diff --git a/media/event/muxer_listener.h b/media/event/muxer_listener.h
index 0abfaeb1b2..d24b811a96 100644
--- a/media/event/muxer_listener.h
+++ b/media/event/muxer_listener.h
@@ -17,8 +17,12 @@ namespace event {
 // to add GetStatus() method somewhere (maybe in MuxerListener, maybe not).
 class MuxerListener {
  public:
-  MuxerListener() {};
-  virtual ~MuxerListener() {};
+  enum ContainerType {
+    kContainerUnknown = 0,
+    kContainerMp4,
+    kContainerMpeg2ts,
+    kContainerWebM
+  };
 
   // Called when muxing starts. This event happens before any other events.
   // For MPEG DASH Live profile, the initialization segment information is
@@ -27,7 +31,8 @@ class MuxerListener {
   // specified in |stream_infos|.
   virtual void OnMediaStart(const MuxerOptions& muxer_options,
                             const std::vector<StreamInfo*>& stream_infos,
-                            uint32 time_scale) = 0;
+                            uint32 time_scale,
+                            ContainerType container_type) = 0;
 
   // Called when all files are written out and the muxer object does not output
   // any more files.
@@ -57,6 +62,9 @@ class MuxerListener {
   virtual void OnNewSegment(uint64 start_time,
                             uint64 duration,
                             uint64 segment_file_size) = 0;
+ protected:
+  MuxerListener() {};
+  virtual ~MuxerListener() {};
 };
 
 }  // namespace event
diff --git a/media/event/vod_media_info_dump_muxer_listener.cc b/media/event/vod_media_info_dump_muxer_listener.cc
index 504121c7e2..eb1e379656 100644
--- a/media/event/vod_media_info_dump_muxer_listener.cc
+++ b/media/event/vod_media_info_dump_muxer_listener.cc
@@ -37,7 +37,8 @@ void VodMediaInfoDumpMuxerListener::SetContentProtectionSchemeIdUri(
 void VodMediaInfoDumpMuxerListener::OnMediaStart(
     const MuxerOptions& muxer_options,
     const std::vector<StreamInfo*>& stream_infos,
-    uint32 time_scale) {
+    uint32 time_scale,
+    ContainerType container_type) {
   DLOG(INFO)
       << "VodMediaInfoDumpMuxerListener does not care about OnMediaStart.";
 }
diff --git a/media/event/vod_media_info_dump_muxer_listener.h b/media/event/vod_media_info_dump_muxer_listener.h
index d5206e92f8..bf941f9735 100644
--- a/media/event/vod_media_info_dump_muxer_listener.h
+++ b/media/event/vod_media_info_dump_muxer_listener.h
@@ -35,7 +35,8 @@ class VodMediaInfoDumpMuxerListener : public MuxerListener {
   // MuxerListener implementation.
   virtual void OnMediaStart(const MuxerOptions& muxer_options,
                             const std::vector<StreamInfo*>& stream_infos,
-                            uint32 time_scale) OVERRIDE;
+                            uint32 time_scale,
+                            ContainerType container_type) OVERRIDE;
 
   virtual void OnMediaEnd(const std::vector<StreamInfo*>& stream_infos,
                           bool has_init_range,
diff --git a/media/event/vod_mpd_notify_muxer_listener.cc b/media/event/vod_mpd_notify_muxer_listener.cc
index 490842fb45..a9708a5086 100644
--- a/media/event/vod_mpd_notify_muxer_listener.cc
+++ b/media/event/vod_mpd_notify_muxer_listener.cc
@@ -23,7 +23,8 @@ VodMpdNotifyMuxerListener::~VodMpdNotifyMuxerListener() {}
 void VodMpdNotifyMuxerListener::OnMediaStart(
     const MuxerOptions& muxer_options,
     const std::vector<StreamInfo*>& stream_infos,
-    uint32 time_scale) {}
+    uint32 time_scale,
+    ContainerType container_type) {}
 
 void VodMpdNotifyMuxerListener::OnMediaEnd(
     const std::vector<StreamInfo*>& stream_infos,
diff --git a/media/event/vod_mpd_notify_muxer_listener.h b/media/event/vod_mpd_notify_muxer_listener.h
index 34b68beee3..bdb2e940c0 100644
--- a/media/event/vod_mpd_notify_muxer_listener.h
+++ b/media/event/vod_mpd_notify_muxer_listener.h
@@ -24,7 +24,8 @@ class VodMpdNotifyMuxerListener : public MuxerListener {
   // MuxerListener implementation.
   virtual void OnMediaStart(const MuxerOptions& muxer_options,
                             const std::vector<StreamInfo*>& stream_infos,
-                            uint32 time_scale) OVERRIDE;
+                            uint32 time_scale,
+                            ContainerType container_type) OVERRIDE;
 
   virtual void OnMediaEnd(const std::vector<StreamInfo*>& stream_infos,
                           bool has_init_range,
diff --git a/media/mp4/mp4_muxer.cc b/media/mp4/mp4_muxer.cc
index 93625fb6d7..74d0217dc9 100644
--- a/media/mp4/mp4_muxer.cc
+++ b/media/mp4/mp4_muxer.cc
@@ -284,7 +284,10 @@ void MP4Muxer::FireOnMediaStartEvent() {
   std::vector<StreamInfo*> stream_info_vec;
   GetStreamInfo(&stream_info_vec);
   const uint32 timescale = segmenter_->GetReferenceTimeScale();
-  muxer_listener()->OnMediaStart(options(), stream_info_vec, timescale);
+  muxer_listener()->OnMediaStart(options(),
+                                 stream_info_vec,
+                                 timescale,
+                                 event::MuxerListener::kContainerMp4);
 }
 
 void MP4Muxer::FireOnMediaEndEvent() {