Sky's HDTV

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

AIUI there are pros & cons of 720p versus 1080i. 1080i is better for
sports & action whereas on more static pictures like documentaries
720p gives a better picture.

Other way round. 720p is better for sport and action, 1080i is better for
everything else.

Can (either of) you explain why this is?

"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.

Thus spaketh Alan Truelove:
"DAB sounds worse than FM" wrote in message
...

AIUI there are pros & cons of 720p versus 1080i. 1080i is better for
sports & action whereas on more static pictures like documentaries
720p gives a better picture.

Other way round. 720p is better for sport and action, 1080i is
better for everything else.

Can (either of) you explain why this is?

I think with interlace because of fast movement, objects can disappear or
become fuzzy, as by the time the 2nd half of the picture (field) is drawn the
fast moving object (a ball for example) would have moved, so you end up with
the two fields of the frame miss-matching.

Hopefully someone else may be able to better explain it, my brain is a little
tired.

"Alan Truelove" wrote in message
news:[email protected] eranews...
"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.



in some circumstances it does look nicer - it effectively has a higher frame
rate.


--
Gareth.
my Dad took me out for the evening and some girl was being a right
embarrassment
trying to get off with him, i had to pretend that i was his girlfreind
so that the stupid bitch would leave him alone, and we had a right
good laugh ahout it too.
'varizo' 26th Nov 04
http://www.audioscrobbler.com/user/dsbmusic/

Alan Truelove wrote:
Bart Simpson" wrote in message
oups.com...

Can't wait to find out how much all this is going to cost.

Exactly. And the content won't be any better than it is now either.

A complete and utter waste of money.


Who's forcing you to get HDTV from Sky??


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

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Alan Truelove wrote:
"DAB sounds worse than FM" wrote in message
...

AIUI there are pros & cons of 720p versus 1080i. 1080i is better for
sports & action whereas on more static pictures like documentaries
720p gives a better picture.

Other way round. 720p is better for sport and action, 1080i is
better for everything else.

Can (either of) you explain why this is?


720p uses 50 progressively scanned frames per second, whereas 1080i uses
25 interlaced scanned frames per second, or 50 fields per second.
Because interlaced uses fields, then motion can introduce artefacts,
whereas 720p50 shouldn't.

1080i provides a far higher resolution than 720p, so with everything
else being equal (such as display size, bit rate), then the amount of
detail fit into the screen is far higher for 1080i than for 720p.


--
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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?


In one word: resolution. Interlacing halves the raw bit rate compared to
progressive for the same resolution. Or, interlacing doubles the
resolution for the same bit rate. (that's ignoring some details, but if
I quoted them all then I'd be here all day and all night)

But interlacing requires a vertical lowpass filter to be used, which
reduces the theoretical vertical resolution by a factor of between 0.7
and 0.8, call it 0.75 for argument's sake.

Overall:

For 720p: Resolution = 1280 x 720 = 921,600 pixels

For 1080i: Resolution = 0.75 x 1920 x 1080 = 1,555,200

So, the resolution is 69% greater for 1080i than for 720p.

Basically, the number of pixels that fit into a given angle that you can
resolve for 1080i is 69% greater than for 720p, therefore, the detail
and picture quality is greater for 1080i compared to 720p, and the
trade-off you pay for that is the inclusion of interlacing.

Unfortunately, it seems that Sky, the BBC and all the European public
service broadcasters want to use 720p, because it has a 12.5% reduction
in bit rate, and maybe a little bit more due to savings in coding. Call
it a 15% drop in bit rate, and the general public are none the wiser,
but it's not really HDTV, it's more like medium definition TV.


Are Sky short of
bandwidth??


No.


Please, somebody more knowledgeable than I, explain this (apparently
bizarre) decision.


No, you're alrigtht, they're going to go for the low resolution option
instead, while the rest of the world gets 1080i.


--
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Bart Simpson wrote:

Can't wait to find out how much all this is going to cost.


You'll find out what it costs once Sky have calculated how to
squeeze the maximum amount of dosh from subscribers
while giving them the smallest possible quality improvement.
You can expect HDTV to give better pictures but not
that much better.

Heracles Pollux wrote:
The best thing ITV, C4 and five can do is to encourage as many
people on to free-to-air platforms, because rather than being little
fishes in large ponds on satellite or cable, they're bigger fish in
smaller ponds on FTA systems. And if they, along with the BBC,
transmit HD on Freesat then that would give people an incentive to
get Freesat, and less of an incentive to get Sky for HDTV.



That can't happen unless everyone at the same time buys a new DTT set
top box, the "old" DVB-T signal is switched off, and then a new HDTV
signal takes over. We have not got everyone to buy a DTT box yet!


