  Networked Music Performance (NMP) systems involve musicians located in
different places who perform music while staying synchronized via the Internet.
The maximum end-to-end delay in NMP applications is called Ensemble Performance
Threshold (EPT) and should be less than 25 milliseconds. Due to this
constraint, NMPs require ultra-low delay solutions for audio coding, network
transmission, relaying and decoding, each one a challenging task on its own.
There are two directions for study in the related work referring to the NMP
systems. From the audio perspective, researchers experiment on low-delay
encoders and transmission patterns, aiming to reduce the processing delay of
the audio transmission, but they ignore the network performance. On the other
hand, network-oriented researchers try to reduce the network delay, which
contributes to reduced end-to-end delay. In our proposed approach, we introduce
an integration of dynamic audio and network configuration to satisfy the EPT
constraint. The basic idea is that the major components participating in an NMP
system the application and the network interact during the live music
performance. As the network delay increases, the network tries to equalize it
by modifying the routing behavior using Software Defined Networking principles.
If the network delay exceeds a maximum affordable threshold, the network reacts
by informing the application to change the audio processing pattern to overcome
the delay increase, resulting in below EPT end-to-end delay. A full prototype
of the proposed system was implemented and extensively evaluated in an emulated
environment.
