Real Media (file extension .rm)

RM (Real Media), and its brother RA (Real Audio), are proprietary standards developed by Real Networks.  Real Networks designed the formats specifically for “streaming” applications, that is, the playing of material as it is received over the Internet.  Real Networks’ target customer base consists of website owners who want to make streaming audio and video available to their website visitors.  (Real Networks distribute the PC software component, RealPlayer, free to anyone who wants to play streaming audio or video.)  The advantage of streaming audio/video is that the user does not have to wait for the complete audio clip or video clip to download before he or she can start playing it.  It is particularly useful for live webcasts of radio and television channels, where the material has no beginning or end.

Real Networks’ products are designed with a specific segment of the streaming audio/video market in mind, namely website owners who want their visitors to play the audio/video content but not be able to save it on their hard drives or pass it on to others.  Real Networks have gone to great lengths to prevent a user capturing their customers’ streaming audio/video material, as follows:

§        The Real Networks software that goes on the website engages in a “secret handshake” with the RealPlayer client before it will start the streaming process.  This is intended to stop anyone using any other player to play their format.  It also stops users simply downloading the audio/video file.

§        The transfer of the stream is done using a proprietary protocol called “rtsp” (IP port number 554), rather than one of the common protocols like ftp.

§        The website owner can use one or more levels of abstraction to hide the actual name of the source from the user.  So, rather than just having a link on the website to a URL like www.nicevideos.com/clips/theactualclip.rm, the link will typically contain a “.ram” file such as ibetyoucantfindmyclip.ram.  The “.ram” file is what Real Networks refer to as a metafile (what, in the old days, people called a pointer).  It simply points to the URL of the .rm file.  (It can also hold a playlist of two or more .rm or .ra  files.)  The website owner may also add a second level of abstraction using an SMIL metametafile (extension .smi), which points to  the .ram file (that points to the .rm file) and is called something like ibetyoureallycantfindmyclipnow.smi.

Besides playing streaming audio/video, RealPlayer will also play an RM or RA file stored on a PC’s hard drive.  (Note: if you try to play a file with an extension of .ram, RealPlayer will initiate a streaming session over the Internet to the URL to which the .ram file points.)   The RA or RM files that are stored on a PC's hard drive are audio/video material that has been prepared using Real Networks’ encoding software and then distributed as a normal file (e.g. via email).

Real Networks have tried to convince the world that there is a fundamental difference between the structure of the bit-stream that is sent from a website to RealPlayer in streaming mode and the structure of a RM file stored on a PC.  In fact this is nonsense.  The structure is exactly the same (just as the structure of a streamed MPEG-2 video signal on a TV cable or satellite service is the same as on a DVD).  The only difference is in the header: the bit-stream, in streaming mode, has a header in which a “don’t-let-the-user-save-this-file” flag is set to “yes”.  All or part of any audio/video stream, regardless of whether it is a fixed-length clip or a continuous broadcast, can be turned into a Windows file if it is properly “topped and tailed”.  (However, Real Networks have sued companies that have tried to distribute software that does this, such as the early versions of StreamboxVCR, and they have won court orders to stop the distribution of such software.)

Real Networks’ focus on streaming applications, together with the steps they have taken to limit users’ direct access to RM and RA files, and to keep details of the formats secret, has prevented the RM format becoming of general use for storing and transmitting video material.  Real Networks have also annoyed users by making the free RealPlayer client a very “badly behaved” piece of software.  It makes unwanted changes to the user’s Windows set-up, putting RealPlayer buttons all over the place.  It launches advertisements instead of getting on with playing the audio/video.  And it constantly pesters the user to download upgrades.  Some reviewers have even described RealPlayer as “spyware”.  Over time, these factors will probably lead to RM and RA being displaced by Microsoft’s Windows Media Video (.wmv) format for both streaming and non-streaming uses.

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Transmission and Recording Standards: DV (tape and FireWire), Cable, and Satellite