Is NTL 'Digital' a digital service?

JimiMac

I just changed from NTL analogue to NTL 'Digital' recently and I was surprised that they didn't have to run a new cable into the house. I was still using a cathode ray TV but the signal was still noticeably better.
Today I got a new LCD screen but during the tune-up, there was a message telling me there was no digital signal?

icdg

Yes, NTL Digital is a digital service, ie it utilises the DVB-C system. You'll need to connect the STB to your TV via SCART and switch to the AV channel on your set.

Your new LCD TV may have an integrated DTT (DVB-T, digital terrestrial) tuner however - many new TVs do - and the "no digital signal recieved" may relate to the fact that it is not picking up a DTT signal. Only in Dublin and Louth - and with a good aerial - will you be able to pick up any DTT in the Republic of Ireland and in those areas, with an integrated DTT tuner, you will only be able to pick up the four Irish terrestrials as the rest of the trial is encrypted. The terrestrial forum is the place to ask questions about that though.

JimiMac

I thought 'cable' was terrestrial. How do people get terrestrial if it's not via 'cable'?

Alun

JimiMac wrote: »

I thought 'cable' was terrestrial. How do people get terrestrial if it's not via 'cable'?

Terrestrial means through a normal roof aerial.

Mossy Monk

JimiMac wrote: »

I thought 'cable' was terrestrial. How do people get terrestrial if it's not via 'cable'?

Cable is generally delivered underground, terrestrial is over the air to a television aerial.

watty

Cable, "Terrestrial" (via Aerial) or Satellite can each be Analogue or Digital.

There are 5 or 6 standards for Digital TV via aerial (always called Terrestrial). DTT = Digital Terrestrial Television, uses the DVB-t standard in Europe.
-t, -c or -s suffix refer to Via Aerial (Terrestrial), Cable or Satellite, which are similar standards but use different modulation due to different characteristics of the Broadcast medium
Satellite = DVB-s (and now DVB-s2) is QPSK because plenty of bandwidth and small signal
Cable = DVB-c Strong single path signal so uses QAM64 on a single carrier
Terrestrial (Aerial) = DVB-t is often multipath and moderate signal so uses a very large number of carriers modulated more slowly (OFDM) with QAM16 to QAM64

So while an analogue TV Terrestrial aerial tuner will work on clear (Un-encrypted, un-scrambled) cable analogue signals as the frequencies overlap, a Terrestrial (Aerial) Digital Tuner won't work with Cable Digital as it is a different Modulation technique.

Some of the NTL channels may be from "off air" or analogue sources so even on Cable Digital (i.e. all the way from NTL to you it is on a cable) may lack features or quality on entirely digital sourced and delivered Terrestrial (Aerial) or Satellite (Dish) signal.

JimiMac

I must admit I'm a bit lost with all these terms. The reason I was asking is that I recently purchased a UK model TV with a DVB-T tuner. I was told the set would be ok with NTL digital. I have NTL working ok but I am a bit disappointed with the picture.
Would the picture be a lot better with DTT? I recently got the house refurbished and don't really fancy running new cables and fitting aerials/dishes etc. On the other hand, I would like to get the best performance from my new flatscreen which I have waited a long time to get.
Is there any way of improving the picture but sticking with NTL digital?

Mossy Monk

JimiMac wrote: »

I must admit I'm a bit lost with all these terms. The reason I was asking is that I recently purchased a UK model TV with a DVB-T tuner. I was told the set would be ok with NTL digital. I have NTL working ok but I am a bit disappointed with the picture.

DVB-T is terrestrila so it will have nothing to do with NTL Digital. Any tv with a scart socket will work with NTL Digital.

Tomas_V

JimiMac wrote: »

I have NTL working ok but I am a bit disappointed with the picture.

The picture quality from NTL Digital is generally acceptable and certainly better than that from analogue.

Check and make sure that you're using a fully-wired RGB SCART cable, that it's plugged into an RGB capable socket on your TV and that you've enabled RGB output on the NTL box. If for some reason, you're presently seeing a 'composite' video signal, this might explain your disappointment.

