[opendtv] Re: 20050509 Mark's Monday Memo

  • From: Craig Birkmaier <craig@xxxxxxxxx>
  • To: opendtv@xxxxxxxxxxxxx
  • Date: Mon, 23 May 2005 13:28:53 -0400

At 11:42 AM -0400 5/23/05, Manfredi, Albert E wrote:
>Reception and local display is one thing, broadcast
>transmission standards are another. One size does have to
>serve all receivers for an *efficient* *broadcast* system,
>where you don't want to create separate simulcast streams.

I can't agree with this statement. I believe that there may well be 
cases where simulcasting on "different services" can be justified. 
This is mostly a question of what the market demands.

Take a news channel for example.

There will always be demand from fixed receivers for this service, 
and as such it makes sense to deliver it at SD quality levels or 
better. But there will also be demand for a low bit rate service for 
portable/mobile receivers during certain day parts. Logic says that 
the service to fixed receivers can be based on more efficient use of 
the channel in terms of bits/Hz, and that the mobile/portable service 
should be optimized for robustness (and most likely lower image 
quality) using less bits/Hz. If the marketplace supports this, and 
the news organization can make money with both services, why not 

>The only constraining factor in DTV broadcast transmission
>should be use of your channel capacity. If you want to use
>the channel for multiple streams, or even a lot of
>non-real-time file transfers, that would obviously dictate
>a reduction in quality levels of your real-time streams.

True. But this statement also reflects a major flaw in U.S. spectrum policy.

Why is our policy based on the idea that this capacity belongs to the 
broadcaster? For decades this has been the case because there was no 
real alternative. You needed the whole channel for one unique 
service. Now - as Bert points out -  with digital, we are giving 
broadcasters additional flexibility to create new revenue streams.

The question is one that was of great concern to broadcasters while 
the ATSC standard was being developed. They characterized the new 
standard as HD only right up to the bitter end. Why?

Because it would only take 1-2 MHz to move broadcasters to a digital 
service that is equivalent to NTSC. So they said they needed 6MHz to 
do HD, then when they knew they had prevailed, theyasked to change 
the rules so that they could expand their franchise, without the risk 
that new competitors could also get some DTV spectrum.

The only equitable way to deal with this is to decouple content and 
carriage. Broadcasters SHOULD NOT be given a channel and the right to 
squander it as they feel fit. What we need is a system where ANYONE 
can pay the market rate for delivering a service. This will assure 
that the system is being used at its best economic efficiency when 
there is peak demand. We have already seen that broadcasters are more 
interested in tying up the DTV spectrum than using it.

Would Pax be running all of those infomercials if they had to pay 
market rates for the spectrum they are using?

>1080 at 24 or 30p should work just fine. And with fast new
>gear, deinterlacing 1080 at 60i into 1080 at 60p might just
>provide better images than rescaling to 720 at 60p. I
>wonder if anyone has done the comparison?


Obviously 1080P formats are not interlaced formats.

As for comparisons, you can cheat a million ways.

The only meaningful comparison is when you are stressing the system - 
i.e. trying to push a lot of detail through the channel with fast 
action, as is the case with sports. In this case 1080i is severely 
handicapped. When de-interlaced it may look better on wide shots with 
little or no action, but as soon as you go to tighter shots with 
action, 720@60P will be superior, even without digital compression in 
the signal path.
>Luckily, since all these options are already available,
>we don't NEED TO CARE, do we. I don't understand why you
>feel so compelled to carry the banner for 720p. The best
>format to use will change over time, as displays get
>bigger and higher quality. There's just no need to make a
>religious war of this.

It's not a religious war...It's physics.

You don't need 2 Mpixel displays until they are larger than most 
people will EVER buy for their homes. And PLEASE don't try to tell me 
that 2 Mpixels on a 30 inch screen is better than 1 Mpixel. It is a 
matter of screen size and viewing distance...not religion.

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