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The ELAN tab

Your own annotation tiers, drawn on the same timeline as the signals. This is the tab that connects hand coding to everything else: click an annotation and the video, the transcript and every analysis tab move to it.

  • Tab id elan, label ELAN Annotations, order 50, drawn into elanContainer.
  • Gate: !!cfg.include_elan — any truthy value switches it on.
  • Reads assets/elan/{videoID}.eaf directly, with fetch and the browser's own XML parser. It is the only tab that reads an input file rather than an analysis payload, and the only one whose data no analysis step produces.

What it reads out of the .eaf

Three element types, and nothing else:

element what is taken
TIME_SLOT TIME_SLOT_ID and TIME_VALUE. Values are milliseconds in the file and are divided by 1000, so the tab works in seconds like every other tab
TIER TIER_ID, used as the tier's name and its identity everywhere else
ALIGNABLE_ANNOTATION TIME_SLOT_REF1 and TIME_SLOT_REF2 for the extent, and the text of ANNOTATION_VALUE

Only ALIGNABLE_ANNOTATION is read. ELAN's other annotation type, REF_ANNOTATION — the one used by every dependent tier, where an annotation hangs off a parent annotation instead of naming its own time slots — is ignored completely. If your coding scheme puts the interesting labels on dependent tiers, those tiers will be missing from this tab and nothing will say so.

Two more silent drops, both by the same rule of "if it has no extent, it is not drawn":

  • An annotation whose TIME_SLOT_REF1 or TIME_SLOT_REF2 names a slot that is not in the file is skipped.
  • A tier left with no annotations after that is dropped from the tier list entirely, rather than shown empty.

If no tier survives, the tab reports "Failed to load ELAN data: No alignable annotations found in EAF file." rather than drawing an empty timeline. On a file full of dependent tiers that is the message you will get, and the cause is the paragraph above — not a missing or unreadable file, which is what the wording suggests.

What it draws

One horizontal lane per tier, labelled down the left. Each annotation is a filled block spanning its own start and end, drawn at two-thirds opacity with a solid border in the same colour.

Colours come from a fixed 20-entry palette, cycled if you have more than 20 tiers. The index used is the tier's position in the original file order, not its position among the tiers currently shown — so hiding a tier does not recolour the ones left behind.

The left margin sizes itself to the longest visible tier name, at roughly 7 px per character, clamped between 120 px and 220 px. Names longer than that are cut off by the margin rather than shrinking the plot.

Hovering an annotation gives its tier, its text (or (empty) when the ANNOTATION_VALUE is blank), its start and end to two decimals, and its duration. The hover targets are invisible square markers at each annotation's midpoint, so hover is keyed to the middle of a block, not anywhere along it — on a long annotation you have to aim at the centre.

Choosing tiers

Above the plot is one checkbox per tier, plus all and none. The selection is held on the host as app.elanSelectedTiers.

  • Switching tab keeps it.
  • Switching recording clears it, because tier names belong to the recording and need not carry over.
  • Switching theme keeps it. A theme change re-renders everything, which means re-entering the data load for the same recording — and that used to clear the selection on its way past, until v1.4.2. It now clears only when the recording actually changes.

Deselecting every tier collapses the plot to zero height: the y-axis range becomes [0, 0] and the playhead's band and line are drawn with no height to occupy, so they disappear too. You get an empty frame rather than an empty timeline with a playhead on it.

The playhead

Clicking seeks to that time — but the only clickable things are the invisible midpoint markers, so you must click at or near an annotation's centre, the same aiming constraint as hovering. Clicking empty timeline does nothing.

When a time is selected the tab draws two things across every lane: a translucent band spanning playhead ± windowSize / 2, and a dotted vertical line at the playhead itself. Window size is read live from the Window Size control, defaulting to 5 seconds.

onTimeUpdate redraws the whole plot rather than moving the shapes. With many annotations this is the more expensive of the two strategies the tabs use — the cross-wavelet tab moves shapes instead — but it keeps the tier filter and the highlight in one code path.

The time axis

The x-axis spans the recording, from 0 to the last sample in any loaded series — the same extent the time slider uses — so the lanes line up with every other tab and an unannotated head or tail of the recording is visible as empty space rather than cropped away.

Until v1.4.2 it did not. The tab asked the host for a field the host has never set, so the request always failed and Plotly autoscaled to the annotated span: annotations sat at their true times, but a file whose first annotation began at 40 s drew a timeline starting near 40 s.

Where it lives

packages/dims-tabs/elan.js. It adds loadELANData, displayELANTab, _renderELANPlot and updateELANHighlight to the host via DIMS.extendHost.