[ModifyChapters] add --round-cuts-to-keyframes option

test/test_postprocessors.py

@@ -558,6 +558,53 @@ class TestModifyChaptersPP(unittest.TestCase):
                 '[SponsorBlock]: Sponsor', 'c',
             ]), [])
 
+    def test_round_remove_chapter_Common(self):
+        keyframes = [1, 3, 5, 7]
+        chapters = self._pp._round_remove_chapters(keyframes, [
+            {'start_time': 0, 'end_time': 2},
+            {'start_time': 2, 'end_time': 6, 'remove': True},
+            {'start_time': 6, 'end_time': 10, 'remove': False},
+        ])
+        self.assertEqual(chapters, [
+            {'start_time': 0, 'end_time': 2},
+            {'start_time': 3, 'end_time': 5, 'remove': True},
+            {'start_time': 6, 'end_time': 10, 'remove': False},
+        ])
+
+    def test_round_remove_chapter_AlreadyKeyframe(self):
+        keyframes = [1, 3, 5, 7]
+        chapters = self._pp._round_remove_chapters(keyframes, [
+            {'start_time': 0, 'end_time': 2},
+            {'start_time': 3, 'end_time': 7, 'remove': True},
+            {'start_time': 6, 'end_time': 10, 'remove': False},
+        ])
+        self.assertEqual(chapters, [
+            {'start_time': 0, 'end_time': 2},
+            {'start_time': 3, 'end_time': 7, 'remove': True},
+            {'start_time': 6, 'end_time': 10, 'remove': False},
+        ])
+
+    def test_round_remove_chapter_RemoveEnd(self):
+        keyframes = [1, 3, 5, 7]
+        chapters = self._pp._round_remove_chapters(keyframes, [
+            {'start_time': 0, 'end_time': 2},
+            {'start_time': 3, 'end_time': 8, 'remove': True},
+        ])
+        self.assertEqual(chapters, [
+            {'start_time': 0, 'end_time': 2},
+            {'start_time': 3, 'end_time': 8, 'remove': True},
+        ])
+
+    def test_round_remove_chapter_RemoveAfterLast(self):
+        keyframes = [1, 3, 5, 7]
+        chapters = self._pp._round_remove_chapters(keyframes, [
+            {'start_time': 0, 'end_time': 2},
+            {'start_time': 8, 'end_time': 9, 'remove': True},
+        ])
+        self.assertEqual(chapters, [
+            {'start_time': 0, 'end_time': 2},
+        ])
+
     def test_make_concat_opts_CommonCase(self):
         sponsor_chapters = [self._chapter(1, 2, 's1'), self._chapter(10, 20, 's2')]
         expected = '''ffconcat version 1.0

yt_dlp/__init__.py

@@ -677,6 +677,7 @@ def get_postprocessors(opts):
             'remove_ranges': opts.remove_ranges,
             'sponsorblock_chapter_title': opts.sponsorblock_chapter_title,
             'force_keyframes': opts.force_keyframes_at_cuts,
+            'round_to_keyframes': opts.round_cuts_to_keyframes,
         }
     # FFmpegMetadataPP should be run after FFmpegVideoConvertorPP and
     # FFmpegExtractAudioPP as containers before conversion may not support

yt_dlp/options.py

@@ -1778,6 +1778,17 @@ def create_parser():
         '--no-force-keyframes-at-cuts',
         action='store_false', dest='force_keyframes_at_cuts',
         help='Do not force keyframes around the chapters when cutting/splitting (default)')
+    postproc.add_option(
+        '--round-cuts-to-keyframes',
+        action='store_true', dest='round_cuts_to_keyframes', default=False,
+        help=(
+            'Rounds cuts to the nearest keyframe when removing sections. '
+            'This may result in some more content being included than specified, but makes problems around cuts '
+            'less likely'))
+    postproc.add_option(
+        '--no-round-cuts-to-keyframes',
+        action='store_false', dest='round_cuts_to_keyframes',
+        help='Do not rounds cuts to the nearest keyframe when removing sections (default)')
     _postprocessor_opts_parser = lambda key, val='': (
         *(item.split('=', 1) for item in (val.split(';') if val else [])),
         ('key', remove_end(key, 'PP')))

yt_dlp/postprocessor/ffmpeg.py

@@ -393,6 +393,32 @@ class FFmpegPostProcessor(PostProcessor):
         string = string[1:] if string[0] == "'" else "'" + string
         return string[:-1] if string[-1] == "'" else string + "'"
 
+    def get_keyframe_timestamps(self, path, opts=[]):
+        if self.probe_basename != 'ffprobe':
+            if self.probe_available:
+                self.report_warning('Only ffprobe is supported for keyframe timestamp extraction')
+            raise PostProcessingError('ffprobe not found. Please install or provide the path using --ffmpeg-location')
+
+        self.check_version()
+
+        cmd = [
+            self.probe_executable,
+            encodeArgument('-select_streams'),
+            encodeArgument('v:0'),
+            encodeArgument('-show_entries'),
+            encodeArgument('packet=pts_time,flags'),
+            encodeArgument('-print_format'),
+            encodeArgument('json'),
+        ]
+
+        cmd += opts
+        cmd.append(self._ffmpeg_filename_argument(path))
+        self.write_debug(f'ffprobe command line: {shell_quote(cmd)}')
+        stdout, _, _ = Popen.run(cmd, text=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE, stdin=subprocess.PIPE)
+        result = json.loads(stdout)
+
+        return [float(packet['pts_time']) for packet in result['packets'] if 'K' in packet['flags']]
+
     def force_keyframes(self, filename, timestamps):
         timestamps = orderedSet(timestamps)
         if timestamps[0] == 0:

