We have a HLS stream with two audio variants, both in aacl, one with 2 channels, and the other one with 6 channels. When trying to validate it with the streamvalidator we got the following MUST FIX:
But the playback on iOS using the AVPlayer is working with no noticeable issues. Can you please detail where is this limitation coming from? Supported at what level? Is it a decoder issue? Is it really a must fix? What are the potential risks of ignoring it?
According to the HLS Authoring Specification for Apple Devices the only multichannel audio we support is AC-3 and E-AC-3.
The hlsreport script is complaining that the audio in Rendtion #5 is multichannel, but not one of these formats.
Since you have 2-channel audio the stream is playable on all devices.
It may be that the 6-channel version is playing when you have multi-channel output (or playing some of the channels) but we do not officially support that.
Since we do not support it, you have no guarantee that such audio will continue to work in future versions.
The 'Must Fix' category is not only for things that are broken. It also covers things that are unsupported, or that we believe are ill-advised.