diff --git a/src/mp4box/avc1.rs b/src/mp4box/avc1.rs
index 2c1bba3..f051c6c 100644
--- a/src/mp4box/avc1.rs
+++ b/src/mp4box/avc1.rs
@@ -55,11 +55,11 @@ impl Avc1Box {
 
 impl Mp4Box for Avc1Box {
     fn box_type(&self) -> BoxType {
-        BoxType::Avc1Box
+        return self.get_type();
     }
 
     fn box_size(&self) -> u64 {
-        HEADER_SIZE + 8 + 70 + self.avcc.box_size()
+        return self.get_size();
     }
 }
 
diff --git a/src/mp4box/co64.rs b/src/mp4box/co64.rs
index cbb64f2..829acf8 100644
--- a/src/mp4box/co64.rs
+++ b/src/mp4box/co64.rs
@@ -22,11 +22,11 @@ impl Co64Box {
 
 impl Mp4Box for Co64Box {
     fn box_type(&self) -> BoxType {
-        BoxType::Co64Box
+        return self.get_type();
     }
 
     fn box_size(&self) -> u64 {
-        HEADER_SIZE + HEADER_EXT_SIZE + 4 + (8 * self.entries.len() as u64)
+        return self.get_size();
     }
 }
 
diff --git a/src/mp4box/ctts.rs b/src/mp4box/ctts.rs
index d794dd1..db0ccd3 100644
--- a/src/mp4box/ctts.rs
+++ b/src/mp4box/ctts.rs
@@ -28,11 +28,11 @@ pub struct CttsEntry {
 
 impl Mp4Box for CttsBox {
     fn box_type(&self) -> BoxType {
-        BoxType::CttsBox
+        return self.get_type();
     }
 
     fn box_size(&self) -> u64 {
-        HEADER_SIZE + HEADER_EXT_SIZE + 4 + (8 * self.entries.len() as u64)
+        return self.get_size();
     }
 }
 
diff --git a/src/mp4box/edts.rs b/src/mp4box/edts.rs
index 381c35b..2cd0d09 100644
--- a/src/mp4box/edts.rs
+++ b/src/mp4box/edts.rs
@@ -28,15 +28,11 @@ impl EdtsBox {
 
 impl Mp4Box for EdtsBox {
     fn box_type(&self) -> BoxType {
-        BoxType::EdtsBox
+        return self.get_type();
     }
 
     fn box_size(&self) -> u64 {
-        let mut size = HEADER_SIZE;
-        if let Some(ref elst) = self.elst {
-            size += elst.box_size();
-        }
-        size
+        return self.get_size();
     }
 }
 
diff --git a/src/mp4box/elst.rs b/src/mp4box/elst.rs
index 6cec343..ebbbaf0 100644
--- a/src/mp4box/elst.rs
+++ b/src/mp4box/elst.rs
@@ -37,18 +37,11 @@ impl ElstBox {
 
 impl Mp4Box for ElstBox {
     fn box_type(&self) -> BoxType {
-        BoxType::ElstBox
+        return self.get_type();
     }
 
     fn box_size(&self) -> u64 {
-        let mut size = HEADER_SIZE + HEADER_EXT_SIZE + 4;
-        if self.version == 1 {
-            size += self.entries.len() as u64 * 20;
-        } else {
-            assert_eq!(self.version, 0);
-            size += self.entries.len() as u64 * 12;
-        }
-        size
+        return self.get_size();
     }
 }
 
diff --git a/src/mp4box/ftyp.rs b/src/mp4box/ftyp.rs
index 62d3dc2..dfdf524 100644
--- a/src/mp4box/ftyp.rs
+++ b/src/mp4box/ftyp.rs
@@ -22,11 +22,11 @@ impl FtypBox {
 
 impl Mp4Box for FtypBox {
     fn box_type(&self) -> BoxType {
-        BoxType::FtypBox
+        return self.get_type();
     }
 
     fn box_size(&self) -> u64 {
-        HEADER_SIZE + 8 + (4 * self.compatible_brands.len() as u64)
+        return self.get_size();
     }
 }
 
diff --git a/src/mp4box/hdlr.rs b/src/mp4box/hdlr.rs
index c7931aa..62d7a32 100644
--- a/src/mp4box/hdlr.rs
+++ b/src/mp4box/hdlr.rs
@@ -23,11 +23,11 @@ impl HdlrBox {
 
