[downloader/external] Add support for custom options (Fixes #4885, closes #5098)

youtube_dl/YoutubeDL.py

@@ -249,10 +249,10 @@ class YoutubeDL(object):
     hls_prefer_native: Use the native HLS downloader instead of ffmpeg/avconv.
 
     The following parameters are not used by YoutubeDL itself, they are used by
-    the FileDownloader:
+    the downloader (see youtube_dl/downloader/common.py):
     nopart, updatetime, buffersize, ratelimit, min_filesize, max_filesize, test,
     noresizebuffer, retries, continuedl, noprogress, consoletitle,
-    xattr_set_filesize.
+    xattr_set_filesize, external_downloader_args.
 
     The following options are used by the post processors:
     prefer_ffmpeg:     If True, use ffmpeg instead of avconv if both are available,

youtube_dl/__init__.py

@@ -9,6 +9,7 @@
 import io
 import os
 import random
+import shlex
 import sys
 
 
@@ -255,6 +256,9 @@ def _real_main(argv=None):
             xattr  # Confuse flake8
         except ImportError:
             parser.error('setting filesize xattr requested but python-xattr is not available')
+    external_downloader_args = None
+    if opts.external_downloader_args:
+        external_downloader_args = shlex.split(opts.external_downloader_args)
     match_filter = (
         None if opts.match_filter is None
         else match_filter_func(opts.match_filter))
@@ -359,6 +363,7 @@ def _real_main(argv=None):
         'no_color': opts.no_color,
         'ffmpeg_location': opts.ffmpeg_location,
         'hls_prefer_native': opts.hls_prefer_native,
+        'external_downloader_args': external_downloader_args,
     }
 
     with YoutubeDL(ydl_opts) as ydl:

youtube_dl/downloader/common.py

@@ -42,6 +42,8 @@ class FileDownloader(object):
     max_filesize:       Skip files larger than this size
     xattr_set_filesize: Set ytdl.filesize user xattribute with expected size.
                         (experimenatal)
+    external_downloader_args:  A list of additional command-line arguments for the
+                        external downloader.
 
     Subclasses of this one must re-define the real_download method.
     """

youtube_dl/downloader/external.py

@@ -51,6 +51,13 @@ def _source_address(self, command_option):
             return []
         return [command_option, source_address]
 
+    def _configuration_args(self, default=[]):
+        ex_args = self.params.get('external_downloader_args')
+        if ex_args is None:
+            return default
+        assert isinstance(ex_args, list)
+        return ex_args
+
     def _call_downloader(self, tmpfilename, info_dict):
         """ Either overwrite this or implement _make_cmd """
         cmd = self._make_cmd(tmpfilename, info_dict)
@@ -79,6 +86,7 @@ def _make_cmd(self, tmpfilename, info_dict):
         for key, val in info_dict['http_headers'].items():
             cmd += ['--header', '%s: %s' % (key, val)]
         cmd += self._source_address('--interface')
+        cmd += self._configuration_args()
         cmd += ['--', info_dict['url']]
         return cmd
 
@@ -89,15 +97,16 @@ def _make_cmd(self, tmpfilename, info_dict):
         for key, val in info_dict['http_headers'].items():
             cmd += ['--header', '%s: %s' % (key, val)]
         cmd += self._source_address('--bind-address')
+        cmd += self._configuration_args()
         cmd += ['--', info_dict['url']]
         return cmd
 
 
 class Aria2cFD(ExternalFD):
     def _make_cmd(self, tmpfilename, info_dict):
-        cmd = [
+        cmd = [self.exe, '-c']
-            self.exe, '-c',
+        cmd += self._configuration_args([
-            '--min-split-size', '1M', '--max-connection-per-server', '4']
+            '--min-split-size', '1M', '--max-connection-per-server', '4'])
         dn = os.path.dirname(tmpfilename)
         if dn:
             cmd += ['--dir', dn]

youtube_dl/options.py

@@ -435,8 +435,12 @@ def _hide_login_info(opts):
     downloader.add_option(
         '--external-downloader',
         dest='external_downloader', metavar='COMMAND',
-        help='(experimental) Use the specified external downloader. '
+        help='Use the specified external downloader. '
              'Currently supports %s' % ','.join(list_external_downloaders()))
+    downloader.add_option(
+        '--external-downloader-args',
+        dest='external_downloader_args', metavar='ARGS',
+        help='Give these arguments to the external downloader.')
 
     workarounds = optparse.OptionGroup(parser, 'Workarounds')
     workarounds.add_option(