Q-LAN

showstack / protocols / q-lan

Also called QLAN.

QSC's gigabit audio and video transport for the Q-SYS ecosystem, carrying low-latency streams between Cores, peripherals and cameras with PTPv2 clocking. It is what a Q-SYS install runs on even when Dante or AES67 cards are also fitted.

Audio transportProprietary, documentedQSCReported

Stewarded by QSC (Q-SYS).

Media Large, continuous, on time and in order

Continuous streams that are large enough to be sized properly, and that must arrive in order and on time.

What kills it. Anything that starves the link — usually a management transfer nobody scheduled — and jitter that outruns the receive buffer.

The four flows, and why the model is worth having →

What it carries

Audio bit depth: 32-bit
Audio encoding: 32-bit floating point linear PCM

Audio: QSC documents the word length and the packet layout — 16 samples for each of up to 16 channels per stream packet, 1100 octets including overhead, up to 128 streams per Core — but does not state a sample rate in current documentation. The 48 kHz figure widely quoted for Q-LAN traces back to a 2009 white paper, so it is deliberately not repeated here. Confirm against your Q-SYS release.

What goes wrong

Q-LAN marks its PTPv2 clock DSCP 46 (EF) and audio DSCP 34, while Dante marks AUDIO as DSCP 46. Shared fabric puts Dante audio in the queue that carries the Q-LAN clock and can starve it: separate by VLAN or remap.

Q-LAN audio moves in fixed 16-channel streams at 48 kHz/32-bit (roughly 33 Mbps each), so channel counts round up to the next stream whether you use the channels or not.

Like every PTP-clocked transport it assumes IGMP snooping with a querier and no Energy Efficient Ethernet on AV ports; QSC's switch requirements are explicit about both.

What speaks Q-LAN (1)

Product	Direction	Notes
Q-SYS Core 510i QSC (Q-SYS)	bidirectional	Native transport to Q-SYS peripherals, cameras and other Cores.

Typical use

Q-SYS Core to peripheral audio and video transport in installed systems
Corporate, hospitality and themed-venue AV backbones built on Q-SYS

Sources

Q-LAN Networking, Q-SYS 8.1 help — QSC primary
Quality of Service settings across QLAN, Dante, and AES67 — Q-SYS (QSC) primary
Q-SYS Networked Systems Technical Notes (Q-LAN) — QSC primary
Q-SYS Ethernet switch requirements — Q-SYS (QSC) primary

Understand the mechanism

Show networks Numbers that stand for signals

Something wrong, or missing?

Known gaps on this entry: default_ports, first_published, implementations, spec_url. If you can source one of them, that is a ten minute pull request.

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