Answer

To ensure consistent end-to-end latency and sufficient quality of transmitted media, Q-SYS utilizes time-sensitive protocols to synchronize and transport payload through the network. The primary synchronization protocols, PTPv1 (Dante) and PTPv2 (Q-LAN, AES67, etc.), continuously measure the network's latency and update each participating peer's timing parameters. Changes in network latency, referred to as ‘jitter’, can cause devices to lose synchronization for short periods, potentially causing audible artifacts in signals transmitted into a given space.

Media payload packets such as Q-LAN require regular, timely delivery for good-quality signals to reach listeners. For example, a single Q-LAN stream is comprised of 3000 packets per second.  If packets are delivered late due to jitter or excess end-to-end latency, one can quickly see how the signal quality would start to suffer.  

To quantify this, The Q-SYS network must meet specific timing performance criteria under load:

• The maximum allowable jitter for PTPv2 clock steering is +/-30µ seconds. Any jitter within the network exceeding this threshold will result in PTPv2 issues.
• The maximum acceptable latency for Q-LAN audio packets is 280µ seconds. If the latency within the network exceeds this limit, it will lead to issues with audio quality.

In standard Ethernet networks that do not employ prioritization, time-sensitive packets can be delivered inconsistently or even out of order depending on the other traffic flowing on the network. This can happen even in cases where bandwidth is plentiful. Q-SYS recommends employing Quality of Service (QoS) to ensure that the network can meet the criteria above. QoS allows for time-sensitive protocols to be prioritized and guarantees delivery with minimal jitter and latency.

For detailed information on the suggested QoS settings, please see the following information in Q-SYS Help, Q-SYS QoS.