Sky's HDTV

Ben wrote:
Alan Truelove wrote:
"Charlie Pearce"
wrote in message ...


"WHAT FORMAT WILL SKY'S HDTV SYSTEM USE?
* Sky 's HDTV broadcasting system and HDTV receiver will support two
HDTV formats: 720 / P / 50 (Progressively Scanned picture) and 1080
/ I / 25 (Interlaced picture)


Why the fork would anyone designing for a new system, consider
interlacing the picture??!?!?

Interlacing is an old form of compression necessary back in the dark
ages (with a decline in quality when compared to progressive
display), so why bring it in in this day & age? Are Sky short of
bandwidth?? Please, somebody more knowledgeable than I, explain this
(apparently
bizarre) decision.

Luckily, in the US where the 720p60 and 1080i30 standards coexist,
they have the good sense to film all the big shows in 1080p24. That
means that when they get shown over here they will be 1080i25
segmented frame, i.e. no temporal difference between the fields in a
frame - effectively 1080p25 by the back door.

Except that they won't have the vertical resolution - because as part of the
conversion from 1080/24p to 1080/50i it is likely that a degree of vertical
filtering will need to be introduced to reduce the vertical interline
twitter - unless it has already been introduced "in camera" because the same
issue would be present when displaying in 1080/60i in the US.

If a 1080p image is converted to 1080i by simply segmenting the fields, with
no filtering, you get quite annoying interline twitter on HF vertical
detail.

Steve

DAB sounds worse than FM wrote:
Charlie Pearce wrote:

[snip]

However, Sky does
accept that for some types of programming, the higher screen
resolution offered by the 1080 Interlaced format may be preferable.


All types of programming other than sport and action movies.

Where does the "action movie" issue come from - surely if shot on film they
have no motion above 25fps - so the benefit of 50p vs 50i is moot isn't it?
Both are more than capable of carrying 25p material with no real compromise
on motion. There are certainly no real interlace losses in 50i when it
carries 25p material - the interlace quality issues kick in with 50p
sources.

Steve

On Thu, 03 Mar 2005 23:51:28 GMT, "DAB sounds worse than FM"
wrote:

Yep, it seems they've decided to use 720p, and to be honest, I don't
think 720p should even be called HD.

Given that the receiver will support 720p and 1080i, and that Sky
themselves say that for some programming 1080i is preferable to 720p,
I don't know where you get that idea from.

In article , DAB sounds worse
than FM wrote:

Stephen Neal wrote:
DAB sounds worse than FM wrote:
Charlie Pearce wrote:

[snip]

However, Sky does
accept that for some types of programming, the higher screen
resolution offered by the 1080 Interlaced format may be preferable.


All types of programming other than sport and action movies.

Where does the "action movie" issue come from - surely if shot on
film they have no motion above 25fps - so the benefit of 50p vs 50i
is moot isn't it?


Yes, forgot about that. So Sky really doesn't have a good reason not to
go for 1080i.

Apart from the fact that the lynchpin of their business model is sport.

Stan

Stephen Neal wrote:
Paul Schofield wrote:
"DAB sounds worse than FM" wrote in message
...
Mike Henry wrote:
In [email protected] ews, "Alan
Truelove" wrote:

"DAB sounds worse than FM" wrote in message
...

[snip]

From Sky's point of view this seems a bit of a no-brainer. The
largest majority of their subscribers do so for the football and
first run movies. It would seem that if sport and fast moving action
films are going to look better with the progressive scan system,
then that is the system they will choose.

Fast moving action films - if shot on film - have no motion above 24
frames per second (or 25 frames per second if shown in 50Hz regions).
There is thus no benefit between a 720/25p (not proposed) and a
720/50p transmission system - as all the 50p system is doing is
carrying the same identical frame twice. (Unless the transmission
scheme is intelligent, can detect this, and thus use twice as much
bandwith for each source frame and thus massively increase picture
quality?) A 1080/50i


Don't you mean 1080i25 rather than 1080i50? I thought the last number
was the frame rate?


system can still carry a 25p (sourced from 24p)
film source with full motion and no real interlacing issues. The
only issue is that 1080i wil be vertically pre-filtered to reduce
interlace interline twitter - it won't have the full 1080 line
vertical resolution many people assume.


