The PA specification is unclear about exactly what returning paAbort from a callback means. There are various possible interpretations/implementations. What is possible is often determined by the platform, so we will never have complete consistency, but abort should probably mean "abort as quickly as possible". Here are some options:

1. do the same as paComplete (ie play out all remaining data)
2. immediately stop queuing more data with the native api. mark the stream as finished/inactive.
3. as for (2) but also tell the native api to stop immediately/abort

In PA/WMME we could call waveOutReset from the callback to effect (3). At present we don't.