NTL Digital Picture Quality

Phibsboro

Hi,

I got NTL Dgitial in over the weekend after finally getting fed up with the s$%^e picture I was getting from their analogue service. The move was also prompted by my xmas pressie to myself - a new 32" LCD telly, which really needs a clean signal to shine.

So, the installer comes on Sat, installs my box and voila - a really, really disappointing picture The quality is just dreadful - there are artefacts everywhere. Emerdale on TV3 was bascially unwatchable - everytime someone moved, their face would dissolve into a blur. Any large pans cause a similar effect. The FA cup on BBC (in widescreen admittedly which was a nice improvement over analogue) was a disaster - any quick movement and again there were tons of artefacts. And of course the grass was more like a snooker table when the camera panned. Note that these artefacts are not big blockiness like when the picture is about to drop, its a fuzziness where it looks like there is just not enough information to properly resolve the picture. I have had three friends down over the weekend and they all agree thats its dreadful.

It basically looks like I am getting really (really!) low bitrates on all channels, but not low enough to cut off completely. I was so tempted to get the installer to take it away, but he suggested I book a service call and see what they could do.

So, the question - is this normal? Can anyone who has NTL digital comment on their perception of the quality? Anyone else using it with a good telly?

Are there any techies here who might offer some advice on what I might ask the support guys to do?

Amy comments or help would be really appreciated.

Cheers,
C

Alun

I have ntl digital (in Bray) and haven't got any real problems with it, especially on the "main" channels. The bitrate is a bit low on some of the more obscure channels, but I hardly ever watch them.

Having said that I have been noticing a small amount of pixellation, especially on scene changes on the BBC channels recently. It hasn't got to the level that I'm prepared to risk my sanity by actually calling ntl, but if it gets any worse I may do.

Did the engineer who installed the box do any testing of the connection before or after installing? Mine didn't (he was just a subcontractor), but a few days later a guy from ntl itself turned up with a testing gadget to test the signal quality and ask if I was having any problems. Maybe you should get them to call and check?

There's also a thread somewher here outlining how to get to the diagnostics screen of the STB, which can give information about error rates and the like with some figures regarding acceptable ranges.

spockety

I've had it for 3 years now. My observations are basically that Sky Movies 1-9 have absolutely perfect quality, must be very high bitrates. Sky Sports has almost as good quality, only the pitch looks like it has colours grouped, but I don't really notice it, or it doesn't detract from the viewing pleasure. RTE1/2, UTV, CH4, Sky One, E4, Sky Mix all seem fine also, but not as good as Sky Movies, then TV3 and TG4 are not as good at all, but again not so bad that it wrecks the viewing.

I'm watching this on a 48 inch widescreen TV, so if it was even slightly bad, it would be totally unwatchable, and I'm not unhappy with it.

Sounds like you may have a problem,

HTH,
J.

JDxtra

Your 32" LCD telly is not helping either. Its response time is probably far less than a regular CRT television. Try ntl:digital on your old TV and see how it looks.

The 'general' picture quality of ntl:digital should be okay. However they are compressing the hell out of some channels and on close inspection even RTE One looks like it is being played via Real Player on a PC!

TV3 reception has never been perfect on ntl:digital. There are artefacts all over the screen. I assume this is causing your LCD screen problems as it is trying to compensate for the artefacts using some form digital processing which is actually making it look worse.

Phibsboro

thanks for that guys - I'll book a call today.

Re reponse time, the telly is quoted as low as 8ms in some reviews and can hold perfectly fast moving dvd and divx scenes. It does have digital processing but the picture appears to be as bad with this turned on or off. Unfortunately my previous telly was LCD too so that isn't going to help.

Aside from calling support, I will also bring the telly on a tour - I'm going to connect to another NTL digital source and also a Sky dish. Hopefully I'll find the other digital source is way better and I'll have some frame of reference to complain about. Failing that, I believe from other forums that Sky looks great on this telly so if thats the case I'll just have to forego c4 and utv.

I'll let you know how things go....

C

cgarvey

Phibsboro wrote:

Hi,
So, the question - is this normal? Can anyone who has NTL digital comment on their perception of the quality? Anyone else using it with a good telly?

