HDTVs and audio
 

Dave Plowman (News) wrote:

I'd say a digital CRT set pretty rare. Can't remember ever seeing one.

There were a few. I remember a few Sonys owned by customers. There was
also a cheapo set that very obviously had the DTT crudely inserted. The
two sets of on-screen graphics were quite different. It was possible to
select RGB on the DTT menu and then find that the picture had PAL artifacts.

There again, I once encountered a telly with built-in Sky!

Bill

HDTVs and audio
 

In article ,
Bill Wright wrote:
You're going to be *very* disappointed when you change from CRT to LCD.
Until the memory of what a TV picture should look like fades.


I think the point has been reached where LCD represents what TV should
look like at least as well as CRT. The geometry is invariably better,
for one thing.

Yes, the geometry is generally good unlike many widescreen CRT sets. It's
the colour which is poor, especially round the critical fleshtones area.

--
*How's my driving? Call 999*

Dave Plowman London SW
To e-mail, change noise into sound.

HDTVs and audio
 

Bill Wright wrote:

I think the point has been reached where LCD represents what TV
should look like at least as well as CRT. The geometry is invariably
better, for one thing.

And, according to what I've read, the contrast ratio. Apparently the
*actual* contrast ratio delivered by CRT TVs was pretty crap compared
with modern LCDs and plasmas (of course).

--
SteveT

HDTVs and audio
 

Dave Plowman (News) wrote:

Yes, the geometry is generally good unlike many widescreen CRT sets.

"Generally"? How can it be anything other than perfect?

It's the colour which is poor, especially round the critical
fleshtones area.

Oh, I remember some really crap flesh tones on CRT TVs, too. In fact,
why should flesh tones be any worse on LCD TVs? Are you suggesting
that the gamut of the LCD filters is worse than the gamut of the CRT
phosphors? Do we have any evidence of this?

In my experience the biggest source of damage to flesh tones is an
incorrectly set up receiver (e.g. too much colour or too much contrast,
or too much other fancy processing) rather than something inherent in
the technology itself.

My Sony has excellent flesh tone rendition. It uses an LCD. My mum's
Samsung has poor flesh tones (cartoon-like). It also uses an LCD. It
was ever thus.

--
SteveT

HDTVs and audio
 

Steve Thackery wrote:

In my experience the biggest source of damage to flesh tones is an
incorrectly set up receiver (e.g. too much colour or too much contrast,
or too much other fancy processing) rather than something inherent in
the technology itself.

Agreed.


My Sony has excellent flesh tone rendition. It uses an LCD. My mum's
Samsung has poor flesh tones (cartoon-like). It also uses an LCD. It
was ever thus.


Agreed.

Bill

HDTVs and audio
 

On 04/01/2014 00:27, Steve Thackery wrote:



My Sony has excellent flesh tone rendition. It uses an LCD. My mum's
Samsung has poor flesh tones (cartoon-like). It also uses an LCD. It
was ever thus.




people have short memories.
surely I wasn't the only one who upon visiting people with colour CRT
sets would be greeted by tv shows in which the people appeared to be
dayglo orange? - I bought a colour set and I want proper colour!

--
Gareth.
That fly.... Is your magic wand.

HDTVs and audio
 

Johny B Good wrote:
On Thu, 02 Jan 2014 16:22:35 -0600, "Steve Thackery"
wrote:

Johny B Good wrote:

Once you've tried this exercise in observation, you'll be able
to better relate to the use of 'overscanning' in a modern day TV
sets when you come to google for references to this effect.

Well, I don't use overscanning. All of my viewing is in HD where
possible, and I have the TV set to pixel-to-pixel mapping at all
times.

To be honest I don't notice any of the typical compression
artefacts in HD, but I do get annoyed at how "soft" they've made
the pictures (presumably to reduce the bandwidth requirements).
They aren't *really* 1920 x 1080, because the fine details smooth
out at a far larger scale than the individual pixels. They're just
transmitted as such.

To be fair, it's not a particularly noticable effect until you get
bored by the picture content and let your gaze wander off to the
edges. Once you've spotted this 'edge effect' (usually on very slow
pans with bland mid tone backgrounds), you're more likely to spot it
almost every time the picture content becomes less than attention
grabbing.

