NTL Digital Video Compression
 

Hi, I recently purchased a £30 Digital Freeview box for the 28" widescreen TV in my dining room and have got to say that the picture is stunning and really pin sharp.

Now this has highlighted to me how pixelated and low quality the NTL picture is compared to the Freeview. Surely it should be the other way round? Watching a show like the X Factor or ANT and Dec on the NTL box is like watching a downloaded WMV file and is really blocky (especially when on the audience).

Just wondered if this is the normal or whether I should contact them about it. Is just a case of NTL cable digital using a high compression level?

Thanks

PS, also they seem to have stopped sending me invoices for the TV and Phoneline now. Seems they just take the money now :mad:

Re: NTL Digital Video Compression
 

Yes, they do this to save paper if your bill is the same for three months running.

Re: NTL Digital Video Compression
 

I noticed that ITV seemed to be utilising less bandwidth per channel on NTL than the BBC. I thought it would change when I got $ky but I think ITV is still more compressed than the Beeb. Still, it's infinetely better than some of the 'channels' I now have access to. I am very surprised, though, at how pixellated the Sky Sports channels can get ... I reckon you can't choose anything better than a football pitch to judge the quality of a digital TV picture and the Sky Sports pictures, to my eye, are no better than watching a game on ITV or C5 ... when the camera moves even a little, the players look like they're wading around on a bright green duvet instead of a grass pitch.

Offtopic, but I remember a similar discussion on here a while ago about DAB quality - that on digital radio, even the Beeb is going for quantity over quality and broadcasting streams that are effectively sub-FM standard on certain channels.

Re: NTL Digital Video Compression
 

Certainly are, from wiki
Currently, 98% of all stereo radio stations on DAB in the UK use 128 kbit/s joint stereo, which is incapable of providing the same level of audio quality as FM. Speech services usually use 64 kbit/s mono. The only good audio quality service is currently BBC Radio 3, which is usually transmitted at 192 kbit/s in true stereo, but does not sound as good as it does on FM.
The audio is encoded as MPEG 1 Layer 2 (MP2), which is approximately 50% less efficient than MP3, meaning that MP2 requires a 50% higher bit rate to achieve a given level of audio quality than MP3. For example, blind listening tests have shown that MP3 now performs very well at a bit rate of 128 kbit/s, and MP2 would require a bit rate of at least 192 kbit/s to provide the same level of audio quality. Some channels, such as E4 use a shorter picture to reduce bandwidth also.
NTL don't encode / reencode the signals, just play them out, so you should see the same image from all platforms.

EDIT - on the original picture topic, it is all down to bandwidth again. When DVD and compressed encoding first came there was a lot of concern that cartoons, animation, old movies would not convert well, but cleanup, cell realignment and general care in encoding and use of good bandwidth as ensured this has not happened. Just take a look at Bambi, or the Incredibles (or apparantly Japanese Animi) to see for yourself. But DVD can offer up to 8MB of bandwidth for the picture and audio.

Re: NTL Digital Video Compression
 

I noticed the other day that on my dads SKY digi, UKstyle was very pixillated and the sound quality was terrable. It was very over compressed like a 64kbit/s Mp3

Re: NTL Digital Video Compression
 

Something doesn't seem right, as the ntl picture for ITV is a straight relay of the Freeview signal, and so they should both look the same.

Re: NTL Digital Video Compression
 

something is wrong with Ntl's compression.. its Just bloody horrible, most of the Sci-fi and national geographic channels are terrible.

the old Analogue service was better than this, even terrestrial TV is of much Higher quality than Ntl's tripe.

Re: NTL Digital Video Compression
 

Many of the channels you infer above are broadcast at a lower bandwidth than the movie chanels and BBC1, ITV1 etc. You can actually see the pixelation on the E4 logo for example.

Digital is better is not always true, DAB radio uses such low bitrates that it is worse than FM on most channels. Same, but to a lesser extent with DTV as that uses a better compression method.

NTL/TW plans to use a better compression algorithm MPEG4 for broadcasting the next generation of pictures this should also help matters.

