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Jun 25, 2026

Heratio Help Center article. Category: Viewers & Media.

Mirador Tools

User Guide

Two power-user toggles in the Mirador window menu - a "Comparison glass" for before/after-style slider review, and "A/V playback + transcript" for video and audio canvases.

Overview

+-------------------------------------------------------------+
|   MIRADOR WINDOW MENU                                       |
+-------------------------------------------------------------+
|                                                             |
|   [Magnifier]                                  [O]          |
|   [Scalebar]                                   [O]          |
|   [Comparison glass]                           [O]   <- #700|
|   [A/V playback + transcript]                  [O]   <- #701|
|                                                             |
+-------------------------------------------------------------+

Open the window menu (the "..." or hamburger icon at the top of any Mirador window) to see the toggles. Each switch is per-window.

Comparison glass (#700)

The comparison glass lays a second open Mirador window's canvas over the right half of the active window, with a draggable vertical seam. Drag the yellow handle left or right to reveal more of either side.

How to use it

  1. In Mirador, open the first canvas you want to compare. (Add Resource -> pick the manifest -> open the canvas.)
  2. Open a SECOND Mirador window in the same workspace, on the OTHER canvas. They can be from the same manifest (e.g. before / after photographs of the same artefact) or different manifests.
  3. In the FIRST window's top-menu, flip on "Comparison glass". A yellow vertical seam with a circular knob appears.
  4. Drag the knob left or right. The right-hand side of the active window is now painted with the second window's current view. Zoom and pan in EITHER window - the comparison repaints continuously.
  5. Flip the switch off to dismiss. Each window remembers its own state.

When the toggle does nothing

If you don't have a second window open the switch will flick off again and the browser console will log [HeratioComparison] open a second Mirador window in this workspace to compare against. Open another window and try again.

Tips

  • The comparison uses INDEPENDENT navigation. That's by design - it lets you line up a detail at one zoom level on the right against the full image on the left.
  • The seam plays nicely with the magnifier loupe and the scalebar - all three can be on at once.
  • Cross-origin manifests sometimes block canvas reading; if the right side is empty check the browser console for a partner canvas not readable warning.

A/V playback + transcript (#701)

When a canvas has a video or audio file attached (a Video, Sound or Audio painting body in the IIIF manifest), this toggle replaces the image viewer with a real <video> or <audio> element and shows the canvas-level transcript on the right.

How to use it

  1. Open a manifest that contains an A/V canvas. (Typical Heratio path: an oral-history MP3, a born-digital lecture MP4, or a digitised reel-to-reel WAV.)
  2. Navigate to the A/V canvas in the Mirador window.
  3. Open the window menu and flip on "A/V playback + transcript". A media player appears in place of the image; a Transcript panel slides in on the right.
  4. Press Play. As the media advances, the transcript highlights the active line and auto-scrolls.
  5. CLICK any transcript line to seek the media to that timestamp. Useful for jumping to a specific quote in a long oral history.

When the toggle does nothing

If the active canvas has no A/V body (it is an image-only canvas) the switch flicks back off and the browser console logs [HeratioAv] no Video/Sound body on the active canvas; A/V mode not applicable. Pick an A/V canvas from the manifest's canvas list and try again.

What the transcript shows

The panel reads /api/iiif/transcript?canvasId=<the-canvas-id> on the Heratio backend. Each row carries a Media-Fragment timestamp (e.g. t=12.3,15.6). If no transcript has been generated yet the panel shows No transcript for this canvas. - playback still works.

Tips

  • Comparison glass + A/V can be combined: open two A/V canvases in two windows, flip A/V on in both, then flip Comparison on in the first - useful for waveform A/B between two recordings.
  • The transcript respects ODRL rights policies the same as the image OCR layer; canvases under restricted access return an empty transcript even when the underlying media plays.

Issue references

  • #700 - Comparison glass / dual-pane slider
  • #701 - A/V plugin bundling + manifest detection + transcript panel

Reference docs

  • docs/reference/mirador-comparison-glass.md - implementation notes for the comparison glass
  • docs/reference/mirador-av-transcript.md - implementation notes for the A/V plugin + transcript endpoint contract