[opendtv] Re: Half Truths - Was More 1080p@60

Craig Birkmaier wrote:

At 3:19 PM -0500 12/8/07, Albert Manfredi wrote:

Craig Birkmaier wrote:


 If we had switched to 60 fps for DTV, it would be necessary to have
 a conversion box to feed the NTSC transmitter at 59.94.
That was exactly my point, although of course I was assuming that the 60 Hz issue continues to exist. Cliff disagrees. If the issue doesn't exist anymore, then ATSC already allows for 24/30/60, so it would be up to broadcasters and networks to stop using the odd rates in production. Same sort of thing which also applies to interlace over ATSC (or DVB-T). When its reason for existing goes away, essentially with CRTs, it can simply be dropped.
I did not interpret Cliff in this way,
I did not intend the interpretation Bert made. I meant *only* that the adoption of 3.579545 for CSC instead of the original 3.583125 was later shown to be 'probably unnecessary' by RCA in terms of it's original intent: to eliminate the moire pattern caused by the CSC beating with the 4.5 mHz audio subcarrier on the screen of ***pre-color*** B&W sets. 
but it raises an interesting question:
Do the legacy NTSC receivers that are still in use have the ability to lock up to a source stream that is broadcast at 60 Hz rather than 59.94 Hz? 
Yes.
If the answer is yes, then we should have abandoned 59.94 at the BEGINNING of the DTV transition. 

Has anyone ever tried this with 60Hz source?

Yes.


If receivers are/were NOT the problem, then broadcasters are the problem.

Yes!!!
The question then becomes, will modern broadcast gear lock up to a 60Hz reference? 
Very doubtful. I have some past experience with this.
In 1988, long before 3D comb filters were ~standard in TVs, High Resolution Sciences patented a system 
to eliminate 'chroma crawl' from NTSC video.
They did this by making changes to the NTSC standard such that there were only 227 cycles 
of  subcarrier per H instead of 227.5.
See: http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?tp=&arnumber=10735&isnumber=525 
And:  http://www.freepatentsonline.com/4660074.html
It works very well. The images from this system viewed on TVs no longer showed *ANY* cross chroma/cross luminance artifacts. Pinstripe suits looked like pinstripe suits.
This system was test broadcast over satellite to hundreds of cable systems across the US. Only one cable system engineer called to ask if there were problems with our sync generator because their frame syncs, used to eliminate adjacent channel interference on their cable systen would not pass the 
'non standard' signal.
There is apparently one other patented system to fix the CC/CL artifact problem: 
http://www.freepatentsonline.com/4833523.html
by John T. Lentz. It references the High Resolution Sciences patent, above.






 Apparently nobody in this thread fully understand the problem
Whether that's true or not, I would say that apparently no one was considering *why* the odd rates were being retained, until Cliff yesterday, responding to my post. I saw a lot of careful explaining how inconvenient the odd rates are in production, which is not in dispute. Cliff seems to believe that there is no reason to retain the rates even for analog transmission, so of course that would change things. But again, ATSC does not mandate their use. It just allows it. 
Again, probably most NTSC broadcast gear is not capable of operating at 60.
Anything that uses black burst as a reference will get very upset with 60/15750/3.583125, even though it is only 0.0010001 different. This is a point on which I'd love to be proven wrong. 
Cliff
There were many discussions about this when the standard was being developed. SOme people suggested that we could switch after the transition. But I have heard noting more about this since. 




 So once again Bert, thanks for giving this proposal the "incredible"
 designation!


Always happy to oblige!



:-)

Regards
Craig






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