As the player program is refilling it's cache from disk, network-traffic seems to stop completely for some seconds, though this is probably due to the realtime-environment in which the player is running.

Yes. If you're talking about protocol traffic to emplode/emptool, then the player thread which services this traffic runs at lower priority than the other player threads. If you're talking about another process running alongside the player, then unless it's SCHED_RR it'll be running at much lower priority than the player -- indeed, if any SCHED_RR thread or process is runnable, no other process will run.

Peter