--- a/dom/media/mediasource/TrackBuffersManager.cpp
+++ b/dom/media/mediasource/TrackBuffersManager.cpp
@@ -569,18 +569,18 @@ TrackBuffersManager::CodedFrameRemoval(T
   return dataRemoved;
 }
 
 void
 TrackBuffersManager::UpdateBufferedRanges()
 {
   MonitorAutoLock mon(mMonitor);
 
-  mVideoBufferedRanges = mVideoTracks.mBufferedRanges;
-  mAudioBufferedRanges = mAudioTracks.mBufferedRanges;
+  mVideoBufferedRanges = mVideoTracks.mSanitizedBufferedRanges;
+  mAudioBufferedRanges = mAudioTracks.mSanitizedBufferedRanges;
 
 #if DEBUG
   if (HasVideo()) {
     MSE_DEBUG("after video ranges=%s",
               DumpTimeRanges(mVideoTracks.mBufferedRanges).get());
   }
   if (HasAudio()) {
     MSE_DEBUG("after audio ranges=%s",
@@ -1679,22 +1679,23 @@ TrackBuffersManager::InsertFrames(TrackB
     }
   }
 
   TrackBuffer& data = trackBuffer.mBuffers.LastElement();
   data.InsertElementsAt(trackBuffer.mNextInsertionIndex.ref(), aSamples);
   trackBuffer.mNextInsertionIndex.ref() += aSamples.Length();
 
   // Update our buffered range with new sample interval.
+  trackBuffer.mBufferedRanges += aIntervals;
   // We allow a fuzz factor in our interval of half a frame length,
   // as fuzz is +/- value, giving an effective leeway of a full frame
   // length.
   TimeIntervals range(aIntervals);
   range.SetFuzz(trackBuffer.mLongestFrameDuration.ref() / 2);
-  trackBuffer.mBufferedRanges += range;
+  trackBuffer.mSanitizedBufferedRanges += range;
 }
 
 void
 TrackBuffersManager::RemoveFrames(const TimeIntervals& aIntervals,
                                   TrackData& aTrackData,
                                   uint32_t aStartIndex)
 {
   TrackBuffer& data = aTrackData.mBuffers.LastElement();
@@ -1775,19 +1776,22 @@ TrackBuffersManager::RemoveFrames(const 
       MSE_DEBUG("NextInsertionIndex got reset.");
     } else if (aTrackData.mNextInsertionIndex.ref() > lastRemovedIndex + 1) {
       aTrackData.mNextInsertionIndex.ref() -=
         lastRemovedIndex - firstRemovedIndex.ref() + 1;
     }
   }
 
   // Update our buffered range to exclude the range just removed.
-  removedIntervals.SetFuzz(TimeUnit::FromMicroseconds(maxSampleDuration/2));
   aTrackData.mBufferedRanges -= removedIntervals;
 
+  // Recalculate sanitized buffered ranges.
+  aTrackData.mSanitizedBufferedRanges = aTrackData.mBufferedRanges;
+  aTrackData.mSanitizedBufferedRanges.SetFuzz(TimeUnit::FromMicroseconds(maxSampleDuration/2));
+
   data.RemoveElementsAt(firstRemovedIndex.ref(),
                         lastRemovedIndex - firstRemovedIndex.ref() + 1);
 }
 
 void
 TrackBuffersManager::RecreateParser(bool aReuseInitData)
 {
   MOZ_ASSERT(OnTaskQueue());

--- a/dom/media/mediasource/TrackBuffersManager.h
+++ b/dom/media/mediasource/TrackBuffersManager.h
@@ -250,16 +250,19 @@ private:
     Maybe<size_t> mNextInsertionIndex;
     // Samples just demuxed, but not yet parsed.
     TrackBuffer mQueuedSamples;
     // We only manage a single track of each type at this time.
     nsTArray<TrackBuffer> mBuffers;
     // Track buffer ranges variable that represents the presentation time ranges
     // occupied by the coded frames currently stored in the track buffer.
     media::TimeIntervals mBufferedRanges;
+    // Sanitized mBufferedRanges with a fuzz of half a sample's duration applied
+    // This buffered ranges is the basis of what is exposed to the JS.
+    media::TimeIntervals mSanitizedBufferedRanges;
     // Byte size of all samples contained in this track buffer.
     uint32_t mSizeBuffer;
     // TrackInfo of the first metadata received.
     nsRefPtr<SharedTrackInfo> mInfo;
     // TrackInfo of the last metadata parsed (updated with each init segment.
     nsRefPtr<SharedTrackInfo> mLastInfo;
 
     // If set, position of the next sample to be retrieved by GetSample().