JimiMac

Tomas_V wrote: »

The picture quality from NTL Digital is generally acceptable and certainly better than that from analogue.

Check and make sure that you're using a fully-wired RGB SCART cable, that it's plugged into an RGB capable socket on your TV and that you've enabled RGB output on the NTL box. If for some reason, you're presently seeing a 'composite' video signal, this might explain your disappointment.

Thanks for your helpful reply Tomas.
Jim

who is this

JimiMac wrote: »

I must admit I'm a bit lost with all these terms. The reason I was asking is that I recently purchased a UK model TV with a DVB-T tuner. I was told the set would be ok with NTL digital. I have NTL working ok but I am a bit disappointed with the picture.
Would the picture be a lot better with DTT? I recently got the house refurbished and don't really fancy running new cables and fitting aerials/dishes etc. On the other hand, I would like to get the best performance from my new flatscreen which I have waited a long time to get.
Is there any way of improving the picture but sticking with NTL digital?

While the service is digital, the box used to decode it (all of them last time I checked, but who knows with all that detailed information available at upc.ie ) cannot output a digital signal (e.g. DVI or HDMI) so it is being delivered to the box digitally, but to be delivered to the TV it has to be converted to analogue. This could account for baddish quality (although IMO in this case, is unlikely to be)

Tomas_V

Tomas_V wrote: »

The picture quality from NTL Digital is generally acceptable and certainly better than that from analogue.

I have NTL digital in the house on a 42" LG LCD and the picture is terrible on most channels - lots of compression artifacts. My uncle in Ballyfermot seems to have the same image quality on a 42" Sony set. So unless it's down to the LCD TVs I suspect that NTL are using too low a bitrate or cramming too many channels on one frequency.

Sponge Bob

I am surprised that ye are only at the 'suspicious' stage

Have you compared it to SKY SD ( not HD) at all ??

watty

to fit more channels in less bandwidth NTL has generally higher compression.
NTL has about 500MHz of bandwidth, some is used on Analogue and Broadband.

Satellite has about 4000MHz of bandwidth as the IF can be in one of four modes.

Also NTL channels may not be direct sources or may be reconverted. Thus Cable can't at all compete with Satellite for Quality. They will soon have to ditch Analogue as it uses a lot of space better used for Broadband or Digital.

Tomas_V

watty wrote: »

Thus Cable can't at all compete with Satellite for Quality.

Thus, the marketeers invented the meaningless term 'digital quality' to mislead the public.

watty

Indeed as anyone that has played with MP3s knows 64kbps = tin can and string quality and 256kbps nearly OK and uncompressed CD (Digital) best.

Digital can be any quality the provider decides.

ro2

watty wrote: »

NTL has about 500MHz of bandwidth, some is used on Analogue and Broadband.

How much bandwidth would be freed up by turning off analogue?

DingDong

ro2 wrote: »

How much bandwidth would be freed up by turning off analogue?

Roughly you get about 10 digital channels for one analogue.

CO19

DingDong wrote: »

Roughly you get about 10 digital channels for one analogue.

Really :eek:? that's brilliant ,the sooner NTL turn off the analogue the better, then maybe we'll get loads more better channels from them.
Also what's going to happen for people who don't have digital from NTL when the time comes to turn off the analogue ? will they be automatically upgraded to digital or will they be cut off ?

Freddie59

watty wrote: »

Indeed as anyone that has played with MP3s knows 64kbps = tin can and string quality and 256kbps nearly OK and uncompressed CD (Digital) best.

Digital can be any quality the provider decides.

I've converted all my CDs to MP3 for playback on PC and have tried both 128 and 256. To the ear, IMHO, there is no discernable difference. You do notice it at 64 though.

DingDong

CO19 wrote: »

Really :eek:? that's brilliant ,the sooner NTL turn off the analogue the better, then maybe we'll get loads more better channels from them.
Also what's going to happen for people who don't have digital from NTL when the time comes to turn off the analogue ? will they be automatically upgraded to digital or will they be cut off ?

No idea when they will switch the service off or what will happen to analogue only customers. I can only guess they will offer some sort of basic DTV service free.

