updated from upstream | 20/10/2021 at 11:45

17 files changed, 122 insertions, 101 deletions

diff --git a/test/test_utils.py b/test/test_utils.py
index 9a5e3f0f0..d84c3d3ee 100644
--- a/test/test_utils.py
+++ b/test/test_utils.py
@@ -1390,21 +1390,21 @@ The first line
   </body>
 </tt>'''.encode('utf-8')
         srt_data = '''1
-00:00:02,080 --> 00:00:05,839
+00:00:02,080 --> 00:00:05,840
 <font color="white" face="sansSerif" size="16">default style<font color="red">custom style</font></font>
 
 2
-00:00:02,080 --> 00:00:05,839
+00:00:02,080 --> 00:00:05,840
 <b><font color="cyan" face="sansSerif" size="16"><font color="lime">part 1
 </font>part 2</font></b>
 
 3
-00:00:05,839 --> 00:00:09,560
+00:00:05,840 --> 00:00:09,560
 <u><font color="lime">line 3
 part 3</font></u>
 
 4
-00:00:09,560 --> 00:00:12,359
+00:00:09,560 --> 00:00:12,360
 <i><u><font color="yellow"><font color="lime">inner
  </font>style</font></u></i>
 
diff --git a/yt_dlp/YoutubeDL.py b/yt_dlp/YoutubeDL.py
index 18ab19e09..d1ab540d2 100644
--- a/yt_dlp/YoutubeDL.py
+++ b/yt_dlp/YoutubeDL.py
@@ -87,10 +87,10 @@ from .utils import (
     parse_filesize,
     PerRequestProxyHandler,
     platform_name,
+    Popen,
     PostProcessingError,
     preferredencoding,
     prepend_extension,
-    process_communicate_or_kill,
     register_socks_protocols,
     RejectedVideoReached,
     render_table,
@@ -577,12 +577,9 @@ class YoutubeDL(object):
                     stdout=slave,
                     stderr=self._err_file)
                 try:
-                    self._output_process = subprocess.Popen(
-                        ['bidiv'] + width_args, **sp_kwargs
-                    )
+                    self._output_process = Popen(['bidiv'] + width_args, **sp_kwargs)
                 except OSError:
-                    self._output_process = subprocess.Popen(
-                        ['fribidi', '-c', 'UTF-8'] + width_args, **sp_kwargs)
+                    self._output_process = Popen(['fribidi', '-c', 'UTF-8'] + width_args, **sp_kwargs)
                 self._output_channel = os.fdopen(master, 'rb')
             except OSError as ose:
                 if ose.errno == errno.ENOENT:
@@ -3278,11 +3275,11 @@ class YoutubeDL(object):
         if self.params.get('compat_opts'):
             write_debug('Compatibility options: %s\n' % ', '.join(self.params.get('compat_opts')))
         try:
-            sp = subprocess.Popen(
+            sp = Popen(
                 ['git', 'rev-parse', '--short', 'HEAD'],
                 stdout=subprocess.PIPE, stderr=subprocess.PIPE,
                 cwd=os.path.dirname(os.path.abspath(__file__)))
-            out, err = process_communicate_or_kill(sp)
+            out, err = sp.communicate_or_kill()
             out = out.decode().strip()
             if re.match('[0-9a-f]+', out):
                 write_debug('Git HEAD: %s\n' % out)
diff --git a/yt_dlp/cookies.py b/yt_dlp/cookies.py
index 049ec9fb1..5f7fdf584 100644
--- a/yt_dlp/cookies.py
+++ b/yt_dlp/cookies.py
@@ -17,7 +17,7 @@ from .compat import (
 from .utils import (
     bug_reports_message,
     expand_path,
-    process_communicate_or_kill,
+    Popen,
     YoutubeDLCookieJar,
 )
 
