June 25, 2007

How to Win the HD Battle

By Mike Robuck

High-definition channels are at the front of consumer's minds as the prices drop on HDTV sets and the average size of the screens grows a few inches each year. HD is also the front line in the battle for subscribers between the cable industry and its competitors, so last Thursday's Expo workshop "Delivering HDTV Content Efficiently While Maintaining the Highest Standards of Quality" was on target in helping cable operators offer better HD services.

The session featured three vendor panelists and then two cable operator "commentators" who spoke after the vendors made their presentations.

Imagine's Marc Tayer, senior vice president, marketing and business development, spoke about how variable bit rate (VBR) stat-muxing can be used to save bandwidth in HD VOD and switched digital video (SDV) while also improving the quality of the videos. Using Imagine's solution, cable operators can save up to 50 percent more streams per QAM at the same video quality, Tayer said.

Everstream SVP Marketing and Business Development Barry Hardek detailed a formula for determining "at risk" capacity for VOD streams as HD streams were added during peak periods. Hardek said cable operators could add more VOD capacity through node splits, more QAMs to existing service groups and using SDV. They can also manage their VOD capacity more efficiently through lower or VBR encoding and by adopting MPEG-4 platforms.

"MPEG 4 isn't quite here yet," said Ren Finley, Comcast Media Center's director, advanced engineering. "A 42-inch TV is great at showing the defects in video quality. "We need to optimize what we have to preserve the quality."

CMC's solution includes rigorous encoding before putting three channels in one QAM. By adding the three channels in one QAM, operators can see a 50 percent increase in HD programming. To do this, CMC quantified all its channels and broke them down into the following categories: difficult, which includes sports programming, normal and easy. To put three channels in one QAM, CMC uses one channel from each category, with the "easy" channel balancing out the "difficult" channel. CMC also took its ad spot encoding down from 15 Mbps to 11.5 Mbps.

"I would say we all owe Comcast a round of applause for the work the CMC has done," James Kelso, Cox's vice president, video engineering. "They've been driving the vendors hard to the benefit of all of us. Secondly, I think we're all fools if we don't put (HD) quality at the head of the stack. There should be no trade off between quality and quantity."

Kelso also said cable operators should also prepare for 1080p streams showing up from networks. While MPEG-2 set-top boxes can't handle the 1080p streams, Bresnan's Pragash Pillai said one way of making a softer transition to MPEG-4 boxes would be to offer a separate HD VOD tier to premium customers.

"We don't want to buy boxes in 2008 that don't do MPEG-4," Kelso said. "I bet Verizon will roll out 1080p as soon as it hits their doorstep."

- Mike Robuck