Radio World Buyer’s Guide articles are intended to help readers understand why their colleagues chose particular products to solve various technical situations. This month’s articles focus on codecs and STLs.
I’ve recently had the opportunity to work with 2wcom’s MPX-2c codecs in a challenging scenario.
The MPX-2c is a two-channel MPX composite audio codec designed for use as an IP STL. The 2c offers many features out of the box, including 1PPS sync, linear encoding of MPX signals to multiple destinations, FEC, dual-streaming and three NICs. It is designed so all add-on options, such as μMPX, RIST/SRT and MPE, are added through license keys, requiring no hardware changes. Additionally, my setup included the internal GPS receiver, which is available as a hardware option.
In my case, these units were installed at the main FM and its booster sites in a single-frequency network built by GeoBroadcast Solutions. The internet at the main site was brought in through a wireless internet provider and suffered from congestion and packet loss. Linear MPX requires roughly 3.5 Mbps of bandwidth per channel, which overloaded the internet connection and caused audio dropouts on the boosters.
Under the advice of 2wcom’s engineers, we added the μMPX and RIST options. Encoding with μMPX at the highest-quality setting of 512k reduced overall bandwidth usage by roughly 80 percent, which had a significant impact on stream stability. To further reduce the impact of packet losses through the WISP, I experimented with various configurations of redundant streams, FEC and increased buffering.
Deploying μMPX in the SFN environment did not impact timing; the boosters remained in perfect sync so long as the same settings were applied to all active streams.
The support team at 2wcom was outstanding, even scheduling online meetings outside their normal working hours to assist me in initial setup of the units and troubleshooting the packet loss.
In the end, the WISP service at the site had to be replaced, but combining the highly customizable advanced features of the MPX-2c codecs significantly improved audio playout quality and stability, even on a severely diminished internet connection. I am impressed with these units, their flexibility and the ease of setup and use in a real-world SFN environment.
