[opendtv] Re: Food for thought

At 5:21 PM -0500 2/20/07, Manfredi, Albert E wrote:


Obviously, anyone starting out with a compulsory simulcast today, for
HDTV, would use H.264. But the reality from the BBC experience was that
to get the good HDTV with H.264 takes the same bit rate as from H.262.
Possibly, due in part to the I-frame frequency issue.
Can you provide a reference for this position from the BBC. I have a very difficult time believing that they would say this, especially given the tests conducted by the EBU.
But even more important, I just read the BBC report and could not find any such reference. In fact, they only used H.264 in the trial, and speak several time in the document to the bandwidth savings that it affords. 



The comment is factual, from the BBC report I pointed out recently, so
there's no need to launch into H.264 ads.
Nor is there any reason to launch false attacks. Coding technology has improved - the BBC noted that they were using first generation products and that the trial required a bit of debugging. Even with this the comments from those tested in the report are "glowing." 


In my view, the correct time for US OTA broadcasters to switch to a new
codec will be when HDTV from the new codec and SDTV from H.262 take up
NO MORE THAN what H.262 needs for HDTV now. At that point, John Shutt
can simulcast the HD and SD with no more spectrum than he needs today
for HD, and convince viewers to ugrade to the new codec. But H.264 is
not up to this, quite.
Its being done all the time Bert. But SD and HD quality are not points along some line of resolution. They are a continuum, and one cannot make claims such as these without specifying where on the continuum each lies. 

Brace yourself Bert for a revelation. A mia culpa if you will.
Several years ago I bought a cheap Radio Shack indoor antenna when the Fox affiliate pulled its signal from Cox during a retransmission consent battle. The analog image quality I could achieve on the southeast corner of my home was dismal. DTV was not yet on the air nor did I have a receiver.
A few days ago a friend pushed the right buttons, noting that he and his wife were watching DTV in their new travel trailer under all kinds of conditions. So I took that old antenna and hooked it up to my daughters 32" Samsung LCD panel TV with integrated ATSC tuner (no digital cable tuner). I put the antenna in the window which faces west toward the transmitters that range from 20 miles SW to 15 miles NW with PBS about five miles to the north.
I launched the learn sequence for both the cable and off air inputs. It found every DTV station in the area and handled the PSIP properly for the FOx and ABC affiliates, placing the DT channels adjacent to the analog channels using the same numbers with sub-channels. The FOx affiliate is the most distant, and the signal was riding on the hairy edge, But after i tucked the cable behind some furniture, the antenna now sits on the floor, six inches below the window and everything is working with only occasional hits. The analog signals from the same antenna location are significantly impaired by can be watched.
Now for the point to this story. We were just watching a program on CW, so i asked if we could look at the digital version on the ABC affiliate sub-channel. Frankly, there was little difference, except for the long delay for the cable version - on the order of 2-3 seconds. The cable version is analog and it had about the same level of resolution as the DT subchannel which is shared with the ABC 720p encoding - it looks like all programming that is not HD is upconverted to 720P for emission coding.
So the moral to this story is that you can abuse encoding technology in many ways, and you can come up with all kinds of misleading comparisons. But the reality is that encoding technology has improved more than enough to justify the deployment of next generation codecs. The problem is that the people turning the knobs on those encoders are not using the added efficiency to improve the quality of the images that are being delivered. 

Perhaps the BBC will be the exception.

Regards
Craig



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