In most cases the ASF and RM files come encapsulated in a format that cannot be played back from a local computer. There are many items that need to be removed, changed or added in the broadcasted stream. The most complicated is to detect and recalculate the frame times and frame counts which are inserted allover the broadcast in mini headers for each individual stream that forms the video/audio.
Real Player usually has 2 streams but Windows Media has much more (for example a live TV show will have as many streams as the number of video cameras and microphones used in the broadcast).
The simple way to do this is to use DLL's from Microsoft or RealPlayer which do everything for you: make the connection, parse the stream and give you an ASF or RM file output. The only problem with this is that it is illegal. These DLL's are not public domain.
The problem becomes even more complicated with Real Player which includes an encrypted authentication for every RTSP stream accessed. In this case, when you use their DLL to do the authentication you break the DMCA (Digital Millennium Act) law which is what happened with Streambox. The court decision in the Streambox case specifies that Real Player streams can only be accessed using the Real Player. Only Real Player can access the DLL.
WM Recorder brings up the Real Player every time you play or record a stream with it. Real Player brings up the DLL which makes the connection and does the authentication then WM Recorder only get the stream data. It is much more complicated
than what other
stream recording programs do.
The reward for doing this is that WM Recorder can control the connection as it wants. For example a 4 hours BBC radio show can be recorded in 10 minutes or less using the Turbo Mode.
Same with ASF although Microsoft does not use a password. Using their DLLs is also illegal. Again,
the reward for WM Recorder is the capability of recording DRM and password authenticated streams which are not included in the DLLs used by all other stream recording programs.