[Accessibility] Configure embedded video player to generate spoken output from captions #6460

Describe the bug

According to 301 559, Section 7.1.5: Where ICT displays video with synchronized audio, it shall have a mode of operation to provide a spoken output of the available captions, except where the content of the displayed captions is not programmatically determinable.

The embedded video player in DSpace currently does not allow users to generate or provide spoken output of the available captions. The video player also doesn't allow screen readers to access captions or caption files.

To Reproduce

Upload a video file (mp4) and a transcript file (.vtt) to DSpace and play them. Test with screen reader, such as through the Silktide plugin.

Expected behavior

The video player should allow users to generate spoken output of available captions. Ideally, deliver the audio file with spoken subtitles in a separate audio track and allow for mixing in the end user's device. See also Notes 1-4 for this criterion (https://www.etsi.org/deliver/etsi_en/301500_301599/301549/03.02.01_60/en_301549v030201p.pdf).

Consider switching to a more accessibility-friendly player, such as the Able player.