Re: NTL Digital Video Compression
 

I find this all very concerning. I have recently had an NTL engineer over because the quality of the TV picture is (and always has been) really poor, obvious compression artifacts on fast moving pictures, mushy pea football pitches etc. The engineer could do nothing and his supervisor has just called me. He admits that this is down to the high levels of compression they are using as they are trying to get 300 channels down the limited bandwidth available.

Is SKY any better? If so I will move, however will try writing to Simon Duffy first as a matter of principal.

The worrying thing is that these wonderful new digital TV and Radio services are being pushed on the unsuspecting public as the ultimate in picture and sound quality, and most people just sheepishly accept what they are told without question. Meanwhile the government is busy rubbing its hands at the thought of all of the lovely money it is going to make when it forces analogue to close down and sells of the spare bandwidth - leaving the poor consumer with nothing but 1,000s of channels of digital mush - effectively taking us back 20-30 years in terms of transmission quality.

Is it only me or is any one else concerned by this? Should the broadcasters not have some obligation to provide content of a minimum technical quality? Is there any organised pressure group to campaign for this?

As for HDTV, I can't imagine what they will do to that. 720p at 8mbps anyone?

Re: NTL Digital Video Compression
 

NTL do not re-encode, they just broadcast so the same signal is recieved on your NTL, SKY and Freeview box. The hardware in the box may slightly impact the decoding quality, but it is principally bandwidth. Football is one of those things that DTV was not going to improve, too much differing motion and without high bandwidth, which it does not get you get the problems you detail.
You should find that BBC1/2 give very good pictures, as the BBC use more bandwidth on these channels, but bandwidth costs and as a result channels such as E4 use less.

HDTV will use MP4 compression so should get more image down the same pipe.

Re: NTL Digital Video Compression
 

That is not true.

For most of the Sky owned channels, for example, ntl receive the channels via a direct link from Sky, and encode them themselves.

Having said that, there isn't much of a difference between the picture one gets from Sky and from ntl.

Re: NTL Digital Video Compression
 

Yes it is, nor is it a downside as you seam to be making out.No, "Most of the sky owned channels" are turned around at MPEG level from other platforms. Only sky one and the sky premium channels get the treatment you describe.But as the sky premium channels are received by ntl in a totaly uncompressed format (270Mbits/second SDI video), and are then encoded at a bitrate that is higher than the other channels, you achally get a better (bitrate) picture on the sky premium channels on NTL, than you would do with sky.

For more infomation, read this more detailed explination:
http://forum.digitalspy.co.uk/board/...19&postcount=5

-Chris

Re: NTL Digital Video Compression
 

I would beg to differ on that one, the picture quality, I have sky and feel their picture quality better than NTL.

Re: NTL Digital Video Compression
 

Once again though, this could be due to better quality decoding hardware in the Sky STBs.

Re: NTL Digital Video Compression
 

And I would agree ;)

But some people seem to think that the picture is the same picture you eventually get whether you have NTL or SKY, I have had NTL and have SKY now, and can see your explanation as a good one.

Re: NTL Digital Video Compression
 

Is there any way that the consumer can ascertain the bitrate of the channel being watched, on either Sky or NTL?

Re: NTL Digital Video Compression
 

I find the picture quality from my (thier) Pace 4000s to be very good.

Re: NTL Digital Video Compression
 

And that is ok, a lot of people may find a particular brand of hifi equipment to be very good, but equally a lot may not.
In my experience I have found sky plus picture quality to be better to that I had with NTL, the reason for this could be the design of the two boxes, better components used by sky in their boxes could be the reason, it is the only reason I can think of, because the NTL stb had been properly installed, the cables I use are the same cables, the only difference seems to be the actual boxes themselves.

Re: NTL Digital Video Compression
 

Its possible to find out for sky using a DVB-S tuner card and decent spec PC, but for cable... well... I could tell you how to find the bitrates for cable... but then id have to kill you;)

-Chris

Re: NTL Digital Video Compression
 

The same can't always be said for the 4010 boxes, unfortunately. One some channels (IIRC it's those channels who use non-standard resolutions) the 4010 boxes have faint vertical lines on the picture, mostly noticeable on dark scenes.

