LCD's TV's create there own MPEG artefacts

"John Russell" wrote in message
...
I have been tempted to buy a Toshiba LCD TV. Considering how good my
SKY+ broadcasts are on a CRT I wasn't expecting any problems. Well I
shocked by how poor the picture is. After much deliberation I realised
what the problem is. An LCD is a Digital Display, it has to work out
what colour each LCD element has to be. So it has to work using
video, and that means its digitises the analogue inputs connected, and
that creates the MPEG artefacts.

Re the mpeg reference, that's complete & utter rubbish. See David
Robinson's post. If you are seeing mpeg artifacts they'll have been in
the original stream.

Indeed. Alternatively, he might be mistaking other (genuine)
artefacts for MPEG ones.

Nothing to worry about then!
I shall rephrase and say I'm seeing digitisation artefacts.

I quite agree that LCD TV's appear to show MPEG artefacts which are not
there on a CRT, and they make the pictures look cartoon like into the
bargain. Why they do it could be down to a combination of several types of
picture processing but mainly it will be sharpening. Another factor may be
deinterlacing which will make certain parts of one field remain fixed on the
screen for the duration of 2 fields and could be causing some of the
increased visibility of the MPEG artefacts.

Also it might be that the picture processing was optimised for the US market
where the screen would only need to display Analogue NTSC or full HD.
Neither of these will have MPEG artefacts of the same size as those in our
625 line RGB signals. Analogue NTSC, if it has MPEG artefacts at all, will
have them at a larger size with lower amplitude, while with HD they will be
of a much smaller size. Perhaps the sharpening works well on these signals,
but on our signals it exaggerates details of just the wrong size, and brings
out our MPEG artefacts.

In any case what we need is regulation, and an organisation like BREMA to
set down standards for flatscreen, LCD and Plasma TV's with Benchmarking for
TVs along the same lines as the Benchmarking of aerials for Freeview. We
should specify standards for Flatscreens and place an import levy on models
which do not meet the standard. The standard should specify that flatscreens
will be manufactured with a native resolution which matches the TV
broadcasts they are intended to receive in Europe, 576 x 1024 for standard
definition or 1080 x 1920 for HD, and that resizing and picture processing
should be off by default, for the purpose of displaying the original signal
as faithfully as possible with the minimum of processing.

"Paul Ratcliffe" wrote in message
...
On Mon, 13 Nov 2006 18:06:31 -0000, John Russell

wrote:

ITU-R BT.656?
Raw, clocked, parallel 10 or 8-bit 4:2:2 YCbCr with separate sync
lines?
Something else?

No TV is going to MPEG _encode_ something on the way to displaying it
(unless it has a built in PVR/HDD which works from analogue inputs).

And the process of going from analogue to 10 or 8 bit is called
digitisation!
The analogue doesn't magically change and it doesn't follow that this
process is going to be perfect.

For all intents and purposes it is perfect. You clearly have no
understanding
of the difference between digitisation and compression, hence the rubbish
you
write in this thread.
I suggest you shut up before you make an even bigger **** of yourself than
you currently have.

A nice polite comment!

"Stephen" wrote in message
...
"John Russell" wrote in message
...
I have been tempted to buy a Toshiba LCD TV. Considering how good my
SKY+ broadcasts are on a CRT I wasn't expecting any problems. Well I
shocked by how poor the picture is. After much deliberation I
realised
what the problem is. An LCD is a Digital Display, it has to work out
what colour each LCD element has to be. So it has to work using
video, and that means its digitises the analogue inputs connected,
and
that creates the MPEG artefacts.

Re the mpeg reference, that's complete & utter rubbish. See David
Robinson's post. If you are seeing mpeg artifacts they'll have been in
the original stream.

Indeed. Alternatively, he might be mistaking other (genuine)
artefacts for MPEG ones.

Nothing to worry about then!
I shall rephrase and say I'm seeing digitisation artefacts.

