feat(stream): cache extracted subtitles to a hidden .unarr sidecar
On-demand WebVTT extraction re-ran ffmpeg on every /sub request and, for 50GB+ remuxes, couldn't finish a full text track within the 60s HTTP timeout → the web player got a 500 and no subtitles. Extract each text subtitle ONCE — during the library scan (no HTTP deadline, generous per-file timeout) and write-through on the first on-demand request — into a hidden ".unarr/<name>.s<index>.vtt" sidecar next to the media file. The /sub handler serves a fresh sidecar instantly (mtime-invalidated when the media is replaced), so playback subtitles are instant and huge files work. - mediainfo.sidecar: cache paths, mtime freshness, atomic write, ExtractSubtitleVTT, IsTextSubtitleCodec (shared classifier, mirrors engine + web whitelists). - library.PrewarmSidecars: bounded, idempotent, ctx-cancellable background pass run after every scan (manual + daemon auto-scan). - subtitleHandler: cache-read → hit; miss → extract → write-through. - config: library.cache_subtitles (default true), wired via SetCacheSubtitles. Local-only by design: nothing extracted is uploaded — the sidecar is the user's own content, private to their disk.
This commit is contained in:
Deivid Soto
parent
7417fad45f
commit
178c16f458
6 changed files with 353 additions and 33 deletions
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@ -21,6 +21,7 @@ import (
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"time"
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"github.com/anacrolix/torrent"
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"github.com/torrentclaw/unarr/internal/library/mediainfo"
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)
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// StreamURLs holds all available stream URLs keyed by network type.
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@ -105,6 +106,12 @@ type StreamServer struct {
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// Listen() via SetFFmpegPath; read-only thereafter so the handler needs no lock.
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ffmpegPath string
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// cacheSubtitles enables write-through caching of extracted WebVTT to the
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// hidden ".unarr" sidecar dir next to the media (mirrors the scan-time
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// prewarm). Set once before Listen() via SetCacheSubtitles; default false here,
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// flipped on from config (default true) by the daemon. read-only thereafter.
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cacheSubtitles bool
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lastActivity atomic.Int64
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maxByteOffset atomic.Int64 // highest sequential read position (main playback connection)
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totalFileSize atomic.Int64
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@ -204,6 +211,13 @@ func (ss *StreamServer) SetFFmpegPath(path string) {
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ss.ffmpegPath = path
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}
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// SetCacheSubtitles toggles write-through caching of extracted WebVTT into the
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// hidden ".unarr" sidecar dir next to the media file (library.cache_subtitles,
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// default true). Call before Listen(); read-only thereafter.
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func (ss *StreamServer) SetCacheSubtitles(on bool) {
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ss.cacheSubtitles = on
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}
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// SetCORSAllowedOrigins replaces the operator-supplied extra origins. The
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// default allowlist (torrentclaw.com / app.torrentclaw.com / localhost dev
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// ports) is always merged in. Call before Listen().
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@ -1003,45 +1017,51 @@ func (ss *StreamServer) subtitleHandler(w http.ResponseWriter, r *http.Request)
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return
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}
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// A full subtitle track is small (KBs–low MBs); 60s is ample even for a
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// long movie's text track and bounds a hung/corrupt ffmpeg.
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ctx, cancel := context.WithTimeout(r.Context(), 60*time.Second)
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defer cancel()
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// -map 0:s:<index> selects the Nth subtitle stream (same ordering as the
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// library scan / probe.json / burn-in si=N). `-c:s webvtt -f webvtt` converts
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// srt/ass/mov_text/etc. to WebVTT on stdout. `?` makes the map non-fatal if
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// the stream is absent (yields empty output rather than a hard error).
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args := []string{
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"-nostdin",
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"-loglevel", "error",
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"-i", rawPath,
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"-map", fmt.Sprintf("0:s:%d?", index),
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"-c:s", "webvtt",
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"-f", "webvtt",
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"-",
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}
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cmd := exec.CommandContext(ctx, ss.ffmpegPath, args...)
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var stderr strings.Builder
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cmd.Stderr = &stderr
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out, err := cmd.Output()
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if err != nil || len(out) == 0 {
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log.Printf("[sub] extract failed (i=%d path=%q): err=%v %s",
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index, rawPath, err, strings.TrimSpace(stderr.String()))
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http.Error(w, "subtitle extract failed", http.StatusInternalServerError)
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// Cache hit: serve a fresh sidecar (written by the scan-time prewarm or a
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// prior request) instantly, skipping ffmpeg. This is also what makes huge
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// remuxes work — the prewarm extracts without the on-demand HTTP timeout
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// below, so by play time the hit avoids the 60s ceiling that was returning
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// 500s on 50GB+ files.
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if vtt, ok := mediainfo.ReadCachedSubtitle(rawPath, index); ok {
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ss.writeVTT(w, vtt)
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return
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}
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// A full subtitle track is small (KBs–low MBs); 60s is ample for a normal
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// movie's text track and bounds a hung/corrupt ffmpeg. Giant remuxes can
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// exceed this on first play — the prewarm pre-fills the cache so this
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// on-demand path is the fallback, not the steady state.
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ctx, cancel := context.WithTimeout(r.Context(), 60*time.Second)
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defer cancel()
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out, err := mediainfo.ExtractSubtitleVTT(ctx, ss.ffmpegPath, rawPath, index)
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if err != nil {
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log.Printf("[sub] extract failed (i=%d path=%q): %v", index, rawPath, err)
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http.Error(w, "subtitle extract failed", http.StatusInternalServerError)
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return
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}
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// Write-through so the next request is a cache hit. Best-effort: a read-only
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// media mount just logs and serves the in-memory bytes.
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if ss.cacheSubtitles {
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if werr := mediainfo.WriteCachedSubtitle(rawPath, index, out); werr != nil {
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log.Printf("[sub] cache write skipped (i=%d path=%q): %v", index, rawPath, werr)
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}
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}
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ss.writeVTT(w, out)
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}
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// writeVTT writes the standard WebVTT response headers + body for both the
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// cache-hit and freshly-extracted paths of subtitleHandler.
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func (ss *StreamServer) writeVTT(w http.ResponseWriter, vtt []byte) {
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w.Header().Set("Content-Type", "text/vtt; charset=utf-8")
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// path+index is stable content for the daemon's lifetime; let the browser
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// cache so re-selecting a track doesn't re-run ffmpeg. private — the user's
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// own file.
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// cache so re-selecting a track doesn't re-fetch. private — the user's file.
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w.Header().Set("Cache-Control", "private, max-age=3600")
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w.Header().Set("Content-Length", strconv.Itoa(len(out)))
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w.Header().Set("Content-Length", strconv.Itoa(len(vtt)))
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//nolint:gosec // G705: WebVTT served as text/vtt to a <track> element — not
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// HTML, so cue text can't execute; the path is token-scoped + stat'd as a
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// regular file, and ffmpeg only emits well-formed WebVTT.
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if _, err := w.Write(out); err != nil {
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if _, err := w.Write(vtt); err != nil {
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log.Printf("[sub] write failed: %v", err)
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}
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}
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