@@ -599,14 +599,14 @@ def _get_mac_keyring_password(browser_keyring_name, logger):
         return password.encode('utf-8')
     else:
         logger.debug('using find-generic-password to obtain password')
-        proc = subprocess.Popen(['security', 'find-generic-password',
-                                 '-w',  # write password to stdout
-                                 '-a', browser_keyring_name,  # match 'account'
-                                 '-s', '{} Safe Storage'.format(browser_keyring_name)],  # match 'service'
-                                stdout=subprocess.PIPE,
-                                stderr=subprocess.DEVNULL)
+        proc = Popen(
+            ['security', 'find-generic-password',
+             '-w',  # write password to stdout
+             '-a', browser_keyring_name,  # match 'account'
+             '-s', '{} Safe Storage'.format(browser_keyring_name)],  # match 'service'
+            stdout=subprocess.PIPE, stderr=subprocess.DEVNULL)
         try:
-            stdout, stderr = process_communicate_or_kill(proc)
+            stdout, stderr = proc.communicate_or_kill()
             if stdout[-1:] == b'\n':
                 stdout = stdout[:-1]
             return stdout
diff --git a/yt_dlp/downloader/common.py b/yt_dlp/downloader/common.py
index 9081794db..6cfbb6657 100644
--- a/yt_dlp/downloader/common.py
+++ b/yt_dlp/downloader/common.py
@@ -12,6 +12,7 @@ from ..utils import (
     format_bytes,
     shell_quote,
     timeconvert,
+    timetuple_from_msec,
 )
 from ..minicurses import (
     MultilineLogger,
@@ -75,14 +76,12 @@ class FileDownloader(object):
 
     @staticmethod
     def format_seconds(seconds):
-        (mins, secs) = divmod(seconds, 60)
-        (hours, mins) = divmod(mins, 60)
-        if hours > 99:
+        time = timetuple_from_msec(seconds * 1000)
+        if time.hours > 99:
             return '--:--:--'
-        if hours == 0:
-            return '%02d:%02d' % (mins, secs)
-        else:
-            return '%02d:%02d:%02d' % (hours, mins, secs)
+        if not time.hours:
+            return '%02d:%02d' % time[1:-1]
+        return '%02d:%02d:%02d' % time[:-1]
 
     @staticmethod
     def calc_percent(byte_counter, data_len):
diff --git a/yt_dlp/downloader/external.py b/yt_dlp/downloader/external.py
index 40b9dcfe3..ce3370fb7 100644
--- a/yt_dlp/downloader/external.py
+++ b/yt_dlp/downloader/external.py
@@ -22,7 +22,7 @@ from ..utils import (
     handle_youtubedl_headers,
     check_executable,
     is_outdated_version,
-    process_communicate_or_kill,
+    Popen,
     sanitize_open,
 )
 
@@ -116,9 +116,8 @@ class ExternalFD(FragmentFD):
         self._debug_cmd(cmd)
 
         if 'fragments' not in info_dict:
-            p = subprocess.Popen(
-                cmd, stderr=subprocess.PIPE)
-            _, stderr = process_communicate_or_kill(p)
+            p = Popen(cmd, stderr=subprocess.PIPE)
+            _, stderr = p.communicate_or_kill()
             if p.returncode != 0:
                 self.to_stderr(stderr.decode('utf-8', 'replace'))
             return p.returncode
@@ -128,9 +127,8 @@ class ExternalFD(FragmentFD):
 
         count = 0
         while count <= fragment_retries:
-            p = subprocess.Popen(
-                cmd, stderr=subprocess.PIPE)
-            _, stderr = process_communicate_or_kill(p)
+            p = Popen(cmd, stderr=subprocess.PIPE)
+            _, stderr = p.communicate_or_kill()
             if p.returncode == 0:
                 break
             # TODO: Decide whether to retry based on error code
@@ -152,11 +150,11 @@ class ExternalFD(FragmentFD):
             fragment_filename = '%s-Frag%d' % (tmpfilename, frag_index)
             try:
                 src, _ = sanitize_open(fragment_filename, 'rb')
-            except IOError:
+            except IOError as err:
                 if skip_unavailable_fragments and frag_index > 1:
-                    self.to_screen('[%s] Skipping fragment %d ...' % (self.get_basename(), frag_index))
+                    self.report_skip_fragment(frag_index, err)
                     continue
-                self.report_error('Unable to open fragment %d' % frag_index)
+                self.report_error(f'Unable to open fragment {frag_index}; {err}')
                 return -1
             dest.write(decrypt_fragment(fragment, src.read()))
             src.close()
@@ -199,8 +197,8 @@ class CurlFD(ExternalFD):
         self._debug_cmd(cmd)
 
         # curl writes the progress to stderr so don't capture it.
-        p = subprocess.Popen(cmd)
-        process_communicate_or_kill(p)
+        p = Popen(cmd)
+        p.communicate_or_kill()
         return p.returncode
 