Still significantly higher resolution, though. Using the figure for an
actual camera from he

http://www.videosystems.com/e-newsle...tWork_1_10_05/

"And, indeed, the measured resolution of the FX1 is almost 800 lines."

1080i:

1920 x 800 = 1,536,000 pixels

720p:

1280 x 720 = 921,600 pixels

1,536,000 / 921,600 = 1.667

or 1080i has a 67% greater resolution than 720p.




--
Steve - www.digitalradiotech.co.uk - Digital Radio News & Info

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Stephen Neal wrote:
DAB sounds worse than FM wrote:
Charlie Pearce wrote:

[snip]

However, Sky does
accept that for some types of programming, the higher screen
resolution offered by the 1080 Interlaced format may be preferable.


All types of programming other than sport and action movies.

Where does the "action movie" issue come from - surely if shot on
film they have no motion above 25fps - so the benefit of 50p vs 50i
is moot isn't it?


Yes, forgot about that. So Sky really doesn't have a good reason not to
go for 1080i.


Both are more than capable of carrying 25p material
with no real compromise on motion. There are certainly no real
interlace losses in 50i when it carries 25p material - the interlace
quality issues kick in with 50p sources.


Right.


--
Steve - www.digitalradiotech.co.uk - Digital Radio News & Info

Find the cheapest Freeview, DAB & MP3 Player Prices:
http://www.digitalradiotech.co.uk/fr..._receivers.htm
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http://www.digitalradiotech.co.uk/mp...e_capacity.htm

Stan The Man wrote:
In article , DAB sounds worse
than FM wrote:

Stephen Neal wrote:
DAB sounds worse than FM wrote:
Charlie Pearce wrote:

[snip]

However, Sky does
accept that for some types of programming, the higher screen
resolution offered by the 1080 Interlaced format may be
preferable.


All types of programming other than sport and action movies.

Where does the "action movie" issue come from - surely if shot on
film they have no motion above 25fps - so the benefit of 50p vs 50i
is moot isn't it?


Yes, forgot about that. So Sky really doesn't have a good reason not
to go for 1080i.

Apart from the fact that the lynchpin of their business model is
sport.


No, they can use 720p for sport, and 1080i for everything else if they
want to.


--
Steve - www.digitalradiotech.co.uk - Digital Radio News & Info

Find the cheapest Freeview, DAB & MP3 Player Prices:
http://www.digitalradiotech.co.uk/fr..._receivers.htm
http://www.digitalradiotech.co.uk/da...tal_radios.htm
http://www.digitalradiotech.co.uk/mp...rs_1GB-5GB.htm
http://www.digitalradiotech.co.uk/mp...e_capacity.htm

"Stephen Neal" wrote in message
...

1080/50i doesn't have a higher frame rate than 720/50p. It has an
identical field rate, and half the frame rate... I think what you are
getting at is that 1080/25p, which uses the same bandwith as 1080/50i, has
half the motion capture quality - however this is not the case when
comparing 720/50p and 1080/50i. 50p captures motion better, but 1280x720
is lower resolution (at least horizontally) than 1920x1080 or 1440x1080.

Oh God. Now I'm really lost. Care to start again....?

"Stephen Neal" wrote in message
...

If a 1080p image is converted to 1080i by simply segmenting the fields,
with no filtering, you get quite annoying interline twitter on HF vertical
detail.

So why convert to interlace at all?? Does it really go back to what I
said at the beginning about Sky not having enough bandwidth. That was just
a tongue-in-cheek remark, but it seems to be coming more and more true.

"Ad" wrote in message
...

I think HDTV will be for people with plenty of money or those who got the
room for it to make any difference.
Putting a T.V anoy larger than 32inches in my sitting room would be a
waste of time and money.

I am down on record as saying I don't see the point of HD. Unless the
material is specifically recorded at the higher definition(s), then there
will be no benefit from viewing it on HD equipment. How many programmes
do you know are currently being recorded in HD??

Think of it like DD5.1. Great when you hear it, but how many programmes
on normal TV channels do you know, are being broadcast with it??
Absolutely none. Not a sausage. Not one programme goes out with DD5.1 (let
alone DTS) on BBC, nor on Sky One, and nor on any of the other non-movie
channels.