chris@tharr.UUCP (Chris Allen) (11/14/90)
I have seen a number of adverts recently for Nicam Stereo televisions.
Can anyone recommend any papers on the operation of Nicam Stereo?
Also any decoder chips that are available?
Thanks in advance.
Chris Allen.
--
chris@tharr.uucp ..!ukc!axion!tharr!chris
Disclaimer: The views expressed above are those of my employer..
<-- tharr free public access to Usenet in the UK 0234 261804 -->richi@hpopd.HP.COM (Richard Jennings) (11/15/90)
/ hpopd:sci.electronics / chris@tharr.UUCP (Chris Allen) / 1:18 pm Nov 14, 1990 / I have seen a number of adverts recently for Nicam Stereo televisions. Can anyone recommend any papers on the operation of Nicam Stereo? Also any decoder chips that are available? ---------- Look in the new Maplin catalogue (get it from WH Smith) for chipsets, modules & a complete decoder chip. If, like me, you're considering modifying an existing TV, I think you'll need to replace the IF filter (?) to leave the NICAM carrier alone for a start. Don't expect many replies from the US, except perhaps "what's NICAM?", coz they use Luddite FM subcarrier analogue for their stereo TV (but, of course, they had it before we got it). NB, noticed last night that Blackadder IV is in Stereo... richi.
richi@hpopd.HP.COM (Richard Jennings) (11/16/90)
> Richard, I know for a fact that ITT Semiconductor sells the chips for > Nicam audio.I belive this stands for Near Instantaneous Companding.If > you don't have an address I know I have it at work.Fax me your number > and I will fax you the data sheet I have.My fax number is 415-967-0772 > > > Regards > Norman Gillaspie > ISS Engineering Norman, Well, thanks, but it wasn't me that asked! - it was Chris Allen (chris@tharr.UUCP)... NICAM == Near-Instantaneous Companded Audio Multiplexing, I believe :-). Here's my understanding, cobbled together from the marketing FUD & the data sheets etc. that I've seen (+ some guesswork, marked [*]). Anyone want to correct my understanding? Multiplexing, because two audio channels and one control channel have to be put onto one data stream. Audio, for obvious reasons. [*!] Companded, because there isn't a linear relation between digital quantisation step and its analog[ue] equivalent. [*] Near-Instantaneous, because the multiplexing implies a finite lag between the audio data being put onto the stream and the conversion to analogue form of those data. Invented by the BBC. Paradoxical how the BBC aren't advertising the fact that they are transmitting programmes now in NICAM, although the Independent networks are shouting loudly about it. Perhaps this is because the Beeb want to wait until most of the country's transmitters are NICAM-capable? The control channel is there to tell the receiver what sort of data these are, e.g. Stereo or two-channel bi-lingual (try doing that with sub-carrier FM!). There is some redundancy in the control bandwidth, to allow for extensions to the standard later, just as the BBC added into the Teletext standard, when they invented that. [sound of richi's chest puffing out in nationalistic, almost, but not quite, xenophobic pride.] The audio data are 14-bit, but becuase of the companding, the dynamic range is "comparable to CD" (at least on 99% of your average TV audio material). richi.
heke@stekt.oulu.fi (Heikki Paananen) (11/16/90)
I say, as you already know, Maplin supplies stuff for NICAM. Details
can be found from Maplin magazine issue 34 (ordering code XA34M).
price is 1.45NV (pounds). They also supply some ready-to-build
NICAM projects. Try NICAM 728 Stereodecoder module. In kit form it
costs 79.95 (code LP02C) and assembled version costs 109.95 (AM00A).
Writ to: MAPLIN ELECTRONICS
P.O.BOX 3
Rayleigh
Essex
SS6 2BR
ENGLAND
phone: 0702 554161 (sales 24-hour)
0702 552911 (customer services)
--------------------------------------------------------------------------
Heikki Paananen heke@stekt.oulu.fi
The University of Oulu so-hsp@finou.oulu.fi
Department of electrical eng. hpa@stek1.oulu.fi
Finland
-------------------------------------------------------------------------
Stuck in the Omniland.....rustyh@wam.umd.edu (Rusty Haddock) (11/17/90)
In article <26050001@hpopd.HP.COM> richi@hpopd.HP.COM (Richard Jennings) writes: >/ hpopd:sci.electronics / chris@tharr.UUCP (Chris Allen) / 1:18 pm Nov 14, 1990 / >I have seen a number of adverts recently for Nicam Stereo televisions. >Can anyone recommend any papers on the operation of Nicam Stereo? >---------- > >Don't expect many replies from the US, except perhaps "what's NICAM?", coz >they use Luddite FM subcarrier analogue for their stereo TV (but, of >course, they had it before we got it). > NICAM : Near Instantaneous CompAnding From what I remember, A section of the audio signal (something like 100ms) signal is digitised at 16bits, the most significant bits of the "loudest" sample are examined to determine how many bits to "shift left" each sample of the section of audio. The weighting factor is transmitted at the head of a "Packet" of data that consits of the most significant 10 bits of each sample that has been shifted left by the weighting factor. Sort of leading zero suppression. Knowledge of the whole 100ms of audio is needed before you compand and thus "near instantaneous".) You end up with something like 10.2 bits per sample. Its a great idea that I think engineers ath the BBC came up with. It is not possible to transmitt the signal here in the US (or Australia) in the sameway its sent in the UK because the sound carrier is too close to the video here (4.5MHz in US and 5MHz in Australia but 6MHz in UK). (BTW the figures here are very rubbery but the method is right). -- Michael Katzmann NV3Z / VK2BEA / G4NYV ...uunet!opel!arinc!vk2bea!michael -- Rusty Haddock o {uunet,att,rutgers}!mimsy.umd.edu!fe2o3!rusty Laurel, Maryland o "IBM sucks silicon!" -- PC Banana Jr, "Bloom County"