diff --git a/atom/atom.go b/atom/atom.go
index f92cbab..f2551cd 100644
--- a/atom/atom.go
+++ b/atom/atom.go
@@ -1 +1,45 @@
 package atom
+
+import (
+	"io"
+)
+
+func WalkFile(w Walker, r io.Reader) (err error) {
+	var moov *Movie
+	var moof *MovieFrag
+
+	for {
+		var lr *io.LimitedReader
+		var cc4 string
+		if lr, cc4, err = ReadAtomHeader(lr, ""); err != nil {
+			return
+		}
+
+		switch cc4 {
+		case "moov":
+			if moov, err = ReadMovie(lr); err != nil {
+				return
+			}
+			WalkMovie(w, moov)
+
+		case "moof":
+			if moof, err = ReadMovieFrag(lr); err != nil {
+				return
+			}
+			WalkMovieFrag(w, moof)
+
+		case "mdat":
+			w.StartStruct("MovieData")
+			w.Name("Length")
+			w.Int64(lr.N)
+			w.EndStruct()
+		}
+
+		if _, err = ReadDummy(r, int(lr.N)); err != nil {
+			return
+		}
+	}
+
+	return
+}
+
diff --git a/atom/dumper.go b/atom/dumper.go
index 262ed13..d77ea0a 100644
--- a/atom/dumper.go
+++ b/atom/dumper.go
@@ -93,3 +93,4 @@ func (self Dumper) Bytes(val []byte) {
 func (self Dumper) TimeStamp(val TimeStamp) {
 	self.Println(fmt.Sprintf("%s: %d", self.name, int(val)))
 }
+
diff --git a/atom/genStruct.js b/atom/genStruct.js
index 53c8b38..ef38ead 100644
--- a/atom/genStruct.js
+++ b/atom/genStruct.js
@@ -12,6 +12,7 @@ var atoms = {
 				['header', '*movieHeader'],
 				['iods', '*iods'],
 				['tracks', '[]*track'],
+				['movieExtend', '*movieExtend'],
 			]],
 		],
 	},
@@ -382,6 +383,28 @@ var atoms = {
 		cc4: 'tfhd',
 	},
 
+	movieExtend: {
+		cc4: 'mvex',
+		fields: [
+			['$atoms', [
+				['tracks', '[]*trackExtend'],
+			]],
+		],
+	},
+
+	trackExtend: {
+		cc4: 'trex',
+		fields: [
+			['version', 'int8'],
+			['flags', 'int24'],
+			['trackId', 'int32'],
+			['defaultSampleDescIdx', 'int32'],
+			['defaultSampleDuration', 'int32'],
+			['defaultSampleSize', 'int32'],
+			['defaultSampleFlags', 'int32'],
+		],
+	},
+
 	/*
 	// need hand write
 	trackFragRun: {
diff --git a/atom/struct.go b/atom/struct.go
index bc49400..573df51 100644
--- a/atom/struct.go
+++ b/atom/struct.go
@@ -6,9 +6,10 @@ import (
 )
 
 type Movie struct {
-	Header *MovieHeader
-	Iods   *Iods
-	Tracks []*Track
+	Header      *MovieHeader
+	Iods        *Iods
+	Tracks      []*Track
+	MovieExtend *MovieExtend
 }
 
 func ReadMovie(r *io.LimitedReader) (res *Movie, err error) {
@@ -41,6 +42,12 @@ func ReadMovie(r *io.LimitedReader) (res *Movie, err error) {
 				}
 				self.Tracks = append(self.Tracks, item)
 			}
+		case "mvex":
+			{
+				if self.MovieExtend, err = ReadMovieExtend(ar); err != nil {
+					return
+				}
+			}
 
