What's your use case, please?
I think our primary concern with allowing refresh of less than 1 second (heck; less than 5 seconds or more even...) is putting excessive loads on external services like weather radar and the MTG (Media Tile Generator). Such services should actually not need refreshing more frequently than 15 minutes or even 1 hour.
I suppose local cameras could handle less than 1 second; if they don't already supply an MJPEG stream (usually 10fps to 60fps).
Hmmmmm .... my use case is for VDOT cameras. I was hoping for a .5 or .1 second refresh interval so I could see the traffic feeds a little clearer. With only a 1 second refresh, it's difficult to gauge what traffic actually looks like; however, I also see your concern of server load. I would deny this if server load were heavy. In my case, it's only for a still image refresh from www.trafficview.org. Here's a direct link to one of the tiles I'm using: https://cctv-tn1.trafficview.org/thumbnail/VDOT_86765?force=true&_=1527275467248
That site (VDOT) is delivering snapshots only (right? I don't get it streaming).
Are you certain that they update their web image more frequently than 1 per second??
It seems like it, yes, but no, there's no way to get them to update more than 1 second as far as I can see. The images weren't updating at all until I added a "1" to the actiontiles media settings, so it seems that the update is done per image by actiontiles, not vdot's website.
The VDOT image is certain a still snapshot (it's a JPEG, not an MJPEG).
But when we pull the image it is coming from their image server. We really can't endorse hitting their servers more than once per second. It may be fine if one person is using it, but if we add this as a Feature, it could end up being thousands.
Embedding an image from another service is stretching legal boundaries as it is.
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