Hides the default page title on nodes where the title is set as a field via Display Suite

template.php

/**
 * Implements hook_process_page.
 */

function sipk_process_page(&$variables) {
  // Remove the title from pages that have been set with Display Suite.
  $content = $variables['page']['content'];
  // Check to see if this is a node page.
  if (isset($content['system_main']['nodes'])) {
    // Grab the node render array.
    $node = array_shift($content['system_main']['nodes']);
    // Check to see if the node title is set as a field.
    if (isset($node['title'])) {
      // Remove the title.
      $variables['title'] = "";
    }
  }
} //sipk_process_page