I am streaming music from a single controlling PC ("sender") to multiple PCs (receivers) on my LAN as described here:

https://www.freedesktop.org/wiki/Software/PulseAudio/Documentation/User/Network/#index2h3

All my PC's run Arch Linux and my backend is Phonon VLC (same setup on all, if that matters). My LAN is a wired Gigabit Ethernet. The problem I am having is that the receivers are out of sync by a very noticeable amount -- a full second or two.

All computers on my LAN use ntp and all show that they are synchronized and accurate:

sudo timedatectl status
System clock synchronized: yes
NTP service: active

My current setup is very simple for testing right now:

sender

pactl load-module module-null-sink sink_name=rtpsink1
pactl load-module module-rtp-send source=rtpsink1.monitor
pactl load-module module-combine-sink sink_name=rtp1combined slaves=abcd,wxyz

receivers

pactl load-module module-rtp-recv

All computers, including the sender, are playing audio. If I stand in a central location where I can here them all, none of them are in sync. The difference can be as great as at least a full second (maybe more).