Function cleanup_rate 

pub fn cleanup_rate(settings: &CaptureSettings) -> i32

The rate (kbps) a constant-rate cleanup’s sweep is paced to and its frames capped by: what the path carries (CaptureSettings::video_link_kbps), never under the session’s rate nor over CLEANUP_RATE_MAX times it, and the session’s rate where the path’s is not known. A still screen’s refresh at the paint-over quantizer is many seconds of a low rate (1080p text at 500 kbps, 20 s), which a path faster than the stream carries at once and one near its rate only at that rate.