Parses creation date from media metadata.

The getID3 library doesn’t have a standard method for getting creation dates,
so the location of this data can vary based on the MIME type.

function wp_get_media_creation_timestamp( $metadata ) {
	$creation_date = false;

	if ( empty( $metadata['fileformat'] ) ) {
		return $creation_date;
	}

	switch ( $metadata['fileformat'] ) {
		case 'asf':
			if ( isset( $metadata['asf']['file_properties_object']['creation_date_unix'] ) ) {
				$creation_date = (int) $metadata['asf']['file_properties_object']['creation_date_unix'];
			}
			break;

		case 'matroska':
		case 'webm':
			if ( isset( $metadata['matroska']['comments']['creation_time'][0] ) ) {
				$creation_date = strtotime( $metadata['matroska']['comments']['creation_time'][0] );
			} elseif ( isset( $metadata['matroska']['info'][0]['DateUTC_unix'] ) ) {
				$creation_date = (int) $metadata['matroska']['info'][0]['DateUTC_unix'];
			}
			break;

		case 'quicktime':
		case 'mp4':
			if ( isset( $metadata['quicktime']['moov']['subatoms'][0]['creation_time_unix'] ) ) {
				$creation_date = (int) $metadata['quicktime']['moov']['subatoms'][0]['creation_time_unix'];
			}
			break;
	}

	return $creation_date;
}