Digital TV: the picture really is horrible!

In message , Paul Ratcliffe
writes
On Wed, 29 Aug 2007 13:22:49 -0000, Mark Carver wrote:

On Aug 29, 1:55 pm, "Graham Harvest" wrote:

Do broadcasters still put a line of colour bars in the vertical interval?
I'm sure they all used to do this last time I checked (early 90's) and often
had a 2T pulse too.

No colour bars, you're thinking of the first few active picture lines
on Test Card F ?
However there is ISTR a linearity staircase, and 2T pulse and bar. UK
standard signal, carried on lines 19/332 and 20/333 I think ?

On analogue OB links there was often an ITS inserter to put colour bars in on
a couple of lines. All gone away now of course. Maybe that's what he was
thinking of.

Unfortunately, the absence of suitable VIT signals prevents any real
assessment of the quality of the signal when it is converted back into
the real world of 625-line video. There's not even any teletext (which
can be used to give some indication of performance). For example, nobody
can measure the scart video feed out of a set-top box, except, perhaps,
maybe by looking at the shape of the sync pulses and the ratio of sync
to colour burst. I believe that the excuse is "It's digital, so it we
don't need them".
--
Ian

Ian Jackson wrote:

Unfortunately, the absence of suitable VIT signals prevents any real
assessment of the quality of the signal when it is converted back into
the real world of 625-line video. There's not even any teletext (which
can be used to give some indication of performance). For example, nobody
can measure the scart video feed out of a set-top box, except, perhaps,
maybe by looking at the shape of the sync pulses and the ratio of sync
to colour burst. I believe that the excuse is "It's digital, so it we
don't need them".

Even it they did carry the signals on DVB, what could you learn from them ?
Any lossy video compression system will mangle them. That's why old style
teletext data on DVB-S (and DVB-T in some countries) is not directly encoded,
but the data is carried in a non compressed transparent data channel, within
the transport steam. The VBI teletext data is then re-inserted by the receiver.

The idea behind VITS signals is to assess degradation on analogue signal
paths. Often the only analogue signal path these days is from the D-A
converter in your receiver, to the CRT. There's nothing at the broadcaster's
end, not even within the camera, (unless you consider the lens and prism :-) )


--
Mark
Please replace invalid and invalid with gmx and net to reply.

schrieb:

Of course the obvious argument is that if you're going to deliver
10Mbps+, you might as well deliver HD. I don't believe shows like
Dance X would be artefact-free if encoded to HD 1080i50 in real time
at 10Mbps, even with MPEG-4 / AVC, but I could be wrong.


Hello,
you are wrong really! If you have a chance please look on Astra
satellite 19 deg. east where a "HDTV showcase" for the IFA show in
Berlin is running with DVB-S on 12.422 MHz, polarisation horizontal, FEC
3/4, symbolrate 27,500, H.264 with 720p. The same program in SD is
broadcast on "Einsfestival", of course in german language both. On a
Full-HD display fed via HDMI there is a difference, bitrate is not the
main parameter to describe high definition!
ARD and ZDF are tranmitting their SD programs with 6 - 8 Mb/s peak,
nobody complaining any more...

Klaus

In article , Paul Ratcliffe
scribeth thus
On Fri, 31 Aug 2007 10:55:42 +0100, tony sayer wrote:

Now then ... something funny happened last nite!.. I had my accountant
on the phone yesterday afternoon asking me to advise him on a problem,
well couple of problems he was having with his TV reception. Being the
ever helpful and wondering why the aerial system he had was so bad I
chucked the ladder on the car and ventured forth...

I really hope you sent him a bill....

Well there is a bit of back scratching going on, but it was rather
interesting to see what the typical TV viewer observes these days!..

Aren't those Sky dishes the most flimsy bit of cack out?. Do they have
someone press them out of recycled tin cans?...
--
Tony Sayer

"Richard L" wrote in message
...
In message
"Lord Turkey Cough" wrote:


wrote in message
ps.com...
I've been too busy to watch TV recently, so maybe I'd forgotten how
bad it could look, but...

I had chance to catch the last episode of Mountain on Sunday night,
and saw some of Dance X (?) the night before.

I enjoyed Mountain. Not too much distracting "filmic effect" (only on
a few shots), and only the MPEG encoding of moving fine details let it
down. Great programme.