Alun

CO19 wrote: »

Really :eek:? that's brilliant ,the sooner NTL turn off the analogue the better, then maybe we'll get loads more better channels from them.

IMO there are plenty of channels as it is, if not too many. I'd prefer it if they got rid of some of the dross and increased the quality of what they already offer.

DingDong

Alun wrote: »

IMO there are plenty of channels as it is, if not too many. I'd prefer it if they got rid of some of the dross and increased the quality of what they already offer.

You mean you don't want more shopping channels .

Alun

DingDong wrote: »

You mean you don't want more shopping channels .

Correct, and music channels too.

Pat Gleeson

Karsini wrote: »

I have NTL digital in the house on a 42" LG LCD and the picture is terrible on most channels - lots of compression artifacts..

Take this as strictly IMO, but I wouldn't buy any LCD any bigger than 32" for any TV provider, especially cable (NTL or Chorus). Even some channels on Sky are poor when looked at via LCD, Setanta, ITV and BBC come to mind.
Any CRT is better than LCD* for SD content, which is why I have a plasma - way better SD performance than LCD, and superb HD.

*or plasma

CO19

Alun wrote: »

IMO there are plenty of channels as it is, if not too many. I'd prefer it if they got rid of some of the dross and increased the quality of what they already offer.

They do have a fair amount but they should put the 2 channels i.e Living 2,Bravo 2,TCM 2 etc on with a few others too to liven up their current selection.

lawhec

If I can expand on what Watty said earlier...

Analogue TV transmission

Terrestrial - Uses VHF & UHF frequencies (from around 40MHz to 70MHz for Low-VHF, 174MHz to 230MHz for High-VHF and 470MHz to 860MHz for UHF internationally, Low-VHF is no longer used in Ireland and only UHF is used in the UK) transmitted from masts & towers. In an 8MHz frequency block (for Ireland & UK, 7MHz & 6MHz are used in some other countries) contains the main AM b/w picture, colour information, FM mono sound carrier & NICAM carrier. Reception is by an aerial normally roof mounted or in some cases indoors (attic or set-top aerial) depending on signal strength and local conditions.

Satellite - Uses microwave frequencies known as the Ku Band (10.7 to 12.7GHz). Analogue satellite television is rapidly dying, only the Astra 1 satellite group has any significant number of broadcasts in Europe, the rest are either entirely or around 90-95% digital. Dishes instead of roof-top aerials are used to reflect & increase received signals from satellite(s) some 36,000 km up on to the receiving aerial known as a LNB or Low Noise Block. The LNB is powered by a DC voltage present in the coax cable between itself and the receiver (which powers the LNB) which down converts the received signal to a frequency that can be sent across the cable to the tuner in the receiver. The receiver can use voltage switching to change the polarity (horizontal or vertical) of the receiving "aerial" of the LNB and through the use of a 22khz tone can also tell what part of the satellite frequency band to cover (either "low" or "high"). Received signal is similar to that of terrestrial except that FM is used for the picture and individual FM carries are used for stereo sound, with separate ones allowing for radio stations to be carried alongside the TV programme. This requires a bigger bandwidth than terrestrial TV.

Cable - similar principles to terrestrial TV, the same tuner can be used for analogue cable TV. As the "broadcast" made on cable should be more tightly controlled, enclosed in a closed network and should have good signal strength, channels can be more tightly packed together, normally using adjacent 8MHz channels, to provide the respective choice. Some providers may scramble their channels, requiring a decoder to be placed between the cable and the TV to unscramble them, very common in the UK but less so in Ireland except for premium services.

Digital television transmission.

Terrestrial, Satellite and Cable in Europe all use the DVB standard, but use their own subsets that make the three of them incompatible with each other.

Terrestrial - uses the same 8Mhz (7MHz on VHF) blocks that an analogue signal uses. Each block is known as a "multiplex". Terrestrial broadcasting from transmitter to receiver has to overcome hurdles regarding signal strength, interference, noise and multipath (commonly seen as "ghosting" on analogue signals) therefore uses a system called DVB-T which is designed to carry signals ruggedly. Different parameters can be set up by the multiplex owner which in general are a trade off between ruggedness of reception and the amount of data that can be transmitted - a multiplex which has a high available data rate will have less reception coverage than one with a low data rate, of course the latter means less video & audio streams can be transmitted but will be received in worse conditions where the former won't.

