支持 ASS 字幕原样渲染与字幕显示设置

internal/handler/routes_authenticated_core.go

@@ -54,6 +54,7 @@ func registerAuthedMediaRoutes(authed *gin.RouterGroup, svc *service.Container)
 	authed.DELETE("/media/:id", middleware.AdminRequired(), deleteMediaHandler(svc))
 	authed.GET("/media/:id/subtitles", listSubtitlesHandler(svc))
 	authed.GET("/subtitles/:id", serveSubtitleHandler(svc))
+	authed.GET("/subtitles/:id/ass", serveASSSubtitleHandler(svc))
 	authed.POST("/media/:id/nfo", middleware.AdminRequired(), exportNFOHandler(svc))
 	authed.POST("/libraries/:id/nfo", middleware.AdminRequired(), exportLibraryNFOHandler(svc))
 }

internal/handler/subtitles.go

@@ -34,6 +34,22 @@ func listSubtitlesHandler(svc *service.Container) gin.HandlerFunc {
 	}
 }
 
+func serveASSSubtitleHandler(svc *service.Container) gin.HandlerFunc {
+	return func(c *gin.Context) {
+		path := c.Query("path")
+		if path == "" {
+			c.JSON(http.StatusBadRequest, gin.H{"error": "missing path"})
+			return
+		}
+		c.Header("Content-Type", "text/plain; charset=utf-8")
+		c.Header("Cache-Control", "no-cache, no-store, must-revalidate")
+		if err := svc.Subtitle.ServeASS(c.Request.Context(), c.Param("id"), path, c.Writer); err != nil {
+			c.JSON(http.StatusNotFound, gin.H{"error": err.Error()})
+			return
+		}
+	}
+}
+
 func serveSubtitleHandler(svc *service.Container) gin.HandlerFunc {
 	return func(c *gin.Context) {
 		path := c.Query("path")

internal/service/subtitle.go

@@ -234,7 +234,7 @@ func discoverExternalSubtitleTracks(m *model.Media) []SubtitleTrack {
 				Path:     filepath.Join(c, e.Name()),
 				Codec:    codec,
 				Source:   "external",
-				Delivery: "webvtt",
+				Delivery: subtitleDeliveryForCodec(codec),
 			})
 		}
 	}
@@ -297,6 +297,18 @@ func (s *SubtitleService) discoverEmbedded(ctx context.Context, media *model.Med
 	return subtitleTracksFromProbe(probe), nil
 }
 