Here's a mockup I made for an eariler thread that shows what I'm talking about (although the lines aren't quite so severe in reality).

http://homepage.mac.com/lwernham/.Pictures/Lines.jpg

Re: NTL Digital Video Compression
 

No, thats not a known problem, my 4010 is working fine and doesnt suffer that issue. Your box is clearly faulty and I would contact them to arrange a replacement.Since when has sky sports used non-standard resolutions?

-Chris

Re: NTL Digital Video Compression
 

Strange, this is what I was told by an NTL person at another forum:

And I can confirm that it also happens on my brother's Samsung and my friend's 4010 box.

If the only option is to go back to a 4001 box then no thanks.

They don't. That picture is a mockup. It just happens that I already had a screengrab of Sky Sports handy and I didn't want to have to boot up my PC just to grab another one. Channels that I have seen this problem on include the ITV channels, Bravo and NASN.

Re: NTL Digital Video Compression
 

If this problem was affecting every ntl customour with a pace 4xxx series box (apart from the 4001) or samsung box and was annoying as you say, then im pretty certain that ntl wouldent have many customours left!Its not the only option because I have a 4010 and have *never* seen this issue. I would think that a low quality scart lead, problem with your TV or dud box is most likely the case here.
-Chris

Re: NTL Digital Video Compression
 

Hard for me to comment as I have only had sky digi once and was about 4 years ago and have seen it the odd few times at friends/family. Each time I seen it the picture has looked fine enough for me to not notice anything. Ntl I have analogue which I guess doesnt have the problem so I cant comment on that.

Re: NTL Digital Video Compression
 

I have Sky myself, very good picture, have visited many NTL customers house who have digital STB and the picture can vary depending on the TV they have. Both NTL and Sky have good picture quality, and like i have said the picture whether it be Sky or NTL will vary depending on the TV being used. This as i have said is after seeing many different Tv's and the picture quality whether on Sky or NTL.

So it depends on what you mean by the quality of the picture, obviously if your talking analogue, "is it a clear picture or grainy picture", with digital the bit rate will affect the data transfer to the STB, so are you talking about the picture pixelating freezing ect. This will happen both on Sky as well as NTL depending on various factors for example, the installation, quality of the STB ect. So by finding out the bit rate will you assume one is better than the other because it has a higher bit rate without really knowing why.

Re: NTL Digital Video Compression
 

One comment I would make. If it is the case that Sky premium content is delivered uncompressed and compressed by NTL, there is a huge difference between Sky One and Sky Two. The former is a good quality picture but the latter is quite obviously pixelated. Most annoying.

Re: NTL Digital Video Compression
 

Interesting. That sortof confirms what I was saying, because Sky one is encoded by ntl themselfs at a higher bitrate, but Sky two is turned around at MPEG level from sky digital and is the same as would be recived with a sky satellite reciver.

Im surprised that it makes that so much difference that you can visably notice the different levels of compression between the two channels. Still, it could be worse, if you had sky then your sky one would be at the same low bitrate as sky two:erm:

-Chris

Re: NTL Digital Video Compression
 

After having Sky for years and now NLT and Freeview for the last year, I am pretty used to Digital TV and I can honestly say that with NTL, the picture and sound quality, on a lot of the channels, has decreased in the last month or 2. I dont know who encodes their channels but there really is something going on.

QVC is a prime example the picture is terrible. Funny how this seems to have started roundabout when the recent new channels were added.

Also, every now and then the screen goes black as the signal goes out of synch and it needs to catch up or whatever it does.

I still have Sky for the free to air channels and I end up watching them, or even Freeview, as the picture and sound is far better.

What is going on?

Re: NTL Digital Video Compression
 

That sounds more like your signal level has fallen to your STB than a reduction in bandwidth.

Re: NTL Digital Video Compression
 

Do NTL charge channels based on how high a bitrate they use?

It would make sense to want more money from ITV 1 if they are using twice as much bandwidth as, say, UK TV Repeats-That-Were-Crap-First-Time-Round 3 +1.