 impl Mp4Box for HdlrBox {
     fn box_type(&self) -> BoxType {
-        BoxType::HdlrBox
+        return self.get_type();
     }
 
     fn box_size(&self) -> u64 {
-        HEADER_SIZE + HEADER_EXT_SIZE + 20 + self.name.len() as u64 + 1
+        return self.get_size();
     }
 }
 
diff --git a/src/mp4box/mdhd.rs b/src/mp4box/mdhd.rs
index e8563b0..7696088 100644
--- a/src/mp4box/mdhd.rs
+++ b/src/mp4box/mdhd.rs
@@ -50,20 +50,11 @@ impl Default for MdhdBox {
 
 impl Mp4Box for MdhdBox {
     fn box_type(&self) -> BoxType {
-        BoxType::MdhdBox
+        return self.get_type();
     }
 
     fn box_size(&self) -> u64 {
-        let mut size = HEADER_SIZE + HEADER_EXT_SIZE;
-
-        if self.version == 1 {
-            size += 28;
-        } else {
-            assert_eq!(self.version, 0);
-            size += 16;
-        }
-        size += 4;
-        size
+        return self.get_size();
     }
 }
 
diff --git a/src/mp4box/mdia.rs b/src/mp4box/mdia.rs
index c1d4cb8..e8ea27a 100644
--- a/src/mp4box/mdia.rs
+++ b/src/mp4box/mdia.rs
@@ -22,11 +22,11 @@ impl MdiaBox {
 
 impl Mp4Box for MdiaBox {
     fn box_type(&self) -> BoxType {
-        BoxType::MdiaBox
+        return self.get_type();
     }
 
     fn box_size(&self) -> u64 {
-        HEADER_SIZE + self.mdhd.box_size() + self.hdlr.box_size() + self.minf.box_size()
+        return self.get_size();
     }
 }
 
diff --git a/src/mp4box/minf.rs b/src/mp4box/minf.rs
index b2f8547..1dad192 100644
--- a/src/mp4box/minf.rs
+++ b/src/mp4box/minf.rs
@@ -30,19 +30,11 @@ impl MinfBox {
 
 impl Mp4Box for MinfBox {
     fn box_type(&self) -> BoxType {
-        BoxType::MinfBox
+        return self.get_type();
     }
 
     fn box_size(&self) -> u64 {
-        let mut size = HEADER_SIZE;
-        if let Some(ref vmhd) = self.vmhd {
-            size += vmhd.box_size();
-        }
-        if let Some(ref smhd) = self.smhd {
-            size += smhd.box_size();
-        }
-        size += self.stbl.box_size();
-        size
+        return self.get_size();
     }
 }
 
diff --git a/src/mp4box/moov.rs b/src/mp4box/moov.rs
index 41c2823..3a9cae5 100644
--- a/src/mp4box/moov.rs
+++ b/src/mp4box/moov.rs
@@ -25,15 +25,11 @@ impl MoovBox {
 
 impl Mp4Box for MoovBox {
     fn box_type(&self) -> BoxType {
-        BoxType::MoovBox
+        return self.get_type();
     }
 
     fn box_size(&self) -> u64 {
-        let mut size = HEADER_SIZE + self.mvhd.box_size();
-        for trak in self.traks.iter() {
-            size += trak.box_size();
-        }
-        size
+        return self.get_size();
     }
 }
 
diff --git a/src/mp4box/mp4a.rs b/src/mp4box/mp4a.rs
index b90ed37..8a44cff 100644
--- a/src/mp4box/mp4a.rs
+++ b/src/mp4box/mp4a.rs
@@ -50,15 +50,11 @@ impl Mp4aBox {
 
 impl Mp4Box for Mp4aBox {
     fn box_type(&self) -> BoxType {
-        BoxType::Mp4aBox
+        return self.get_type();
     }
 
     fn box_size(&self) -> u64 {
-        let mut size = HEADER_SIZE + 8 + 20;
-        if let Some(ref esds) = self.esds {
-            size += esds.box_size();
-        }
-        size
+        return self.get_size();
     }
 }
 
diff --git a/src/mp4box/mvhd.rs b/src/mp4box/mvhd.rs
index ea5387d..377bab8 100644
--- a/src/mp4box/mvhd.rs
+++ b/src/mp4box/mvhd.rs
@@ -48,19 +48,11 @@ impl Default for MvhdBox {
 
