Inaccurate docs/comments about ActiveStorage video previewer defaults could be improved about rails

[zzak]

Is the same true if you aren't using ffmpeg with at least the supported version?

Meaning we probably should document both? 🤷

[searls]

@zzak if I read correctly, I think the change effectively raised (or specified) the minimum required ffmpeg version to one that supported the new CLI args with 7.0 and was why it wasn't backported to 6.1

[zzak]

Ahh ok, #42471 helped me make sense of this. I missed that load_defaults hook.

The reason why the old default is hard-coded is to avoid a breaking change and to rely on load_defaults instead.

In hind-sight it might have been good to make accept? check the version, as I'm not sure how ubiquitous the supported version of ffmpeg was at the time.

Yeah we should update the doc in those places, it's safe to assume the docs are written with the knowledge of the current load_defaults already in place. The configuring guide is where the lore comes into play.

[zzak]

...uses scene change detection to generate preview images of videos.

Or something to that extent seems reasonable to me.