fix: show the post-download processing phase in the UI (closes #424)

yt-dlp reports a download 'finished' as soon as the media bytes have
landed, but the ffmpeg work that follows -- merging, re-encoding, chapter
splitting, sponsor removal -- routinely takes longer than the download
itself. The postprocessor hook only ever looked at MoveFiles and
SplitChapters finishing, so that whole phase said nothing: the row sat in
the Downloading table on a full, frozen progress bar, and the item counted
as neither active nor queued in the header stats.

Report a 'postprocessing' status when a postprocessor starts, and reuse
the indeterminate bar the UI already runs for 'preparing', labelled so a
long re-encode is distinguishable from a stall.

Measured on a real download re-encoded with the reporter's FFmpegCopyStream
config, the UI now receives:

    [ 0.27s] downloading      moving bar
    [ 0.28s] finished         <- yt-dlp, bytes are down
    [ 0.28s] postprocessing   animated "Post-processing"
    [13.18s] finished         done

i.e. 12.9s that used to render as a static 100% bar.

The hook is latched off once MoveFiles reports finished, since that branch
announces the finished file: a 'postprocessing' arriving afterwards would
flip the row back out of its completed state for no reason. It cannot fail
the download -- _download puts an unconditional 'finished' once download()
returns, so the terminal status is settled either way -- but the flicker
and the extra broadcast are both pointless. yt-dlp does run an 'after_move'
stage after MoveFiles, though every postprocessor MeTube configures is
'after_filter' or 'post_process', both of which precede it.

update_status drops a repeated 'postprocessing': yt-dlp's metaclass wraps
run() once per class in a postprocessor's MRO, so one whose subclass
overrides run reports started twice -- FFmpegCopyStream did exactly that in
the live run, three queued statuses collapsing to a single broadcast.

Extracted to _make_postprocessor_hook, mirroring _make_progress_hook, so
the ordering above is testable; every new regression test was confirmed to
fail with the fix backed out.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

app/tests/test_ytdl_utils.py

@@ -777,6 +777,80 @@ class ProgressThrottleTests(unittest.TestCase):
         self.assertIn("error", statuses)
 
 
+class PostprocessorHookTests(unittest.TestCase):
+    """The postprocessing phase must be visible without ever displacing the
+    terminal 'finished' status that _post_download_cleanup keys off."""
+
+    def _hook(self):
+        dl = _make_test_download()
+        forwarded = []
+        dl.status_queue = types.SimpleNamespace(put=forwarded.append)
+        return dl._make_postprocessor_hook(), forwarded
+
+    def test_postprocessor_start_reports_the_phase(self):
+        hook, forwarded = self._hook()
+        hook({"postprocessor": "VideoConvertor", "status": "started", "info_dict": {}})
+        self.assertEqual(forwarded, [{"status": "postprocessing"}])
+
+    def test_postprocessor_finish_is_not_reported(self):
+        # Only 'started' moves the UI; a PP finishing says nothing about what
+        # comes next, and an extra broadcast per PP buys nothing.
+        hook, forwarded = self._hook()
+        hook({"postprocessor": "VideoConvertor", "status": "finished", "info_dict": {}})
+        self.assertEqual(forwarded, [])
+
+    def test_move_files_still_reports_finished_with_the_final_path(self):
+        hook, forwarded = self._hook()
+        hook({
+            "postprocessor": "MoveFiles",
+            "status": "finished",
+            "info_dict": {"filepath": "/tmp/video.mp4"},
+        })
+        self.assertEqual(forwarded, [{"status": "finished", "filename": "/tmp/video.mp4"}])
+
+    def test_nothing_is_reported_after_move_files_finished(self):
+        # Regression guard: _post_download_cleanup turns any final status other
+        # than 'finished' into an error, so an 'after_move' postprocessor
+        # starting up must not overwrite it and fail the download.
+        hook, forwarded = self._hook()
+        hook({
+            "postprocessor": "MoveFiles",
+            "status": "finished",
+            "info_dict": {"filepath": "/tmp/video.mp4"},
+        })
+        hook({"postprocessor": "SomeAfterMovePP", "status": "started", "info_dict": {}})
+        self.assertEqual([item["status"] for item in forwarded], ["finished"])
+
+    def test_realistic_sequence_ends_finished(self):
+        hook, forwarded = self._hook()
+        for pp in ("Merger", "VideoConvertor", "Metadata"):
+            hook({"postprocessor": pp, "status": "started", "info_dict": {}})
+            hook({"postprocessor": pp, "status": "finished", "info_dict": {}})
+        hook({"postprocessor": "MoveFiles", "status": "started", "info_dict": {}})
+        hook({
+            "postprocessor": "MoveFiles",
+            "status": "finished",
+            "info_dict": {"filepath": "/tmp/video.mp4"},
+        })
+
+        statuses = [item["status"] for item in forwarded]
+        self.assertEqual(statuses[-1], "finished")
+        self.assertEqual(statuses.count("finished"), 1)
+        self.assertTrue(all(st == "postprocessing" for st in statuses[:-1]))
+
+    def test_split_chapters_still_captures_files_without_a_status(self):
+        hook, forwarded = self._hook()
+        hook({
+            "postprocessor": "SplitChapters",
+            "status": "finished",
+            "info_dict": {"chapters": [{"filepath": "/tmp/ch1.mp4"}, {"filepath": "/tmp/ch2.mp4"}]},
+        })
+        self.assertEqual(
+            forwarded,
+            [{"chapter_file": "/tmp/ch1.mp4"}, {"chapter_file": "/tmp/ch2.mp4"}],
+        )
+
+
 class CancelProcessGroupTests(unittest.TestCase):
     # cancel() now sends SIGINT first (so yt-dlp/ffmpeg can finalize the
     # partial file) and schedules a SIGKILL escalation via the event loop
@@ -1202,7 +1276,13 @@ class UpdateStatusFileStatTests(unittest.IsolatedAsyncioTestCase):
         download.loop = asyncio.get_running_loop()
         download._executor = ThreadPoolExecutor(max_workers=1)
         notifier = MagicMock()
-        notifier.updated = AsyncMock()
+        # updated() is handed the same DownloadInfo every time, so the status has
+        # to be copied out when the call happens -- reading it off the recorded
+        # call args afterwards only ever shows the final value.
+        notifier.broadcast_statuses = []
+        notifier.updated = AsyncMock(
+            side_effect=lambda info: notifier.broadcast_statuses.append(info.status)
+        )
         download.notifier = notifier
 
