The camera follows your cursor. On Wayland, in 56 MB.

for j in 0..pcount {
    let name = prop_name(j);
    if name.starts_with(b"FB_ID\0") {
        fb_id = pval;
    } else if name.starts_with(b"CRTC_X\0") {
        crtc_x = Some((pval as u32) as i32);
    } else if name.starts_with(b"CRTC_Y\0") {
        crtc_y = Some((pval as u32) as i32);
    }
}
// fb_id changes when the cursor shape changes
let nx = (cx as f32 / self.screen_w).clamp(0.0, 1.0);

let k_zoom = cfg.spring_stiffness.clamp(20.0, 260.0);
let c_zoom = 2.0 * k_zoom.sqrt();
let k_pan  = (k_zoom * 0.78).clamp(18.0, 220.0);
let c_pan  = 2.0 * k_pan.sqrt();

let ax = -k_pan * (self.cam_x - self.target_x) - c_pan * self.vel_x;
let az = -k_zoom * (self.cam_zoom - self.target_zoom)
         - c_zoom * self.vel_zoom;

self.vel_x += ax * dt;
self.cam_x += self.vel_x * dt;
// clamp the centre so the crop never samples outside [0, 1]

SPA_PARAM_BUFFERS_dataType,
  SPA_POD_CHOICE_FLAGS_Int(
    (1 << SPA_DATA_MemFd) |
    (1 << SPA_DATA_MemPtr) |
    (1 << SPA_DATA_DmaBuf))

/* encoder pipe */
"-c:v h264_nvenc -preset p4 -tune hq"
" -rc vbr -cq 19 -b:v 0 -pix_fmt yuv420p"
" -movflags +faststart"