private static String normalizeParameterValue(String attribute, String value) {
        checkNotNull(value); // for GWT
        checkArgument(ascii().matchesAllOf(value), "parameter values must be ASCII: %s", value);
        return CHARSET_ATTRIBUTE.equals(attribute) ? Ascii.toLowerCase(value) : value;
    }
Creates a media type with the "video" type and the given subtype.

@throws IllegalArgumentException if subtype is invalid
core/src/main/java/com/linecorp/armeria/common/MediaType.java