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Chaining

Chaining refers to the practice of keeping the timing boundaries of adjacent events flush against each other — eliminating unintended gaps while still respecting the minimum inter-event gap required by your delivery specification. The Snap To Start and Snap To End controls are the primary tools for this, allowing you to close a gap between events with a single action rather than manually editing timecodes.

Prerequisites​

  • A project is open with at least one Event Group containing two or more events.
  • One event is selected in the editor.
  • Snap To Start: secondary toolbar; configurable keyboard shortcut.
  • Snap To End: secondary toolbar; configurable keyboard shortcut.

Snap To Start​

Snap To Start sets the start time of the currently selected event to match the end time of the previous event. In practice, this closes any gap between the end of the previous event and the beginning of the selected event, chaining the two events together at a single boundary point.

This operation is most useful after you have retimed an adjacent event and its end time has shifted, leaving the selected event starting too late. Rather than manually editing the start timecode, Snap To Start resolves the gap in one action.

Snap To End​

Snap To End sets the end time of the currently selected event to match the start time of the next event. This closes any gap between the end of the selected event and the beginning of the subsequent event.

This is particularly useful when you have extended the start of the next event and want to ensure that the current event now ends exactly where the next one begins — maintaining a clean, seamless flow between the two.

Why chaining matters​

Unintended timing gaps between caption events can cause visible flicker or a momentary absence of text during continuous speech, which is disorienting for viewers and may fail broadcast QC requirements. In formats like SCC and MCC, unnecessary gaps between events can also affect the decoders handling of caption mode transitions. Keeping adjacent events chained — especially during the final timing pass — ensures a clean and professional deliverable.

Note that chaining events flush against each other is distinct from setting a deliberate inter-event gap as required by some style guides (for example, Netflix requires a minimum two-frame gap). If your specification requires a minimum gap, use the appropriate style guide settings rather than Snap To Start or Snap To End, which remove the gap entirely.

Practical guidance​

Snap To Start and Snap To End are most efficient during a dedicated timing review pass, where the goal is to clean up boundary inconsistencies that accumulated during the draft captioning stage. Working through events sequentially and applying Snap To Start on each event that has a gap before it is a fast way to chain an entire sequence.

All Snap operations are recorded in the undo history.

Troubleshooting​

Snap To Start has no effect​

Confirm that the selected event is not the first event in the group — there must be a previous event whose end time can be used as the new start. Also verify that the previous event has a valid end timecode.

Snap To End has no effect​

Confirm that the selected event is not the last event in the group, and that the next event has a valid start timecode.

After snapping, the event duration is now too short​

Snap operations adjust a single boundary without checking whether the resulting duration falls below the Event Group's minimum duration setting. If the gap you are closing is large, review the event duration after snapping and adjust the opposite boundary manually if needed.

Source notes​

  • Components: src/components/toolbar/controls/SnapToStart.svelte, src/components/toolbar/controls/SnapToEnd.svelte