diff --git a/src/mp4box/tfhd.rs b/src/mp4box/tfhd.rs
index e67e5cb..5b529e6 100644
--- a/src/mp4box/tfhd.rs
+++ b/src/mp4box/tfhd.rs
@@ -22,6 +22,8 @@ impl TfhdBox {
     pub const FLAG_DEFAULT_SAMPLE_DURATION: u32 = 0x08;
     pub const FLAG_DEFAULT_SAMPLE_SIZE: u32 = 0x10;
     pub const FLAG_DEFAULT_SAMPLE_FLAGS: u32 = 0x20;
+    pub const FLAG_DURATION_IS_EMPTY: u32 = 0x10000;
+    pub const FLAG_DEFAULT_BASE_IS_MOOF: u32 = 0x20000;
 
     pub fn get_type(&self) -> BoxType {
         BoxType::TfhdBox
diff --git a/src/mp4box/traf.rs b/src/mp4box/traf.rs
index 51f812d..d53d713 100644
--- a/src/mp4box/traf.rs
+++ b/src/mp4box/traf.rs
@@ -19,6 +19,9 @@ impl TrafBox {
     pub fn get_size(&self) -> u64 {
         let mut size = HEADER_SIZE;
         size += self.tfhd.box_size();
+        if let Some(ref tfdt) = self.tfdt {
+            size += tfdt.box_size();
+        }
         if let Some(ref trun) = self.trun {
             size += trun.box_size();
         }
@@ -104,6 +107,12 @@ impl<W: Write> WriteBox<&mut W> for TrafBox {
         BoxHeader::new(self.box_type(), size).write(writer)?;
 
         self.tfhd.write_box(writer)?;
+        if let Some(ref tfdt) = self.tfdt {
+            tfdt.write_box(writer)?;
+        }
+        if let Some(ref trun) = self.trun {
+            trun.write_box(writer)?;
+        }
 
         Ok(size)
     }