Fix bug of incomplete waveform when playing new track twice in quick succession

backend/audiocache.go

@@ -26,8 +26,10 @@ type AudioCache struct {
 }
 
 type cacheEntry struct {
-	done   bool
+	done            bool
-	cancel context.CancelFunc
+	refCount        int
+	pendingDeletion bool
+	cancel          context.CancelFunc
 }
 
 // AudioCacheRequest represents a request to prefetch and cache an audio file.
@@ -62,19 +64,52 @@ func (a *AudioCache) PathForCachedFile(id string) string {
 	return ""
 }
 
+// IsFullyDownloaded returns true if the file for the given id is fully downloaded.
+func (a *AudioCache) IsFullyDownloaded(id string) bool {
+	return a.PathForCachedFile(id) != ""
+}
+
 // PathForCachedFile returns the local filesystem path for a cached track,
 // including one that is in the process of downloading.
 // If it is not cached or downloading, it returns an empty string.
 func (a *AudioCache) PathForCachedOrDownloadingFile(id string) string {
+	return a.pathForCachedOrDownloadingFile(id, false)
+}
+
+// ObtainReferenceToFile returns the local filesystem path for a cached track,
+// including one that is in the process of downloading, and obtains a refernce
+// to it such that it will not be deleted until ReleaseReferenceToFile is called.
+
+// If it is not cached or downloading, it returns an empty string.
+func (a *AudioCache) ObtainReferenceToFile(id string) string {
+	return a.pathForCachedOrDownloadingFile(id, true)
+}
+
+func (a *AudioCache) pathForCachedOrDownloadingFile(id string, obtainReference bool) string {
 	a.mutex.Lock()
 	defer a.mutex.Unlock()
 
-	if _, ok := a.entries[id]; ok {
+	if entry, ok := a.entries[id]; ok {
+		if obtainReference {
+			entry.refCount++
+		}
 		return a.pathForID(id)
 	}
 	return ""
 }
 
+func (a *AudioCache) ReleaseReferenceToFile(id string) {
+	a.mutex.Lock()
+	defer a.mutex.Unlock()
+
+	if e, ok := a.entries[id]; ok {
+		e.refCount--
+		if e.refCount == 0 && e.pendingDeletion {
+			a.deleteEntry(id, e)
+		}
+	}
+}
+
 // CacheFile begins downloading a file (if not already downloading) and stores it
 // to the cache directory under its ID as filename. The download is asynchronous.
 func (a *AudioCache) CacheFile(id, dlURL string) {
@@ -119,10 +154,11 @@ func (a *AudioCache) CacheOnly(keep string, fetch []AudioCacheRequest) {
 		if id != keep && !slices.ContainsFunc(fetch, func(a AudioCacheRequest) bool {
 			return a.ID == id
 		}) {
-			_ = e
+			if e.refCount == 0 {
-			e.cancel()
+				a.deleteEntry(id, e)
-			_ = os.Remove(a.pathForID(id))
+			} else {
-			delete(a.entries, id)
+				e.pendingDeletion = true
+			}
 		}
 	}
 
@@ -156,3 +192,9 @@ func (a *AudioCache) Shutdown() {
 func (a *AudioCache) pathForID(id string) string {
 	return filepath.Join(a.baseCacheDir, id)
 }
+
+func (a *AudioCache) deleteEntry(id string, e *cacheEntry) {
+	e.cancel()
+	_ = os.Remove(a.pathForID(id))
+	delete(a.entries, id)
+}

backend/playbackmanager.go

@@ -78,9 +78,9 @@ func NewPlaybackManager(
 	return pm
 }
 
-func (p *PlaybackManager) findWfmImageJob(id string) (*WaveformImageJob, bool) {
+func (p *PlaybackManager) findWfmImageJob(id string, uncanceledOnly bool) (*WaveformImageJob, bool) {
 	for _, j := range p.wfmImageJobs {
-		if j != nil && j.ItemID == id {
+		if j != nil && j.ItemID == id && (!uncanceledOnly || !j.Canceled()) {
 			return j, true
 		}
 	}
@@ -106,8 +106,10 @@ func (p *PlaybackManager) addOnTrackChangeHook() {
 	p.engine.onBeforeSongChange = append(p.engine.onBeforeSongChange, func(item mediaprovider.MediaItem) {
 		if p.engine.playbackCfg.UseWaveformSeekbar {
 			if p.wfmGen != nil && item != nil && item.Metadata().Type == mediaprovider.MediaItemTypeTrack {
-				// start generating waveform image for next-up track
+				if _, ok := p.findWfmImageJob(item.Metadata().ID, true); !ok {
-				p.addWfmImageJob(p.wfmGen.StartWaveformGeneration(item.(*mediaprovider.Track)))
+					// start generating waveform image for next-up track
+					p.addWfmImageJob(p.wfmGen.StartWaveformGeneration(item.(*mediaprovider.Track)))
+				}
 			}
 		}
 	})
@@ -168,13 +170,15 @@ func (p *PlaybackManager) handleWaveformImageSongChange(item mediaprovider.Media
 
 	if item != nil {
 		// cancel possible waveform generation job for previous track
-		if old, ok := p.findWfmImageJob(p.lastPlayingID); ok {
+		if p.lastPlayingID != item.Metadata().ID {
-			old.Cancel()
+			if old, ok := p.findWfmImageJob(p.lastPlayingID, false); ok {
+				old.Cancel()
+			}
+			p.lastPlayingID = item.Metadata().ID
 		}
-		p.lastPlayingID = item.Metadata().ID
 
 		var job *WaveformImageJob
-		if j, ok := p.findWfmImageJob(item.Metadata().ID); ok {
+		if j, ok := p.findWfmImageJob(item.Metadata().ID, true); ok {
 			job = j
 		} else if tr, ok := item.(*mediaprovider.Track); ok {
 			job = p.wfmGen.StartWaveformGeneration(tr)

backend/util/filestreamer.go

@@ -77,14 +77,25 @@ func (fs *FileStreamerServer) streamHandler(w http.ResponseWriter, _ *http.Reque
 
 	flusher, canFlush := w.(http.Flusher)
 
