Two pieces of good news from Harmonic for TV channel-sharers — whether they’ve signed on to a sharing agreement as part of the TV spectrum repack or they’re looking at how to implement a strategy to keep ATSC 1 service on-air while taking the long road to an ATSC 3.0 market transition — emerged April 23 after the company’s NAB Show press conference.
While mingling with several Harmonic employees, I asked if it is possible to find still more efficiency with MPEG 2 compression. What I wanted to get at is whether broadcasters can expect encoder technology to squeeze another digital subchannel or two into a 6 MHz assignment — something that could give broadcasters more options as they hammer out their sharing agreements.
Andy Warman, director of production and playout strategy and market development at Harmonic, confirmed that, indeed, more MPEG 2 efficiencies are possible and that the company will be demoing that at its NAB Show booth (SU1210).
Jean Macher, director broadcast market development Americas at Harmonic, provided further details.
“We keep pushing the envelope on compression efficiency, and you will see that on the booth with a stat mux carrying four 720p channels in 19.4 Mbits,” he said.
Harmonic also is tackling the issue of fairness, which left unaddressed could be a point of contention between broadcasters sharing a single channel, said Macher.
“When it comes to channel-sharing agreements, you need a way to make it fair and guarantee the broadcasters sharing the channel get the correct amount of bandwidth [defined in their channel sharing agreement],” he said.
A traditional stat mux inherently isn’t set up to address this issue. It examines the video signals it receives and dynamically allocates bandwidth at any given moment to the signal that needs it the most, such as a NASCAR race getting more and a talking head news show getting less.
Channel sharing introduces a foreign element to this mix, specifically fairness in bit allocation to competing parties. That never was envisioned when the stat mux was designed in the first place.
Harmonic is addressing that issue at the NAB Show.
“We came up with a new way of doing the statistical multiplexing where it is possible to define a guaranteed average bit rate in the long term while keeping the advantage of stat mux efficiency,” said Macher.
In the short term, this type of strategy will make the repack easier. Longer term, when the FCC authorizes 3.0, this attention to stat mux fairness will affect far more broadcasters than in the repack as the industry begins sharing channels en masse to keep ATSC 1 service on air locally while they build out and light up next-gen TV.
To learn more, visit the Harmonic website.