OMI glTF Subgroup Meeting 2021-09-02

[robertlong]

We want to decide on two things:

1. Are we going to stick with supporting MP3 as the default audio format or are we going to forgo a default format and use extensions to define the formats used in a glTF file?

2. We're currently using a volume field for emitters. Are we going to switch to gain as a unitless multiplier of the source audio, a decibel gain ratio, or an absolute volume decibel value? If we go with an absolute value, how will that work?

@mrmetaverse will also lead us in a short session to start defining our group's working agreement as we discussed in the OMI Weekly Meeting.

[robertlong]

The feedback from the meeting was that we will go with mp3 as the default audio format and future extensions may be used to add additional formats. However, we currently have no plans for additional extensions.

We found that we will want to make the audio emitter's source field optional to allow for required audio format extensions or future extensions that may provide other options for audio sources.

We also discussed audio loudness units and came to a general consensus that moving from a 0 - Infinity volume field to a 0 - Infinity gain field makes the most sense. It will be a unitless multiplier and can be converted to decibels in tooling/engines. For normalizing audio volumes in a scene, authoring tools should be responsible for adjusting gain based on their own heuristics.

Additional extensions may be authored down the line that will provide for "physical audio" definitions and can augment the audio emitter with the relevant fields.