I know there's a lot of demand for 720p output from the ATEM Mini's, and it would be nice for our use case as well, which is quite different from those who struggle with upload limitations. We have pretty much unlimited upload bandwidth, but we would like a smaller bandwidth (output) video to reduce latency to a minimum (for live interactions).
Did some testing with the
Streaming.xml file and YouTube as a streaming-platform and came to some interesting conclusions:
Lowering the resolution in Streaming.xml drastically (leaving out all other options, basically forcing an ATEM Mini Pro to choose from 240p options only), definitely lowers the image quality. For example:
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<config resolution="240p" fps="30">
...with a 4000000 bitrate will give you a truly horrible image, but YouTube still reports it's 1920x1080@30fps. So yeah, something is definitely happening inside the ATEM, and the datarate is dropping, often to under 1Mb/s. YouTube will start to continuously barf about having a too low datarate, which is quite ironic.
Lowering the framerate to 24fps has no influence on the YouTube output stream. It will always be 30fps. I read somewhere that 24fps is no longer supported at YouTube.
Using YouTube's lowest latency settings and matching the output close to what YouTube expects (4.5mbps:1080p@30fps), and setting the client player to that quality results in sometimes surprisingly low latency (under two seconds). Choosing a different (lower) quality in the YouTube player usually shows a higher latency in the "Stats for nerds" (right-click the player). Could this be a "passthrough"?
Whatever I tried on an Owncast server, I could never get the latency under 8 seconds, even when in "passthrough"-mode. It shows that it's hard to compete with dedicated streaming giants, I guess
So yes, I think the often-heard request for more flexibility in what resolution the ATEM Mini's output would be very welcome. For our use case, we might get people on low-bandwidth connections to see our shows with a lower latency (when YouTube would pass through highest quality 720p). I think for many livestreaming cases, 1080p is overkill. We'd rather spend the same bandwidth on a higher image quality 720p stream.