I quite agree that LCD TV's appear to show MPEG artefacts which are not
there on a CRT, and they make the pictures look cartoon like into the
bargain. Why they do it could be down to a combination of several types of
picture processing but mainly it will be sharpening. Another factor may be
deinterlacing which will make certain parts of one field remain fixed on
the
screen for the duration of 2 fields and could be causing some of the
increased visibility of the MPEG artefacts.

Also it might be that the picture processing was optimised for the US
market
where the screen would only need to display Analogue NTSC or full HD.
Neither of these will have MPEG artefacts of the same size as those in our
625 line RGB signals. Analogue NTSC, if it has MPEG artefacts at all, will
have them at a larger size with lower amplitude, while with HD they will
be
of a much smaller size. Perhaps the sharpening works well on these
signals,
but on our signals it exaggerates details of just the wrong size, and
brings
out our MPEG artefacts.

In any case what we need is regulation, and an organisation like BREMA to
set down standards for flatscreen, LCD and Plasma TV's with Benchmarking
for
TVs along the same lines as the Benchmarking of aerials for Freeview. We
should specify standards for Flatscreens and place an import levy on
models
which do not meet the standard. The standard should specify that
flatscreens
will be manufactured with a native resolution which matches the TV
broadcasts they are intended to receive in Europe, 576 x 1024 for standard
definition or 1080 x 1920 for HD, and that resizing and picture processing
should be off by default, for the purpose of displaying the original
signal
as faithfully as possible with the minimum of processing.



At last a sensible answer from someone who can admit LCD's "contribute" to
producing problems created else where in the chain.

TV's are not like hi-fi. If you buy an expensive Hi-If system you can make
sure you buy a front end is good enough to match the clarity of the amp and
speakers. TV's deal with "broadcast media" and have to handle the crap
supplied to them. CRT's appear to be much better at that!

"John Russell" wrote in message
...

"Stephen" wrote in message
...
"John Russell" wrote in message
...
I have been tempted to buy a Toshiba LCD TV. Considering how good my
SKY+ broadcasts are on a CRT I wasn't expecting any problems. Well I
shocked by how poor the picture is. After much deliberation I
realised
what the problem is. An LCD is a Digital Display, it has to work out
what colour each LCD element has to be. So it has to work using
video, and that means its digitises the analogue inputs connected,
and
that creates the MPEG artefacts.

Re the mpeg reference, that's complete & utter rubbish. See David
Robinson's post. If you are seeing mpeg artifacts they'll have been
in
the original stream.

Indeed. Alternatively, he might be mistaking other (genuine)
artefacts for MPEG ones.

Nothing to worry about then!
I shall rephrase and say I'm seeing digitisation artefacts.

I quite agree that LCD TV's appear to show MPEG artefacts which are not
there on a CRT, and they make the pictures look cartoon like into the
bargain. Why they do it could be down to a combination of several types
of
picture processing but mainly it will be sharpening. Another factor may
be
deinterlacing which will make certain parts of one field remain fixed on
the
screen for the duration of 2 fields and could be causing some of the
increased visibility of the MPEG artefacts.

Also it might be that the picture processing was optimised for the US
market
where the screen would only need to display Analogue NTSC or full HD.
Neither of these will have MPEG artefacts of the same size as those in
our
625 line RGB signals. Analogue NTSC, if it has MPEG artefacts at all,
will
have them at a larger size with lower amplitude, while with HD they will
be
of a much smaller size. Perhaps the sharpening works well on these
signals,
but on our signals it exaggerates details of just the wrong size, and
brings
out our MPEG artefacts.

In any case what we need is regulation, and an organisation like BREMA to
set down standards for flatscreen, LCD and Plasma TV's with Benchmarking
for
TVs along the same lines as the Benchmarking of aerials for Freeview. We
should specify standards for Flatscreens and place an import levy on
models
which do not meet the standard. The standard should specify that
flatscreens
will be manufactured with a native resolution which matches the TV
broadcasts they are intended to receive in Europe, 576 x 1024 for
standard
definition or 1080 x 1920 for HD, and that resizing and picture
processing
should be off by default, for the purpose of displaying the original
signal
as faithfully as possible with the minimum of processing.



At last a sensible answer from someone who can admit LCD's "contribute" to
producing problems created else where in the chain.

