Add method to find start pts

video-dev#2930
alangdm · Sep 15, 2020 · 5deccde · 5deccde
1 parent 63b7fed
commit 5deccde
Showing 1 changed file with 21 additions and 16 deletions.
diff --git a/src/remux/mp4-remuxer.js b/src/remux/mp4-remuxer.js
@@ -34,6 +34,25 @@ class MP4Remuxer {
     this.ISGenerated = false;
   }
 
+  getVideoStartPts (videoSamples) {
+    let rolloverDetected = false;
+    const startPTS = videoSamples.reduce((minPTS, sample) => {
+      const delta = sample.pts - minPTS;
+      if (delta < -4294967296) { // 2^32, see PTSNormalize for reasoning, but we're hitting a rollover here, and we don't want that to impact the timeOffset calculation
+        rolloverDetected = true;
+        return minPTS;
+      } else if (delta > 0) {
+        return minPTS;
+      } else {
+        return sample.pts;
+      }
+    }, videoSamples[0].pts);
+    if (rolloverDetected) {
+      logger.debug('PTS rollover detected');
+    }
+    return startPTS;
+  }
+
   remux (audioTrack, videoTrack, id3Track, textTrack, timeOffset, contiguous, accurateTimeOffset) {
     // generate Init Segment if needed
     if (!this.ISGenerated) {
@@ -50,21 +69,7 @@ class MP4Remuxer {
         // if first audio DTS is not aligned with first video DTS then we need to take that into account
         // when providing timeOffset to remuxAudio / remuxVideo. if we don't do that, there might be a permanent / small
         // drift between audio and video streams
-        let rolloverDetected = false;
-        const startPTS = videoTrack.samples.reduce((minPTS, sample) => {
-          const delta = sample.pts - minPTS;
-          if (delta < -4294967296) { // 2^32, see PTSNormalize for reasoning, but we're hitting a rollover here, and we don't want that to impact the timeOffset calculation
-            rolloverDetected = true;
-            return minPTS;
-          } else if (delta > 0) {
-            return minPTS;
-          } else {
-            return sample.pts;
-          }
-        }, videoTrack.samples[0].pts);
-        if (rolloverDetected) {
-          logger.debug('PTS rollover detected');
-        }
+        const startPTS = this.getVideoStartPts(videoTrack.samples);
         const tsDelta = audioTrack.samples[0].pts - startPTS;
         const audiovideoTimestampDelta = tsDelta / videoTrack.inputTimeScale;
         audioTimeOffset += Math.max(0, audiovideoTimestampDelta);
@@ -177,7 +182,7 @@ class MP4Remuxer {
         }
       };
       if (computePTSDTS) {
-        const startPTS = videoSamples.reduce((minPTS, sample) => Math.min(minPTS, sample.pts), videoSamples[0].pts);
+        const startPTS = this.getVideoStartPts(videoSamples);
         const startOffset = Math.round(inputTimeScale * timeOffset);
         initDTS = Math.min(initDTS, videoSamples[0].dts - startOffset);
         initPTS = Math.min(initPTS, startPTS - startOffset);