def ffmpeg_command(
    frame_rate: float = 10.0,  # CHANGEME
    input_files: str = "pic%04d.png",  # pic0001.png, pic0002.png, ...
    output_file: str = "test.mp4",
):
    """
    Build up the command string for running ``ffmpeg``.
    http://hamelot.io/visualization/using-ffmpeg-to-convert-a-set-of-images-into-a-video/

    :param frame_rate: desired video framerate, in fps
    :param input_files: shell-like wildcard pattern (globbing)
    :param output_file: name of video output
    :return: command to be executed in the shell for producing video from the input files
    """
    return (
        rf"ffmpeg -framerate {frame_rate} -pattern_type glob -i '{input_files}' "
        rf"-c:v libx264 -vf fps=25 -pix_fmt yuv420p {output_file}"
    )