def is_valid_chunk(signature: bytes) -> bool:
    """Check if the first four bytes of a chunk are valid Usm chunks.
    Returns true if valid, and false if invalid or the given input is less
    than four bytes.
    """
    if len(signature) < 4:
        return False

    valid_signatures = [
        bytes("CRID", "UTF-8"),  # CRI USF DIR STREAM
        bytes("@SFV", "UTF-8"),  # Video
        bytes("@SFA", "UTF-8"),  # Audio
    ]
    return signature[:4] in valid_signatures