HLS Authoring Specification for Apple TV

2.4 You SHOULD NOT use HE-AAC if your audio bit rate is above 64 kb/s.

I saw this requirement in the HLS Authoring Specification for Apple TV.

And in the section 2.8, it says AAC is recommended upto 160 kb/s

Does that mean that we can use LC-AAC or is it a typo or something?

Bit rate recommendationsAudio channelsFormatTotal (kb/s)2.0 (stereo)

AAC

32 to 160

5.1 (surround)

Dolby Digital

384

5.1 (surround)

Dolby Digital Plus

192

7.1 (surround)

Dolby Digital Plus

256


https://developer.apple.com/library/tvos/documentation/General/Reference/HLSAuthoringSpec/Requirements.html#//apple_ref/doc/uid/TP40016596-CH2-SW1

Accepted Reply

AC3 will only be selected if the device is attached to a multichannel capable output.


You'll want to provide a low bitrate option using AAC-HE (associated with your low bitrate video variants), a high bitrate stereo option using AAC-LC (associated with your higher bitrate video variants), and then if you have a multichannel payload, provide that using AC3. AVFoundation will only download the segments required based on output hardware and the available bandwidth.

Replies

Hi Dvyz,


For stereo audio above 64 kbps, you should use regular AAC (i.e. LC-AAC). Below that, you can use HE-AAC.

Thank you. Can we use AC3 for Above 64kbps? we are planning to use 96kbps and we have AC3 alternate audio. We may have to make that primary if possible.

AC3 will only be selected if the device is attached to a multichannel capable output.


You'll want to provide a low bitrate option using AAC-HE (associated with your low bitrate video variants), a high bitrate stereo option using AAC-LC (associated with your higher bitrate video variants), and then if you have a multichannel payload, provide that using AC3. AVFoundation will only download the segments required based on output hardware and the available bandwidth.