No more analogue BBC2

Well, I think many older tvs do display it as noise, though it tends to be a
different sort of dottyness to the no signal variety. More modern sets seem
to just give a blue, green or black screen I'm told.

Brian

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"Max Demian" wrote in message
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"Ar" wrote in message
...
In the gradual roll out of fleaview, the largest TV region, London, has
just switched off BBC2 analogue, and moved ITV1 into it's frequency......
so pressing 2 gets you ITV, and 3 gets you static snow.

Why snow, when the vacated channel (UHF23) now carries the digital PSB1? I
would have thought it would show something other than snow, even if an
analogue tuner doesn't know what to do with it. 'Snow' normally implies
that there's no signal, so the gain of the tuner rises to the maximum. Or
maybe digital channels are double sideband as opposed to the single
sideband of analogue?

--
Max Demian

Basil Jet wrote:
On 2012\04\05 19:37, John Hall wrote:
In ,
writes:
On Thu, 05 Apr 2012 18:41:30 +0100, wrote:

Sorry, I'll try that again

There is a difference berween the empty channel snow and a DTT
multiplex, albeit a subtle one. It's more coarse-grained.

I think the difference in the appearance of DTT snow and 'real' snow on
the analogue screen owes a lot to the characteristics of the receiver.
It is very obvious on some receivers and invisible on others.

Bill

On 05/04/12 19:49, Graham. wrote:
When the BBC started test transmissions of NICAM TV sound I was
alerted to something visibly different as you tuned through the
signal. You got the chroma subcarrier pattern in one direction and the
NICAM noise in the other.

Yes yes, but NICAM was an improvement over Freeview SD sound.

192k bit rate (or worse) instead of 728k (even though 14 bit) for
NICAM... NICAM beats Freeview sound quality.

A quick DVB check right now shows..

BBC1 256k (but has been known to be a lot lower than that)
BBC2 256k (also known to be a lot lower than that)
ITV1 192k
Channel4 192k
Five 192k
Sky News 192k

On Sat, 07 Apr 2012 17:00:02 +0100, Ar wrote:

On 05/04/12 19:49, Graham. wrote:
When the BBC started test transmissions of NICAM TV sound I was
alerted to something visibly different as you tuned through the
signal. You got the chroma subcarrier pattern in one direction and the
NICAM noise in the other.

Yes yes, but NICAM was an improvement over Freeview SD sound.

192k bit rate (or worse) instead of 728k (even though 14 bit) for
NICAM... NICAM beats Freeview sound quality.

A quick DVB check right now shows..

BBC1 256k (but has been known to be a lot lower than that)
BBC2 256k (also known to be a lot lower than that)
ITV1 192k
Channel4 192k
Five 192k
Sky News 192k

Is that MP2 or MP3? Either way, it's a lot better than DAB radio.

On Saturday, April 7th, 2012, at 17:22:03h +0100, Scott asked:

Is that MP2 or MP3?

MPEG-1 Audio Layer II (often referred to as MP2) is used for
DAB and DVB and some PAL DVDs.

MPEG-2 Audio Layer III (often referred to as MP3) is not
used in DAB or DVB or DVDs but is used for Internet Radio.

On Sat, 07 Apr 2012 17:00:02 +0100, Ar wrote:

On 05/04/12 19:49, Graham. wrote:
When the BBC started test transmissions of NICAM TV sound I was
alerted to something visibly different as you tuned through the
signal. You got the chroma subcarrier pattern in one direction and the
NICAM noise in the other.

Yes yes, but NICAM was an improvement over Freeview SD sound.

192k bit rate (or worse) instead of 728k (even though 14 bit) for
NICAM... NICAM beats Freeview sound quality.

A quick DVB check right now shows..

BBC1 256k (but has been known to be a lot lower than that)
BBC2 256k (also known to be a lot lower than that)
ITV1 192k
Channel4 192k
Five 192k
Sky News 192k

Poor old NICAM.
There it is at the end of it's life, after giving us the best sound
quality available from any broadcast medium, and most listeners didn't
give it a moment of appreciation.

Thank you NICAM 728, you will be missed.

--
Graham.
%Profound_observation%

In article , Graham. wrote:
Poor old NICAM.
There it is at the end of it's life, after giving us the best sound
quality available from any broadcast medium, and most listeners didn't
give it a moment of appreciation.

Thank you NICAM 728, you will be missed.

Yes, I thought superduper digital sound qualiy was the future of
broadcasting. How could I have guessed they'd close the system down and
replace it with a worse one? One step forward, two steps back.

I still have my Maplin kit receiver in my junk room. No use to anyone
now. Not much point even putting it on Ebay. Sigh

Rod.
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http://sourceforge.net/projects/virtual-access/

Ar wrote:
On 05/04/12 19:49, Graham. wrote:

192k bit rate (or worse) instead of 728k (even though 14 bit) for
NICAM... NICAM beats Freeview sound quality.

The bit rates aren't directly comparable, because NICAM is a simple,
companded system, whereas the modern systems use sophisticated
compression schemes matched to the characteristics of human hearing.

In practice, the real comparison can probably only be made subjectively.

Although NICAM companding is more sophisticated than telelphone
companding, there is a big difference between a stereo 128kbps MP3
signal and a pair of A-Law companded 64kpbs telephone lines, also used
for stereo, even though both have an aggregate bit rate of 128kbps.

In message , David Woolley
writes
Ar wrote:
On 05/04/12 19:49, Graham. wrote:
192k bit rate (or worse) instead of 728k (even though 14 bit) for
NICAM... NICAM beats Freeview sound quality.

The bit rates aren't directly comparable, because NICAM is a simple,
companded system, whereas the modern systems use sophisticated
compression schemes matched to the characteristics of human hearing.

In practice, the real comparison can probably only be made subjectively.

Although NICAM companding is more sophisticated than telelphone
companding, there is a big difference between a stereo 128kbps MP3
signal and a pair of A-Law companded 64kpbs telephone lines, also used
for stereo, even though both have an aggregate bit rate of 128kbps.

RF-wise, a NICAM signal occupies around 300kHz (similar to what you need
for a Band 2 FM radio signal). I presume that the more 'modern' digital
modes are far more economical in bandwidth.
--
Ian

Ian Jackson wrote:


RF-wise, a NICAM signal occupies around 300kHz (similar to what you need
for a Band 2 FM radio signal). I presume that the more 'modern' digital
modes are far more economical in bandwidth.

It is QPSK, which is the degenerate case of QAM, so it would be
considered 4 QAM (compared with the 16 QAM used by BBC before DSO, and
the 64 used by ITV, and by everyone after (256 for HD, ISTR)).

DVB-T doesn't, however, achieve two or four times the bit rate, as a
large proportion of the raw bits are used for error correction (the
Coded part of coded orthogonal...).

Note the numbers are the number of possible states per signalling unit
on a single sub-carrier, not the number of bits per signalling unit.

The other difference with DVB-T is that the latter uses a large number
of sub-carriers (somewhat less than 8,000, post DSO), which reduces the
baud rate drastically, hence making it more multi-path tolerant, and
spreads the spectrum more evenly.

Ultimately, the bit rate in a given bandwidth is limited by signal to
noise ratio, rather than technology. I believe COFDM is getting quite
close to the theoretical limit.

As to the audio coding, the use of codes like MP3 mean that the raw bit
rate can be a lot lower, for a given subjective quality, to a human user
of the sound.

It is the audio coding that probably has the most effect on bandwidth,
although, there is no dedicated audio spectrum with DVB-T.