It is common for radio stations to broadcast their content over the radio and the Internet simultaneously (called simulcasting). Internet radio broadcasts enable regional radio stations to access a much wider audience at a low additional operating cost. However, certain problems may arise when local advertising content is broadcast over the Internet. Local advertising is often not suitable for a global audience, and therefore it is sometimes necessary to substitute Internet-specific ads for local advertisements. This task is made more difficult because of the need for it to be done in real-time.
The most effective advertisement replacement technique is to use
a server-side playlist containing excl and
priorityClass playlist elements in coordination with an
encoder that has been configured to send a script command to the
Windows Media server. This script command signals the start of the
advertising segment. The signal is interpreted at the publishing
point by the excl playlist element. If the script command
value matches the begin attribute value of the excl
element, the content in the excl element interrupts the live
stream. The replacement advertising content is contained within a
priorityClass element which has a peers attribute
pause. When the replacement advertisement
pause value causes playback to resume with
the live stream.
This advertisement replacement strategy works best if the length of the local advertisement and the replacement advertising content match. Differences in the lengths of the two types of content can cause the server to return to the original content late or prematurely.
The key to successful advertisement replacement is seamless switching. The transition from one content source to another should occur quickly in order to appear as professional as possible. Transition delays of more than two-tenths of a second can cause a late return to the live stream after a break. To reduce the delay, you can configure the encoder to send a cueing script command prior to the switching command. When the server receives the cueing command, it prebuffers data from the upcoming advertisement before the switch.