Hi Richard -- Yes, that is a recent change we made to Cascade related to web browsers implementing stricter policies on autoplaying videos with sound. We are working on a blog post related to this, but to summarize...as of last week, Chrome has updated its autoplay policy to block autoplaying videos with sound (for some additional technical info you can see this article on the Google Developers site).
In Cascade Builder, the audio configuration options for videos added as immersive background media are now Button to Enable and Mute (previously, the options were On and Mute). Since Chrome (and likely other browsers in the future) is now blocking apps from autoplaying videos with sound, Cascade stories now initially mute audio for any videos that autoplay. This applies to videos added as immersive background media. There is an unmute/mute button in the lower right corner that can be used to toggle sound on and off.
There is no change in how videos in narrative sections or panels work; they continue to require the reader to click the video to play it and sound will begin immediately. If you have a video with narration we recommend that you add it in-line in a narrative section or panel so readers don't miss any of the narration. You can configure the size of a video in a narrative section if you want it to be larger.
Background videos in immersive sections work best when they set the mood rather than have narration (which splits the reader's attention between the panel text and the video narration), so there's no change in how we'd recommend you'd use background video. For example, see this story from the Fish and Wildlife Service that uses background video with ambient sound very effectively.
Please let me know if you have any questions.
Owen Evans
Lead Product Engineer | StoryMaps
