Try to skip extended header in MetaBox.

Fixes #102

Author: w-flo

src/mp4box/meta.rs

@@ -84,15 +84,29 @@ impl<R: Read + Seek> ReadBox<&mut R> for MetaBox {
     fn read_box(reader: &mut R, size: u64) -> Result<Self> {
         let start = box_start(reader)?;
 
-        let (version, _) = read_box_header_ext(reader)?;
-        if version != 0 {
-            return Err(Error::UnsupportedBoxVersion(BoxType::UdtaBox, version));
-        }
+        // Some mp4 files directly start the hdlr box here (like Quicktime)
+        // and skip the extended header in meta boxes.
+        let start_stream_pos = reader.stream_position()?;
+        let try_read_header = BoxHeader::read(reader)?;
+
+        let hdlr_header = if try_read_header.name == BoxType::HdlrBox {
+            // This file skipped the extended header.
+            try_read_header
+        } else {
+            // File probably has the extended header, go back and parse it.
+            reader.seek(SeekFrom::Start(start_stream_pos))?;
+            let (version, _) = read_box_header_ext(reader)?;
+            if version != 0 {
+                return Err(Error::UnsupportedBoxVersion(BoxType::UdtaBox, version));
+            }
+
+            let hdlr_header = BoxHeader::read(reader)?;
+            if hdlr_header.name != BoxType::HdlrBox {
+                return Err(Error::BoxNotFound(BoxType::HdlrBox));
+            }
+            hdlr_header
+        };
 
-        let hdlr_header = BoxHeader::read(reader)?;
-        if hdlr_header.name != BoxType::HdlrBox {
-            return Err(Error::BoxNotFound(BoxType::HdlrBox));
-        }
         let hdlr = HdlrBox::read_box(reader, hdlr_header.size)?;
 
         let mut ilst = None;