Cablevision Gains Bragging Rights for First Next-Gen 3D Telecast

Comcast wanted to be the first to broadcast the newest generation of 3D (non-anaglyph) content to paying subscribers with a 3DTV in their home, so it chose to do so with the Masters Golf Tournament on April 7th. But then BSkyB decided to up the ante. It announced it would launch its 3D satellite TV offering with the match between Manchester United and Chelsea on Easter Saturday, April 3rd. Not to be outdone, Cablevision, one of the US’s smaller cable operators, hastily arranged to broadcast a game between New York’s two Hockey teams: the Rangers and the Islanders. On March 24th, Cablevision, in cooperation with Madison Square Garden, became the first cable operator to broadcast next-generation 3D content to ordinary paying subscribers. Of course, these subscribers had to have a 3DTV, which limited the audience significantly.

The game was broadcast live on channel 1300 and was visible on any 2DTV as a side-by-side image. The game was also shown in Madison Square Garden’s theater to an audience of 1500-2000 invited guests using a digital cinema projector.

I was able to travel into New York to see the 3D set up at the Garden, but unfortunately, had to leave before seeing the game. The live 3D was provided by a crew from 3Ality, who was kind enough to host my visit and show me around.

At the skating rink, 3Ality’s CTO, Howard Postley, showed us the 3D cameras that were arrayed on two sides of the rink. There were six 3D rigs: 3 beamsplitter types; 2 side-by-side and one robotic side-by-side. The robotic rig was developed by a group from the Woods Hole Oceanographic Institute, but was off-line prior to the show. The other rigs were 3Ality’s with the side-by-side rigs located in the higher stadium positions to allow for a larger interocular distance between the cameras. Two beamsplitter rigs were perhaps 20 rows up from the ice, with the other on a movable dolly.

All the output from these rigs runs to a dedicated truck where 3Ality manages the 3D image. A "convergence puller" is assigned to each camera and is responsible for adjusting the interocular distance between the cameras and the "toe-in," or convergence, of the cameras. Additional electronics are used to automatically adjust the two images to compensate for small differences in the lens and alignment. Additional electronics make sure the chroma and luminance are balanced between the cameras to acceptable values.

In general, the interocular distance is reduced as the focus on the shot changes from far away to close up. Convergence is adjusted to toe-in as zoom is employed. These are not hard and fast rules, however, so a lot of skill and experience is necessary to do this properly in real time. You can’t "fix in post" when doing a live telecast, noted Ray Hannisian, the company’s chief stereographer, who was acting as the "conductor," supervising the six convergence pullers.

We next went over to the director’s truck. Here, additional 3D footage was being assembled as filler content, as there were no commercials planned for the telecast. The director was experienced in 3D live events and understood that the shots had to be composed, shot and cut differently to create a compelling 3D experience. He is responsible for selecting the shots for the telecast and inserting graphics, but 3Ality is on the hook for the quality of the 3D images.

Postley told us that the final cuts are multiplexed and encoded using the RealD scheme. This features a version of checkerboard or quincunx filtering (sampling) of the two video streams, which are then packed in a side-by-side configuration for transmission. This encoded signal is now a 20 Mbps 1920 x 1080/60i feed that goes directly to the Cablevision plant for distribution to subscribers. This high quality feed is passed right through to subscribers into the set top box and over HDMI to the 3DTV.

According to Postley, there was some discussion about decoding the RealD signal at the Cablevision plant and re-encoding in a non-proprietary filtering and packing format (the simple decimated side-by-side format which is a mandatory broadcast format according the HDMI 1.4a). But ultimately, the signal was passed right thru to consumers. The upside of this approach should be a higher quality image. The downside is that the signal should only be viewable on 3D displays that have RealD decoding embedded in them, such as the 3DTV sets from Panasonic and Samsung (who was a sponsor of the event).

This event was a historic milestone, not unlike the first HD broadcasts to handfuls of consumers in 1999. As a result, I recorded the event on my Cablevision DVR, but until I have a 3D display with a RealD decoder (or external box to decode it), I won’t be able to see the game in 3D. Kind of a pity. Oh, I heard the Rangers won, by the way.

By Chris Chinnock, DisplayDaily