 
@@ -476,7 +474,7 @@ class FFmpegFD(ExternalFD):
         args.append(encodeFilename(ffpp._ffmpeg_filename_argument(tmpfilename), True))
         self._debug_cmd(args)
 
-        proc = subprocess.Popen(args, stdin=subprocess.PIPE, env=env)
+        proc = Popen(args, stdin=subprocess.PIPE, env=env)
         if url in ('-', 'pipe:'):
             self.on_process_started(proc, proc.stdin)
         try:
@@ -488,7 +486,7 @@ class FFmpegFD(ExternalFD):
             # streams). Note that Windows is not affected and produces playable
             # files (see https://github.com/ytdl-org/youtube-dl/issues/8300).
             if isinstance(e, KeyboardInterrupt) and sys.platform != 'win32' and url not in ('-', 'pipe:'):
-                process_communicate_or_kill(proc, b'q')
+                proc.communicate_or_kill(b'q')
             else:
                 proc.kill()
                 proc.wait()
diff --git a/yt_dlp/downloader/fragment.py b/yt_dlp/downloader/fragment.py
index d0eaede7e..c345f3148 100644
--- a/yt_dlp/downloader/fragment.py
+++ b/yt_dlp/downloader/fragment.py
@@ -72,8 +72,9 @@ class FragmentFD(FileDownloader):
             '\r[download] Got server HTTP error: %s. Retrying fragment %d (attempt %d of %s) ...'
             % (error_to_compat_str(err), frag_index, count, self.format_retries(retries)))
 
-    def report_skip_fragment(self, frag_index):
-        self.to_screen('[download] Skipping fragment %d ...' % frag_index)
+    def report_skip_fragment(self, frag_index, err=None):
+        err = f' {err};' if err else ''
+        self.to_screen(f'[download]{err} Skipping fragment {frag_index:d} ...')
 
     def _prepare_url(self, info_dict, url):
         headers = info_dict.get('http_headers')
@@ -355,8 +356,7 @@ class FragmentFD(FileDownloader):
             # not what it decrypts to.
             if self.params.get('test', False):
                 return frag_content
-            padding_len = 16 - (len(frag_content) % 16)
-            decrypted_data = aes_cbc_decrypt_bytes(frag_content + bytes([padding_len] * padding_len), decrypt_info['KEY'], iv)
+            decrypted_data = aes_cbc_decrypt_bytes(frag_content, decrypt_info['KEY'], iv)
             return decrypted_data[:-decrypted_data[-1]]
 
         return decrypt_fragment
@@ -444,7 +444,7 @@ class FragmentFD(FileDownloader):
         def append_fragment(frag_content, frag_index, ctx):
             if not frag_content:
                 if not is_fatal(frag_index - 1):
-                    self.report_skip_fragment(frag_index)
+                    self.report_skip_fragment(frag_index, 'fragment not found')
                     return True
                 else:
                     ctx['dest_stream'].close()
diff --git a/yt_dlp/downloader/http.py b/yt_dlp/downloader/http.py
index 2e95bb9d1..6290884a8 100644
--- a/yt_dlp/downloader/http.py
+++ b/yt_dlp/downloader/http.py
@@ -191,11 +191,13 @@ class HttpFD(FileDownloader):
                     # Unexpected HTTP error
                     raise
                 raise RetryDownload(err)
+            except socket.timeout as err:
+                raise RetryDownload(err)
             except socket.error as err:
-                if err.errno != errno.ECONNRESET:
+                if err.errno in (errno.ECONNRESET, errno.ETIMEDOUT):
                     # Connection reset is no problem, just retry
-                    raise
-                raise RetryDownload(err)
+                    raise RetryDownload(err)
+                raise
 
         def download():
             nonlocal throttle_start
diff --git a/yt_dlp/downloader/rtmp.py b/yt_dlp/downloader/rtmp.py
index 6dca64725..90f1acfd4 100644
--- a/yt_dlp/downloader/rtmp.py
+++ b/yt_dlp/downloader/rtmp.py
@@ -12,6 +12,7 @@ from ..utils import (
     encodeFilename,
     encodeArgument,
     get_exe_version,
+    Popen,
 )
 
