Technical Q&A QA1811

Audio Server PlugIn - The AudioServerPlugIn_MachServices plist Key

Q:  How does my user-space plug-in talk to other processes?

A: An AudioServerPlugIn operates in a limited environment. First and foremost, an AudioServerPlugIn may not make any calls to the client HAL API in the CoreAudio.framework. This will result in undefined (but generally bad) behavior.

Further, the host process is sandboxed. As such, an AudioServerPlugIn may only read files in its bundle in addition to the system libraries and frameworks. It may not access user documents or write to any filesystem locations other than the system's cache and temporary directories as derived through Apple API. The host provides a means for the plug-in to store and retrieve data from persistent storage.

An AudioServerPlugIn may communicate with other processes on the system. However, the plug-in must list the name of the mach services to be accessed in the plug-in bundle's info.plist in a key named "AudioServerPlugIn_MachServices". The value of this key is an array of the names of the mach services that need to be accessed.

Figure 1  AudioServerPlugIn_MachServices Usage.

See the AudioServerPlugIn.h header file for further details regarding Audio Server plug-ins.

Sample Code

Core Audio User-Space Driver Examples

Document Revision History


First Version


New document that discusses the use of the AudioServerPlugIn_MachServices key to talk to other processes.