When a 'ML_BUFFERS_COMPLETE' message is sent, what does that actually officially mean? The specs state that the "buffer has been processed", but that is rather vague.

Does it simply mean the device/module is done with the buffer memory, and that can now be reused?

Or, does it mean the device has finished sending the contents of that buffer to the output jack? (i.e. audio data, for example, has finished coming out of the speakers.)