优化转码逻辑

internal/service/transcoder.go

@@ -50,6 +50,7 @@ type TranscoderService struct {
 	mu          sync.Mutex
 	jobs        map[string]*hlsJob
 	strmResolve func(ctx context.Context, raw string) (*StrmPlayResult, error)
+	probe       *FFprobeService
 }
 
 // hlsJob holds the live state of one ffmpeg run.
@@ -61,6 +62,9 @@ type hlsJob struct {
 	lastAccess time.Time
 	playlistOK bool
 	encoder    string
+	// startSec is the source seek offset fed to ffmpeg (-ss). The HLS
+	// playlist itself always starts at t=0 for that session.
+	startSec float64
 }
 
 var (
@@ -92,13 +96,24 @@ func (t *TranscoderService) PlaylistPath(mediaID string) string {
 	return filepath.Join(t.HLSDir(mediaID), "index.m3u8")
 }
 
-// EnsureJob makes sure a transcode is running for mediaID. The function is
-// non-blocking: it returns the playlist path immediately. The caller is
-// expected to poll until WaitReady reports true.
+// EnsureJob makes sure a transcode is running for mediaID from the start of
+// the source. Prefer EnsureJobFrom when the player seeks into the middle.
 func (t *TranscoderService) EnsureJob(ctx context.Context, mediaID string) (string, error) {
+	return t.EnsureJobFrom(ctx, mediaID, 0)
+}
+
+// EnsureJobFrom starts (or reuses) an HLS job that seeks the source to
+// startSec before encoding. Reusing only happens when an active job already
+// matches that offset; otherwise the previous job is cancelled and the HLS
+// cache dir is wiped so the player can jump without waiting for a full
+// head-to-tail transcode.
+func (t *TranscoderService) EnsureJobFrom(ctx context.Context, mediaID string, startSec float64) (string, error) {
 	if !t.cfg.Transcoder.Enabled {
 		return "", ErrTranscodeDisabled
 	}
+	if startSec < 0 {
+		startSec = 0
+	}
 	m, err := t.repo.Media.FindByID(ctx, mediaID)
 	if err != nil {
 		return "", err
@@ -106,11 +121,16 @@ func (t *TranscoderService) EnsureJob(ctx context.Context, mediaID string) (stri
 	if m == nil {
 		return "", ErrMediaNotFound
 	}
+
 	t.mu.Lock()
-	if _, ok := t.jobs[mediaID]; ok {
-		t.touchJobLocked(mediaID)
-		t.mu.Unlock()
-		return t.PlaylistPath(mediaID), nil
+	if existing, ok := t.jobs[mediaID]; ok {
+		if sameHLSStart(existing.startSec, startSec) {
+			t.touchJobLocked(mediaID)
+			t.mu.Unlock()
+			return t.PlaylistPath(mediaID), nil
+		}
+		existing.cancel()
+		delete(t.jobs, mediaID)
 	}
 	t.mu.Unlock()
 
@@ -118,27 +138,34 @@ func (t *TranscoderService) EnsureJob(ctx context.Context, mediaID string) (stri
 	if err != nil {
 		return "", err
 	}
+	input.StartSec = startSec
+	t.maybeFillDuration(ctx, m, input)
 	if _, err := t.resolveFFmpegPath(); err != nil {
 		return "", err
 	}
 
+	outDir := t.HLSDir(mediaID)
+	// Wipe prior segments so a mid-file restart cannot serve stale early chunks.
+	_ = os.RemoveAll(outDir)
+	if err := os.MkdirAll(outDir, 0o750); err != nil {
+		return "", err
+	}
+
 	t.mu.Lock()
-	if _, ok := t.jobs[mediaID]; ok {
-		t.touchJobLocked(mediaID)
-		t.mu.Unlock()
-		return t.PlaylistPath(mediaID), nil
+	if existing, ok := t.jobs[mediaID]; ok {
+		if sameHLSStart(existing.startSec, startSec) {
+			t.touchJobLocked(mediaID)
+			t.mu.Unlock()
+			return t.PlaylistPath(mediaID), nil
+		}
+		existing.cancel()
+		delete(t.jobs, mediaID)
 	}
 	if max := t.maxConcurrent(); max > 0 && len(t.jobs) >= max {
 		t.mu.Unlock()
 		return "", ErrTranscodeBusy
 	}
 
-	outDir := t.HLSDir(mediaID)
-	if err := os.MkdirAll(outDir, 0o750); err != nil {
-		t.mu.Unlock()
-		return "", err
-	}
-
 	jobCtx, cancel := context.WithCancel(context.Background())
 	job := &hlsJob{
 		mediaID:    mediaID,
@@ -147,6 +174,7 @@ func (t *TranscoderService) EnsureJob(ctx context.Context, mediaID string) (stri
 		startedAt:  time.Now(),
 		lastAccess: time.Now(),
 		encoder:    t.effectiveEncoder(),
+		startSec:   startSec,
 	}
 	t.jobs[mediaID] = job
 	t.mu.Unlock()
@@ -156,6 +184,14 @@ func (t *TranscoderService) EnsureJob(ctx context.Context, mediaID string) (stri
 	return t.PlaylistPath(mediaID), nil
 }
 
+func sameHLSStart(a, b float64) bool {
+	const tol = 0.75
+	if a < b {
+		return b-a < tol
+	}
+	return a-b < tol
+}
+
 // SetStrmPlayTargetResolver wires STRM URL resolution so ffmpeg can transcode
 // remote .strm media (HTTP 直链 or local source path) after direct play fails.
 func (t *TranscoderService) SetStrmPlayTargetResolver(resolve func(ctx context.Context, raw string) (*StrmPlayResult, error)) {
@@ -165,6 +201,40 @@ func (t *TranscoderService) SetStrmPlayTargetResolver(resolve func(ctx context.C
 	t.strmResolve = resolve
 }
 
+// SetProbe wires ffprobe so STRM/HLS jobs can persist source duration when the
+// media row still has duration_sec=0 (common for .strm that was never probed).
+func (t *TranscoderService) SetProbe(probe *FFprobeService) {
+	if t == nil {
+		return
+	}
+	t.probe = probe
+}
+
+func (t *TranscoderService) maybeFillDuration(ctx context.Context, m *model.Media, input transcodeInput) {
+	if t == nil || t.probe == nil || m == nil || m.DurationSec > 0 || strings.TrimSpace(input.Source) == "" {
+		return
+	}
+	var (
+		res *ProbeResult
+		err error
+	)
+	if isHTTPSource(input.Source) {
+		res, err = t.probe.ProbeHTTP(ctx, input.Source, input.Headers)
+	} else {
+		res, err = t.probe.Probe(ctx, input.Source)
+	}
+	if err != nil || res == nil || res.DurationSec <= 0 {
+		return
+	}
+	m.DurationSec = res.DurationSec
+	if t.repo == nil || t.repo.DB == nil {
+		return
+	}
+	if err := t.repo.DB.WithContext(ctx).Model(&model.Media{}).Where("id = ?", m.ID).Update("duration_sec", res.DurationSec).Error; err != nil && t.log != nil {
+		t.log.Debug("persist probed duration failed", zap.String("media_id", m.ID), zap.Error(err))
+	}
+}
+
 func (t *TranscoderService) resolveTranscodeInput(ctx context.Context, m *model.Media) (transcodeInput, error) {
 	if m == nil {
 		return transcodeInput{}, ErrMediaNotFound