aubuf with smart maximum

[cspiel1]

The Discussion feature https://github.com/baresip/re/discussions is very handy. Should we also enable this for rem?

This is not an issue, more a discussion about aubuf.

The idea is to have an audio buffer that have:

• min frame size
• max frame size
• smart max frame size, with silence detection (supporting the multiple sample formats)

If a smart max size is specified (smaller than the max size) and an upper boundary for the sample value, then a frame is dropped only if it is a silence frame.

About the solution:

• aubuf seems only buffer byte arrays
• maybe audio processing should be converted to track auframe queues

[sreimers]

This PR adds aubuf auframe support #7
It still needs to be better tested, but should be almost ready.

[cspiel1]

So now this would make it possible to add a silence detection for all supported sample formats, right?

[sreimers]

Yes that should be possible. This week I am a bit busy due to other project deadlines. Will test and merge the PR next week.