One of the demos on Day 1 of BBCTextAV was the BBC's FastForward, which synchronises scrubbing of video with the text transcript (navigating through either video or text changes your position in the other).
This would be useful functionality to have available for IIIF AV content, where the text transcript comprises textual annotations on the time dimension of the canvas. So we decided to build a proof of concept viewer.
We had access to metadata for ~3500 German parliamentary debates. We transformed this metadata to IIIF Manifests, ending up with one Manifest per debate, each with one Canvas representing the duration of the debate, annotated with a video file to provide the AV content. Other sources of textual data were available, but for this MVP we used the WEBVTT files as source for the transcripts.