- Multi-audio items now ship every audio track as an HLS rendition in one session
(stream.py var_stream_map -> master.m3u8), so hls.js switches audio CLIENT-SIDE with
no ffmpeg restart, same timeline, no gap/drift. /session gains ?multi=1 (forces HLS
even for direct-playable multi-audio files); K is probed from the video variant seg.
- Restore the selected audio track on AUDIO_TRACKS_UPDATED, not MANIFEST_PARSED (the
renditions aren't parsed yet on MANIFEST_PARSED, so the set was dropped -> after F5 the
UI showed the restored track but playback stayed on the default).
- Resume position now survives F5: a pagehide keepalive beacon (plexProgressBeacon)
saves the current position on reload/close/navigate, since React effect cleanup does
not run on a full reload; seekTo writes the target into absRef immediately so a save
right after a seek is accurate.
Streaming / subtitle sync (the core fix):
- stream.py: add -copyts so HLS segments carry the true absolute PTS, and measure
the real keyframe start K from seg_0 (ffprobe) -> return it as the session start.
Fixes the seconds-long subtitle lead caused by using the requested seek offset
instead of the keyframe ffmpeg actually lands on with video stream-copy.
- Add -noaccurate_seek so the re-encoded audio starts at the same keyframe as the
video (was starting (X-K)s later -> seconds of silence after each seek/audio switch).
- Compensate the fixed ~1.0s lag hls.js introduces for non-zero-start copyts streams,
folded into the session start so the clock, seeking and the subtitle shift are all
content-accurate.
- /subtitle gains an offset param; _shift_vtt shifts absolute cues onto the session's
zero-based clock and DROPS fully-past cue blocks (collapsing them to 0->0 made every
past cue active at currentTime 0 on resume -> a pile-up until playback advanced).
Audio:
- /session + stream.py gain an audio A/V-sync offset (-itsoffset, full +/-, second
input only when non-zero).
Player settings & personalization (per-account, persisted -> survive F5):
- storage.ts: useAccountPersistedObject (per-account JSON prefs blob).
- PlexPlayer: volume/mute, audio+subtitle language (index-based match, fixes the F5
audio-revert), sync offsets, seek steps, subtitle style, auto-hide, play intent.
- Hotkeys A (cycle audio) / S (cycle subtitle), mouse-wheel volume, Ctrl+arrow fine
seek, per-user plain/fine seek-step + auto-hide toggle.
- Subtitle appearance: size / colour / vertical position / background via ::cue + line.
- UI: split into a Tracks quick-menu + a tabbed gear panel (Sync | Playback | Subtitle);
both dismiss on outside-click; edge-aware control tooltips.
- i18n en/hu/de for all new strings.
Selecting a subtitle restarted the HLS session with `-map 0:s:{ord}`, assuming an
EMBEDDED stream. Films whose subs are external sidecar .srt files (Plex reports
them, but they aren't in the mkv) matched no stream; the master-playlist's
declared subtitle group then made ffmpeg fail → "Playback couldn't start".
Subtitles now go through a new GET /api/plex/subtitle/{rk}/{ord} → text/vtt
(external subs fetched from Plex via the stream key + SRT→VTT; embedded text subs
extracted with ffmpeg; image subs → 415), served as native <video><track> that
the browser overlays. So choosing/switching a subtitle is instant with NO session
restart, and stream.py drops all subtitle muxing (`-sn`, no master playlist).
Image-based subs (PGS/VobSub) are marked text=false and hidden in the picker.
Verified on prod's Nymphomaniac Vol. II: HU sidecar → 1693 WebVTT cues, no crash.
Backend: item detail returns audio_streams + subtitle_streams (from Plex Part.Stream
ordinals). The HLS session accepts audio/subtitle stream ordinals — the selected audio
is mapped (transcoded to AAC), a selected subtitle is muxed in as a WebVTT rendition
via a MASTER playlist (-master_pl_name + -var_stream_map sgroup:subs) so ffmpeg keeps
it in sync per-session. Selecting a track forces the HLS path (even for direct files).
Generic /stream/{rk}/hls/{filename} endpoint serves the master/media/vtt/ts artifacts.
Frontend: gear menu lists real audio + subtitle tracks; changing one restarts the
session at the current position (seek-restart mechanism). hls.js subtitle enabled on
SUBTITLE_TRACKS_UPDATED (not just MANIFEST_PARSED, else the VTT is never fetched).
Cues auto-nudged to line 88% (the full-height <video> clips a default bottom-edge cue).
Controls no longer auto-hide while the menu is open. plex.player.* i18n en/hu/de.
Verified in a real browser (2 Broke Girls S1E1, 2 audio + 2 subs): menu shows the real
tracks, enabling English subtitles renders them correctly positioned; backend master
playlist + vtt segments validated over HTTP.
Validated end-to-end on a real remux file (h264+ac3 mkv). The riskiest part of the
Plex epic — on-the-fly playback from the local file — now proven.
- app/plex/stream.py: seek-restart HLS session model (one ffmpeg per item, restarted
at a seek offset via -ss). Video stream-COPY (I/O-bound, CPU-light — fine on the
GPU-less prod host) + audio→aac only when not already aac. Maps first video+audio,
drops subtitles (no VTT rendition clutter). Session cap + idle reaper.
- routes: POST /stream/{rk}/session?start= (direct→raw url, remux→HLS session,
transcode→501 P3), GET /stream/{rk}/file (206 range, direct), /index.m3u8, /seg_n.ts.
- KEY FINDINGS (hard-won): (1) ffmpeg -hls_playlist_type VOD does NOT write the
playlist mid-run (only at finalize) → use EVENT (append-only, appears immediately),
which suits the seek-restart model; (2) naive per-segment copy + keyframe-indexed
extraction are both unreliable (non-uniform/imprecise segments) — ffmpeg's own HLS
muxer is the only correct segmenter; (3) dev slowness was the Windows /downloads
bind-mount write + SMB read → PLEX_HLS_DIR env points scratch at fast container-local
/var/tmp on dev (prod keeps download_root, fast local disk).