TV's are not like hi-fi. If you buy an expensive Hi-If system you can make
sure you buy a front end is good enough to match the clarity of the amp
and speakers. TV's deal with "broadcast media" and have to handle the crap
supplied to them. CRT's appear to be much better at that!


If the artefacts I'm seeing now, and not before, are inherent too DVB
shouldn't decoders remove them? Having to wait to end of the chain to remove
them is a bit like having Dolby noise reduction but not having the
de-emphasis in the cassette player, but in the amp instead.

The only time I ever say the "mosaic" artefact with my previous CRT's was
when I had contrast enhancement enabled. I didn't need to use an MPEG filter
on a high setting to remove them, just turning off contrast enhancement was
enough!

Lurking in this thread, I've suspected all along that your problem is a
combination of:

* Perhaps your new TV is bigger than your old one, or is additionally HD,
in which case flaws in the signal would be more visible.

* A natural tendency of the owner of a new product to examine it more
critically for a while, and therefore to notice things more than with the
one it replaced.

* The better definition of an LCD showing up deficiencies in the source
signal that were less obvious on a CRT. In particular, the pixels of the
former turn on and off relatively suddenly (although they do have time
delays) while with the latter, the initial excitation intensity of the
phosphor dot dies away exponentially, and the persistence of the phosphor
and the intensity of the beam's initial impulse on it must be arranged in
such a way that despite this exponential decay the picture persists long
enough for the two half scans of an interlaced image to overlap; all this
means that the initial intensity of the dot has to be very bright indeed,
and hence that any given dot doesn't just turn on and off but cycles through
a very wide range of intensities. I have a feeling (that is to say, it
seems to me a reasonable guess but I am not aware of any scientific
investigation) that maybe this interacts with our persistence of vision to
lose some detail in the picture, and hence that deficiencies in the original
signal are not so noticeable on a CRT.

BTAIM, Your last post proves that the problems are with the signal rather
than the LCD, because you were able to adjust the settings in the CRT first
to see them and then to remove them again. There may also be a setting that
you can adjust in the LCD. With mine, I tend to turn off as much processing
as possible, so that the TV just displays the signal as received.

I notice compression artefacts on many Freeview broadcasts - FTA satellite
tends to be better - and even on some DVDs. Commonly they occur in
detailed pictures containing significant movement - shoals of fish or
flocks of birds wheeling and turning en masse, or close-ups of flames, you
know the sort of thing. But they're flaws in the signal, you can't really
blame the receiver technology for faithfully reproducing the signal.

"John Russell" wrote in message
...

If the artefacts I'm seeing now, and not before, are inherent too DVB
shouldn't decoders remove them? Having to wait to end of the chain to
remove
them is a bit like having Dolby noise reduction but not having the
de-emphasis in the cassette player, but in the amp instead.

The only time I ever say the "mosaic" artefact with my previous CRT's was
when I had contrast enhancement enabled. I didn't need to use an MPEG
filter
on a high setting to remove them, just turning off contrast enhancement
was
enough!

Java Jive wrote:

[...] and hence that deficiencies in the original
signal are not so noticeable on a CRT.

A nice idea and there may be something in it, but if you cast your mind
back to the time when lots of people started buying 100Hz CRT sets, the
same discussions arose. "Why does Sky look worse on my 100Hz Sony?", all
that kind of stuff.

In general, a likely cause of accidental enhancement of compression
artefacts in interlaced source material is a deinterlacing algorithm
mistaking block noise for genuine motion which it then tries to interpolate.

--
TTFN, Andrew Hodgkinson
Find some electronic music at: Photos, wallpaper, software and mo
http://pond.org.uk/music.html http://pond.org.uk/

John Russell wrote:

If the artefacts I'm seeing now, and not before, are inherent too DVB
shouldn't decoders remove them?

....more usefully, the broadcasters shouldn't add them in the first
place.

Are you going to tell them, or shall I? After all, it's _my_ BBC.

(Ah, no, that was last year - now "this is what we do" so get stuffed
if you don't like it!)


FWIW it's possible to view an SD interlaced picture on an LCD and have
it look OK - but it takes some serious yet careful processing.

