ex.rs

fn make_movie(width: i32, height: i32, framerate: i32, frames: i32) {
    let mut surface =
        ImageSurface::create(Format::ARgb32, width, height).expect("Couldn't create surface");
    let mut child = Command::new("cmd")
        .args(&["/C", &format!(
            "ffmpeg -f rawvideo -pix_fmt bgra -s {width}x{height} -i - -pix_fmt yuv420p -r {framerate} -y out.mp4",
            width = width,
            height = height,
            framerate = framerate,
        )])
        .stdin(Stdio::piped())
        .spawn()
        .expect("failed to execute process");
    {
        // limited borrow of stdin
        let child_stdin = child.stdin.as_mut().expect("failed to get stdin");

        (0..frames).for_each(|f| {
            draw(&surface, f);
            let d = surface.get_data().expect("Failed to get_data");
            child_stdin.write_all(&d).expect("Failed to write to file");
        });
    }
    child.wait().expect("child process wasn't running");
}