Low frame rate on Raspberry Pi 3

[Ewan Roycroft]

Hi,

I am running Cobalt on a Raspberry Pi 3 and have noticed that the frame rate seems to be limited to 30 fps. Despite the Pi outputting 60 fps, a HDMI capture device connected to the output shows that every other frame is being dropped and the fps overlay indicates a minimum frame interval of >30 ms.

I have tested using my own webpage as well as the YouTube app. The latter has once or twice indicated a minimum interval of ~16 ms, but very rarely.

Looking at the source code, it appears the Pi is throttled to 8 ms / 120 fps (https://cobalt.googlesource.com/cobalt/+/refs/heads/master/starboard/raspi/shared/graphics.cc#30).

Is there some other part of the code throttling the frame rate? Is there some way to up the average to 60 fps?

Thanks,

Ewan Roycroft