To transform un objet in ByteArray i use the code :

var buffer:ByteArray = new ByteArray();
buffer.writeObject( myObject );

And to transform the ByteArray in a new object :

var o:* = buffer.readObject();

For me this solution is a good solution to send objects with AMF3. AMF3
support ByteArray, XML(E4X), Number, Boolean, String, Object, Array and
class mapping (use registerClass). I don't think AMF3 support the
BitmapData type ?

EKA+ :)