diff --git a/youtube_dl/YoutubeDL.py b/youtube_dl/YoutubeDL.py
index dc4005a18..018d585ee 100755
--- a/youtube_dl/YoutubeDL.py
+++ b/youtube_dl/YoutubeDL.py
@@ -1771,7 +1771,7 @@ class YoutubeDL(object):
             self.to_stdout(formatSeconds(info_dict['duration']))
         print_mandatory('format')
         if self.params.get('forcejson', False):
-            self.to_stdout(json.dumps(info_dict, default=lambda _:'<not serialized>'))
+            self.to_stdout(json.dumps(info_dict))
 
     def process_info(self, info_dict):
         """Process a single resolved IE result."""
@@ -1879,15 +1879,16 @@ class YoutubeDL(object):
                         except (OSError, IOError):
                             self.report_error('Cannot write subtitles file ' + sub_filename)
                             return
-                    elif callable(sub_info.get('downloader')):
-                        sub_info.get('downloader')(self, encodeFilename(sub_filename))
                     else:
+                        fd = get_suitable_downloader(sub_info, self.params)(self, self.params)
                         try:
-                            sub_data = ie._request_webpage(
-                                sub_info['url'], info_dict['id'], note=False).read()
-                            with io.open(encodeFilename(sub_filename), 'wb') as subfile:
-                                subfile.write(sub_data)
-                        except (ExtractorError, IOError, OSError, ValueError) as err:
+                            if self.params.get('verbose'):
+                                self.to_screen('[debug] Invoking subtitle downloader on %r' % sub_info.get('url'))
+                            # The FD is supposed to encodeFilename()
+                            if not fd.download(sub_filename, sub_info):
+                                # depending on the FD, it may catch errors and return False, or not
+                                raise DownloadError('Subtitle download failed')
+                        except (compat_urllib_error.URLError, compat_http_client.HTTPException, socket.error, OSError, IOError, YoutubeDLError) as err:
                             self.report_warning('Unable to download subtitle for "%s": %s' %
                                                 (sub_lang, error_to_compat_str(err)))
                             continue
@@ -2076,7 +2077,7 @@ class YoutubeDL(object):
                 raise
             else:
                 if self.params.get('dump_single_json', False):
-                    self.to_stdout(json.dumps(res, default=lambda _:'<not serialized>'))
+                    self.to_stdout(json.dumps(res))
 
         return self._download_retcode
 
diff --git a/youtube_dl/downloader/__init__.py b/youtube_dl/downloader/__init__.py
index 2e485df9d..f3200566e 100644
--- a/youtube_dl/downloader/__init__.py
+++ b/youtube_dl/downloader/__init__.py
@@ -33,7 +33,8 @@ def get_suitable_downloader(info_dict, params={}):
     """Get the downloader class that can handle the info dict."""
     protocol = determine_protocol(info_dict)
     info_dict['protocol'] = protocol
-
+    print('SACHA> ', protocol)
+    
     # if (info_dict.get('start_time') or info_dict.get('end_time')) and not info_dict.get('requested_formats') and FFmpegFD.can_download(info_dict):
     #     return FFmpegFD
 
diff --git a/youtube_dl/extractor/common.py b/youtube_dl/extractor/common.py
index 058e224d4..e45c67f94 100644
--- a/youtube_dl/extractor/common.py
+++ b/youtube_dl/extractor/common.py
@@ -1708,6 +1708,7 @@ class InfoExtractor(object):
                 subtitles[media['LANGUAGE']] = [{
                     'url': format_url(media['URI']),
                     'ext': media.get('SUBFORMAT', 'webtt'),
+                    'protocol': 'm3u8_native',
                 }]
                 return
             if media_type not in ('VIDEO', 'AUDIO'):
diff --git a/youtube_dl/extractor/francetv.py b/youtube_dl/extractor/francetv.py
index 2d12e6dfb..95ef0bf6c 100644
--- a/youtube_dl/extractor/francetv.py
+++ b/youtube_dl/extractor/francetv.py
@@ -206,10 +206,6 @@ class FranceTVIE(InfoExtractor):
             info['title'] += ' - %s' % info['subtitle']
         info['title'] = info['title'].strip()
 
-        for lang, sts in info['subtitles'].items():
-            for st in sts:
-                st['downloader'] = lambda ydl, filename: PROTOCOL_MAP['m3u8_native'](ydl, ydl.params).download(filename, st)
-
         return {
             'id': video_id,
             'title': self._live_title(info['title']) if is_live else info['title'],
diff --git a/youtube_dl/utils.py b/youtube_dl/utils.py
index ecf744041..ef0afd686 100644
--- a/youtube_dl/utils.py
+++ b/youtube_dl/utils.py
@@ -1830,7 +1830,7 @@ def write_json_file(obj, fn):
 
     try:
         with tf:
-            json.dump(obj, tf, default=lambda _:'<not serialized>')
+            json.dump(obj)
         if sys.platform == 'win32':
             # Need to remove existing file on Windows, else os.rename raises
             # WindowsError or FileExistsError.