Stereo audio: Terrestrial vs NTL

[Swipe]

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

[abailey152]

Originally Posted by Swipe

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

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.

[JonSav]

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.

[Swipe]

Originally Posted by abailey152

By quality, what do you mean? Clarity, better stereo separation, broader bandwidth?

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.

[knighty]

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.

[Tristan]

Originally Posted by knighty

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.

Well there we have it boys, an expert

[dino]

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.

Originally Posted by dino

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.

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.

[dino]

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

Originally Posted by dino

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

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.

[ccursons]

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

Originally Posted by ccursons

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

OK then its hello and goodbye then ?

OK good luck with 'free' view.

[abailey152]

Originally Posted by Swipe

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.

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?

[Tod]

Originally Posted by Proppinupthebar

OK good luck with 'free' view.

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

[SMHarman]

Originally Posted by Swipe

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.

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?