Stereo audio: Terrestrial vs NTL
 

I'm a bit baffled by this and I'm sure there'll be someone on here who will be able to explain this. I am in an ex-cwc area and have a PACE 2000 box connected to my TV via scart. I am confused as to why the stereo audio quality is far superior on terrestrial channels (via aerial on the roof) than through my STB. When I switch to say BBC1 on terrestrial I get an On Screen Display (OSD) telling me that the audio is Nicam Stereo, however when I switch to AV1 (cable) I get no OSD. The audio setup on my TV is set to Dolby Pro Logic.

So if terrestrial audio is broadcast in Nicam Stereo what kind of stereo is broadcast via NTL on the PACE 2000 box? Whatever it is it's inferior to terrestrial. Is there a specific setting which I can set my TV to in its audio setup to obtain a better sound, as I stated its set to Dolby Pro Logic at present. Other audio effects options I have are Dolby 3 Stereo, Pro Logic Phantom, Panorama, Pseudo Surround and off.

I await your feedback :)

Re: Stereo audio: Terrestrial vs NTL
 

By quality, what do you mean? Clarity, better stereo separation, broader bandwidth? If you are getting noise on the NTL audio, you need to find out if it is the output from the STB, the cable or the SCART input on the TV which is at fault. My STB's audio volume is noticeably lower than terrestrial, consequently the TV volume has to be raised, and this tends to amplify some noise on some programmes (slight hiss when the audio is quiet).

Nicam is the encoding used to send stereo audio over the standard analogue terrestrial broadcast system (UHF). NTL Digital doesn't need to use Nicam. I'm not sure how the encoding of audio and video works but it's in the digital domain, and the STB decodes, and separates it. The signals are then separate when presented to your TV via the SCART connection.

I remember that the old CWC analogue STB used to encode the stereo audio using Nicam as it used to connect to the TV via the aerial RF lead (it had no other connection!), but I now have a Pace 4000i (digital) and this definitely does not do this with its RF output (standard Mono I'm afraid :( ).

Dolby Pro Logic endoding should survive the transmission and decoding process, so should be present in programmes which are transmitted using Dolby both in Nicam and through NTL Digital.

Re: Stereo audio: Terrestrial vs NTL
 

the RF from the STB is a mono output. If your using a SCART lead, then the Right/Left Audio signals are send throught separate pins, so the TV does not recieve a NICAM signal.

Re: Stereo audio: Terrestrial vs NTL
 

By quality I mean a better stereo sound i.e. the small speakers contain more separation whereas through the STB more sound seems to come through the center speaker.

Re: Stereo audio: Terrestrial vs NTL
 

In a nutshell digital audio on ntl is compressed to **** and the decompression isn't great in the stb.

The analog signal is the clean signal from the broadcaster that hasn't been murdered, (processed) by ntl's dtv process....

Any more complicated explanations are a waste of time, it's the same the world over and always will be, unless perhaps HDtv takes off.

Re: Stereo audio: Terrestrial vs NTL
 

Well there we have it boys, an expert :rolleyes:

Re: Stereo audio: Terrestrial vs NTL
 

I understand NICAM stereo is a digital bit stream; the sound is compressed at a rate of 32khz / 14 bit accuracy (compared to 44khz / 16 bit accuracy for CD). The raw broadcast data is fed into NICAM encoders at the broadcast end and is decoded at the TV end. I think NICAM compression is lossless, but stand to be corrected on that.

NTL on the other hand uses a lossy compression technique; the audio layer of MPEG-2. Not sure whether they use the same raw broadcast data, but both methods employ encoders / decoders and are digital.

Re: Stereo audio: Terrestrial vs NTL
 

NICAM is a method developed to deliver stereo audio via an age old RF method of distribution, it uses QPSK modulation piggy backed along with the AM video and FM mono sound. Its lossless but its not really perfect, it is limited on its bit accuracy (14 bits maybe as you say) and so quantisation noise can occur.

MPEG is fundementally lossy, thats how the companies can fit in 8, 10 whatever channels into the same space previously occupied by a single analogue channel. The audio ntl get for the most part are recieved from Sky/DTT and are sent out without any real processing by ntl. By that I mean the MPEG audio sent out on ntl is the same audio sent out by the broadcasters on other platforms.

Re: Stereo audio: Terrestrial vs NTL
 

Thanks for the clarification, Proppinupthebar. I suppose then, as an analogy, that NTL/Sky/Freeview digital audio is to Nicam as MP3 or ATRAC is to CD. I can tell the difference between the original audio on CD and MP3 or WMV's when played through my laptop. So then, I guess that NICAM could sound better than NTL. S'funny, I remember being conned about picture quality as well :)

Re: Stereo audio: Terrestrial vs NTL
 

You can't tell the difference if the bitrate is hi enough, which for most channels it will be. NICAM will have more quantisation noise as it has a lower number of bits available per original sample, most MPEG audio will be at a higher sampling rate as well (48kHz typically).