The next best option is to turn all the processing off, which will
leave you with...

Broadcast stream
MPEG-decoder
DA
SCART
AD
bob de-interlace
resize
(often) frame-rate convert (sadly)
display driver
display

With a CRT, you avoid bob de-interlace, resize, and (unless you buy a
100Hz TV) frame-rate convert. No wonder it looks better!

With LCD or plasma, you will typically have de-noise and over-sharpen
in there somewhere, unless you specifically switch them off.

Hope this helps. If you hadn't insisted that your TV was MPEG encoding
everything, you could have had a nice answer immediately!

Cheers,
David.

wrote in message
oups.com...
John Russell wrote:

If the artefacts I'm seeing now, and not before, are inherent too DVB
shouldn't decoders remove them?

...more usefully, the broadcasters shouldn't add them in the first
place.

Are you going to tell them, or shall I? After all, it's _my_ BBC.

(Ah, no, that was last year - now "this is what we do" so get stuffed
if you don't like it!)


FWIW it's possible to view an SD interlaced picture on an LCD and have
it look OK - but it takes some serious yet careful processing.

The next best option is to turn all the processing off, which will
leave you with...

Broadcast stream
MPEG-decoder
DA
SCART
AD
bob de-interlace
resize
(often) frame-rate convert (sadly)
display driver
display

With a CRT, you avoid bob de-interlace, resize, and (unless you buy a
100Hz TV) frame-rate convert. No wonder it looks better!

With LCD or plasma, you will typically have de-noise and over-sharpen
in there somewhere, unless you specifically switch them off.

Hope this helps. If you hadn't insisted that your TV was MPEG encoding
everything, you could have had a nice answer immediately!

That certainly doesn't excuse the response of one person who shall remain
nameless because I can't be bothered to find his post in the thread!

At last a sensible answer from someone who can admit LCD's "contribute"
to producing problems created else where in the chain.
TV's are not like hi-fi. If you buy an expensive Hi-If system you can
sure you buy a front end is good enough to match the clarity of the amp
and speakers. TV's deal with "broadcast media" and have to handle the
supplied to them. CRT's appear to be much better at that!

If the artefacts I'm seeing now, and not before, are inherent to DVB
shouldn't decoders remove them?

They are supposed to be at an acceptably low level already and should not
need removing.

Having to wait to end of the chain to remove
them is a bit like having Dolby noise reduction but not having the
de-emphasis in the cassette player, but in the amp instead.

I think it's more like having a normal cassette player or CD player with a
very strange kind of "hi-fi" amplifier which applies several types of
processing to the audio, and doesn't let you turn the processing off.

Something vaguely equivalent would be an amp that takes in digital audio at
one sampling frequency, changes it to another sampling frequency, applies a
low pass filter to avoid aliasing caused by the resampling, then a special
kind of hf boost which creates higher frequencies which weren't there in the
first place from lower ones, to try and make up for the loss of bandwidth
due to the resampling, then adds a bit of compressor/limiting and peak
clipping to try and make the sound a bit more "punchy". In other words a
complete mess which would end up producing a distorted and unnatural sound.
This is the sort of thing LCD and Plasma TV's do, which is why they produce
the kind of distorted and unnatural pictures we see.

On Tue, 14 Nov 2006 16:04:56 -0000, "Stephen"
wrote:

...
This is the sort of thing LCD and Plasma TV's do, which is why they produce
the kind of distorted and unnatural pictures we see.

Well, I don't see them on my Sony KDL-V32A12U Bravia. Having said that,
I spent several days tweaking it to get an acceptable picture which,
'out of the box', it wasn't.

I still reckon that it now gives the best picture that I've seen outwith
a studio production control room.

As an aside, we were in Currys this morning and I commented on the crap
pictures on their tellys. The man agreed.

--
Alan White
Twenty-eight miles NW of Glasgow, overlooking Lochs Long and Goil in Argyll, Scotland.
Webcam and weather:- http://windycroft.gt-britain.co.uk/weather
Some walks and treks:- http://windycroft.gt-britain.co.uk/walks