Satellite - uses a system called DVB-S or a new variant DVB-S2. Uses the same KuBand frequencies as analogue. These signals are weak but reasonably stable, don't (normally) suffer from multipath and the frequencies used are better immune to noise while the very narrow beam width or "sight" of the receiving dish (around 2 degrees) gives intense focus away from nearby satellites on the same frequency so don't need as much error-correction as terrestrial does. Data rate for a multiplex is dependent on the symbol rate (the higher the rate, the bigger the bandwidth) and the Field Error Correction or FEC. An FEC of 1/2 reserves around half the signal for error correction while 7/8 reserves only around 12.5%. The less signal used for error correction, either the satellite output needs to be higher or the receiving dish needs to be bigger to compensate. The principle of the LNB and tuner properties for polarisation & band switching is the same as analogue.

Cable - while the DVB-T system can be used for Cable, a different system has been developed for cable called DVB-C which takes advantage of the closed network that cable provides i.e. if it is set up properly it shouldn't have to worry about noise, multipath, signal strength etc. that affects terrestrial and even satellite systems. This environment allows for a very high data rate for each multiplex by using little error correction and a less rugged form of transmission, allowing in some cases two to three times as much data available on the multiplex using the same amount of bandwidth that a DVB-T multiplex does. DVB-C is used in some places for MMDS as the transmission nature of the microwave signal used and the narrow beam width of the receiving antennas can allow for a less rugged broadcast system to be used.

Any TV that is sold as having a built in digital tuner should be assumed to have a DVB-T one.

I hopefully have summed it up. Any mistakes feel free to correct me.

JHMEG

Pat Gleeson wrote: »

Any CRT is better than LCD* for SD content, which is why I have a plasma - way better SD performance than LCD, and superb HD.

Full HD (ie 1080 lines) plasma is rare enough and also expensive.

Also any plasma TV will consume approx twice the electricity an LCD of similar size consumes (the new LED backlight LCDs are even more efficient), and about 5 times what a CRT will.
Typical 32" CRT = 90 watt
Typical 42" LCD = 220 watt
Typical 42" plasma = 450 watt

Many countries are considering banning plasmas due to their excessive power consumption.

Screen burn is also a problem with plasma.

So.. stick with your CRT if you've ntl digital.

watty

Upto 1/6th of the backlight in an LCD is wasted due to the coloured stripes and polarisers needed to make it work. The only electrons wasted in a CRT are the ones hitting the slot mask (a small proportion compared with early CRTs). The CRT does not use filters, each colour is a phosphor.

Sadly OLEDs are not LEDs. They often use the same filters as LCDs, but need no waste-full polarisers, they are often violet or ultraviolet organic electroluminescent arrays with white phosphor. Some very small ones do use tri-colour OLED, but the blue fades faster.

Unlike real GaAsP crystal LEDs, the amorphous organic electroluminescent diodes (OLEDS) fade with use.

So OLEDs do give better contrast than LCD but only slight power saving (CRT still more efficent) but may have the fading/screen burn issues of Plasma.

The biggest problem with LCD, OLED, SED, Plasma and DLP compared with CRT is the fixed resolution. Only one source resolution displays best. But TV has many resolutions unless it is 1920 x1080i HD. (unlike USA with 3 "enhanced digital" modes, we in Europe are only doing 1920x1080i for HD)
Also all broadcast transmissions except 720p are interlaced. Few LCD/Plasma/OLED/DLP do true interlace, most deinterlace. Many have poor deinterlace and de-interlace can never be perfect. All CRTs do perfect interlace.

Oddly my laptop is Interlaced display, but only at 60Hz, so poor for European TV (OK for US /Japanese though). Most laptops / LCDs are progressive only.

No-one needs to band plasma. The manufacturers are dropping making them. Panasonic may be only manufacturer committed at present. They simply cost too much to make.

