Drawing TTF text and Rects , i think that is expensive. This is post inference.
Not to mention GPU is slow, or run slow. I don’t have any rk3566 to compare to, only rk3568 which is much, much faster.
Do you have Zero 3W around to check if my findings below are correct?
cat /sys/class/devfreq/fde40000.npu/cur_freq
900000000
cat /sys/class/devfreq/fde60000.gpu/cur_freq
400000000