A Radio World ebook explores trends and best practices in codecs for radio broadcasting applications.
Tony Gervasi is Intraplex sales manager at GatesAir, which he joined in 2018. He is former senior VP of engineering and technology for Nassau Broadcasting Partners and has held roles as a DOE, chief engineer and DJ. He is also an award-winning restaurateur with his son Chef Michael.
Radio World: Tony what would you say is the most important trend in the design or use of broadcast codecs?
Tony Gervasi: Distribution — it’s more than just point-to-point. It’s NOC to multi-city and satellite replacement distribution. I am currently working with multiple large broadcasting companies, both radio and TV, on designing new public and private IP distribution systems.
RW: How widespread are IP-based systems for STL applications now?
Gervasi: Most stations have some type of IP-based codec for STLs. We pair our 950 MHz STL system with our IPL codecs for the most flexibility. With the HDL-IPL pairing, you can transport baseband FM with RDS and E2X data over the 950 radio using one of the three WAN ports on the IPL unit, and have a backup path over the public internet.
RW: How do today’s codecs avoid problems with dropped packets?
Gervasi: Intraplex offers multiple ways to make up for lost or dropped packets:
- Forward Error Correction (FEC) with or without interleave — The IPL units offer four choices of FEC but at the expense of additional bandwidth. FEC is very effective for random/isolated losses.
- Secure Reliable Transport (SRT) — This open-source transport protocol is similar to TCP, however it is performed on the application layer using UDP as the underlying transport. SRT supports retransmission of lost packets while maintaining low latency, 120 ms by default. SRT also supports AES encryption. SRT does require a bidirectional UDP path.
- Dynamic Stream Splicing — This is exclusive to GatesAir Intraplex. DSS sends grouped streams via path diversity, time diversity or both, providing “hitless” operation.
RW: What are the implications of FM-MPX and microMPX to the way the radio industry chooses and deploys codecs?
Gervasi: GatesAir Intraplex IPL series support FM-MPX, uMPX as well as our proprietary FM-MPX, which transports uncompressed baseband MPX with RDS in 1.64 Mbps.
The current IPL line allows you to select from analog audio, AES3 audio and AES192 as I/O. This provides the most flexibility, as you can deploy audio today and then when you’re ready, convert to MPX / uMPX.
Something unique to the IPL series codec is the ability to transport MPX/RDS with E2X data for HD. By “marrying” the E2X data to the MPX data, once time alignment is set it will not drift. We have stations that are sending this MPX/RDS/E2X bundle to multiple transmitter sites via one IPL unit. And they don’t have to worry about having time alignment hardware for each site. The audio processing and importer/exporter are located at the studio, allowing for easy deployment and maintenance.
RW: What tools are available for sending audio to multiple locations at once?
Gervasi: The Intraplex IPL series codec allows for multi-coding for each audio input with transport up to 12 unique destinations, meaning you can send uncompressed audio to Location A, Opus to Location B, and AAC to Location C. There are some limitations due to sample and coding overhead.
RW: Can you tell us about a recent installation or application for codecs that you found notable?
Gervasi: Currently I’m working with three major groups on centralized NOC distribution direct to transmitter sites, using the Intraplex Ascent Server — our high-density audio codec with up to 24 channels of inputs — and Ascent Media Gateway, our multi-point distribution system.
We are providing the transport layer not only for audio but for metadata for RDS/HD, GPIO for local firing of elements and VGPIO for insertion of local IDs that are embedded in the IPL codec. We will be expanding the local insertion option for extended audio as well as local ad insertion.
RW: How can an engineer protect codecs and their related infrastructure from cyberattacks?
Gervasi: Protect the codec behind a firewall and only open the ports that are required.
Change the default passwords. I know this sound basic, but there are many devices out there that still have the default log-in. Also disable any protocols that are not being used. The IPL series allows the end user to disable HTTP/HTTPS, FTP/SFTP, SNMP, etc.
If your codec allows, you may want to include white-listing IP address(es) for management.
Read more on this topic in the free ebook “Trends in Codecs 2026.”
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