[opendtv] Re: Some results - 1080p @ 60 is Next?

  • From: "peter wilson" <peter.wilson@xxxxxxxxxx>
  • To: <opendtv@xxxxxxxxxxxxx>
  • Date: Fri, 4 May 2007 23:39:41 +0100

I just got into the opendtv folder after NAB and have the following comments
to make.

First the EBU tests

These followed on from IBC 2005 when certain personalities + the EBU
virtually ordered European Broadcasters to use 720P for transmission. There
was a severe back track as nobody had "done" the science on 1080P50 but
stated that it was essentially impossible.

Hans was tasked with making a series of tests to prove that 720P was
superior for transmission and carried out some very thorough tests. The
result of these tests were shown at IBC 2006 using the demonstration rig in
the slides Hans sent to the reflector.

What was very interesting was that I and many others heard the story and saw
something else. We heard the EBU preference for 720P but saw that 1080P50
used no more bit rate than 1080I25 but looked better than both 720P and
1080I25.

So the fact is it becomes a business decision, if a business model supports
an 18MBPS premium service in 1080P50 then so be it, it costs no more than
1080I25. If the business model supports two channels of 720P then so be it.
The EBU tests are very useful technical markers but the commercial model
will prevail.

The BBC has been developing its own Open Technology compression system
called Dirac, this has been aimed at 1080P50 capability almost from the
outset. 
http://dirac.sourceforge.net/
http://www.bbc.co.uk/rd/projects/dirac/index.shtml
http://schrodinger.sourceforge.net/

Moving on to the carriage of 1080P50 the BBC has also developed a version of
Dirac called Dirac Pro which is being standardised as SMPTE VC2.
The first application of this is a mezzanine Codec which compresses either a
dual HDSDI or SMPTE 272 3Gbps 1080P50 signal into a regular 1080I SMPTE 292
connection. This system has a very novel feature in that the bitstream is
carried in such a way that a viewable picture is possible by regular HD
equipment.

The BBC openly state that they will move a significant proportion of high
end production to 1080P50 by 2010.

The BBC's Hardware Partner Numedia Technology has built this Dirac Pro (VC2)
Codec into a small Palm sized box which can compress 2-1 with less than 10
watts power consumption and six lines latency. Future versions will support
HD into 270 Mbps SD.
These boxes are probably the first on the market to actually process data at
3Gbps and comfortably support 100 metres of 1694 cable @ 3Gbps which is I am
sad to say better than many manufacturers currently get from 1.5 Gbps
regular HD.
www.numediatechnology.com

I heard that there were 1080P Vision switchers in private suites at NAB and
most router companies were touting 3G capability. 1080P consumer displays
abound in the shops but there is still the weirdness of European and Asian
market displays supporting 50 and 60 but US displays only supporting 60.

Moving on to the down up down discussion the reasons are complicatedly
simple.

True 1080I systems have a very high performance but passed away in the early
90's due to cost. They are interlaced so there is the fundamental vertical
performance issue which manifests itself as resolution pumping on small
vertical movements. Vertical alias was not common on the early 90's systems
as the camera and lens optics were outstanding.

Modern HD systems are optimised for price performance not performance.
Camera optics are a compromise and the Vertical cutoff tends to severely
compromised on cheap camera's. Either too much or too little. This leads to
soft verticals or excess Alias.

Its relatively easy to take a 1080P image and interlace it using a Digital
Filter which can have a very precise frequency response optimised for max
vertical resolution within the system alias limit.

When I say relatively easy I mean by a standards conversion manufacturer.
The filters are much more complex than a standard Sinc. Most filters bundled
in software packages do not cut the mustard.

Best Regards,
Peter Wilson
www.hddc.co.uk




-----Original Message-----
From: opendtv-bounce@xxxxxxxxxxxxx [mailto:opendtv-bounce@xxxxxxxxxxxxx] On
Behalf Of John Shutt
Sent: 04 May 2007 22:26
To: opendtv@xxxxxxxxxxxxx
Subject: [opendtv] Re: Some results - 1080p @ 60 is Next?

Oops, in cutting and pasting I missed the following:


----- Original Message ----- 
From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>

> To remain within the existing ATSC transmission standards, my take is
> that:
>
> 1. If your acquisition is 1080p or 720p, you should use 720p
> transmission.
>
> 2. If your acquisition is 1080i, then you should use 1080i transmission.
>
> 3. And furthermore, going to 1080i or 1080p acquisition is the right
> decision for the future. Preferably, of course, 1080p.

Your conclusions are the opposite of the EBU findings, keeping in mind that 
theirs was a demonstration, not an exhaustive study.  The EBU conclusion 
reads:

------------------
From the considerations given in this Appendix we can conclude the 
following:

* The spectral distribution of a 720p/50 and an 1080i/25 signal is basically

similar in spatiotemporal
volume;

* The 720p/50 signal should provide better movement portrayal and the 
1080i/25 system should provide more detail via the higher horizontal 
resolution;

* Kell and interlaced factor both "reduce" the available resolution while 
the interlaced factor reduces the vertical resolution of the 1080i/25 
signal. Considering all factors, a 720p/50 signal seems to have more 
advantages than a 1080i/25 signal;

* A concatenation of different HDTV formats and operating with horizontal 
sub-sampling should be avoided.
------------------

>
> Not being a broadcaster, I do not understand intuitively why production
> facilities can't be adjustable to 1080i or 720p.

Because most HD broadcast equipment is designed to be switchable between 
1808i and 720p, but does not do so "on the fly."  You cannot edit 1080i and 
720p scenes together.  You have to convert one or the other to a common 
format, and every conversion introduces errors and cross converters are not 
cheap.  You must operate in one format only, so it is best to optimize all 
of your chain for that format.

John


 
 
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