H264 Decoding using Source Reader and Custom Bytestream

I am trying to decode H264 data on Win 7.  My source of compressed H264 data is not a file or network, the source is the memory itself. I get the H264 compressed data in the memory frame by frame. I want to synchronously decompress each frame as I get it. I am trying to follow the example in the link http://msdn.microsoft.com/en-us/library/dd389281(VS.85).aspx. But the example uses a URL to create the source reader. But since my source of compressed data is memory I am thinking of writing custom byte stream which reads data from memory.