PRSS Evolution: From SOSS to ContentDepot
The distribution of high-quality audio to member stations has undergone a significant technological transformation. Moving from early analog systems, the Public Radio Satellite System (PRSS) evolved through the digital automation of the Satellite Operations Support System (SOSS) and eventually transitioned to the modern, IP-based architecture of ContentDepot.
The Satellite Operations Support System (SOSS)
Introduced around 1994, the Satellite Operations Support System (SOSS) replaced first-generation analog PRSS systems. This upgrade shifted the infrastructure from analog feeds to digital audio, introducing automated receiver selection and tuning managed by a dedicated PC.
The SOSS utilized SCPC (Single Channel Per Carrier) digital uplinks across two satellite transponders using Musicam encoding. The hardware chain began with a Satellite System Corporation Model 4421 downconverter, which processed L-band input from the dish's LNB (Low Noise Block) and provided a 70 MHz IF (Intermediate Frequency) bus.
This bus fed seven ComStream ABR-700 digital audio satellite demodulators (demods):
- Six Audio Demods: Labeled "NPR A" through "NPR F," these handled the primary program feeds.
- One Data Demod: Known as the Downlink Service Channel (DSC), this unit handled data only.
The DSC demod interfaced with a SOSS PC running custom software on OS/2 Warp. By receiving frequency and transponder data via the DSC, the software could automatically tune the audio demodulators, eliminating the manual tuning required by previous analog systems. Control was facilitated by an ARTIC board (A Real-Time Interface Co-Processor) installed in the PC, which used RS-485 serial connections to manage the demodulators.
Beyond audio delivery, the SOSS integrated DACS messaging and provided recording control for stand-alone recorders and audio servers within radio broadcast automation systems. It also allowed operators to route live feeds, such as breaking news, to any of the six available demodulators.
[ไม่มีภาพประกอบ]Transition to ContentDepot
In 2007, the SOSS was retired in favor of ContentDepot, the current PRSS system. This marked a fundamental shift from linear SCPC digital bitstreams to a TCP/IP-based one-way satellite connection.
Under the ContentDepot model, member stations use the ContentDepot Portal—an internet-accessible website—to log in and subscribe to specific programs and live feeds. The delivery mechanism differs based on the content type:
- Pre-recorded Programs: Delivered as file transfers in the form of MP2-encoded ACM-based WAV files. These are received by a storage receiver (a combined satellite data receiver and file server) manufactured by International Datacasting.
- Live Feeds: Delivered as streaming MP2 audio via IP multicast streams over the same satellite transponder. These are processed by a specialized stream decoder.
By 2014, hardware efficiency improved with the introduction of a custom version of the "Superflex Pro Audio" receiver from International Datacasting. This single rack-mounted unit combines both the stream decoder for live audio and the storage receiver for pre-recorded files, replacing the need for separate hardware units.
[ไม่มีภาพประกอบ]Key Facts
- SOSS Era: Transitioned PRSS from analog to digital audio around 1994 using Musicam encoding and SCPC.
- SOSS Hardware: Utilized seven ComStream ABR-700 demodulators and an OS/2 Warp-based PC with an ARTIC board.
- ContentDepot Era: Launched in 2007, replacing linear feeds with TCP/IP-based satellite delivery.
- ContentDepot Delivery: Uses MP2-encoded WAV files for programs and IP multicast for live streams.
- Modern Hardware: The Superflex Pro Audio receiver integrates both storage and live decoding into one system.
- Legacy Use: One ABR-700 demod and the downconverter remain in use as a "squawk box" for NPR verbal announcements.
| Feature | SOSS (1994) | ContentDepot (2007) |
|---|---|---|
| Signal Type | Linear Digital (SCPC) | TCP/IP-based (One-way) |
| Encoding | Musicam | MP2 (WAV/Multicast) |
| Tuning Method | Automated via SOSS PC | Web-based Portal Subscription |
| Hardware | ABR-700 Demods & ARTIC Board | International Datacasting Receivers |
| Delivery Mode | Continuous Stream | File Transfer & IP Multicast |
Frequently Asked Questions
What was the primary purpose of the SOSS PC?
The SOSS PC ran custom software under OS/2 Warp to automatically tune audio demodulators based on data received from the Downlink Service Channel (DSC), replacing the manual tuning process of analog systems.
How does ContentDepot handle pre-recorded programs versus live feeds?
Pre-recorded programs are delivered as MP2-encoded ACM-based WAV files via file transfer to a storage receiver. Live feeds are delivered as IP multicast streams of MP2 audio, which are processed by a stream decoder.
What is the function of the ARTIC board in the SOSS system?
The ARTIC (A Real-Time Interface Co-Processor) board provided the RS-485 serial connections necessary for the SOSS PC to control the six audio demodulators.
What hardware does the current ContentDepot system use?
As of 2014, the system uses a custom version of the International Datacasting "Superflex Pro Audio" receiver, which integrates both live stream decoding and program storage in one rack-mounted unit.
Are any SOSS components still in use today?
Yes, NPR still utilizes one ABR-700 demodulator and the original downconverter as a "squawk box" for making verbal announcements to member stations.