yt_dlp/postprocessor/modify_chapters.py

@@ -1,3 +1,4 @@
+import bisect
 import copy
 import heapq
 import os
@@ -13,13 +14,16 @@ DEFAULT_SPONSORBLOCK_CHAPTER_TITLE = '[SponsorBlock]: %(category_names)l'
 
 class ModifyChaptersPP(FFmpegPostProcessor):
     def __init__(self, downloader, remove_chapters_patterns=None, remove_sponsor_segments=None, remove_ranges=None,
-                 *, sponsorblock_chapter_title=DEFAULT_SPONSORBLOCK_CHAPTER_TITLE, force_keyframes=False):
+                 *, sponsorblock_chapter_title=DEFAULT_SPONSORBLOCK_CHAPTER_TITLE, force_keyframes=False,
+                 round_to_keyframes=False):
         FFmpegPostProcessor.__init__(self, downloader)
         self._remove_chapters_patterns = set(remove_chapters_patterns or [])
-        self._remove_sponsor_segments = set(remove_sponsor_segments or []) - set(SponsorBlockPP.NON_SKIPPABLE_CATEGORIES.keys())
+        self._remove_sponsor_segments = set(remove_sponsor_segments or []) - set(
+            SponsorBlockPP.NON_SKIPPABLE_CATEGORIES.keys())
         self._ranges_to_remove = set(remove_ranges or [])
         self._sponsorblock_chapter_title = sponsorblock_chapter_title
         self._force_keyframes = force_keyframes
+        self._round_to_keyframes = round_to_keyframes
 
     @PostProcessor._restrict_to(images=False)
     def run(self, info):
@@ -35,7 +39,12 @@ class ModifyChaptersPP(FFmpegPostProcessor):
         if not chapters:
             chapters = [{'start_time': 0, 'end_time': info.get('duration') or real_duration, 'title': info['title']}]
 
-        info['chapters'], cuts = self._remove_marked_arrange_sponsors(chapters + sponsor_chapters)
+        chapters += sponsor_chapters
+        if self._round_to_keyframes:
+            keyframes = self.get_keyframe_timestamps(info['filepath'])
+            self._round_remove_chapters(keyframes, chapters)
+
+        info['chapters'], cuts = self._remove_marked_arrange_sponsors(chapters)
         if not cuts:
             return [], info
         elif not info['chapters']:
@@ -54,7 +63,8 @@ class ModifyChaptersPP(FFmpegPostProcessor):
                 self.write_debug('Expected and actual durations mismatch')
 
         concat_opts = self._make_concat_opts(cuts, real_duration)
-        self.write_debug('Concat spec = {}'.format(', '.join(f'{c.get("inpoint", 0.0)}-{c.get("outpoint", "inf")}' for c in concat_opts)))
+        self.write_debug('Concat spec = {}'.format(
+            ', '.join(f'{c.get("inpoint", 0.0)}-{c.get("outpoint", "inf")}' for c in concat_opts)))
 
         def remove_chapters(file, is_sub):
             return file, self.remove_chapters(file, cuts, concat_opts, self._force_keyframes and not is_sub)
@@ -117,7 +127,8 @@ class ModifyChaptersPP(FFmpegPostProcessor):
                 continue
             ext = sub['ext']
             if ext not in FFmpegSubtitlesConvertorPP.SUPPORTED_EXTS:
-                self.report_warning(f'Cannot remove chapters from external {ext} subtitles; "{sub_file}" is now out of sync')
+                self.report_warning(
+                    f'Cannot remove chapters from external {ext} subtitles; "{sub_file}" is now out of sync')
                 continue
             # TODO: create __real_download for subs?
             yield sub_file
@@ -314,13 +325,33 @@ class ModifyChaptersPP(FFmpegPostProcessor):
         in_file = filename
         out_file = prepend_extension(in_file, 'temp')
         if force_keyframes:
-            in_file = self.force_keyframes(in_file, (t for c in ranges_to_cut for t in (c['start_time'], c['end_time'])))
+            in_file = self.force_keyframes(in_file,
+                                           (t for c in ranges_to_cut for t in (c['start_time'], c['end_time'])))
         self.to_screen(f'Removing chapters from {filename}')
         self.concat_files([in_file] * len(concat_opts), out_file, concat_opts)
         if in_file != filename:
             self._delete_downloaded_files(in_file, msg=None)
         return out_file
 
+    @staticmethod
+    def _round_remove_chapters(keyframes, chapters):
+        result = []
+        for c in chapters:
+            if not c.get('remove', False) or not keyframes:
+                result.append(c)
+                continue
+
+            start_frame = bisect.bisect_left(keyframes, c['start_time'])
+            if start_frame >= len(keyframes):
+                continue
+
+            c['start_time'] = keyframes[start_frame]
+            if c['end_time'] < keyframes[-1]:
+                c['end_time'] = keyframes[bisect.bisect_right(keyframes, c['end_time']) - 1]
+            result.append(c)
+
+        return result
+
     @staticmethod
     def _make_concat_opts(chapters_to_remove, duration):
         opts = [{}]