Website for the 2020 Linux Audio Conference held in Bordeaux, France
25-27 Nov 2020 Talence (France)
EXPRESS DATA PATH KERNEL OBJECTS FOR REAL-TIME AUDIO STREAMING OPTIMIZATION
Christoph Kuhr  1@  , Alexander Carôt@
1 : -

Using a JACK media clock listener to synchronize JACK to an AVTP
media clock talker results in performance issues when used with a
raw Ethernet socket under Linux. The packet rate of a class A AVTP
audio stream of 8 kHz triggers too many interrupts in the CPU. As
a result a JACK audio cycle has only 125 μsec to process the au-
dio data of all JACK clients. This restriction prevents such a system
from real-time signal processing. The extended Berkley Packet Fil-
ter in combination with the express data path kernel features, that are
integrated in the Linux kernel since version 4.8, are investigated. We
could optimize the media clock synchronization by using a eBPF
XDP program for pre processing of the stream packets. Our de-
scribed solution is meant as an alternative to the usage of generic
raw sockets.


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