--- a/dom/media/mediasource/MediaSourceReader.cpp
+++ b/dom/media/mediasource/MediaSourceReader.cpp
@@ -44,16 +44,17 @@ using mozilla::dom::TimeRanges;
 namespace mozilla {
 
 MediaSourceReader::MediaSourceReader(MediaSourceDecoder* aDecoder)
   : MediaDecoderReader(aDecoder)
   , mLastAudioTime(0)
   , mLastVideoTime(0)
   , mPendingSeekTime(-1)
   , mWaitingForSeekData(false)
+  , mSeekToEnd(false)
   , mTimeThreshold(0)
   , mDropAudioBeforeThreshold(false)
   , mDropVideoBeforeThreshold(false)
   , mAudioDiscontinuity(false)
   , mVideoDiscontinuity(false)
   , mEnded(false)
   , mMediaSourceDuration(0)
   , mHasEssentialTrackBuffers(false)
@@ -883,24 +884,28 @@ MediaSourceReader::OnVideoSeekFailed(nsr
   mVideoSeekRequest.Complete();
   mPendingSeekTime = -1;
   mSeekPromise.Reject(aResult, __func__);
 }
 
 void
 MediaSourceReader::DoAudioSeek()
 {
-  if (SwitchAudioSource(&mPendingSeekTime) == SOURCE_NONE) {
+  int64_t seekTime = mPendingSeekTime;
+  if (mSeekToEnd) {
+    seekTime = LastSampleTime(MediaData::AUDIO_DATA);
+  }
+  if (SwitchAudioSource(&seekTime) == SOURCE_NONE) {
     // Data we need got evicted since the last time we checked for data
     // availability. Abort current seek attempt.
     mWaitingForSeekData = true;
     return;
   }
   GetAudioReader()->ResetDecode();
-  mAudioSeekRequest.Begin(GetAudioReader()->Seek(GetReaderAudioTime(mPendingSeekTime), 0)
+  mAudioSeekRequest.Begin(GetAudioReader()->Seek(GetReaderAudioTime(seekTime), 0)
                          ->RefableThen(GetTaskQueue(), __func__, this,
                                        &MediaSourceReader::OnAudioSeekCompleted,
                                        &MediaSourceReader::OnAudioSeekFailed));
   MSE_DEBUG("reader=%p", GetAudioReader());
 }
 
 void
 MediaSourceReader::OnAudioSeekCompleted(int64_t aTime)
@@ -925,17 +930,19 @@ MediaSourceReader::AttemptSeek()
 {
   // Make sure we don't hold the monitor while calling into the reader
   // Seek methods since it can deadlock.
   {
     ReentrantMonitorAutoEnter mon(mDecoder->GetReentrantMonitor());
     if (!mWaitingForSeekData) {
       return;
     }
-    if (!TrackBuffersContainTime(mPendingSeekTime)) {
+
+    mSeekToEnd = IsEnded() && mPendingSeekTime >= mMediaSourceDuration * USECS_PER_S;
+    if (!mSeekToEnd && !TrackBuffersContainTime(mPendingSeekTime)) {
       mVideoSourceDecoder = nullptr;
       mAudioSourceDecoder = nullptr;
       return;
     }
     mWaitingForSeekData = false;
   }
 
   // Decoding discontinuity upon seek, reset last times to seek target.
@@ -949,24 +956,28 @@ MediaSourceReader::AttemptSeek()
   } else {
     MOZ_CRASH();
   }
 }
 
