Thanks for the great work of crafting matroska format parser for golang.
The library is currently used to verify MediaRecorder from our team.
Now, I'm adding test for verifying whether the result mkv from MediaRecorder is muted.
Just curious about whether the library support examining the content of simple block of audio track.
I saw the information parsed from library can identify those audio blocks but the data field here:

it is possible to crash the document parser with an out of memory if io.Reader is corrupt. this is particularly problematic when handling user-supplied data (data streamed a socket for example). a user sending a specially crafted sequence of bytes will crash the go process because because the decoder naively allocates buffers of an arbitrary size:

   182:	}
   183:
   184:	// GetElementContent returns the element's data (if any)
   185:	// Data is present if the element's type is not Master
   186:	func (doc *Document) GetElementContent(el *Element) ([]byte, error) {
=> 187:		buf := make([]byte, el.Size)
   188:
   189:		_, err := io.ReadFull(doc.r, buf)
   190:		if err != nil {
   191:			return nil, err
   192:		}
(dlv) p el.Size
29055659576

The above condition leads to the following crash attempting to allocate 29GB of memory:

fatal error: runtime: out of memory

a simple solution would be to use a fixed buffer and refuse to process an element that is larger than the fixed buffer:

if el.Size > len(self.buffer) {
  return nil, errors.New("invalid size")
}

After install and redme example have error
src/github.com/pixelbender/go-matroska/ebml/decode.go:172: dec.buf.Discard undefined (type *bufio.Reader has no field or method Truncate) src/github.com/pixelbender/go-matroska/ebml/decode.go:197: dec.buf.Discard undefined (type *bufio.Reader has no field or method Truncate) src/github.com/pixelbender/go-matroska/ebml/decode.go:225: dec.buf.Discard undefined (type *bufio.Reader has no field or method Discard) src/github.com/pixelbender/go-matroska/ebml/decode.go:313: dec.buf.Discard undefined (type *bufio.Reader has no field or method Truncate)

go version go1.3.3 linux/arm