Picture quality is another matter, I would say that some channels are taking the urine.

Re: Stereo audio: Terrestrial vs NTL
 

I am new to this site, but can say that not all digital services offer such a huge reduction in sound quality as NTL cable does, I have three freeview boxes in my house and all of them offer sound quality that beats that produced by my cable tv box by a mile, only three months to go then its goodbye cable tv.
HOORAY:wavey:

Re: Stereo audio: Terrestrial vs NTL
 

OK then its hello and goodbye then ?

OK good luck with 'free' view.

Re: Stereo audio: Terrestrial vs NTL
 

That's weird! Not sure why you are getting this imbalance. If the audio track is encoded with Dolby Pro-Logic, then it should sound similar whatever way it is transmitted.

As a work-around, can you tweak the levels of the various channels, to reduce the centre speaker volume, and increase the L + R speakers?

Re: Stereo audio: Terrestrial vs NTL
 

I take it you are implying that freeview is not free because you have to buy the equipment to receive it?
On that basis normal analogue is not free either as you have to buy a TV! lol
:D

Re: Stereo audio: Terrestrial vs NTL
 

Can you actually hear anything from the small speakers. More sound coming from the centre speaker seems to indicate a mono source being fed into the surround decoder. This will all be played out to the centre channel unless you have some DSP onboard your amplifier switched on.

How is the STB connected to the SSAmp. Direct Phono connections?

Edit - just reread the OP. What scart lead connects the STB to the TV. What settings do you have on the TV for audio inputs on the AV channels?

Re: Stereo audio: Terrestrial vs NTL
 

Nope, thats not what I'm saying ;)

Re: Stereo audio: Terrestrial vs NTL
 

I have also noticed the difference when listening in Dolby surround, Dolby Pro logic works by directing certain ranges of sound to certain channels therefore because NTL just doesnt seem to broadcast the same level of detail or the same range (as in as low or as high) as you get with nicam, sky or freeview, the sounds are all rather flat and midrange and therefore the processor will direct them to the centre channel where flat midrange speech is produced.

Re: Stereo audio: Terrestrial vs NTL
 

As I've already said once the majority of channels are recieved from satellite or DTT and hence have exactly the same audio.

Prologic does not steer sounds by their frequency components, it uses phase differences between the left and right channels to do the steering.

Re: Stereo audio: Terrestrial vs NTL
 

I have to agree with swipe, the ntl stereo is just wrong!

Last week I moved my tv (nicam stereo) from one room to another. After 4 years plugged into the ntl box (pace 4000) via fully wired RGB scart I pluged in an aerial and I have to say the whole family was shocked at how the sound 'came alive'!

The difference was amazing, tonal quality, clarity and depth (width) of the soundstage has made us feel like we have a new telly :)

Never mind, Sky is coming next week, it would be Sky+ but you cant get an install until march at the mo as it is SOOOOOOOOOO popular!

Re: Stereo audio: Terrestrial vs NTL
 

How many times does proppin' have to say it - THE SOUND ON SKY IS THE SAME AS NTL FOR MOST CHANNELS.

Re: Stereo audio: Terrestrial vs NTL
 

so when they install Sky they must secretly fill your room with air that conducts sound better then :naughty:

perhaps I (and the ntl eng) connected both my stb's wrongly but terestrial and my brother's Sky just blows away that wet dishcloth sound that claims to be stereo when it leaks out of the stb.

I'm not really fussy, I don't want 5.1 dolby or whatever. I just want stereo with a good realistic soundstage and a full freq. range.

All I know is that nicam through the aerial makes my ntl sound like an AM radio.

Re: Stereo audio: Terrestrial vs NTL
 

All channels or just certain ones?
Are you Langley or Bromley platform?

Re: Stereo audio: Terrestrial vs NTL
 

It may come from the same source, and therefore be the "same" but I can tell you it does not sound the same once it comes out of the STB as Sky does.

I know this from personal experience.

Re: Stereo audio: Terrestrial vs NTL
 

Again, is it all or just some channels?

Re: Stereo audio: Terrestrial vs NTL
 

I would say pretty much all the channels I used to watch, BBC1,BBC2,C4,Sky1,Paramount,music etc

The difference was noticable straight away, definatly more stereo seperation (and thus more noticble Pro Logic) on Sky than NTL, and seemed somewhat clearer sound.
And the only thing that changed when going from NTL to Sky was the STB, same tv, same scart cable, same sound system.

But I've not had NTL for 3 or 4 years now, didnt stay with NTL for long once it went digital, parents had Sky and was jelous by how good theirs was!