+// subtitleDeliveryForCodec selects the browser rendering path for a text
+// subtitle codec. ASS/SSA keep their original bytes and are rendered by
+// libass in the web player; other text formats are converted to WebVTT.
+func subtitleDeliveryForCodec(codec string) string {
+	switch strings.ToLower(strings.TrimSpace(codec)) {
+	case "ass", "ssa":
+		return "ass"
+	default:
+		return "webvtt"
+	}
+}
+
 func subtitleTracksFromProbe(probe embeddedSubtitleProbe) []SubtitleTrack {
 	tracks := make([]SubtitleTrack, 0, len(probe.Streams))
 	for _, stream := range probe.Streams {
@@ -314,7 +326,7 @@ func subtitleTracksFromProbe(probe embeddedSubtitleProbe) []SubtitleTrack {
 		} else if stream.Disposition.Default != 0 {
 			label += "（默认）"
 		}
-		delivery := "webvtt"
+		delivery := subtitleDeliveryForCodec(codec)
 		if imageSubtitleCodecs[codec] {
 			delivery = "burn"
 		}
@@ -464,6 +476,9 @@ func (s *SubtitleService) ServeRaw(ctx context.Context, mediaID, sub string, w i
 	if err != nil || m == nil {
 		return errors.New("media not found")
 	}
+	if strings.HasPrefix(sub, "embedded:") {
+		return errors.New("embedded subtitle is not available in raw mode")
+	}
 	abs, err := filepath.Abs(sub)
 	if err != nil {
 		return err
@@ -472,6 +487,9 @@ func (s *SubtitleService) ServeRaw(ctx context.Context, mediaID, sub string, w i
 	if !pathWithin(abs, mediaDir) {
 		return fmt.Errorf("path escape")
 	}
+	if _, ok := extToCodec[strings.ToLower(filepath.Ext(abs))]; !ok {
+		return errors.New("unsupported subtitle format")
+	}
 	f, err := os.Open(abs) // #nosec G304 -- abs is constrained to the media file directory with pathWithin.
 	if err != nil {
 		return err
@@ -480,3 +498,49 @@ func (s *SubtitleService) ServeRaw(ctx context.Context, mediaID, sub string, w i
 	_, err = io.Copy(w, f)
 	return err
 }
+
+// ServeASS returns an ASS/SSA stream suitable for libass-wasm. External ASS
+// files are sent unchanged; embedded ASS/SSA tracks are remuxed to ASS by
+// ffmpeg. This keeps fonts, positioning and typesetting data available to the
+// browser renderer instead of flattening the track through assToVTT first.
+func (s *SubtitleService) ServeASS(ctx context.Context, mediaID, sub string, w io.Writer) error {
+	m, err := s.repo.Media.FindByID(ctx, mediaID)
+	if err != nil || m == nil {
+		return errors.New("media not found")
+	}
+	if strings.HasPrefix(sub, "embedded:") {
+		index, err := strconv.Atoi(strings.TrimPrefix(sub, "embedded:"))
+		if err != nil || index < 0 {
+			return errors.New("invalid embedded subtitle")
+		}
+		return s.serveEmbeddedASS(ctx, m, index, w)
+	}
+	switch strings.ToLower(filepath.Ext(sub)) {
+	case ".ass", ".ssa":
+		return s.ServeRaw(ctx, mediaID, sub, w)
+	default:
+		return errors.New("subtitle is not ASS/SSA")
+	}
+}
+
+func (s *SubtitleService) serveEmbeddedASS(ctx context.Context, media *model.Media, streamIndex int, w io.Writer) error {
+	input, err := s.resolveInput(ctx, media)
+	if err != nil {
+		return err
+	}
+	bin, err := resolveLocalExecutable(s.cfg.App.FFmpegPath, "ffmpeg")
+	if err != nil {
+		return err
+	}
+	args := []string{"-hide_banner", "-loglevel", "error"}
+	args = append(args, ffmpegHTTPInputArgs(input)...)
+	args = append(args, "-i", input.Source, "-map", "0:"+strconv.Itoa(streamIndex), "-c:s", "ass", "-f", "ass", "-")
+	cmd := exec.CommandContext(ctx, bin, args...) // #nosec G204 -- executable is resolved locally and arguments do not use a shell.
+	cmd.Stdout = w
+	var stderr strings.Builder
+	cmd.Stderr = &stderr
+	if err := cmd.Run(); err != nil {
+		return fmt.Errorf("extract embedded ASS subtitle: %w: %s", err, strings.TrimSpace(stderr.String()))
+	}
+	return nil
+}

internal/service/subtitle_test.go

@@ -100,7 +100,7 @@ func TestEmbeddedSubtitleProbeClassifiesTextAndBitmapTracks(t *testing.T) {
 	if len(tracks) != 2 {
 		t.Fatalf("len(tracks) = %d, want 2", len(tracks))
 	}
-	if tracks[0].Delivery != "webvtt" || tracks[0].Path != "embedded:2" {
+	if tracks[0].Delivery != "ass" || tracks[0].Path != "embedded:2" {
 		t.Fatalf("text track = %#v", tracks[0])
 	}
 	if tracks[1].Delivery != "burn" || tracks[1].StreamIndex != 4 {
@@ -108,6 +108,18 @@ func TestEmbeddedSubtitleProbeClassifiesTextAndBitmapTracks(t *testing.T) {
 	}
 }
 
+func TestSubtitleDeliveryClassifiesASSForLibass(t *testing.T) {
+	if got := subtitleDeliveryForCodec("ass"); got != "ass" {
+		t.Fatalf("ass delivery = %q, want ass", got)
+	}
+	if got := subtitleDeliveryForCodec("ssa"); got != "ass" {
+		t.Fatalf("ssa delivery = %q, want ass", got)
+	}
+	if got := subtitleDeliveryForCodec("subrip"); got != "webvtt" {
+		t.Fatalf("subrip delivery = %q, want webvtt", got)
+	}
+}
+
 func TestNormaliseTimecode(t *testing.T) {
 	cases := map[string]string{
 		"0:00:01":       "00:00:01",
@@ -176,4 +188,17 @@ func TestSubtitleServeRawWritesSourceBytes(t *testing.T) {
 	if got := buf.String(); got != raw {
 		t.Fatalf("ServeRaw returned %q, want raw %q", got, raw)
 	}
+
+	buf.Reset()
+	if err := svc.ServeASS(t.Context(), media.ID, subPath, &buf); err != nil {
+		t.Fatal(err)
+	}
+	if got := buf.String(); got != raw {
+		t.Fatalf("ServeASS returned %q, want raw ASS %q", got, raw)
+	}
+
+	buf.Reset()
+	if err := svc.ServeRaw(t.Context(), media.ID, videoPath, &buf); err == nil {
+		t.Fatal("ServeRaw accepted a non-subtitle file")
+	}
 }