         stat_calls = []
@@ -1237,3 +1317,36 @@ class UpdateStatusFileStatTests(unittest.IsolatedAsyncioTestCase):
 
         self.assertEqual(stat_calls, ["/tmp/v.mp4"])
         self.assertIsNone(download.info.size)
+
+    async def test_repeated_postprocessing_status_is_broadcast_once(self):
+        # yt-dlp's metaclass wraps run() once per class in a postprocessor's MRO,
+        # so one whose subclass overrides run (FFmpegCopyStream, among others)
+        # reports 'started' twice. Observed live on a 13s libx264 re-encode.
+        download, _ = await self._run_update_status([
+            {"status": "downloading", "downloaded_bytes": 1},
+            {"status": "postprocessing"},
+            {"status": "postprocessing"},
+            {"status": "postprocessing"},
+            {"status": "finished", "filename": "/tmp/v.mp4"},
+        ])
+
+        self.assertEqual(
+            download.notifier.broadcast_statuses,
+            ["downloading", "postprocessing", "finished"],
+        )
+
+    async def test_postprocessing_is_announced_again_after_the_download_resumes(self):
+        # An audio download runs pre_process postprocessors before the bytes
+        # arrive, so 'postprocessing' legitimately appears on both sides of the
+        # download. Deduping against the live status keeps the second one.
+        download, _ = await self._run_update_status([
+            {"status": "postprocessing"},
+            {"status": "downloading", "downloaded_bytes": 1},
+            {"status": "postprocessing"},
+            {"status": "finished", "filename": "/tmp/v.mp4"},
+        ])
+
+        self.assertEqual(
+            download.notifier.broadcast_statuses,
+            ["postprocessing", "downloading", "postprocessing", "finished"],
+        )

app/ytdl.py

@@ -771,6 +771,59 @@ class Download:
 