+	bytesRead := int64(0)
 	buf := make([]byte, 4096)
 	for {
 		complete := fs.IsComplete()
+		if !complete {
+			if s, err := os.Stat(fs.Path); err == nil {
+				// make sure we don't read near EOF until file is complete
+				maxToRead := max(0, s.Size()-bytesRead-1024) /*safety buffer*/
+				buf = buf[:min(int64(cap(buf)), maxToRead)]
+			}
+		} else {
+			buf = buf[:cap(buf)]
+		}
 		n, err := file.Read(buf)
 		if err != nil && err != io.EOF {
 			log.Printf("read error: %v", err)
 			break
 		}
+		bytesRead += int64(n)
 
 		if n > 0 {
 			_, err := w.Write(buf[:n])

backend/waveformimage.go

@@ -48,17 +48,22 @@ type WaveformImageJob struct {
 	progress int // first invalid pixel in X direction
 	done     bool
 	cancel   func()
-
+	canceled bool
-	step int
 }
 
 func (w *WaveformImageJob) Cancel() {
-	if w != nil && w.cancel != nil {
+	if w != nil {
-		w.step = -1
+		w.canceled = true
-		w.cancel()
+		if w.cancel != nil {
+			w.cancel()
+		}
 	}
 }
 
+func (w *WaveformImageJob) Canceled() bool {
+	return w.canceled
+}
+
 func (w *WaveformImageJob) Done() bool {
 	w.lock.Lock()
 	defer w.lock.Unlock()
@@ -109,7 +114,7 @@ func (w *WaveformImageGenerator) StartWaveformGeneration(item *mediaprovider.Tra
 	// 3. Begin analyzing the resulting WAV file
 	// 4. Begin generating the image from the analysis data
 	go func() {
-		path := w.audioCache.PathForCachedOrDownloadingFile(job.ItemID)
+		path := w.audioCache.ObtainReferenceToFile(job.ItemID)
 		// wait for file to begin downloading if not already
 		for path == "" {
 			time.Sleep(50 * time.Millisecond)
@@ -117,7 +122,7 @@ func (w *WaveformImageGenerator) StartWaveformGeneration(item *mediaprovider.Tra
 				job.setError(e)
 				return
 			}
-			path = w.audioCache.PathForCachedOrDownloadingFile(job.ItemID)
+			path = w.audioCache.ObtainReferenceToFile(job.ItemID)
 		}
 		// and wait for content to begin being written
 		for {
@@ -130,13 +135,22 @@ func (w *WaveformImageGenerator) StartWaveformGeneration(item *mediaprovider.Tra
 				return
 			}
 		}
-		job.step = 1
 
 		dir := filepath.Dir(path)
-		transcodeFile := filepath.Join(dir, filepath.Base(path)+"_waveform.wav")
+		var transcodeFile string
+		for i := 0; true; i++ {
+			if i > 0 {
+				transcodeFile = filepath.Join(dir, fmt.Sprintf("%s_waveform_%d.wav", filepath.Base(path), i))
+			} else {
+				transcodeFile = filepath.Join(dir, filepath.Base(path)+"_waveform.wav")
+			}
+			if _, err := os.Stat(transcodeFile); os.IsNotExist(err) {
+				break // found a suitable filename that doesn't exist
+			}
+		}
 
 		fileDone := func() bool {
-			return w.audioCache.PathForCachedFile(job.ItemID) != ""
+			return w.audioCache.IsFullyDownloaded(job.ItemID)
 		}
 
 		// If file isn't fully downloaded from server,
@@ -158,8 +172,7 @@ func (w *WaveformImageGenerator) StartWaveformGeneration(item *mediaprovider.Tra
 		// Start converting the file to WAV for analysis
 		var wavConvertDone bool
 		go func() {
-			job.step = 2
+			err := w.convertToWav(ctx, job.ItemID, path, transcodeFile)
-			err := convertToWav(ctx, path, transcodeFile)
 			wavConvertDone = true
 			if err != nil {
 				job.setError(err)
@@ -177,7 +190,6 @@ func (w *WaveformImageGenerator) StartWaveformGeneration(item *mediaprovider.Tra
 				return
 			}
 		}
-		job.step = 3
 
 		// Start analyzing the converted wav file
 		data := &waveformData{}
@@ -392,7 +404,7 @@ func float64ToByte(val float64) byte {
 	return byte(val * 255)
 }
 
-func convertToWav(ctx context.Context, inPath, outPath string) error {
+func (w *WaveformImageGenerator) convertToWav(ctx context.Context, id, inPath, outPath string) error {
 	m := mpv.Create()
 	m.SetOptionString("video", "no")
 	m.SetOptionString("audio-display", "no")
@@ -413,6 +425,7 @@ func convertToWav(ctx context.Context, inPath, outPath string) error {
 	defer m.TerminateDestroy()
 
 	m.Command([]string{"loadfile", inPath, "replace"})
+	defer w.audioCache.ReleaseReferenceToFile(id)
 
 	// Wait for MPV idle or ctx expiry
 	for {