--- a/dom/media/MediaDecoderReader.cpp
+++ b/dom/media/MediaDecoderReader.cpp
@@ -66,21 +66,16 @@ MediaDecoderReader::~MediaDecoderReader(
 void
 MediaDecoderReader::UpdateDuration(const media::TimeUnit& aDuration)
 {
   MOZ_ASSERT(OnTaskQueue());
   mDuration = Some(aDuration);
   UpdateBuffered();
 }
 
-nsresult MediaDecoderReader::ResetDecode(TrackSet aTracks)
-{
-  return NS_OK;
-}
-
 RefPtr<ShutdownPromise>
 MediaDecoderReader::Shutdown()
 {
   MOZ_ASSERT(OnTaskQueue());
   mShutdown = true;
 
   ReleaseResources();
   mBuffered.DisconnectAll();

--- a/dom/media/MediaDecoderReader.h
+++ b/dom/media/MediaDecoderReader.h
@@ -144,17 +144,17 @@ public:
   // made after this should be processed as usual.
   //
   // Normally this call preceedes a Seek() call, or shutdown.
   //
   // aParam is a set of TrackInfo::TrackType enums specifying which
   // queues need to be reset, defaulting to both audio and video tracks.
   virtual nsresult ResetDecode(
     TrackSet aTracks = TrackSet(TrackInfo::kAudioTrack,
-                                TrackInfo::kVideoTrack));
+                                TrackInfo::kVideoTrack)) = 0;
 
   // Requests one audio sample from the reader.
   //
   // The decode should be performed asynchronously, and the promise should
   // be resolved when it is complete.
   virtual RefPtr<AudioDataPromise> RequestAudioData() = 0;
 
   // Requests one video sample from the reader.
@@ -177,23 +177,16 @@ public:
   // ReadUpdatedMetadata will always be called once ReadMetadata has succeeded.
   virtual void ReadUpdatedMetadata(MediaInfo* aInfo) = 0;
 
   // Moves the decode head to aTime microseconds.
   virtual RefPtr<SeekPromise> Seek(const SeekTarget& aTarget) = 0;
 
   virtual void SetCDMProxy(CDMProxy* aProxy) = 0;
 
-  // Tell the reader that the data decoded are not for direct playback, so it
-  // can accept more files, in particular those which have more channels than
-  // available in the audio output.
-  void SetIgnoreAudioOutputFormat()
-  {
-  }
-
   // The MediaDecoderStateMachine uses various heuristics that assume that
   // raw media data is arriving sequentially from a network channel. This
   // makes sense in the <video src="foo"> case, but not for more advanced use
   // cases like MSE.
   virtual bool UseBufferingHeuristics() const = 0;
 
   virtual size_t SizeOfVideoQueueInFrames() = 0;
   virtual size_t SizeOfAudioQueueInFrames() = 0;

--- a/dom/media/MediaFormatReader.cpp
+++ b/dom/media/MediaFormatReader.cpp
@@ -2475,17 +2475,17 @@ MediaFormatReader::ResetDecode(TrackSet 
     mAudio.ResetDemuxer();
     mVideo.mFirstFrameTime = Some(media::TimeUnit::Zero());
     Reset(TrackInfo::kAudioTrack);
     if (mAudio.HasPromise()) {
       mAudio.RejectPromise(NS_ERROR_DOM_MEDIA_CANCELED, __func__);
     }
   }
 
-  return MediaDecoderReader::ResetDecode(aTracks);
+  return NS_OK;
 }
 
 void
 MediaFormatReader::Reset(TrackType aTrack)
 {
   MOZ_ASSERT(OnTaskQueue());
   LOG("Reset(%s) BEGIN", TrackTypeToStr(aTrack));
 

--- a/dom/media/webaudio/MediaBufferDecoder.cpp
+++ b/dom/media/webaudio/MediaBufferDecoder.cpp
@@ -237,21 +237,16 @@ private:
 
 void
 MediaDecodeTask::Decode()
 {
   MOZ_ASSERT(!NS_IsMainThread());
 
   mBufferDecoder->BeginDecoding(mDecoderReader->OwnerThread());
 
-  // Tell the decoder reader that we are not going to play the data directly,
-  // and that we should not reject files with more channels than the audio
-  // backend support.
-  mDecoderReader->SetIgnoreAudioOutputFormat();
-
   mDecoderReader->AsyncReadMetadata()->Then(mDecoderReader->OwnerThread(), __func__, this,
                                        &MediaDecodeTask::OnMetadataRead,
                                        &MediaDecodeTask::OnMetadataNotRead);
 }
 
 void
 MediaDecodeTask::OnMetadataRead(MetadataHolder&& aMetadata)
 {