My telly isn't that good, but I can tell you that I have the same issues on all of the main channels at peak time (not so much/at all off peak). On the UK:TV channels and Bravo, the picture quality is ok, except I get lockups/freezes every 10-20 minutes for about 4 or 5 seconds usually .. very annoying.

NTL's response is that the signals levels are good.

chorus techy

Yup I had the exact same problems when I had ntl digital a while back. During peak time, the service was practically unwatchable, and the readings I took myself weren't great. Of course, anytime ntl called would be during a weekday, when it would be offpeak so the quality was perfect

Seems the network can't cope with the demand when everyone switches on the tv :rolleyes:

chorus techy

I don't, no

Mountjoy Mugger

If NTL claim the signal is good and you disagree, tell them you're getting on to www.Comreg.ie to get an engineer to test the signal quality.

Comreg do this sort of stuff: http://www.comreg.ie/about_us/default.asp?s=2&navid=19

cgarvey

Mountjoy Mugger wrote:

If NTL claim the signal is good and you disagree, tell them you're getting on to www.Comreg.ie to get an engineer to test the signal quality.

Comreg do this sort of stuff:

They do? They'll send out an engineer to test the signal for you? I hadn't heard of that before.

chorus techy

If the service is that bad, then you should set your VCR to tape about an hours worth of TV when you would normally watch it, and flick up and and down through the channels so that the freezing and flickering is all recorded onto the tape. Then, make a copy of the tape, send one to ntl and one to comreg, and see what they say. This is how I fought my case for having to cancel my ntl contract early - I made up a tape of a few nights worth of viewing, and freezing up and then showed the ntl engineer this - and they had no option but to take it away as it was obvious the service was so bad.

Phibsboro

Ive booked a call for Saturday week. The picture has improved slightly on some channels - desperate housewives on C4 last night was actually quite good - not as sharp as I had expected but definitely watchable. If an engineer can get everything to that level I'll stick with it I guess - its so much hassle moving to Sky

C

DingDong

Hey Phibsboro, i wouldnt say their is any thing the ntl engineer can do for you. With digital tv it either on or off their is no in between (besides it freezing or breaking up). For some reason unknown to myself at this time LCD tv look really bad on ntl. Possible because the resolution is too high on them. I know in America if you connect a high definition tv up to a non HDTV source it will look terrible. Anyway let me know how you get on. The only suggestion i can make is sit a far away from the tv your less likely to notice how bad it looks

Phibsboro

Well, I can categorically say that is not the case - reception on digital definitely varies over time and across channels. As other posters on this thread have indicated, it is better on some days/time of day than others. And definitely some channels are better than others. This both surprises and disappoints me. Like you I assumed that digital was digital, it was either perfect(ish) or black screen.

The problem is obviously in the settings in the box re what constitutes a good picture - it is basically set to allow such a low acceptable bitrate that the picture can deteriorate below all reasonable expectations before the picture cuts completely. You can see the effects of this if you watch some of the shopping channels on Sky for example - they pay for a certain bitrate and cos they don't fast moving action etc, they choose the lowest possible bitrate - and it looks like it With NTL its not a question of channels not paying to be shown at the right bitrate, its just the distribution medium (i.e. the cable!) is so poor that an acceptable bitrate can't be delivered consistenly.

Re the telly, I had anticipated that it would have problems with a Standard Definition picture but in fact I was pleasantly surprised with how it dealt with the crap anagloue signal - definitely better than my previous LCD tv. The latest panels and the latest processing add-ons are getting much better at dealing with bad signals. Unfortunately I am sure (cos it varies from day to day) that the artefacts I see are not caused by my telly. The other point against that is that DVD looks great - really, really great. And before you say otherwise, DVD is in fact a Standard Definition output - 480p (or i if you don't have progressive scan). High Definition would be 720p or 1080i (or 1080p if we ever get that much bandwidth!) I would love to know what the pace box outputs in those terms - i.e. not the actual final bitrate (which I would *reallY* love to know - something to send on to comreg) but what output format it is sending...