 impl Mp4Box for MvhdBox {
     fn box_type(&self) -> BoxType {
-        BoxType::MvhdBox
+        return self.get_type();
     }
 
     fn box_size(&self) -> u64 {
-        let mut size = HEADER_SIZE + HEADER_EXT_SIZE;
-        if self.version == 1 {
-            size += 28;
-        } else {
-            assert_eq!(self.version, 0);
-            size += 16;
-        }
-        size += 80;
-        size
+        return self.get_size();
     }
 }
 
diff --git a/src/mp4box/smhd.rs b/src/mp4box/smhd.rs
index 1fc8f1b..454bea9 100644
--- a/src/mp4box/smhd.rs
+++ b/src/mp4box/smhd.rs
@@ -32,11 +32,11 @@ impl Default for SmhdBox {
 
 impl Mp4Box for SmhdBox {
     fn box_type(&self) -> BoxType {
-        BoxType::SmhdBox
+        return self.get_type();
     }
 
     fn box_size(&self) -> u64 {
-        HEADER_SIZE + HEADER_EXT_SIZE + 4
+        return self.get_size();
     }
 }
 
diff --git a/src/mp4box/stbl.rs b/src/mp4box/stbl.rs
index 14c6310..0d37416 100644
--- a/src/mp4box/stbl.rs
+++ b/src/mp4box/stbl.rs
@@ -47,28 +47,11 @@ impl StblBox {
 
 impl Mp4Box for StblBox {
     fn box_type(&self) -> BoxType {
-        BoxType::StblBox
+        return self.get_type();
     }
 
     fn box_size(&self) -> u64 {
-        let mut size = HEADER_SIZE;
-        size += self.stsd.box_size();
-        size += self.stts.box_size();
-        if let Some(ref ctts) = self.ctts {
-            size += ctts.box_size();
-        }
-        if let Some(ref stss) = self.stss {
-            size += stss.box_size();
-        }
-        size += self.stsc.box_size();
-        size += self.stsz.box_size();
-        if let Some(ref stco) = self.stco {
-            size += stco.box_size();
-        }
-        if let Some(ref co64) = self.co64 {
-            size += co64.box_size();
-        }
-        size
+        return self.get_size();
     }
 }
 
diff --git a/src/mp4box/stco.rs b/src/mp4box/stco.rs
index ea86dfc..c63295a 100644
--- a/src/mp4box/stco.rs
+++ b/src/mp4box/stco.rs
@@ -22,11 +22,11 @@ impl StcoBox {
 
 impl Mp4Box for StcoBox {
     fn box_type(&self) -> BoxType {
-        BoxType::StcoBox
+        return self.get_type();
     }
 
     fn box_size(&self) -> u64 {
-        HEADER_SIZE + HEADER_EXT_SIZE + 4 + (4 * self.entries.len() as u64)
+        return self.get_size();
     }
 }
 
diff --git a/src/mp4box/stsc.rs b/src/mp4box/stsc.rs
index 228a10e..78b7686 100644
--- a/src/mp4box/stsc.rs
+++ b/src/mp4box/stsc.rs
@@ -30,11 +30,11 @@ pub struct StscEntry {
 
 impl Mp4Box for StscBox {
     fn box_type(&self) -> BoxType {
-        BoxType::StscBox
+        return self.get_type();
     }
 
     fn box_size(&self) -> u64 {
-        HEADER_SIZE + HEADER_EXT_SIZE + 4 + (12 * self.entries.len() as u64)
+        return self.get_size();
     }
 }
 
diff --git a/src/mp4box/stsd.rs b/src/mp4box/stsd.rs
index 64e1d08..d09da49 100644
--- a/src/mp4box/stsd.rs
+++ b/src/mp4box/stsd.rs
@@ -30,17 +30,11 @@ impl StsdBox {
 
 impl Mp4Box for StsdBox {
     fn box_type(&self) -> BoxType {
-        BoxType::StsdBox
+        return self.get_type();
     }
 
     fn box_size(&self) -> u64 {
-        let mut size = HEADER_SIZE + HEADER_EXT_SIZE + 4;
-        if let Some(ref avc1) = self.avc1 {
-            size += avc1.box_size();
-        } else if let Some(ref mp4a) = self.mp4a {
-            size += mp4a.box_size();
-        }
-        size
+        return self.get_size();
     }
 }
 