However, Dance X... isn't the picture quality shocking? It seems
~5Mbps MPEG-2 just can't cope with flashing lights, fast movement,
detail and smooth gradients on screen at the same time etc.

Perhaps you need a better telly, it looks fine on mine, a Thompson.

There's no such make.

http://www.thomson-europe.com/

idoit.


--
Richard L.

In message , Mark Carver
writes
Ian Jackson wrote:
Unfortunately, the absence of suitable VIT signals prevents any real
assessment of the quality of the signal when it is converted back into
the real world of 625-line video. There's not even any teletext (which
can be used to give some indication of performance). For example,
nobody can measure the scart video feed out of a set-top box, except,
perhaps, maybe by looking at the shape of the sync pulses and the
ratio of sync to colour burst. I believe that the excuse is "It's
digital, so it we don't need them".

Even it they did carry the signals on DVB, what could you learn from them ?
Any lossy video compression system will mangle them. That's why old
style teletext data on DVB-S (and DVB-T in some countries) is not
directly encoded, but the data is carried in a non compressed
transparent data channel, within the transport steam. The VBI teletext
data is then re-inserted by the receiver.

The idea behind VITS signals is to assess degradation on analogue
signal paths. Often the only analogue signal path these days is from
the D-A converter in your receiver, to the CRT. There's nothing at the
broadcaster's end, not even within the camera, (unless you consider the
lens and prism :-) )


That fact that the lossy video compression mangles VIT signals would
seem to be an admission that also mangles signals on the active video
lines. But if you could carry VITS, it would tell you how good the D-A
converter (and the rest of the STB) was.
--
Ian

Lord Turkey Cough wrote:
"Richard L" wrote in message
...
In message
"Lord Turkey Cough" wrote:

wrote in message
ps.com...
I've been too busy to watch TV recently, so maybe I'd forgotten how
bad it could look, but...

I had chance to catch the last episode of Mountain on Sunday night,
and saw some of Dance X (?) the night before.

I enjoyed Mountain. Not too much distracting "filmic effect" (only on
a few shots), and only the MPEG encoding of moving fine details let it
down. Great programme.

However, Dance X... isn't the picture quality shocking? It seems
~5Mbps MPEG-2 just can't cope with flashing lights, fast movement,
detail and smooth gradients on screen at the same time etc.
Perhaps you need a better telly, it looks fine on mine, a Thompson.
There's no such make.

http://www.thomson-europe.com/

idoit.

--
Richard L.


Richard is correct - You said you've got a Thompson, not a Thomson...

BTW It's 'idiot'

Peter

On Fri, 31 Aug 2007 10:21:38 -0000, Gareth Rowlands
wrote:

On Thu, 30 Aug 2007 19:23:56 +0100, Mortimer wrote:

As a matter of interest, what would a £500 LCD make of a studio-bit-rate
signal (always assuming that it knew how to decode it) - would the
picture still look crap because of the differences between the tonal
rendering of LCD/plasma compared with CRT?

The picture still looks crap compared to a CRT because of the lack of
information in the darkest parts of the picture and often (but depending
on the panel) limited viewing angles.

In the great outdoors, LCD displays are not always bright enough for
satisfactory use.

Has anyone looked at the 17" or 23" Humax freeview LCD's available on the
Tottenham Court Road at around 350 quid? These seem to have quite a fair
consistency over wide viewing angles

G.
Bought a 23" Humax last week and the viewing angle is one of the best
I've seen. Before that, I tried a Wharfedale 23", which varied in
picture quality dramatically evrey time I moved my head slightly.

Marky P.

"tony sayer" wrote in message
...
In article , Paul Ratcliffe
Aren't those Sky dishes the most flimsy bit of cack out?. Do they have
someone press them out of recycled tin cans?...

They are an embarrassment.

Bill

Ian Jackson wrote:
In message , Mark Carver
The idea behind VITS signals is to assess degradation on analogue
signal paths. Often the only analogue signal path these days is from
the D-A converter in your receiver, to the CRT. There's nothing at the
broadcaster's end, not even within the camera, (unless you consider
the lens and prism :-) )


That fact that the lossy video compression mangles VIT signals would
seem to be an admission that also mangles signals on the active video
lines. But if you could carry VITS, it would tell you how good the D-A
converter (and the rest of the STB) was.

The test signal would have to be full field, or active picture content would
need to be stationary while you perform the measurements ?


--
Mark
Please replace invalid and invalid with gmx and net to reply.