 		}
 		if _, err = ReadDummy(ar, int(ar.N)); err != nil {
@@ -74,6 +81,11 @@ func WriteMovie(w io.WriteSeeker, self *Movie) (err error) {
 			}
 		}
 	}
+	if self.MovieExtend != nil {
+		if err = WriteMovieExtend(w, self.MovieExtend); err != nil {
+			return
+		}
+	}
 	if err = aw.Close(); err != nil {
 		return
 	}
@@ -98,6 +110,9 @@ func WalkMovie(w Walker, self *Movie) {
 			break
 		}
 	}
+	if self.MovieExtend != nil {
+		WalkMovieExtend(w, self.MovieExtend)
+	}
 	w.EndStruct()
 	return
 }
@@ -2699,3 +2714,161 @@ func WalkTrackFrag(w Walker, self *TrackFrag) {
 	w.EndStruct()
 	return
 }
+
+type MovieExtend struct {
+	Tracks []*TrackExtend
+}
+
+func ReadMovieExtend(r *io.LimitedReader) (res *MovieExtend, err error) {
+
+	self := &MovieExtend{}
+	for r.N > 0 {
+		var cc4 string
+		var ar *io.LimitedReader
+		if ar, cc4, err = ReadAtomHeader(r, ""); err != nil {
+			return
+		}
+		switch cc4 {
+		case "trex":
+			{
+				var item *TrackExtend
+				if item, err = ReadTrackExtend(ar); err != nil {
+					return
+				}
+				self.Tracks = append(self.Tracks, item)
+			}
+
+		}
+		if _, err = ReadDummy(ar, int(ar.N)); err != nil {
+			return
+		}
+	}
+	res = self
+	return
+}
+func WriteMovieExtend(w io.WriteSeeker, self *MovieExtend) (err error) {
+
+	var aw *Writer
+	if aw, err = WriteAtomHeader(w, "mvex"); err != nil {
+		return
+	}
+	w = aw
+	if self.Tracks != nil {
+		for _, elem := range self.Tracks {
+			if err = WriteTrackExtend(w, elem); err != nil {
+				return
+			}
+		}
+	}
+	if err = aw.Close(); err != nil {
+		return
+	}
+	return
+}
+func WalkMovieExtend(w Walker, self *MovieExtend) {
+
+	w.StartStruct("MovieExtend")
+	for i, item := range self.Tracks {
+		if w.FilterArrayItem("MovieExtend", "Tracks", i, len(self.Tracks)) {
+			if item != nil {
+				WalkTrackExtend(w, item)
+			}
+		} else {
+			w.ArrayLeft(i, len(self.Tracks))
+			break
+		}
+	}
+	w.EndStruct()
+	return
+}
+
+type TrackExtend struct {
+	Version               int
+	Flags                 int
+	TrackId               int
+	DefaultSampleDescIdx  int
+	DefaultSampleDuration int
+	DefaultSampleSize     int
+	DefaultSampleFlags    int
+}
+
+func ReadTrackExtend(r *io.LimitedReader) (res *TrackExtend, err error) {
+
+	self := &TrackExtend{}
+	if self.Version, err = ReadInt(r, 1); err != nil {
+		return
+	}
+	if self.Flags, err = ReadInt(r, 3); err != nil {
+		return
+	}
+	if self.TrackId, err = ReadInt(r, 4); err != nil {
+		return
+	}
+	if self.DefaultSampleDescIdx, err = ReadInt(r, 4); err != nil {
+		return
+	}
+	if self.DefaultSampleDuration, err = ReadInt(r, 4); err != nil {
+		return
+	}
+	if self.DefaultSampleSize, err = ReadInt(r, 4); err != nil {
+		return
+	}
+	if self.DefaultSampleFlags, err = ReadInt(r, 4); err != nil {
+		return
+	}
+	res = self
+	return
+}
+func WriteTrackExtend(w io.WriteSeeker, self *TrackExtend) (err error) {
+
+	var aw *Writer
+	if aw, err = WriteAtomHeader(w, "trex"); err != nil {
+		return
+	}
+	w = aw
+	if err = WriteInt(w, self.Version, 1); err != nil {
+		return
+	}
+	if err = WriteInt(w, self.Flags, 3); err != nil {
+		return
+	}
+	if err = WriteInt(w, self.TrackId, 4); err != nil {
+		return
+	}
+	if err = WriteInt(w, self.DefaultSampleDescIdx, 4); err != nil {
+		return
+	}
+	if err = WriteInt(w, self.DefaultSampleDuration, 4); err != nil {
+		return
+	}
+	if err = WriteInt(w, self.DefaultSampleSize, 4); err != nil {
+		return
+	}
+	if err = WriteInt(w, self.DefaultSampleFlags, 4); err != nil {
+		return
+	}
+	if err = aw.Close(); err != nil {
+		return
+	}
+	return
+}
+func WalkTrackExtend(w Walker, self *TrackExtend) {
+
+	w.StartStruct("TrackExtend")
+	w.Name("Version")
+	w.Int(self.Version)
+	w.Name("Flags")
+	w.Int(self.Flags)
+	w.Name("TrackId")
+	w.Int(self.TrackId)
+	w.Name("DefaultSampleDescIdx")
+	w.Int(self.DefaultSampleDescIdx)
+	w.Name("DefaultSampleDuration")
+	w.Int(self.DefaultSampleDuration)
+	w.Name("DefaultSampleSize")
+	w.Int(self.DefaultSampleSize)
+	w.Name("DefaultSampleFlags")
+	w.Int(self.DefaultSampleFlags)
+	w.EndStruct()
+	return
+}