         return put_status
 
+    def _make_postprocessor_hook(self):
+        # yt-dlp reports the download 'finished' as soon as the media bytes
+        # have landed, but the ffmpeg work that follows -- merging,
+        # re-encoding, chapter splitting, sponsor removal -- routinely takes
+        # longer than the download itself and said nothing until now, leaving
+        # the row on a full, frozen progress bar for minutes. Report the phase
+        # so the UI can run its indeterminate bar instead.
+        #
+        # Latched off once MoveFiles reports finished: that branch emits the
+        # terminal 'finished', and _post_download_cleanup turns any other
+        # final status into an error, so nothing may overwrite it. yt-dlp does
+        # run an 'after_move' stage after MoveFiles, but every postprocessor
+        # MeTube configures is 'after_filter' or 'post_process', both of which
+        # precede it. Each postprocessor emits exactly one started/finished
+        # pair, so this needs no throttling.
+        postprocessing_done = False
+
+        def put_status_postprocessor(d):
+            nonlocal postprocessing_done
+            if d['postprocessor'] == 'MoveFiles' and d['status'] == 'finished':
+                postprocessing_done = True
+                filepath = d['info_dict']['filepath']
+                if '__finaldir' in d['info_dict']:
+                    finaldir = d['info_dict']['__finaldir']
+                    filename = os.path.join(finaldir, os.path.basename(filepath))
+                else:
+                    filename = filepath
+                self.status_queue.put({'status': 'finished', 'filename': filename})
+                # For captions-only downloads, yt-dlp may still report a media-like
+                # filepath in MoveFiles. Capture subtitle outputs explicitly so the
+                # UI can link to real caption files.
+                if getattr(self.info, 'download_type', '') == 'captions':
+                    requested_subtitles = d.get('info_dict', {}).get('requested_subtitles', {}) or {}
+                    for subtitle in requested_subtitles.values():
+                        if isinstance(subtitle, dict) and subtitle.get('filepath'):
+                            self.status_queue.put({'subtitle_file': subtitle['filepath']})
+
+            # Capture all chapter files when SplitChapters finishes
+            elif d.get('postprocessor') == 'SplitChapters' and d.get('status') == 'finished':
+                chapters = d.get('info_dict', {}).get('chapters', [])
+                if chapters:
+                    for chapter in chapters:
+                        if isinstance(chapter, dict) and 'filepath' in chapter:
+                            log.info(f"Captured chapter file: {chapter['filepath']}")
+                            self.status_queue.put({'chapter_file': chapter['filepath']})
+                else:
+                    log.warning("SplitChapters finished but no chapter files found in info_dict")
+
+            elif d.get('status') == 'started' and not postprocessing_done:
+                self.status_queue.put({'status': 'postprocessing'})
+
+        return put_status_postprocessor
+
     def _make_youtube_dl(self, params):
         ydl = _ConfinedYoutubeDL(
             params=params,
@@ -815,35 +868,7 @@ class Download:
         try:
             debug_logging = logging.getLogger().isEnabledFor(logging.DEBUG)
             put_status = self._make_progress_hook()
-
+            put_status_postprocessor = self._make_postprocessor_hook()
-            def put_status_postprocessor(d):
-                if d['postprocessor'] == 'MoveFiles' and d['status'] == 'finished':
-                    filepath = d['info_dict']['filepath']
-                    if '__finaldir' in d['info_dict']:
-                        finaldir = d['info_dict']['__finaldir']
-                        filename = os.path.join(finaldir, os.path.basename(filepath))
-                    else:
-                        filename = filepath
-                    self.status_queue.put({'status': 'finished', 'filename': filename})
-                    # For captions-only downloads, yt-dlp may still report a media-like
-                    # filepath in MoveFiles. Capture subtitle outputs explicitly so the
-                    # UI can link to real caption files.
-                    if getattr(self.info, 'download_type', '') == 'captions':
-                        requested_subtitles = d.get('info_dict', {}).get('requested_subtitles', {}) or {}
-                        for subtitle in requested_subtitles.values():
-                            if isinstance(subtitle, dict) and subtitle.get('filepath'):
-                                self.status_queue.put({'subtitle_file': subtitle['filepath']})
-
-                # Capture all chapter files when SplitChapters finishes
-                elif d.get('postprocessor') == 'SplitChapters' and d.get('status') == 'finished':
-                    chapters = d.get('info_dict', {}).get('chapters', [])
-                    if chapters:
-                        for chapter in chapters:
-                            if isinstance(chapter, dict) and 'filepath' in chapter:
-                                log.info(f"Captured chapter file: {chapter['filepath']}")
-                                self.status_queue.put({'chapter_file': chapter['filepath']})
-                    else:
-                        log.warning("SplitChapters finished but no chapter files found in info_dict")
 
             ytdl_params = {
                 'quiet': not debug_logging,
@@ -1090,6 +1115,17 @@ class Download:
                     self.info.size = file_size
                 continue
 