BostonB

Freddie59 wrote: »

I've converted all my CDs to MP3 for playback on PC and have tried both 128 and 256. To the ear, IMHO, there is no discernable difference. You do notice it at 64 though.

You mean to your ear, and with your equipment. Someone else with different ears and better equipment might hear the difference. I hear a difference between 128 and 192. With some music its more obvious than others. Above 192 I can't hear it unless on certain Classical, Acoustic stuff.

I've not been impressed with the quality of NTL/UPC digital anywhere I've seen it. Sky seems better to me. I've also not been that impressed with SD on most LCDs. Maybe I notice because I used to do graphics and artifacts and antilaliasing like effects stand out like a sore thumb to me.

PauloMN

BostonB wrote: »

You mean to your ear, and with your equipment. Someone else with different ears and better equipment might hear the difference. I hear a difference between 128 and 192. With some music its more obvious than others. Above 192 I can't hear it unless on certain Classical, Acoustic stuff.

I've not been impressed with the quality of NTL/UPC digital anywhere I've seen it. Sky seems better to me. I've also not been that impressed with SD on most LCDs. Maybe I notice because I used to do graphics and artifacts and antilaliasing like effects stand out like a sore thumb to me.

Without wishing to veer off-topic, I fail to see the point in all of these digital technologies unless the optimum quality available is used. When I download MP3s, I always download at CD quality (320Kbps or whatever it is) and I definitely notice the difference with lower bitrates, especially on speakers rather than headphones. I absolutely hate that softness and lack of clarity you get with lower bitrates where audio has been compressed to death.

Same with digital TV, although I have found the quality of UPC Digital and Sky Digital is the same on a per channel comparison - it's the difference between channels that is noticeable. I've had both and find that RTE is excellent on both UPC and Sky, but Setanta channels are dire on both. BBC is somewhere in-between, very noticeable compression on dark scenes on BBC programmes on both UPC and Sky.

It's like DAB also from what I've read of the bitrates, although I haven't tried it, it seems that limited bandwidths are used to pile more stations into the same space. Compressing the audio to that level is a step backwards in my book.

Hard to beat clean analogue reception when a good strong signal is available, both on FM radio and UHF television. Great, you can now provide all these fancy digital services to people (which you can also charge royally for), but what's the point when the overall quality is a step back?

JDxtra

Freddie59 wrote: »

I've converted all my CDs to MP3 for playback on PC and have tried both 128 and 256. To the ear, IMHO, there is no discernable difference. You do notice it at 64 though.

I can hear quality problems on MP3 files encoded at 128k (and I'm not the bionic man ). I use 192k or above. But this is off topic...

watty

320K is only "near CD" quality.

Unless you have good source material (not over mixed, over compressed electronic rubbish) and good HiFi you won't hear difference 128k, 256K, 320K or CD.

TV resolution for 4:3 square pixels is 768 x 576.
For 16:9 square pixels it's 1024 x 576.

Animorphic means the pixels are stretched. The highest SD DVD/DTT/Satellite/Cable TV resolution is 720 x 576. Exactly the same number of pixels are used for 16:9 (hence animorphic) than for 4:3, thus the WS is 20% lower quality! Also on a 720 x 576 WS flat screen (LCD, DLP, Plasma) the 4:3 "window boxed" is seriously reduced in quality.

HD uses 1920 x 1080, thus that is square pixels for HD Widescreen. If you crop a little off the top and bottom of SD that is WS or 4:3, then both will display better than any non 720x 576 screen.

But satellite also uses 544 x576, 384x 576, 384 x288 and 704 x 576 (subsitute 480 & 240 for 576/288 in USA and add 840x 480!)
For decent SD Digital TV you need either a CRT or else a native 1920x1080 HD flat screen. A lower resolution Flat screen will give too many rescaling artifacts on anything other than it's native resolution.

A PC resolution 1920 x 1200 is even better as it can display 576 lines perfectly doubled with no cropping. Of course with it there is allways a black boarder.
But almost all Cinema wide screen formats (1.85:1 to 2.7:1) are wider than the 1.78:1 TV WS shape. One Cinema WS shape is only 1.66:1!