Delivering backwards-compatible content (Designing Web Audio)

7.6. Delivering backwards-compatible content

RealSystem G2 incorporates a high degree of backwards compatibility. If you want to take full advantage of the new G2 and SureStream technologies, however, you will need to encode, serve, and play files using G2 software.

There is no need to change your existing 5.0 content for delivery in the G2 system. The G2 server and player can deliver 5.0 content, enabling you to include 5.0 files in SMIL presentations.

The new content you create in RealSystem G2 can also be played by people using a 5.0 player. The G2 SureStream encoder offers the ability to include a backwards-compatibility 5.0 codec. The G2 server can detect the player version and automatically provide the appropriate stream.

If you plan to deliver full SMIL presentations, you will need a G2 server, and these presentations can be viewed properly only in a G2 player. Likewise, the dynamic bandwidth detection abilities of SureStream function only within the G2 system.

If you are delivering SMIL presentations, you can still include RealSystem 5.0 files and have the server automatically provide the appropriate stream to the client. This can be accomplished two ways:

By embedding a single link in your web page to a .ram file, as you would in RealSystem 5.0. The syntax within your .ram file would be as follows:
```
rtsp://my-realserver.com/presentation.smi
-- stop -
pnm://my-realserver.com/video.rm
```
The G2 server will detect the player version, and stream either the SMIL file to G2 players or the single media file to 5.0 players.
By using RAMGEN. Rather than creating a metafile for every link to media content, you can use the /ramgen/ parameter and the altplay option in your URLs. This feature of the G2 server automatically generates .ram files on the fly if needed to serve 5.0 content. The following syntax is used:
```
http://my-realserver.com/ramgen/presentation.smi?altplay=video.rm
```