Designing Web Audio & CD-ROM

Advanced RealAudio applications

Now that you are familiar with broadcasting prerecorded content, let’s explore some of the advanced capabilities of the RealSystem, such as synchronizing media presentations, indexing regions of a large file, broadcasting through firewalls, archiving and delivering RealMedia content with a database, creating RealFlash content, and broadcasting over an Intranet.

Broadcasting through firewalls

When RealAudio first hit the market, many listeners behind corporate firewalls could not receive RealAudio content because all UDP traffic was blocked from their networks. RealAudio, similar to other streaming media formats, uses UDP for bandwidth efficiency. UDP is more efficient because it streams multimedia content without tediously checking for transmission errors. Therefore, in congested networks, UDP tends to step on TCP traffic. TCP, on the other hand, is designed to throttle back during congestion. Primarily for this reason, most firewalls block UDP traffic.

Thus, RealNetworks has incorporated TCP and HTTP streaming in RealSystem 5.0 for broadcasting through firewalls. TCP and HTTP are better than UDP for broadcasting through firewalls since TCP ports are generally open to allow FTP, HTTP, and Telnet traffic through, and HTTP ports are usually always open.

Make sure your RealServer is not set to multicast delivery only. Enable HTTP Cloaking in the RealServer config file (rmserver.cfg ) located in the application root directory. Open the file and change ...