HDTV useful information

[frostbite]

I've nicked this from elsewhere (typos and all) in the hope that it might be useful and not be too much forum drift for SD's patience.

High definition TV (HDTV) is the generic term that is used to describe any television signal that has a higher resolution than the standard TV signal that has been broadcast for nearly 40years. The term HDTV actually covers a range of different standards.

A standard UK television signal comprises 625 lines of information from the top of the screen to the bottom (just 576 of these lines can be seen by the viewer), and 768 lines from left to right. This means that the finer details - especially on newer large-screen TVs - tend to become blurred. HDTV increases the number of lines of information, either to 720x1280 or to 1080x1920. This means that finer details can be represented within the picture.

HDTV can also differ from a standard television broadcast by the way in which the lines of information are refreshed (updated) on the screen. In the standard TV, and in the current 1080x1920 format, the horizontal lines of the picture are renewed alternately - i.e, lines 1,3,5,7...etc. are refreshed to the bottom of the screen, then lines 2,4,6,8.. etc are refreshed. Since UK TV pictures are broadcast at 50hz, this means that every line of the picture only changes at half that rate - 25 times per second. This system is known as interlacing and is usually depicted by the suffix "i".

The alternative system is calle dprogressive scanning, and entails updating each line of the picture in sequence. This means that the whole picture refreshes 50 times per second - double the rate of interlacing. Progressive scanning can give the viewer the perception of higher resolution than an interlaced picture. Progressive scan formats have the suffix "p".

Currently, Sky's HD broadcasts use the 720x1280 progressive scan system (known as (720p), whereas the BBC's HD output is at 1080x1920 interlaced (1080i).

In important factor for HD viewers is that most "HD-ready" TVs can only support 720 line signals (most LCD and plasma TVs currently have 768 lines top-to-bottom). Indeed, the "HD-ready" logo can be applied to any TV that has a minimum of 720 horizontal lines. The small number of plasma TVs that support 1080x1920 are currently priced at the high end of the market, although prices may fall as production increases. Viewers with 768x1024 TVs can still view 1080i HD pictures, but some of the lines of information need to be combined in order to display the picture.

Further, I recently read that ITV & BBC Freeview transmissions are made using a different system, with the ITV type being much more prone to pixellation/breakup.

[Keygrip]

The USA seems to be much more into HD than Europe at the moment.

I remember working with a full HD recording studio - cameras, video recorders, edit suite...the works...back in 1996. That was in Nottingham, UK - but little came of it. It was all Dutch stuff - but nobody seemed to care about HD.

LOTS of picture feeds are HD in the States - their satellite system (DirectTV) is all broadcast in 1080i. My local cable feed is 1080i. Some feeds are 720p.

The purists say there is no discernable difference in picture quality between the two.

A lot of eyes are looking forwards to the next generation of HD. My own tv and dvd player are both 1080p (not a typo, that's 1080 progressive).

It looks gorgeous - and is wonderful to watch with 7.1 surround sound.

[NutLoose]

Sky is also only transmitting at the moment at 70% on HD and has been since launch from what I was told....... as for the Sky HD box of which I recieved before the world cup....... after the world cup.......... before Christmas and after Christmas.........

yep I am on BOX 4 as of the 28th Dec.....

It is actually a cracking bit of kit when working ok, I might of been unlucky, but it is worth it just for the sky plus...

One thing to ensure when buying is it is HDCP complient, that is High Definition Copyright Protection, because you can get HD screens but if they are not complient then they cannot be used as HD Tv's...

[Itswindyout]

cable basher here, from a previous life.

In UK, there is so much hype over DH, that the demos are actually too hash on the ey, it will take a long time before customers are ready to accept pin sharp pictures, (warts and all).

I watched a demo of american football about 5 years ago in HD big screen in FL, it was fantastic, but gave me a headache, after 20 mins.

windy

[Itswindyout]

cable basher here, from a previous life.
In UK, there is so much hype over DH, that the demos are actually too hash on the eyes, it will take a long time before customers are ready to accept pin sharp pictures, (warts and all).
I watched a demo of american football about 5 years ago in HD big screen in FL, it was fantastic, but gave me a headache, after 20 mins.
windy

[GANNET FAN]

Can one of you experts please tell me why sometimes the picture on my new TV freezes for about a second or a section of it breaks up into small squares?

[frostbite]

From what I have seen Mr Gannet, that is pretty much SOP for running a digital setup right now. It may mean that your signal is not 100% all the time, but it just seems to go with the territory.


The message I got from the quote I started the thread with is that now is not a good time to buy an 'HD Ready' set, since the HD standard has yet to be established, and may be higher than some sets are capable of.