C

DingDong

Basically what the engineer probably will do is swap the box(might not do this). This probably will have no affect on the picture. What he might also do is say he has to call back with a test set(TV). Have you plugged a normal TV into the box yet?(it will probably look fine). The only thing I can think of is that their is a error on the line usually cause by loose connections or the cable coming into your house needs to be replaced. But from what i gather from your posts your not having problems with picture breaking or freezing.

The other thing is the basic analogue service has a higher resolution so you get a better picture than digital(You must have a good signal coming in on analogue though).

As for DVD its resolution(and bitrate) is way higher than live TV broadcasts so its going to look perfect.The compression NTL uses is mpeg2 probably with a lot lower bitrate that DVD so they can fit more channels onto the one QAM. I know from time to time the picture going blocky in fast moving scene like someone is doing a bad encoding job.

I seen loads of LCD TVs with NTL and I yet to see one that looks good. I'm not saying their is anything wrong with your TV just it doesn't work out well with NTL. I haven't seen a LCD TV with sky but I can only guess it has too look better.
Anyway Phibsboro I wish you the best of luck and hope you get it sorted. Let me know how you get on with the engineer.

DingDong

Here's a link to a new type set top box that is going to be using soon:
http://www.pacemicro.com/corporate/products/prodinfo.asp?PID=DC210[url]
And the old type:
http://www.pacemicro.com/corporate/products/prodinfo.asp?PID=Di4010N[/url]

Phibsboro

Just to finish this thread (I HATE when I follow a thread and the outcome isn't revealed at the end ) ...

The guy came as arranged on Sat (BTW, have to say that overall I have been impressed with my dealing with NTL - Saturday appointments available and both the install appointment and this one were kept). However, somewhat like going to your doctor, by the time he arrived things had improved so much that the problem wasn't that apparent. I was actually going to cancel him in the week leading up to his visit, but I decided not to in case there was something he could do to improve things further.

Basically, there wasn't much he could do - he slagged off the installer a bit because he felt the signal was very low. He said he would change the outside tap to increase the signal but he wasn't convinced this would improve my picture beyond what I had already. (I'm not actually sure if he has done this or not - it was raining and he said he would do it on Monday - I asked him to leave to indicate if he had, but no note so far....). One thing I would say - like the installer, he thought in terms of analogue signal levels, not in terms of bitrate etc. He main focus was on the signal. He did check the error log on the boxes and confirmed no major issues there.

In other news, I have been goolging the whole concept of digital cable quite a bit. The situation is (apparently!) that digital cable, if it is done correctly, should actually provide at least a good a picture as Sky. Apparently a 64 QAM will deliver approx 30 Mbits per normal (analogue) 6Mhz channel. The key then is how many channels are being squeezed into each QAM? If it is 6 say, then you get approx 5 Mbits, which isn't far off the bitrate of your average DVD! Looking at the picture I am getting tho, it seems unlikely I am getting 5 Mbits per channel, which raises two questions :-

1. Is NTL actually getting anything like 30 Mbits from its QAM?
2. How many channels is NTL squeezing onto each QAM?

In a comparision with Sky, the bitrates output on Sky vary by channel, but go from say 1.5/2 on the shopping ones up to 4+ on BBC and Film 4. I'd love to know what NTL's numbers are and if they vary by channel. Obviously Statistal Muxing (A kind of variable bit rate, a method of encoding that spreads the available bandwidth across channels depending on which channel needs it most at a particular moment) makes things slightly more complicated, but average bit rates are still possible to get. Even at the level of knowing how many channels are going onto each QAM, we could get an average per channel that way.

As a final aside, I have mpeg-4 copies of some HD over-air broadcasts from the states that look fab (way better than the NTL picture). These files run approx 350megs for a broadcast hour (say 50mins) which gives a bitrate of just under 1 Mbit - so if we ever get to using mpeg-4 in a digital cable environment we could get 5/6 times more channels with much better quality

C

DingDong

Glad to hear you got fixed up. At the moment NTL has 10 station on 1 QAM which isn't alot considering some cable company fit 30 onto 1 QAM .
As for your comment on mp4 your dead right the quality and compression is so much better. We can only hope that someday NTL or who ever buys them starts to use it.