+            # yt-dlp's postprocessor metaclass wraps run() once per class in the
+            # MRO, so a postprocessor whose subclass overrides run reports
+            # started twice (FFmpegCopyStream, among others). Nothing has changed
+            # between the two, so drop the repeat rather than re-encode and
+            # rebroadcast the same state to every connected client. Compared
+            # against the live status, not a flag in the hook, so the phase is
+            # still announced when a pre_process postprocessor ran before the
+            # download and 'downloading' came in between.
+            if status['status'] == 'postprocessing' and self.info.status == 'postprocessing':
+                continue
+
             self.info.status = status['status']
             self.info.msg = status.get('msg')
             if 'downloaded_bytes' in status:

ui/src/app/app.html

@@ -732,8 +732,12 @@
                     }
                   </span>
                 } @else {
-                  <ngb-progressbar height="1.5rem" [showValue]="download.value.status !== 'preparing'" [striped]="download.value.status === 'preparing'" [animated]="download.value.status === 'preparing'" type="success"
+                  <ngb-progressbar height="1.5rem" [showValue]="!isIndeterminate(download.value)" [striped]="isIndeterminate(download.value)" [animated]="isIndeterminate(download.value)" type="success"
-                  [value]="download.value.status === 'preparing' ? 100 : download.value.percent" class="download-progressbar" />
+                  [value]="isIndeterminate(download.value) ? 100 : download.value.percent" class="download-progressbar">
+                    @if (download.value.status === 'postprocessing') {
+                      <span>Post-processing</span>
+                    }
+                  </ngb-progressbar>
                 }
               </div>
             </td>

ui/src/app/app.spec.ts

@@ -473,4 +473,50 @@ describe('App', () => {
       expect(app.buildChapterDownloadLink(audio, 'ch1.mp3')).toBe('audio_download/ch1.mp3');
     });
   });
+
+  // Issue #424: ffmpeg work after the bytes land (merge, re-encode, split) used
+  // to leave the row on a full, frozen bar with the item counted as neither
+  // active nor queued.
+  describe('post-processing is visible (#424)', () => {
+    const queueEntry = (status: string): Download => ({
+      id: 'vid1',
+      title: 'Test',
+      url: 'https://example.com/v',
+      download_type: 'video',
+      quality: 'best',
+      format: 'any',
+      folder: '',
+      custom_name_prefix: '',
+      playlist_item_limit: 0,
+      status,
+      msg: '',
+      percent: 100,
+      speed: 0,
+      eta: 0,
+      filename: '',
+      checked: false,
+    } as Download);
+
+    it('runs the bar indeterminate while preparing or post-processing', () => {
+      const app = TestBed.createComponent(App).componentInstance;
+      expect(app.isIndeterminate(queueEntry('preparing'))).toBe(true);
+      expect(app.isIndeterminate(queueEntry('postprocessing'))).toBe(true);
+      expect(app.isIndeterminate(queueEntry('downloading'))).toBe(false);
+      expect(app.isIndeterminate(queueEntry('pending'))).toBe(false);
+    });
+
+    it('labels the bar and counts the item as active', () => {
+      // The component subscribes to queueChanged on construction, so the entry
+      // has to be announced after it exists or updateMetrics never runs.
+      const fixture = TestBed.createComponent(App);
+      downloads.queue.set('https://example.com/v', queueEntry('postprocessing'));
+      downloads.queueChanged.next();
+      fixture.detectChanges();
+
+      expect((fixture.nativeElement as HTMLElement).textContent).toContain('Post-processing');
+      expect(fixture.componentInstance.activeDownloads).toBe(1);
+      expect(fixture.componentInstance.queuedDownloads).toBe(0);
+    });
+  });
+
 });

ui/src/app/app.ts

@@ -1184,6 +1184,14 @@ export class App implements AfterViewInit, OnInit, OnDestroy {
     this.downloads.startById([id]).subscribe((res) => this.handleActionResult(res, 'Start download failed'));
   }
 
+  // 'preparing' (yt-dlp starting up) and 'postprocessing' (ffmpeg merging,
+  // re-encoding or splitting once the bytes have landed) both have real work in
+  // flight with no percentage to report, so the bar runs animated at full width
+  // instead of showing a number that cannot move.
+  isIndeterminate(download: Download): boolean {
+    return download.status === 'preparing' || download.status === 'postprocessing';
+  }
+
   liveCountdownSeconds(download: Download): number | null {
     const ts = download.live_release_timestamp;
     if (ts == null || download.status !== 'scheduled') {
@@ -1697,7 +1705,7 @@ export class App implements AfterViewInit, OnInit, OnDestroy {
       if (download.status === 'downloading') {
         active++;
         speed += download.speed || 0;
-      } else if (download.status === 'preparing') {
+      } else if (download.status === 'preparing' || download.status === 'postprocessing') {
         active++;
       } else if (download.status === 'pending' || download.status === 'scheduled') {
         queued++;