The window must be designed around the slowest channel

What it is

Multichannel synchronization should be designed around the slowest channel. Timing to the fastest channel guarantees the slow one lags; the right move is to make the fast channel wait so all arrive together. The first step in synchrony design is therefore locating the slowest link.

Why it happens

The reason is that the integration window is stricter about lag than about lead: as noted earlier, haptics lagging are harder to accept than haptics leading, and visual–auditory pairings behave similarly. Letting the fast channel wait slightly, with the slow channel setting the timing, therefore works better than asking the slow channel to catch up. The practical method is a latency budget: list each channel's end-to-end latency, take the maximum as the shared baseline, and add compensation delay to the faster ones. Distinguish fixed delay from jitter—fixed delay can be aligned by compensation, while jitter can only be absorbed as extra tolerance.

Studying it

Proceed in two steps: first measure the end-to-end latency distribution per channel (mean and jitter), then use simultaneity judgment to verify that aligning to the slowest channel still reads as one event. Variables include channel pairing, link load, and device type. Outcomes include actual alignment error and integration judgment accuracy. Report both latency statistics, since they call for different handling.

Where it stops holding

When the slowest channel's latency far exceeds the integration window—a network round trip, or scent release—forcing alignment would make other channels wait so long that causality itself breaks, and the right move is to redesign the information rather than keep aligning. If a channel's latency is unpredictable, including it in the synchronization scheme introduces jitter and may need to become an independent later state update.

Applying it

• List mean and jitter of end-to-end latency per channel and use the maximum as the shared baseline.
• Add stable compensation delay to the faster channels so all arrive at the same moment.
• Keep unpredictable channels out of the synchronization scheme, presenting them as independent later updates.
• Verification: measure post-alignment error and users' integration judgments; if they still perceive two events, the slowest channel has exceeded the window.

Related

• Within the group: D4.06.1 Signals from different senses must fall inside one narrow window to fuse · D4.06.3 Window width differs by sensory pairing
• Adjacent: D3.04.4 Network and rendering latency are the usual cause of a broken sync window · I3.02 Optimistic updates and rollback under network latency
• Search terms: latency budget · slowest channel · compensation delay