[nrk] Remove TTML to srt conversion codes

A common routine is implemented in utils.py and can be used via
--convert-subtitles.

youtube_dl/extractor/nrk.py

@@ -4,7 +4,6 @@ from __future__ import unicode_literals
 import re
 
 from .common import InfoExtractor
-from ..compat import compat_str
 from ..utils import (
     ExtractorError,
     float_or_none,
@@ -200,20 +199,10 @@ class NRKTVIE(InfoExtractor):
         url = "%s%s" % (baseurl, subtitlesurl)
         self._debug_print('%s: Subtitle url: %s' % (video_id, url))
         captions = self._download_xml(
-            url, video_id, 'Downloading subtitles',
+            url, video_id, 'Downloading subtitles')
-            transform_source=lambda s: s.replace(r'<br />', '\r\n'))
         lang = captions.get('lang', 'no')
-        ps = captions.findall('./{0}body/{0}div/{0}p'.format('{http://www.w3.org/ns/ttml}'))
-        srt = ''
-        for pos, p in enumerate(ps):
-            begin = parse_duration(p.get('begin'))
-            duration = parse_duration(p.get('dur'))
-            starttime = self._subtitles_timecode(begin)
-            endtime = self._subtitles_timecode(begin + duration)
-            srt += '%s\r\n%s --> %s\r\n%s\r\n\r\n' % (compat_str(pos), starttime, endtime, p.text)
         return {lang: [
             {'ext': 'ttml', 'url': url},
-            {'ext': 'srt', 'data': srt},
         ]}
 
     def _extract_f4m(self, manifest_url, video_id):