优化，现有bug处理

internal/service/scanner_local_ingest.go

@@ -122,11 +122,52 @@ func (s *ScannerService) localMediaScanState(in localMediaScanStateInput) (bool,
 	existing, exists := in.existingMedia[in.cleanPath]
 	isNewMedia := !exists
 	if exists && in.ext != ".strm" && existing.SizeBytes == in.size && !localMetadataNeedsRefresh(existing, in.localMeta) && !localDerivedMetadataNeedsRefresh(existing, in.incoming) {
+		// Unchanged rows are skipped, but a row that never received ffprobe data
+		// still needs a backfill probe so installing ffmpeg later repairs the library.
+		s.queueProbeBackfillIfNeeded(in.path, in.ext, existing)
 		return isNewMedia, true
 	}
 	return isNewMedia, false
 }
 
+// queueProbeBackfillIfNeeded re-queues ffprobe for an unchanged media row that
+// still carries no technical metadata, reporting whether a probe was queued.
+//
+// The incremental skip above only compares file size and metadata, so a library
+// scanned while ffprobe was unavailable kept duration/resolution/codec empty
+// forever: installing ffmpeg and rescanning did nothing, and the only way out was
+// a per-item manual "探测媒体轨". Only the probe is re-queued here — the row
+// itself is not rewritten, so scraped metadata and titles stay untouched.
+func (s *ScannerService) queueProbeBackfillIfNeeded(path, ext string, existing existingLocalMedia) bool {
+	if !mediaExtensionSupportsProbe(ext) || !localMediaProbeDataMissing(existing) {
+		return false
+	}
+	// Without a resolvable ffprobe/ffmpeg every queued probe would just fail, so
+	// only queue when probing is actually possible right now.
+	if s == nil || s.probe == nil || !s.probe.Available() {
+		return false
+	}
+	if !s.queueLocalMediaProbe(path) {
+		return false
+	}
+	if s.log != nil {
+		s.log.Debug("rescan queued ffprobe backfill for media without track metadata", zap.String("path", path))
+	}
+	return true
+}
+
+// localMediaProbeDataMissing reports whether a media row has none of the fields
+// ffprobe fills in. Requiring every field to be empty keeps genuinely probed
+// media (which always yields at least a codec or a duration) out of the backfill
+// path.
+func localMediaProbeDataMissing(existing existingLocalMedia) bool {
+	return existing.DurationSec <= 0 &&
+		existing.Width <= 0 &&
+		existing.Height <= 0 &&
+		strings.TrimSpace(existing.VideoCodec) == "" &&
+		strings.TrimSpace(existing.AudioCodec) == ""
+}
+
 type localScanMediaInput struct {
 	lib           *model.Library
 	root          *model.LibraryRoot