StatMux is a technique that efficiently and dynamically allocates bandwidth among multiple video services within a fixed-bandwidth pool, adjusting the bitrate of each service to optimize overall picture quality.

ATSC 3.0 StatMux differs from ATSC 1.0 StatMux in a few ways, making it much more difficult to implement. ATSC 3.0 is natively SPTS (single program transport stream) and does not have an MPTS like is used for ATSC 1.0 StatMux. So, provisions had to be made to create an intermediate step to pool all services in a group and then separate them back out to SPTS before the DASH packaging.

A second issue with ATSC 3.0 is that the DASH packaging and ROUTE encapsulation adds some delay and buffering to the services and that causes the relatively flat bitrate coming out of the encoder StatMux pool stage to start to vary again, often quite a bit (maybe 5 or more Mb/s). Therefore, some processing in the downstream equipment (signaling server) is needed to restore a relatively flat stat mux pool behavior. There is also an additional step that requires attention, we have to make sure the extra processing we do in the signaling server doesn’t insert too much delay / buffering or the consumer receiver devices can have issues.

This specific customer request from Gray Media was for HVS to develop a custom ATSC 3.0 StatMux that wouldn’t adversely affect any of the available ATSC 3.0 tuners in TVs or set top boxes. HVS pre-qualified and tested several StatMux combinations in our advanced ATSC 3.0 laboratory in the company’s headquarters located in Plymouth, WI. After successful lab testing, HVS then deployed the new configuration at the WVUE TV New Orleans station in time for The Big Game.

For the New Orleans ATSC 3.0 market, HVS configured a Harmonic XOS encoding platform and a DigiCAP DigiCaster ATSC 3.0 air chain as a StatMux. Before configuring the StatMux, the ATSC 3.0 OTA signal was running an average of 4 Mb/s per program service. We equally rated all the program services, but the FOX program feed would still get the most bitrate due to the complexity of the video. After the custom StatMux was set up and tested, it is estimated the average bitrate was closer to 6-7 Mb/s and would max out at around 10 Mb/s when needed. Additionally, the other services had peak bit rates at around 7Mb/s. So, at times, even the non “Big Game” programs benefited more than they would have if they were running the older pre-HVS configuration. In addition to the StatMux configuration, HVS also helped WVUE enable Dolby^® Vision & HDR10+ and Dolby Atmos upmix on this important service.