 void
 MediaSourceReader::DoVideoSeek()
 {
-  if (SwitchVideoSource(&mPendingSeekTime) == SOURCE_NONE) {
+  int64_t seekTime = mPendingSeekTime;
+  if (mSeekToEnd) {
+    seekTime = LastSampleTime(MediaData::VIDEO_DATA);
+  }
+  if (SwitchVideoSource(&seekTime) == SOURCE_NONE) {
     // Data we need got evicted since the last time we checked for data
     // availability. Abort current seek attempt.
     mWaitingForSeekData = true;
     return;
   }
   GetVideoReader()->ResetDecode();
-  mVideoSeekRequest.Begin(GetVideoReader()->Seek(GetReaderVideoTime(mPendingSeekTime), 0)
+  mVideoSeekRequest.Begin(GetVideoReader()->Seek(GetReaderVideoTime(seekTime), 0)
                           ->RefableThen(GetTaskQueue(), __func__, this,
                                         &MediaSourceReader::OnVideoSeekCompleted,
                                         &MediaSourceReader::OnVideoSeekFailed));
   MSE_DEBUG("reader=%p", GetVideoReader());
 }
 
 nsresult
 MediaSourceReader::GetBuffered(dom::TimeRanges* aBuffered)
@@ -1160,16 +1171,28 @@ MediaSourceReader::IsNearEnd(MediaData::
   }
   TrackBuffer* trackBuffer =
     aType == MediaData::AUDIO_DATA ? mAudioTrack : mVideoTrack;
   nsRefPtr<dom::TimeRanges> buffered = new dom::TimeRanges();
   trackBuffer->Buffered(buffered);
   return aTime >= (buffered->GetEndTime() * USECS_PER_S - EOS_FUZZ_US);
 }
 
+int64_t
+MediaSourceReader::LastSampleTime(MediaData::Type aType)
+{
+  ReentrantMonitorAutoEnter mon(mDecoder->GetReentrantMonitor());
+
+  TrackBuffer* trackBuffer =
+  aType == MediaData::AUDIO_DATA ? mAudioTrack : mVideoTrack;
+  nsRefPtr<dom::TimeRanges> buffered = new dom::TimeRanges();
+  trackBuffer->Buffered(buffered);
+  return buffered->GetEndTime() * USECS_PER_S - 1;
+}
+
 void
 MediaSourceReader::SetMediaSourceDuration(double aDuration)
 {
   ReentrantMonitorAutoEnter mon(mDecoder->GetReentrantMonitor());
   mMediaSourceDuration = aDuration;
 }
 
 void

--- a/dom/media/mediasource/MediaSourceReader.h
+++ b/dom/media/mediasource/MediaSourceReader.h
@@ -223,16 +223,17 @@ private:
                                                       int64_t aTolerance /* microseconds */,
                                                       const nsTArray<nsRefPtr<SourceBufferDecoder>>& aTrackDecoders);
   bool HaveData(int64_t aTarget, MediaData::Type aType);
 
   void AttemptSeek();
   bool IsSeeking() { return mPendingSeekTime != -1; }
 
   bool IsNearEnd(MediaData::Type aType, int64_t aTime /* microseconds */);
+  int64_t LastSampleTime(MediaData::Type aType);
 
   nsRefPtr<SourceBufferDecoder> mAudioSourceDecoder;
   nsRefPtr<SourceBufferDecoder> mVideoSourceDecoder;
 
   nsTArray<nsRefPtr<TrackBuffer>> mTrackBuffers;
   nsTArray<nsRefPtr<TrackBuffer>> mShutdownTrackBuffers;
   nsTArray<nsRefPtr<TrackBuffer>> mEssentialTrackBuffers;
   nsRefPtr<TrackBuffer> mAudioTrack;
@@ -262,16 +263,17 @@ private:
   MediaPromiseConsumerHolder<SeekPromise> mAudioSeekRequest;
   MediaPromiseConsumerHolder<SeekPromise> mVideoSeekRequest;
   MediaPromiseHolder<SeekPromise> mSeekPromise;
 
   // Temporary seek information while we wait for the data
   // to be added to the track buffer.
   int64_t mPendingSeekTime;
   bool mWaitingForSeekData;
+  bool mSeekToEnd;
 
   int64_t mTimeThreshold;
   bool mDropAudioBeforeThreshold;
   bool mDropVideoBeforeThreshold;
 
   bool mAudioDiscontinuity;
   bool mVideoDiscontinuity;