 
@@ -26,7 +27,7 @@ class RtmpFD(FileDownloader):
             start = time.time()
             resume_percent = None
             resume_downloaded_data_len = None
-            proc = subprocess.Popen(args, stderr=subprocess.PIPE)
+            proc = Popen(args, stderr=subprocess.PIPE)
             cursor_in_new_line = True
             proc_stderr_closed = False
             try:
diff --git a/yt_dlp/extractor/adn.py b/yt_dlp/extractor/adn.py
index a55ebbcbd..5a1283baa 100644
--- a/yt_dlp/extractor/adn.py
+++ b/yt_dlp/extractor/adn.py
@@ -15,6 +15,7 @@ from ..compat import (
     compat_ord,
 )
 from ..utils import (
+    ass_subtitles_timecode,
     bytes_to_intlist,
     bytes_to_long,
     ExtractorError,
@@ -68,10 +69,6 @@ class ADNIE(InfoExtractor):
         'end': 4,
     }
 
-    @staticmethod
-    def _ass_subtitles_timecode(seconds):
-        return '%01d:%02d:%02d.%02d' % (seconds / 3600, (seconds % 3600) / 60, seconds % 60, (seconds % 1) * 100)
-
     def _get_subtitles(self, sub_url, video_id):
         if not sub_url:
             return None
@@ -117,8 +114,8 @@ Format: Marked,Start,End,Style,Name,MarginL,MarginR,MarginV,Effect,Text'''
                     continue
                 alignment = self._POS_ALIGN_MAP.get(position_align, 2) + self._LINE_ALIGN_MAP.get(line_align, 0)
                 ssa += os.linesep + 'Dialogue: Marked=0,%s,%s,Default,,0,0,0,,%s%s' % (
-                    self._ass_subtitles_timecode(start),
-                    self._ass_subtitles_timecode(end),
+                    ass_subtitles_timecode(start),
+                    ass_subtitles_timecode(end),
                     '{\\a%d}' % alignment if alignment != 2 else '',
                     text.replace('\n', '\\N').replace('<i>', '{\\i1}').replace('</i>', '{\\i0}'))
 
diff --git a/yt_dlp/extractor/openload.py b/yt_dlp/extractor/openload.py
index dfdd0e526..6ec54509b 100644
--- a/yt_dlp/extractor/openload.py
+++ b/yt_dlp/extractor/openload.py
@@ -17,7 +17,7 @@ from ..utils import (
     get_exe_version,
     is_outdated_version,
     std_headers,
-    process_communicate_or_kill,
+    Popen,
 )
 
 
@@ -223,11 +223,10 @@ class PhantomJSwrapper(object):
         else:
             self.extractor.to_screen('%s: %s' % (video_id, note2))
 
-        p = subprocess.Popen([
-            self.exe, '--ssl-protocol=any',
-            self._TMP_FILES['script'].name
-        ], stdout=subprocess.PIPE, stderr=subprocess.PIPE)
-        out, err = process_communicate_or_kill(p)
+        p = Popen(
+            [self.exe, '--ssl-protocol=any', self._TMP_FILES['script'].name],
+            stdout=subprocess.PIPE, stderr=subprocess.PIPE)
+        out, err = p.communicate_or_kill()
         if p.returncode != 0:
             raise ExtractorError(
                 'Executing JS failed\n:' + encodeArgument(err))
diff --git a/yt_dlp/options.py b/yt_dlp/options.py
index f45332ee1..b45b79bc9 100644
--- a/yt_dlp/options.py
+++ b/yt_dlp/options.py
@@ -968,6 +968,10 @@ def parseOpts(overrideArguments=None):
         help="File containing URLs to download ('-' for stdin), one URL per line. "
              "Lines starting with '#', ';' or ']' are considered as comments and ignored")
     filesystem.add_option(
+        '--no-batch-file',
+        dest='batchfile', action='store_const', const=None,
+        help='Do not read URLs from batch file (default)')
+    filesystem.add_option(
         '-P', '--paths',
         metavar='[TYPES:]PATH', dest='paths', default={}, type='str',
         action='callback', callback=_dict_from_options_callback,
diff --git a/yt_dlp/postprocessor/embedthumbnail.py b/yt_dlp/postprocessor/embedthumbnail.py
index 3139a6338..918d3e788 100644
--- a/yt_dlp/postprocessor/embedthumbnail.py
+++ b/yt_dlp/postprocessor/embedthumbnail.py
@@ -26,9 +26,9 @@ from ..utils import (
     encodeArgument,
     encodeFilename,
     error_to_compat_str,
+    Popen,
     PostProcessingError,
     prepend_extension,
-    process_communicate_or_kill,
     shell_quote,
 )
 
