Distributing Public Radio Programming Over Satellite
The functional design of the ContentDepot® is the result of many years of ongoing system consultation both with station and producer advisors as well as with independent system contractors. At the direction of the DI Committee, NPR Distribution developed the following operational requirements for the new system:
- Consolidate ancillary data (metadata) to support new services such as HD Radio
- Accomplish transition with minimal disruption to current station operations
- Be able to adapt over time to new demands and technologies without a complete system rebuild
- Use cost effective, supportable, and off-the-shelf equipment, so that the barrier of entry for new users of the system is lower than with today's system
- Be capable of interfacing to a variety of distribution platforms, not just satellite
- Provide data to producers about who's using their programs
After evaluating available technical solutions, the IP-based ContentDepot solution was implemented because of its ability to meet these requirements and position the public radio distribution system for the future. IP protocols supported by the DVB-S (Digital Video Broadcasting - Satellite) standard are established and stable and already provide an industry-accepted method for transporting audio and data over short and long distances. Industry experts believe that IP transmission will continue to migrate to other applications and platforms throughout the broadcast industry.
Is the IP Streaming solution "cutting edge"?
IP over satellite is a well-established technology that has been subject to rigorous specifications on live audio delivery. Numerous systems use IP technology to deliver audio through local networks. The ContentDepot uses IP streams in a unique, integrated delivery solution.
Are there disadvantages of IP over satellite for live streams?
The only identified disadvantage is a slight increase in latency (delay). In today's satellite system, the end-to-end satellite transmission latency is 290ms behind "real time". This latency is a function of physics (speed of light) and the minor delays caused by encoding an MPEG file to send to the satellite and the decoding that occurs at a station downlink. Using the IP-based technology in the ContentDepot increases this latency by an additional 400ms compared to the previous system. The total latency for satellite transmission for the ContentDepot is 700ms-well within the one-second specification that was established.
How does audio sound when distributed through an IP-based system?
The audio encoding standard for the ContentDepot is MPEG1, Layer 2. The IP over satellite using DVB-S technology is simply a different transport mechanism. It does not alter the quality of the sound being delivered.
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