Usage with live sources
Hi there, I was interesting in using Exhale as a library and encoding live audio (and specifically, muxing into fragmented mp4 with HLS).
The one thing I'm a bit hung up on is what to use for loudness metadata when I'm dealing with a live, non-seekable source. As far as I know, it's not possible to encode loudness info in a setup like this. I can only add the loudness info after analyzing the audio, at which point the event is over and, y'know, it's not live. The HLS specs state:
2.22. For xHE-AAC, loudness metadata MUST be present according to the Basic Loudness Metadata specified in ISO 23003-4 Table I.5; samplePeakLevel or truePeakLevel MUST be present. The methodDefinition SHOULD be 2 for video content.
So, loudness metadata has to be there, but HLS supports live content - so I guess there's some way to indicate that DRC is essentially disabled (setting a peak level to 0?). I don't have the ISO 23003-4 specs, so I don't know how to construct a value for this.