@@ -183,8 +183,8 @@ class EmbedThumbnailPP(FFmpegPostProcessor):
 
                 self._report_run('atomicparsley', filename)
                 self.write_debug('AtomicParsley command line: %s' % shell_quote(cmd))
-                p = subprocess.Popen(cmd, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
-                stdout, stderr = process_communicate_or_kill(p)
+                p = Popen(cmd, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
+                stdout, stderr = p.communicate_or_kill()
                 if p.returncode != 0:
                     msg = stderr.decode('utf-8', 'replace').strip()
                     raise EmbedThumbnailPPError(msg)
diff --git a/yt_dlp/postprocessor/ffmpeg.py b/yt_dlp/postprocessor/ffmpeg.py
index e5595341d..4a0a96427 100644
--- a/yt_dlp/postprocessor/ffmpeg.py
+++ b/yt_dlp/postprocessor/ffmpeg.py
@@ -20,9 +20,9 @@ from ..utils import (
     is_outdated_version,
     ISO639Utils,
     orderedSet,
+    Popen,
     PostProcessingError,
     prepend_extension,
-    process_communicate_or_kill,
     replace_extension,
     shell_quote,
     traverse_obj,
@@ -178,10 +178,8 @@ class FFmpegPostProcessor(PostProcessor):
                     encodeArgument('-i')]
             cmd.append(encodeFilename(self._ffmpeg_filename_argument(path), True))
             self.write_debug('%s command line: %s' % (self.basename, shell_quote(cmd)))
-            handle = subprocess.Popen(
-                cmd, stderr=subprocess.PIPE,
-                stdout=subprocess.PIPE, stdin=subprocess.PIPE)
-            stdout_data, stderr_data = process_communicate_or_kill(handle)
+            handle = Popen(cmd, stdin=subprocess.PIPE, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
+            stdout_data, stderr_data = handle.communicate_or_kill()
             expected_ret = 0 if self.probe_available else 1
             if handle.wait() != expected_ret:
                 return None
@@ -223,7 +221,7 @@ class FFmpegPostProcessor(PostProcessor):
         cmd += opts
         cmd.append(encodeFilename(self._ffmpeg_filename_argument(path), True))
         self.write_debug('ffprobe command line: %s' % shell_quote(cmd))
-        p = subprocess.Popen(cmd, stdout=subprocess.PIPE, stderr=subprocess.PIPE, stdin=subprocess.PIPE)
+        p = Popen(cmd, stdout=subprocess.PIPE, stderr=subprocess.PIPE, stdin=subprocess.PIPE)
         stdout, stderr = p.communicate()
         return json.loads(stdout.decode('utf-8', 'replace'))
 
@@ -284,8 +282,8 @@ class FFmpegPostProcessor(PostProcessor):
                 for i, (path, opts) in enumerate(path_opts) if path)
 
         self.write_debug('ffmpeg command line: %s' % shell_quote(cmd))
-        p = subprocess.Popen(cmd, stdout=subprocess.PIPE, stderr=subprocess.PIPE, stdin=subprocess.PIPE)
-        stdout, stderr = process_communicate_or_kill(p)
+        p = Popen(cmd, stdout=subprocess.PIPE, stderr=subprocess.PIPE, stdin=subprocess.PIPE)
+        stdout, stderr = p.communicate_or_kill()
         if p.returncode not in variadic(expected_retcodes):
             stderr = stderr.decode('utf-8', 'replace').strip()
             self.write_debug(stderr)
diff --git a/yt_dlp/postprocessor/modify_chapters.py b/yt_dlp/postprocessor/modify_chapters.py
index a0818c41b..dca876200 100644
--- a/yt_dlp/postprocessor/modify_chapters.py
+++ b/yt_dlp/postprocessor/modify_chapters.py
@@ -31,8 +31,10 @@ class ModifyChaptersPP(FFmpegPostProcessor):
 
     @PostProcessor._restrict_to(images=False)
     def run(self, info):
+        # Chapters must be preserved intact when downloading multiple formats of the same video.
         chapters, sponsor_chapters = self._mark_chapters_to_remove(
-            info.get('chapters') or [], info.get('sponsorblock_chapters') or [])
+            copy.deepcopy(info.get('chapters')) or [],
+            copy.deepcopy(info.get('sponsorblock_chapters')) or [])
         if not chapters and not sponsor_chapters:
             return [], info
 
