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In my previous post this week, I mentioned that it would be necessary for Comcast customers to upgrade to MPEG4-compatible set-top boxes in order to watch the World Cup 3D coverage. This belief was reinforced by the list of ‘compatible’ set-tops found on the Comcast 3D FAQs Web page, which you can read here. All of these boxes are capable of decoding MPEG4-compressed video, as are the TiVo HD and Premiere XL-series converter boxes.

Subsequent to that post, I received an email from Comcast’s advanced cable labs in Colorado that the ESPN 3D stream was being encoded at about 18 Mb/s with MPEG2 compression, and that it was using the side-by-side frame compatible 3D format, originating as a 1920×1080i signal. (ESPN opted for this format to avoid image degradation that would have resulted from multiple steps of transcoding to get from 1080i/25 to 720p/60.)

I updated my last post to reflect that fact. Now, a conflicting message is coming from another source at Comcast, and you can find the original story at the Cable360.net Web site.

To quote from the story, “…Whether a customer’s provider is cable, telco or satellite, viewers must own a 3D TV and glasses, but Comcast customers have an additional hurdle to jump: They also must have an MPEG-4 set-top box…‘If a customer calls us and says they have a 3D TV and want to watch the World Cup, we’ll provide them with an MPEG-4 set-top,’ said Mark Francisco, a Comcast Fellow, yesterday at a meeting of the Rocky Mountain Chapter of the SCTE in Denver.”

Francisco went on to say that ESPN is available in both MPEG2 and MPEG4 formats, but that Comcast is planning this August to  ‘…switch the firmware that allows MPEG-4 to work. Those (MPEG-4) boxes are always associated with HD households. The vast majority are DVRs.’

It’s understandable to have some confusion around the introduction of a new technology or process. But it would be helpful if a clear and thorough explanation had gotten out earlier about the 3D set-top box compatibility issue. As it was, what ‘buzz’ was being heard implied that only MPEG4-equipped set-tops would work with the ESPN 3D broadcasts (not true) but that newer models of set-tops would be needed (true) and that in fact Comcast IS planning to move to MPEG4 encoding for channels like this in the near future (also true).

If anything, this should be instructive to those readers and seminar attendees who’ve asked me if 3D could be broadcast by terrestrial digital TV stations. Yes, it can, using either the 1080i side-by-side or 720p top+bottom formats. But your current TV won’t know what to do with either of these signals.

Hear that, set-top manufacturers? I think there’s a BIG market for outboard 3D converter boxes to work with older HDMI-equipped HDTV sets. Such a box would recognize and sequence either of the frame-compatible 3D formats into 720p/60 or 1080i/30 frames (as is done now), accepting cable (QAM) and terrestrial (VSB) modulation signals with a loop-through RF connection. A pair or two of 3D active shutter glasses could be included in the package, synchronized by a built-in infrared emitter in the converter box.Sell the whole thing for $299 at best Buy, Wal-Mart, Target, Sears, etc.

I’m not a fan of backwards compatibility in general, but there’s something to be said for it in the case of 3D.

Posted by Pete Putman, June 18, 2010 8:43 AM

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About Pete Putman

Peter Putman is the president of ROAM Consulting L.L.C. His company provides training, marketing communications, and product testing/development services to manufacturers, dealers, and end-users of displays, display interfaces, and related products.

Pete edits and publishes HDTVexpert.com, a Web blog focused on digital TV, HDTV, and display technologies. He is also a columnist for Pro AV magazine, the leading trade publication for commercial AV systems integrators.