Differences

The only difference between a "normal" interrupt and a source for the audioManagement may lie in it's classification, so playing a "normal" interrupt is not different to changing a source. An exception here are the so called "low level interrupts".

Criterias

These are special sources that fulfill the following criteria:

• direct connection to a sink that is "always on", so no extra actions and communications need to be done in order to play audio
• no dependencies to the current system state need to be checked before playing. This means that the source knows if it is allowed to play at the moment it wants to play
• all information for the source that is needed to judge if it is allowed to play or not is either directly retrieved by the source or set static via a property.

This becomes very handy for implementing such things like park distance control. When the source is informed that it needs to output signals (due to an emerging wall for example) it outputs the beeps directly to the amplifier that then overlays the sound to the current active source.
Settings that influence the behavior of low level interrupts like for example volume offset for park distance control or sound on/off for it need to be done via sourceProperties on the source level, so that the judgment and the adoptions that need to be taken can be taken by the source without system interaction. In order to give the AudioManagerController the chance to react on a low level interrupt (by lowering the main volume for example), a feedback path is provided and the AudioManagerController is informed about the current state of the low level interrupt (via hooklInterruptStatusChange).