@@ -126,7 +128,7 @@ class ModifyChaptersPP(FFmpegPostProcessor):
         cuts = []
 
         def append_cut(c):
-            assert 'remove' in c
+            assert 'remove' in c, 'Not a cut is appended to cuts'
             last_to_cut = cuts[-1] if cuts else None
             if last_to_cut and last_to_cut['end_time'] >= c['start_time']:
                 last_to_cut['end_time'] = max(last_to_cut['end_time'], c['end_time'])
@@ -154,7 +156,7 @@ class ModifyChaptersPP(FFmpegPostProcessor):
         new_chapters = []
 
         def append_chapter(c):
-            assert 'remove' not in c
+            assert 'remove' not in c, 'Cut is appended to chapters'
             length = c['end_time'] - c['start_time'] - excess_duration(c)
             # Chapter is completely covered by cuts or sponsors.
             if length <= 0:
@@ -237,7 +239,7 @@ class ModifyChaptersPP(FFmpegPostProcessor):
                     heapq.heappush(chapters, (c['start_time'], i, c))
             # (normal, sponsor) and (sponsor, sponsor)
             else:
-                assert '_categories' in c
+                assert '_categories' in c, 'Normal chapters overlap'
                 cur_chapter['_was_cut'] = True
                 c['_was_cut'] = True
                 # Push the part after the sponsor to PQ.
diff --git a/yt_dlp/postprocessor/sponskrub.py b/yt_dlp/postprocessor/sponskrub.py
index 932555a0e..37e7411e4 100644
--- a/yt_dlp/postprocessor/sponskrub.py
+++ b/yt_dlp/postprocessor/sponskrub.py
@@ -11,9 +11,9 @@ from ..utils import (
     encodeFilename,
     shell_quote,
     str_or_none,
+    Popen,
     PostProcessingError,
     prepend_extension,
-    process_communicate_or_kill,
 )
 
 
@@ -81,8 +81,8 @@ class SponSkrubPP(PostProcessor):
 
         self.write_debug('sponskrub command line: %s' % shell_quote(cmd))
         pipe = None if self.get_param('verbose') else subprocess.PIPE
-        p = subprocess.Popen(cmd, stdout=pipe)
-        stdout = process_communicate_or_kill(p)[0]
+        p = Popen(cmd, stdout=pipe)
+        stdout = p.communicate_or_kill()[0]
 
         if p.returncode == 0:
             os.replace(temp_filename, filename)
diff --git a/yt_dlp/utils.py b/yt_dlp/utils.py
index c42817e75..88adbd3b9 100644
--- a/yt_dlp/utils.py
+++ b/yt_dlp/utils.py
@@ -2272,6 +2272,20 @@ def process_communicate_or_kill(p, *args, **kwargs):
         raise
 
 
+class Popen(subprocess.Popen):
+    if sys.platform == 'win32':
+        _startupinfo = subprocess.STARTUPINFO()
+        _startupinfo.dwFlags |= subprocess.STARTF_USESHOWWINDOW
+    else:
+        _startupinfo = None
+
+    def __init__(self, *args, **kwargs):
+        super(Popen, self).__init__(*args, **kwargs, startupinfo=self._startupinfo)
+
+    def communicate_or_kill(self, *args, **kwargs):
+        return process_communicate_or_kill(self, *args, **kwargs)
+
+
 def get_subprocess_encoding():
     if sys.platform == 'win32' and sys.getwindowsversion()[0] >= 5:
         # For subprocess calls, encode with locale encoding
@@ -2342,14 +2356,25 @@ def decodeOption(optval):
     return optval
 
 
+_timetuple = collections.namedtuple('Time', ('hours', 'minutes', 'seconds', 'milliseconds'))
+
+
+def timetuple_from_msec(msec):
+    secs, msec = divmod(msec, 1000)
+    mins, secs = divmod(secs, 60)
+    hrs, mins = divmod(mins, 60)
+    return _timetuple(hrs, mins, secs, msec)
+
+
 def formatSeconds(secs, delim=':', msec=False):
-    if secs > 3600:
-        ret = '%d%s%02d%s%02d' % (secs // 3600, delim, (secs % 3600) // 60, delim, secs % 60)
-    elif secs > 60:
-        ret = '%d%s%02d' % (secs // 60, delim, secs % 60)
+    time = timetuple_from_msec(secs * 1000)
+    if time.hours:
+        ret = '%d%s%02d%s%02d' % (time.hours, delim, time.minutes, delim, time.seconds)
+    elif time.minutes:
+        ret = '%d%s%02d' % (time.minutes, delim, time.seconds)
     else:
-        ret = '%d' % secs
-    return '%s.%03d' % (ret, secs % 1) if msec else ret
+        ret = '%d' % time.seconds
+    return '%s.%03d' % (ret, time.milliseconds) if msec else ret
 
