Constant CAPPED_VBV_FRAMES 

pub const CAPPED_VBV_FRAMES: f64 = software::CBR_VBV_FRAMES; // 8f64

The buffer, in frames of its peak, a capped constant-quality session takes (CaptureSettings::video_vbv_multiplier): software H.264’s constant-rate buffer, so a cap that binds codes a frame as the constant rate congestion control steers does, and a cap that does not leaves the rate factor its picture.