Function held_key_bits 

fn held_key_bits(bps: u32, width: u32, height: u32) -> f64

The bits a key frame held at a constant rate of bps is given for a width x height picture: HELD_KEY_BUDGET_S of the rate, and at least HELD_KEY_BITS_PER_PIXEL, the maintainer’s rule that a key frame is capped only where the cap leaves the picture good.