Re: Stereo audio: Terrestrial vs NTL
 

http://www.digitalspy.co.uk/article/ds13217.html :p

Re: Stereo audio: Terrestrial vs NTL
 

I'm not saying this is the problem - it's just a possibility. I know about this 'cos it happened with my PC's sound card!

It is possible that the hardware designer had a Friday afternoon moment and one of the audio channels ended up inverted - so that one of the speakers sucks instead of blows. When this happens you can hear there is a stereo signal but it's impossible to 'locate' the sound.

This problem is easy to identify. With the amp switched off, swap the two wires on one of the speakers. Then fire everything up and see if it sounds better.

Re: Stereo audio: Terrestrial vs NTL
 

Thats not bad thinking Altis! That would definitely have the effect of removing the stereo spread. No easy way to check or swop over the connections if using a scart straight into a TV tho. You could cannibalise a scart lead and swop them over yourself but its not soemthing I would encourage.

Re: Stereo audio: Terrestrial vs NTL
 

He has already said that he only changed the box nothing in his cabling or other equiptment. Its not just one person thats heard the difference anyone who compared sky or freeview back to back with NTL can hear it:naughty:

Re: Stereo audio: Terrestrial vs NTL
 

Altis pointed out that the wiring inside the NTL box could have that friday feeling and be a bit backward. This can be remidied by changing the box, or putting a crossover fix in the wiring.

Could be a batch of boxes? Mine certainly gives as good sound as NICAM.

Re: Stereo audio: Terrestrial vs NTL
 

Just to emphasise - I only put this forward as a possibility. I'm not saying that this is even likely to be the cause.

Anyone with access to an STB and a dual-channel oscilloscope could prove this one in an instant. Simply tune the STB to a mono channel, eg World Service(?), and then look at the two audio outputs. If they are in phase then this is not the problem but, if not, your uncle's name is Robert!

I have a 'scope (two, in fact) but we no longer have an STB - otherwise I would have checked this out by now - sorry.

Re: Stereo audio: Terrestrial vs NTL
 

I have the scopes but have yet to find a box affected :) I've swopped the phase on the audio out of a box and the sound does indeed get duller.

Re: Stereo audio: Terrestrial vs NTL
 

Proppin', are you able to test Bromley boxes?

Re: Stereo audio: Terrestrial vs NTL
 

Yes. Any particular model?

Re: Stereo audio: Terrestrial vs NTL
 

My ntl box has far better sound quality than my old Sky box and my Freeview boxes...........again its just luck of the draw i guess!!

Re: Stereo audio: Terrestrial vs NTL
 

Also it's down to personal preference, hell I know some people who think that tape sounds better than CD and someone that thinks their clapped out old car feels better than my nice comfy new-ish one.

Thankfully not everyone thinks the same in this world :D

Personally, I've not noticed a BIG difference in the quality between ntl and Sky but then I've never had ntl through anything other than my computer TV card which claims to do stereo and a set of Creative labs 4.1 speakers.

Re: Stereo audio: Terrestrial vs NTL
 

I think I know why. At the moment Scart and coax is only feeding a mono sound signal. I thought it was the scart leads provided until I used other scarts that do transmit nicam signal from my video to the telly.

I never new the problem before as it is only recently I have gone to nicam with telly/video. I had always fed the jacks to the prologic stereo. Which works fine so there is a stereo signal there.

I think the box is seperating the signal to the jacks. With the coax and Scart combining the left/right channels to make it mono.

Its not a quality issue it just sending mono through the scart.

I have found this with my box settings.

When you check the setting we are supposed to have three scart feed options.

Composite, RGB and S-video. At the moment S-video is not available.

I wondering if this would get round the issue.

If you get a scart lead which has a the facility to feed the left and right channel jacks will you redirect the sound to the video/telly.

Re: Stereo audio: Terrestrial vs NTL
 

As far as i know ( and this was 18 months ago ) NTL digital doesnt carry the nicam flag.

Re: Stereo audio: Terrestrial vs NTL
 

Yep, thats what was said in the first two replies of this thread.

Re: Stereo audio: Terrestrial vs NTL
 

There is no such thing as a NICAM flag....

Re: Stereo audio: Terrestrial vs NTL
 

"C4 is the "Reserve sound switching flag". It is used to notify the receiver that if NICAM is lost then it can switch to the FM mono sound signal which is transmitted for users without NICAM. "

http://www.doc.ic.ac.uk/~nd/surprise...nal/vol2/aps2/


well thats your opinion, however my opinions are backed up with facts.
:)

Re: Stereo audio: Terrestrial vs NTL
 

So theres a little known and irrelevant flag within the nicam data itself. If theres no nicam then theres no flag.
Theres no nicam as the first two answers at the start of the thread stated.