Surround sound from NTL?

digiman

Do NTL broadcast any of their programs in surround sound? I am getting a new surround sound system and would like it to work with NTL if they actually broadcast it. I know that SKY+ can give out Dolby Digital sound. I have the NTL DVR box which has a digital audio output on the back.
Some help would be appreciated.

bcmf

I was under the illusion that only Sky HD box only broadcast in full surround sound.Anything else is a whatever your amp/system can do with a stereo signal which I believe is all that is transmitted.

Kensington

NTL only do stereo sound unfortunately. To get surround sound on broadcast programs, at the moment your only options are either a Sky+ or a Sky HD box and even then it's only the Sky Movies and Sky Box Office channels that transmit Dolby Digital surround sound.

Tomas_V

It's not exaclty true.

Certainly NTL don't transmit digital surround, useful to a 5.1 system.

But...some programmes carry the older Dolby Surround system encoded within the stereo signal. Ironically, you are more likely to get a good surround sound image from analogue/Nicam transmissions than from their heavily compressed digital transmissions.

L1011

Tomas_V wrote: »

Ironically, you are more likely to get a good surround sound image from analogue/Nicam transmissions than from their heavily compressed digital transmissions.

This was indeed the case on Sky when Sky Digital got introduced - one of the analogue boxes, an Amstrad I believe, had an adjustable audio delay on its Pro Logic output, meaning if you were watching the same channel on Sky Digital as Sky Analogue, you could (generally) manage to get the analogue stereo (with Wegener Panda correction) to sync up with the digital picture. Was even a big article in "Television" magazine about doing it

Of course it required two dishes, two decoders, a Pro Logic system, and became pointless by 2000/2001...

Mossy Monk

bcmf wrote: »

I was under the illusion that only Sky HD box only broadcast in full surround sound.

Sky+ does aswell.

Puggy

Do NTL not carry AC3? At least where it was part of the signal reaching them?

Also some FTA satellite channels do AC3.

watty

I can't think of any UK FTA with AC3 / 5.1 apart from BBC HD trial. Little of that useful 5.1
Most channels on Satellite are MP2 sound. Only some Sky Films / Box office regularly in 5.1?

Nicam is fully Digital. Terrestrial analogue in UK/Ireland is Mono only.

Alun

watty wrote: »

Nicam is fully Digital. Terrestrial analogue in UK/Ireland is Mono only.

Nicam sound is digital, yes, but it's transmitted on a separate sub-carrier above the normal mono sound carrier. The BBC have been doing this since the early 90's, and Irish terrestrial uses it as well, AFAIK.

silvine

My amp has Dolby ProLogic II. Am I correct in saying that it will be able to provide surround sound from my NTL box?

Tomas_V

silvine wrote: »

My amp has Dolby ProLogic II. Am I correct in saying that it will be able to provide surround sound from my NTL box?

In principle, yes, as long as NTL have not mangled the audio too much.

ProLogic is not as good as 5.1.

watty

Alun wrote: »

Nicam sound is digital, yes, but it's transmitted on a separate sub-carrier above the normal mono sound carrier. The BBC have been doing this since the early 90's, and Irish terrestrial uses it as well, AFAIK.

Yes 6.5MHz higher. All the irish terrestrial analogue channels use Nicam (digital). But the analogue sound is mono.

Some countries have two separate analogue channels (this is not the same as FM Radio, which uses L+R = Mono and a L-R DSBSC at 38kHz). So Ireland and UK have no Analogue Stereo.

Video Senders use FM Analogue (rather than AM VSB video if Terrestrial and Analogue MMDS) and then two separate FM audio subcarriers on the video. On terrestrial Analogue TV, the FM mono and Nicam digital may appear as subcarriers on some TV designs (newer ones use separate IFs now, not intercarrier), but are truly separate carriers.

watty

Tomas_V wrote: »

In principle, yes, as long as NTL have not mangled the audio too much.

ProLogic is not as good as 5.1.

5.1 is mostly used for special cinematic effects. It's not a natural surround sound. It only works for 5.1 sources.

Prologic can be more natural and will produce some useful surround sound on naturally recorded stereo.

You can't say one system is "better". They address different markets.

have a read of http://www.ambisonic.net/

In the 1970s 4 channel sound (Quadraphonic), ambisonic and binaural
http://www.binaural.com/serendipity/index.php

all tested. The 4 channel Quadraphonic system needed twice the bandwidth and specialist equipment so it died. Prologic, like Ambisonic and Binaural only needs 2 channels so can be carried by all stereo recording/playback and transmission systems, analogue or digital.

Binaural is best for headphones. Sennheiser makes a gadget to convert ordinary stereo to pseudo binaural for headphones. They also sell "dummy heads" for recordings.

To record live stereo with "surround sound" content you actually only need two microphones (we have only two ears!). One approach that works well for regular stereo speakers or Ambisonic or Prologic playback is simply a pair of cardiod microphones crossed at 120 degrees. For Binaural (which can be "decoded" for regular stereo, ambisonic or prologic) use a dummy head. The BBC found that a 6" to 8" perpex disc vertical with a simple electret capsule either side from centre spaced 2" out worked just as well as copy of a human head and fake ears with microphone inserts.

Natural surround sound does not need 6 channels. The two 5.1 systems were invented for the cinema for cinematic post production effects. The centre channel is easily simulated by adding the L + R. All six channels of a 5.1 system could be derived from 3 transmission channels.

The .1 effects channel is 99.9% low frequency so if you have a 5 channel only amplifier make sure the centre speaker has a sub woofer and simply add the LFE .1 channel and the centre channel. They can even be separated after the amp by a subwoofer crossover filter to drive a separte sub woofer cabinet.