Following the announcement that it'd be reducing Nest's video quality to help lower network strain around the world, Google has also revealed that it'll do the same for the Chromecast and smart displays. The move is temporary and comes from a mindset that every bit helps, even if it's just saving everyone a little bit of bandwidth.
The change will roll out over the next few days and will affect both the photo quality and slideshow speed of Chromecasts' Ambient Mode. Google says it may not be noticeable and things will go back to normal once internet resources aren't spread so thin. However, unlike Nest, it doesn't explain whether you'd be able to manually revert those changes or not. Chromecasts already have a setting for slideshow speed, spanning from every 5 seconds to 10 minutes, so that should be manually controllable, but there's no visible setting for image quality yet.
My colleagues here at Android Police were debating whether this would have any impact on bandwidth consumption at home, given that Chromecasts aren't technically streaming, which puts them in a different box from all the other streaming services that have reduced quality so far. But my experience with the Lenovo Smart Display (which offers a similar Ambient Mode to Chromecasts and Nest Hub displays), offers a bit of perspective. Even when idle, and with no one home to issue any requests, my display was using 200MB/day while set to rotate images every minute. I talked about this in my Firewalla review, and explained how reducing the frequency to five minutes dropped that idle usage to 50MB/day. In a month, that goes down from 6GB to 1.5GB, approximately.
Now imagine if someone had set the frequency to 5 seconds and imagine that person having multiple Chromecasts at home (that, as far as I know, keep the photo album going if they're plugged into power even if the TV is off). That would add up really quickly, all for a feature that isn't as essential as work or education. Reducing that superfluous usage makes sense.