Background Audio: Support non-looping audio

Feature Description

Some creators are using background audio to narrate the story.

They would like the page level background audio to be non-looping and to be considered for the “auto” page advancement calculation.

For this to work we’d need to:

• Store the audio length together with the URL when saving the audio
• Add background audio as an <amp-video element instead of with a background-audio attribute
• Update the advancement calculation to take into account the page background audio

Alternatives Considered

Additional Context

Note: narration also means there’s a need for captions, hence the idea of using <amp-video> for audio. See #8821

[swissspidy]

Thanks for raising that; as mentioned in our chat today this is an opportunity to revamp the audio “player” experience a little bit.

Ideally we:

• Use the file’s actual title if available (instead of the file name)
• Display the video length
• Link to the audio file so you could download it / listen to it outside the editor

[spacedmonkey]

Maybe we should only show the looping checkbox if the audio length is present? Meaning on an existing story with audio already set, the loop option you would see it. But if you create a new story or remove & re-add the audio, the loop option would appear. What do you think?