EDIT

function theme_cdm_media_caption($variables) {

  $media = $variables['media'];

  $elements = $variables['elements'];

  $doTitle = !$elements || array_search('title', $elements) !== FALSE;

  $doDescription = !$elements || array_search('description', $elements) !== FALSE;

      $descriptionPrefix = "- ";

    }

    elseif (!($doDescription && $media_metadata['description'])) {

      $out .= '<dt class = "title">' . t('Title') . '</dt> <dd class = "title">' . $media_metadata['filename'] . '</dd>';

      $descriptionPrefix = "- ";

    }

      $out .= $rights . '</dt>';

    }

  }

  $out .= '</dl>';

  // Return value,

  return $out;

      // Do not add margins if no pass partout is shown.

      $margins = '';

    }

    if ($addPassePartout) {

      $out .= '</div>';