In RealMedia files the bitstream is scrambled. To unscramble the stream, perform a XOR on every 32 bits in the frame. The hex value to XOR with is 0x537F6103.
Extra data format
In RealMedia files the extra data is as follows (big-endian order):
INT32 id, always 4 INT16 samples per frame, always 1024 * 2 INT16 delay, not used but always 0x88E INT16 stereo coding mode, 2 - normal stereo, 0x12 - joint stereo
The length of this data is always 10 bytes.