The Java Media Framework (JMF) is an API for incorporating audio, video, and other time-based media into Java applications and applets. It is an optional package that extends the multimedia capabilities on the Java2 platform. The Blackdown JMF is a Performace Pack which includes native code in order to provide faster processing and tighter integration with Linux than the all-Java version.
JACK is a low-latency audio server. It can connect a number of different applications to an audio device, as well as allowing them to share audio between themselves. Its clients can run in their own processes (i.e., as normal applications), or can they can run within the JACK server (as a "plugin"). JACK is different from other audio server efforts in that it has been designed from the ground up to be suitable for professional audio work. This means that it focuses on two key areas: synchronous execution of all clients, and low latency operation.