[GANNET FAN]

Frostbite, many thanks for that. I got a deal on the set that was impossible to refuse! I'm prepared to take the risk - I think

[ORAC]

Can one of you experts please tell me why sometimes the picture on my new TV freezes for about a second or a section of it breaks up into small squares? generally because they're trying to squeeze a quart into a pint pot.

Digital channels are grouped into multiplexes of rstricted capacity - there is isn't enough bandwidth for each channel. They get around this by adjusting the bandwidth for each channel on the fly - a channel with a relatively static display with a low update rate - a discussion programme etc - with give up bandwidth to something with rapid motion like a football match.

Sometimes they get it wrong, sometimes they just run out of bandwidth - which is when you pixelation/stuttering of your picture.

The solution is more bandwidth when the analogue frequencies get shut down. But, seeing as how much money the government auctions them off for, the buyers will try to fit in as much as possible.

I am not sure, even after the success of the recent trial, if freeview/FTA HD channels will ever happen. I would imagine that HD will remain restricted to those willing to pay for the quality/bandwidth, and the remaining bandwidth will fill up with more channels.

[oldbeefer]

I had problems with this momentary freezing until I upgraded to a better aerial. Perfect since then.

[Keygrip]

frostbite - industry buddies (television industry, that is) advise that, indeed, the future has NOT been decided upon and some receivers MIGHT NOT receive the final product.

The battle seems to be between a transmission of 720p or 1080i. A 720p receiver will not work well with a 1080i signal - but a 1080i receiver will work with a 720p signal (or even the current 480i [USA]).

Answer - get yourself a 1080i receiver and all will be well (whichever system they eventually settle for). Would be a bugger for most, though, if they settled on 1080p (which they won't).

[PPRuNe Towers]

The market is a bloodbath out there at the moment and many, many porkettes are being told/sold by sales people.

There is no settled standard yet. That's it, that's all that matters.

However, Mrs Towers has, most regretably, seen and is now a true believer.

I'm going to rent for a year or 18 months - too many 'bargains' being pushed at the punters and the bit rates actually being put out by DAB radio shows me all I need to know. Promises of top quality transmission by the broadcasters is both fabrication and testiculation.

Too many production lines pumping out the wrong technology/tech spec but have to be sold. A marketing campaign to help this nonsense along (HD Ready) is disengenous at best.

Although the first domestic HD recorders have had poor reviews I think I will be aiming for the top level of resolution with the magic letter P following it. I can't remember the last time I recorded anything off air. The BBC are now in bed with a P2P company - Azureus - and broadband or the post is how we get the stuff the whole family watches together these days.

One final point - during a massive changeover of technology like this where a vast amount of transmitted or playback material is in the old legacy, low res format there's an very important extra point to consider. Given two or more finalists in kit you are considering and all things being reasonably equal insist on an extended comparison of the upscaling features - i.e. how low res is tweaked and appears on the screen.

Regards
Rob

[Keef]

Hey Rob - did you pinch that Avatar from Alan, or did he pinch it from you?

[BEagle]

In the US, most non-HDTV was legacy 515-line NTSC (Never Twice Same Color) TV on VHF. Picture quality was often appalling (I shall say nothing about the programme content...:hmm: ) and was very prone to color shift and interference. Hence a better system was needed!

Whereas in the UK, our 625-line UHF PAL system was considerably better. But RF spectrum hungry. So partly to squeeze more channels on to the air, terrestrial digital TV came along. But it was far from mature (OnDigital...) when launched and even Freeview often has limited coverage and can suffer from pixellation (those little squares).

Satellite TV became popular in the UK due to Sky's clever marketing. Equipment was cheap and subscription costs low. The vastly superior BSB DMAC system failed :{ due to the fact that it could only offer 5 (or possibly if the Irish DBS channels were used as well, 10) channels. Sky realised that people wanted quantity of choice and the next step was Sky digital.


Sky digital should be capable of DVD picture quality, which would be all I personally would want. But often the source material is of low quality; however, I'm convinced that they've been squeezing transponder bandwidth to allow more 'adult' and 'shopping' channels. Sky has also increased its subscription costs over the years and now costs nearly £500 per annum excluding the cost of a TV licence!

Now we come to the plasma/LCD/CRT saga. I have yet to see a plasma or LCD picture as easy on the eye as a good CRT picture. A modern DVD viewed in RGB on a CRT TV is warm, well saturated and has pleasant contrast. Whereas most plasma and LCD pictures are excessively harsh and vivid with extremes of deep black and over saturated colour. Freeview on a LCD screen looks generally pretty awful compared with DVD/RGB/CRT. Or even a good Sky digital picture, from a reasonable transponder.

I consider 'HDTV' to be a very far from mature technology in the UK at the moment - and am in absolutely no rush to move to LCD. But for those who must have wall-sized TVs, don't splash out on anything more than normal Sky digital until the systems have settled down. As for blu-ray or HD DVD......why bother?