feat: implement smart speed phase 3 silence compression

client/players/smart-speed/TimeMapper.js

@@ -0,0 +1,89 @@
+class TimeMapper {
+  constructor(silenceRegions = [], compressionRatio = 1.0) {
+    this.ratio = compressionRatio
+    // Only keep regions >= 200ms
+    this.regions = silenceRegions.filter(r => (r.end - r.start) >= 200)
+    
+    // Calculate compressed durations and cumulative time saved
+    this.processedRegions = []
+    let accumulatedSaved = 0
+    
+    for (const r of this.regions) {
+      const originalDuration = r.end - r.start
+      const compressedDuration = this.ratio === 0 ? 0 : originalDuration / this.ratio
+      const saved = originalDuration - compressedDuration
+      
+      this.processedRegions.push({
+        ...r,
+        originalDuration,
+        compressedDuration,
+        saved,
+        accumulatedSavedBefore: accumulatedSaved
+      })
+      
+      accumulatedSaved += saved
+    }
+    
+    this._totalTimeSaved = accumulatedSaved
+  }
+
+  wallClockToAudio(wallMs) {
+    if (this.ratio === 1.0 || this.regions.length === 0) return wallMs
+
+    let audioMs = wallMs
+    
+    for (const r of this.processedRegions) {
+      // The start time of this region in wall-clock time
+      const regionWallStart = r.start - r.accumulatedSavedBefore
+      
+      if (wallMs < regionWallStart) {
+        // Before this region, no more accumulated saved to add
+        break
+      }
+      
+      const regionWallEnd = regionWallStart + r.compressedDuration
+      
+      if (wallMs <= regionWallEnd) {
+        // Inside the compressed region
+        const timeSpentInRegionWall = wallMs - regionWallStart
+        const timeSpentInRegionAudio = timeSpentInRegionWall * this.ratio
+        return r.start + timeSpentInRegionAudio
+      }
+      
+      // After this region, we add the total time saved by this region
+      audioMs = wallMs + (r.accumulatedSavedBefore + r.saved)
+    }
+    
+    return audioMs
+  }
+
+  audioToWallClock(audioMs) {
+    if (this.ratio === 1.0 || this.regions.length === 0) return audioMs
+    
+    let wallMs = audioMs
+    
+    for (const r of this.processedRegions) {
+      if (audioMs < r.start) {
+        break
+      }
+      
+      if (audioMs <= r.end) {
+        // Inside the region
+        const timeSpentInRegionAudio = audioMs - r.start
+        const timeSpentInRegionWall = timeSpentInRegionAudio / this.ratio
+        return r.start - r.accumulatedSavedBefore + timeSpentInRegionWall
+      }
+      
+      // After the region
+      wallMs = audioMs - (r.accumulatedSavedBefore + r.saved)
+    }
+    
+    return wallMs
+  }
+
+  totalTimeSaved() {
+    return this._totalTimeSaved
+  }
+}
+
+module.exports = TimeMapper