diff --git a/src/mp4box/stss.rs b/src/mp4box/stss.rs
index faffe65..6d60bd9 100644
--- a/src/mp4box/stss.rs
+++ b/src/mp4box/stss.rs
@@ -22,11 +22,11 @@ impl StssBox {
 
 impl Mp4Box for StssBox {
     fn box_type(&self) -> BoxType {
-        BoxType::StssBox
+        return self.get_type();
     }
 
     fn box_size(&self) -> u64 {
-        HEADER_SIZE + HEADER_EXT_SIZE + 4 + (4 * self.entries.len() as u64)
+        return self.get_size();
     }
 }
 
diff --git a/src/mp4box/stsz.rs b/src/mp4box/stsz.rs
index ad7dc83..78fc0e6 100644
--- a/src/mp4box/stsz.rs
+++ b/src/mp4box/stsz.rs
@@ -24,11 +24,11 @@ impl StszBox {
 
 impl Mp4Box for StszBox {
     fn box_type(&self) -> BoxType {
-        BoxType::StszBox
+        return self.get_type();
     }
 
     fn box_size(&self) -> u64 {
-        HEADER_SIZE + HEADER_EXT_SIZE + 8 + (4 * self.sample_sizes.len() as u64)
+        return self.get_size();
     }
 }
 
diff --git a/src/mp4box/stts.rs b/src/mp4box/stts.rs
index 192e6a6..bb46d5b 100644
--- a/src/mp4box/stts.rs
+++ b/src/mp4box/stts.rs
@@ -28,11 +28,11 @@ pub struct SttsEntry {
 
 impl Mp4Box for SttsBox {
     fn box_type(&self) -> BoxType {
-        BoxType::SttsBox
+        return self.get_type();
     }
 
     fn box_size(&self) -> u64 {
-        HEADER_SIZE + HEADER_EXT_SIZE + 4 + (8 * self.entries.len() as u64)
+        return self.get_size();
     }
 }
 
diff --git a/src/mp4box/tkhd.rs b/src/mp4box/tkhd.rs
index 022eb1a..9023269 100644
--- a/src/mp4box/tkhd.rs
+++ b/src/mp4box/tkhd.rs
@@ -79,19 +79,11 @@ impl TkhdBox {
 
 impl Mp4Box for TkhdBox {
     fn box_type(&self) -> BoxType {
-        BoxType::TkhdBox
+        return self.get_type();
     }
 
     fn box_size(&self) -> u64 {
-        let mut size = HEADER_SIZE + HEADER_EXT_SIZE;
-        if self.version == 1 {
-            size += 32;
-        } else {
-            assert_eq!(self.version, 0);
-            size += 20;
-        }
-        size += 60;
-        size
+        return self.get_size();
     }
 }
 
diff --git a/src/mp4box/trak.rs b/src/mp4box/trak.rs
index 95440cd..2c9724f 100644
--- a/src/mp4box/trak.rs
+++ b/src/mp4box/trak.rs
@@ -28,17 +28,11 @@ impl TrakBox {
 
 impl Mp4Box for TrakBox {
     fn box_type(&self) -> BoxType {
-        BoxType::TrakBox
+        return self.get_type();
     }
 
     fn box_size(&self) -> u64 {
-        let mut size = HEADER_SIZE;
-        size += self.tkhd.box_size();
-        if let Some(ref edts) = self.edts {
-            size += edts.box_size();
-        }
-        size += self.mdia.box_size();
-        size
+        return self.get_size();
     }
 }
 
diff --git a/src/mp4box/vmhd.rs b/src/mp4box/vmhd.rs
index 0edb8b2..685a3eb 100644
--- a/src/mp4box/vmhd.rs
+++ b/src/mp4box/vmhd.rs
@@ -30,11 +30,11 @@ impl VmhdBox {
 
 impl Mp4Box for VmhdBox {
     fn box_type(&self) -> BoxType {
-        BoxType::VmhdBox
+        return self.get_type();
     }
 
     fn box_size(&self) -> u64 {
-        HEADER_SIZE + HEADER_EXT_SIZE + 8
+        return self.get_size();
     }
 }