Even at its most obvious, the effect isn't a serious distraction in
dire need of removal by 'overscanning'. It's just that this seems to
be the only "good" reason for having an 'overscan' option at all.


Not watching much TV and then watching mostly what little I do in HD, I
hadn't really spotted this previously.

Looking at toy story 3 which I recorded SD and HD out of interest to
compare with dvd/br I can rarely see what you mean (maybe progressive
animation isn't as bitrate challenged as other stuff).

The artifacts I previously mentioned which are stable lines are far more
present time wise, and I suspect are not mpeg, but will mean more bits
are needed near the edges.

Having read a bit about how mpeg works I couldn't really think why it
would treat the edged differently. So I decided to recode the bbc sd to
a really crappy bit rate with ffmpeg and sure enough the edges were
worse than the rest.

Doing the same with the DVD however didn't make the sides any worse than
the rest, so either the fixed artifacts of the broadcast or the fact
that the dvd was full 720 and the bbc was 704 in 720 was to blame, and a
further test with the dvd seems to show that it's the 8px sidebars that
are the problem. If I scale the dvd to 704 add sidebars and then code to
a silly 600kbit as before, the edges do look worse than the rest on pans
just like the bbc version does.

So rather than an mpeg "strategy" I guess this is more a
deficiency/issue/feature to do with black bars. I don't know why but
8px is dct block size for luma, but only half of a 420 chroma block, and
it's also only half a macro block for motion comp - hmm.

HDTVs and audio
 

In article , Andy
Furniss [email protected] wrote:
Johny B Good wrote:


To be fair, it's not a particularly noticable effect until you get
bored by the picture content and let your gaze wander off to the
edges. Once you've spotted this 'edge effect' (usually on very slow
pans with bland mid tone backgrounds), you're more likely to spot it
almost every time the picture content becomes less than attention
grabbing.


Having read a bit about how mpeg works I couldn't really think why it
would treat the edged differently. So I decided to recode the bbc sd to
a really crappy bit rate with ffmpeg and sure enough the edges were
worse than the rest.

Part of the mpeg progess is to find 'moving blocks' so they can be redrawn
with a shift in later frames. Maybe the edge of the image means this can't
work as well because anything moving 'into the picture' can't be reduced
because it is 'new'. No idea if this *is* the reason, though. Not looked
for the effect or thought about this before now.

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

HDTVs and audio
 

Jim Lesurf wrote:
In article , Andy
Furniss [email protected] wrote:
Johny B Good wrote:


To be fair, it's not a particularly noticable effect until you
get bored by the picture content and let your gaze wander off to
the edges. Once you've spotted this 'edge effect' (usually on
very slow pans with bland mid tone backgrounds), you're more
likely to spot it almost every time the picture content becomes
less than attention grabbing.


Having read a bit about how mpeg works I couldn't really think why
it would treat the edged differently. So I decided to recode the
bbc sd to a really crappy bit rate with ffmpeg and sure enough the
edges were worse than the rest.

Part of the mpeg progess is to find 'moving blocks' so they can be
redrawn with a shift in later frames. Maybe the edge of the image
means this can't work as well because anything moving 'into the
picture' can't be reduced because it is 'new'. No idea if this *is*
the reason, though. Not looked for the effect or thought about this
before now.

Yea, I don't know either, but to be clear for anyone reading just this
snipped post - my tests showed that it wasn't actually the edges that
were to blame.

The BBC sample is 704 wide and padded to 720 with 8px black left right.
It seems the padding is the reason. Because the BBC version had some
extra artifacts near the edges that I expected would eat bits I then
tested with my dvd which didn't (wasn't perfect though).

So this is what I see in the tests with the cleaner dvd when coded to a
low bitrate - the dvd has a full 720 picture.

Just recode to low rate = OK edges.

Scale to 704 and pad to 720 like the BBC = bad edges.

Scale to 704 and leave as 704 = OK edges.

Scale to 688 and pad 16px x2 to make 720 = OK edges.