods to the identical goal stage and managing the dynamic vary of every session to suit the playback atmosphere.
As an alternative of burning in a particular goal stage and dynamic vary compression (DRC) profile throughout encoding, xHE-AAC permits us to depart the unique audio traits untouched and delegate loudness administration processing to the consumer by way of loudness metadata, for the optimum audio expertise primarily based on context.
On account of xHE-AAC’s loudness administration, folks can spend extra time immersed of their favourite content material and fewer time twiddling with the quantity management.
Adaptive bit charge audio
Most individuals who use our apps devour media on cellular gadgets and count on the best audio high quality with out interruption. This presents a problem for streaming media as a result of connection high quality varies on cellular and can lead to a really uneven person expertise.
To optimize high quality below dynamic bandwidth constraints, we produce multiple video and audio qualities to match various community circumstances at playback time. Despite the fact that we produce a number of audio lanes, now we have traditionally solely employed adaptive bit rate (ABR) algorithms to modify video qualities throughout playback as a result of it’s tough to allow adaptive bit charge audio with out compromising high quality throughout lane transitions.
In an effort to allow seamless audio ABR, xHE-AAC introduces the idea of rapid playout frames (IPFs) that include all the information vital to begin enjoying a brand new audio lane with out counting on information from different frames. By inserting an IPF in the beginning of every Dynamic Adaptive Streaming over HTTP (DASH) phase and aligning the phase durations of every lane, we will seamlessly change between audio lanes throughout playback to supply the highest-quality audio at any obtainable bandwidth whereas avoiding playback stalls.
After launching audio ABR on Fb for Android, we have been in a position to enhance person expertise by decreasing the variety of periods the place playback stalls.
How we deployed xHE-AAC
We generate xHE-AAC bitstreams utilizing an encoder SDK offered by the Fraunhofer Institute for Built-in Circuits IIS, after which put together the ensuing audio information for DASH streaming with shaka-packager. The xHE-AAC encoder’s two-pass encoding mode is used to measure the enter loudness envelope and common program loudness on the primary move and carry out the precise audio information compression on the second move. As an additional benefit, two-pass encoding permits us to make use of loudness vary management (LRAC) DRC, which mitigates pumping artifacts in any other case launched by single-pass DRC algorithms. 
To arrange an xHE-AAC audio adaptation set for ABR supply, IPFs are inserted at fixed time intervals, audio configuration parameters corresponding to pattern charge and channel configuration are stored fixed, and distinctive stream identifiers are chosen for every lane within the audio adaptation set.
At playback time, we custom-fit the audio to the listening atmosphere by configuring a goal loudness stage and DRC impact kind primarily based on context, and due to the embedded loudness metadata, we will adapt a single xHE-AAC bitstream to a wide range of audio consumption use circumstances, from headphones to gadget audio system and varied ranges of background noise. Lastly, if the consumer is starved for information or bandwidth is plentiful, audio ABR will robotically change audio qualities to make sure that the best audio high quality is performed with out interrupting the playback session.
The place are you able to expertise xHE-AAC immediately?
You possibly can expertise xHE-AAC audio on Fb for iOS and Android, in addition to on focused surfaces on Instagram, corresponding to Reels and Tales. We encourage you to put in the most recent model of Fb and Instagram apps on iOS 13+ and Android 9+ to make sure which you could expertise it.
Acknowledgements
This work is the collective results of your entire Video Infrastructure and Instagram Media Platform groups at Meta in collaboration with Fraunhofer Institute for Built-in Circuits IIS. The creator want to prolong particular due to Abhishek Gera, Tim Harris, Arun Kotidath, Edward Li, Meng Li, Srinivas Lingutla, Denise Noyes, Mohanish Penta, David Ronca, Haixia Shi, Mike Starr, Cosmin Stejerean, Simha Venkataramaiah, Juehui Zhang, Runshen Zhu, and the engineering staff at Fraunhofer Institute for Built-in Circuits IIS.