Freeview is a free-to-air platform, and Freesat will be if it happens,
and I was talking about them donig HDTV on Freesat. I agree that there
isn't much capacity on DTT, although this *might* be increased in the
future, depending on whether Ofcom have the balls to change some muxes
to national SFNs, or introduce new muxes as national SFNs using 8K.


The two systems are incompatible, not backwards compatible, and there
won't be the spectrum for co-running.

And when the existing analogue channels are recycled, would they go
HDTV or rather sell the frequencies for porn and more ****ing shopping
channels? ;-)


They do plan to sell off around 15-18 (IIRC) Band IV and V channels, but
SFNs (single-frequency networks), as the name suggests, use a single
frequency across the whole country. Theoretically, you could have one
DTT mux per frequency channel, and there'd be, say, 50 channels, which
would theoretically give you 50 DTT muxes. That won't happen, but the
DTT frequency planning is pretty inefficient at the moment, and it could
improve significantly if they're clever.


how most DTT channels are still on QAM64 rather than the more robust
QAM16,


As I said above, the 64-QAM DTT muxes have had their transmitter
powers increased, so robustness isn't really a problem any more.



So what was the point of QAM 16 then?


They were probably being conservative, and also the more robust a signal
is, the greater its coverage area is, and when you only have about 70%
population coverage it's probably better to increase population coverage
than increase the overall capacity.

When analogue is switched-off they'll probably change to 64-QAM and
crank the power up. DTT signals are at far lower power than analogue
signals partly so that they don't interfere with analogue TV, and
obviously when analogue is turned off then that isn't a limit any more.


And lastly the BBC who admit to 20% of people being opposed to the
licence fee: Could they realistcally deploy an HDTV system


Yes.


It would be subject to both the DCMS and B of G, I mean "BBC Trust
Committee"'s approval, probably after a wide-ranging industry and
public ****sultation.

There would also be the issue of an increased licence fee settlement
to pay for it.

May be Grade, Jowell, and Gordon Brown will agree this in the
forthcoming "licence fee settlment"?

More BBC trials for not paying the High Definition TV Licence Fee?


Again, I think you overestimate the additional costs for HD, especially
when a lot of equipment will be replaced with HD-capable equipment
simply due to natural wastage.


It will definitely happen, and it'll happen sooner than you think:

http://news.bbc.co.uk/1/hi/technology/4065565.stm

"The BBC will start broadcasting in HDTV when the time is right, and
it would not be just a showcase, but a whole set of programming,"
says Andy Quested, from the BBC's high-definition support group.


Never believe the BBC Press Office! No dates? No costs?


That was the head of the HD department, or whatever, not the Press
Office.


"We have made the commitment to produce all our output in
high-definition by 2010, which would put us on the leading edge."


Well of course the programme storage would move to the highest level
storage standard regardless of transmission because of the issue of
global programme sales and how the BBC is trying to sell more "movies"
to the cinema distributors!


Right, so where are all these other massive additional costs?


My main concern is that the EBU (European Broadcasting Union), who
represent the public service broadcasters (e.g. BBC, ITV, C4) want to
use 720p instead of 1080i, primarily due to bandwidth limits on DTT.
720p requires a slightly lower bit rate than 1080i, but it has far
lower resolution.

It'll be interesting to see what Sky do with their own channels in
this respect. I would've thought they'd go for 1080i, because
bandwidth isn't a problem for them, and it'd give the public service
broadcasters the dilemna that if they used 720p on DTT then Sky's
marketing department could turn round and say that HD on DTT isn't
really HD at all, or at the very least they can legitimately say
that the resolution is significantly higher on Sky.


Freeview plain old DVB-T.

plus

BSKYB will offer the Mercedes BMW of TV services.


Someone else has posted to say that they favour 720p, which is not the
BMW or Mercedes of HDTV, it's more the Morris Minor.



--
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Charlie Pearce wrote:

From http://www.homecinemachoice.com/cgi-...s.php?id=7606:

"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)

* Sky believes the progressively scanned picture format is better
suited for the delivery and viewing of HD content on large screen,
flat panel displays (mostly plasma or LCD) that are increasingly
available in electrical and specialist retailers.


That's just wrong. If you look at pages 41 - 49 in this paper:

http://svt.se/content/1/c6/30/08/47/...exga_final.pdf (3.5 MB)

then that clearly shows that 1080i provides superior picture quality at
all bit rates other than the lowest bit rate tested, apart from the Park
Run.

It seems that Sky just doesn't want to use the slightly higher bit rate
required to provide the better quality that 1080i allows.


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.



--
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