 
 def _ssl_load_windows_store_certs(ssl_context, storename):
@@ -3966,8 +3991,7 @@ def check_executable(exe, args=[]):
     """ Checks if the given binary is installed somewhere in PATH, and returns its name.
     args can be a list of arguments for a short output (like -version) """
     try:
-        process_communicate_or_kill(subprocess.Popen(
-            [exe] + args, stdout=subprocess.PIPE, stderr=subprocess.PIPE))
+        Popen([exe] + args, stdout=subprocess.PIPE, stderr=subprocess.PIPE).communicate_or_kill()
     except OSError:
         return False
     return exe
@@ -3981,10 +4005,9 @@ def get_exe_version(exe, args=['--version'],
         # STDIN should be redirected too. On UNIX-like systems, ffmpeg triggers
         # SIGTTOU if yt-dlp is run in the background.
         # See https://github.com/ytdl-org/youtube-dl/issues/955#issuecomment-209789656
-        out, _ = process_communicate_or_kill(subprocess.Popen(
-            [encodeArgument(exe)] + args,
-            stdin=subprocess.PIPE,
-            stdout=subprocess.PIPE, stderr=subprocess.STDOUT))
+        out, _ = Popen(
+            [encodeArgument(exe)] + args, stdin=subprocess.PIPE,
+            stdout=subprocess.PIPE, stderr=subprocess.STDOUT).communicate_or_kill()
     except OSError:
         return False
     if isinstance(out, bytes):  # Python 2.x
@@ -4855,7 +4878,12 @@ def parse_dfxp_time_expr(time_expr):
 
 
 def srt_subtitles_timecode(seconds):
-    return '%02d:%02d:%02d,%03d' % (seconds / 3600, (seconds % 3600) / 60, seconds % 60, (seconds % 1) * 1000)
+    return '%02d:%02d:%02d,%03d' % timetuple_from_msec(seconds * 1000)
+
+
+def ass_subtitles_timecode(seconds):
+    time = timetuple_from_msec(seconds * 1000)
+    return '%01d:%02d:%02d.%02d' % (*time[:-1], time.milliseconds / 10)
 
 
 def dfxp2srt(dfxp_data):
@@ -6139,11 +6167,11 @@ def write_xattr(path, key, value):
                        + [encodeFilename(path, True)])
 
                 try:
-                    p = subprocess.Popen(
+                    p = Popen(
                         cmd, stdout=subprocess.PIPE, stderr=subprocess.PIPE, stdin=subprocess.PIPE)
                 except EnvironmentError as e:
                     raise XAttrMetadataError(e.errno, e.strerror)
-                stdout, stderr = process_communicate_or_kill(p)
+                stdout, stderr = p.communicate_or_kill()
                 stderr = stderr.decode('utf-8', 'replace')
                 if p.returncode != 0:
                     raise XAttrMetadataError(p.returncode, stderr)
diff --git a/yt_dlp/webvtt.py b/yt_dlp/webvtt.py
index cd936e7e5..962aa57ad 100644
--- a/yt_dlp/webvtt.py
+++ b/yt_dlp/webvtt.py
@@ -13,7 +13,7 @@ in RFC 8216 §3.5 <https://tools.ietf.org/html/rfc8216#section-3.5>.
 
 import re
 import io
-from .utils import int_or_none
+from .utils import int_or_none, timetuple_from_msec
 from .compat import (
     compat_str as str,
     compat_Pattern,
@@ -124,11 +124,7 @@ def _format_ts(ts):
     Convert an MPEG PES timestamp into a WebVTT timestamp.
     This will lose sub-millisecond precision.
     """
-    msec = int((ts + 45) // 90)
-    secs, msec = divmod(msec, 1000)
-    mins, secs = divmod(secs, 60)
-    hrs, mins = divmod(mins, 60)
-    return '%02u:%02u:%02u.%03u' % (hrs, mins, secs, msec)
+    return '%02u:%02u:%02u.%03u' % timetuple_from_msec(int((ts + 45) // 90))
 
 
 class Block(object):