Why interlaced HDTV?

H264 goes the world wrote:
Agamemnon,

Do you know the MPEG4 - Part10, aka H.264 spec? There are features
like PAFF and MBAFF, i.e. Picture Adaptive frame/field and Macroblock
Adaptive Frame/Field. I have seen one encoder already doing PAFF.


Indeed. This is described on pages 7-9 in he

http://www.cs.ubc.ca/~krasic/cpsc538...c-overview.pdf

e.g.

"To provide high coding efficiency, the H.264/AVC
design allows encoders to make any of the following decisions
when coding a frame.

1) To combine the two fields together and to code them as
one single coded frame (frame mode).
2) To not combine the two fields and to code them as separate
coded fields (field mode).
3) To combine the two fields together and compress them as
a single frame, but when coding the frame to split the pairs
of two vertically adjacent macroblocks into either pairs of
two field or frame macroblocks before coding them."

and

"If a frame consists of mixed regions where some regions are
moving and others are not, it is typically more efficient to code
the nonmoving regions in frame mode and the moving regions
in the field mode."



Doing it on the macroblock level is more complex, so it will come in
future releases and also it is more heavy on the decoder side (more
expensive DSPs = more expensive set top).



Surely decoders will include this functionality and it's just a case of
waiting for encoders to implement it?


--
Steve - www.digitalradiotech.co.uk - Digital Radio News & Info

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"Adrian" wrote in message
...
Brian McIlwrath wrote:
Adrian wrote:

I won't be buying one that is less than 1920x1080

You will have a long wait!

I don't mind waiting.


Almost exactly a year ago there was some discussion of this issue in
this group under the thread 'HDTV sets available now', where Stephen
Neal had some useful comments to make.

At that time the same question was being asked, are the sets on the
market capable of the required resolution?
The problem being that the shadow mask had to have a very fine dot
pitch similar to that of a computer monitor if the screen was of
modest size, say around 20 inch.

The industry has moved forward and large screens are the order of the
day, but a year ago Stephen Neal wrote:
Quote "AIUI the only direct view CRT on sale in the US that fully
resolves the 1920x1080 standard is a 34 or 36" Sony - and it is
apparently quite a lot dimmer than the softer models. A larger screen
means a coarser aperture grille can be used whilst still retaining the
resolution across the whole screen area." End quote.

I don't know if any Sony, Panasonic or other CRT's are offering the
native 1920 x 1080 resolution, but if there are any I'd be interested
in model numbers so I can have a look in store to see if they are
still dimmer than their softer counterparts.

Unfortuntely all HDTV demo's are using plasma screens, presumably
because the industry wants to associate HDTV with the latest type of
display and not with what joe public might perceive as old fashioned
tellys.

Roger

"Brian McIlwrath" wrote in message
...
Adrian wrote:

: I won't be buying one that is less than 1920x1080

You will have a long wait!

This September, Philips will be releasing their 1920x1080 "True HD"
sets.
Check out the 37PF9830 for example. Around 4000 euro retail here on
the continent.

On 17 Aug 2005 02:49:06 -0700, "
wrote:

FWIW 50Hz progressive content displayed on a CRT can flicker badly
(depending on the phosphors) unless it's interlaced to 100Hz, and
there's an argument for using more than 50fps anyway to reduce flicker
on CRTs and motion blur on LCDs.

At launch in this country practically nobody will be using a HD CRT
set to view HD material and within a few years the CRT % numbers will
be even lower. We are moving to a world where all displays (LCD,
plasma etc) will be natively progressive and interlaced material will
have to be frame stored within the set. IMHO to spec an interlaced
system for HD which is then going to have to be de-interlaced using
the (variable quality) hardware of the TV is insane.

On flat progressive displays 720p looks the same if not better than
1080i and has the advantage of better rendering of movement.

1080p would of course be preferable to both....

Rgds
Jonatham

In article , Jc wrote:
At launch in this country practically nobody will be using a HD CRT
set to view HD material and within a few years the CRT % numbers will
be even lower. We are moving to a world where all displays (LCD,
plasma etc) will be natively progressive and interlaced material will
have to be frame stored within the set. IMHO to spec an interlaced
system for HD which is then going to have to be de-interlaced using
the (variable quality) hardware of the TV is insane.

Would you suggest the same policy for gamma correction? As it's a
pre-distortion applied in the camera to compensate for the
characteristics of a CRT, we shouldn't, in theory, need it in a flat
panel broadcasting world, and doing without would make post-production
colour correction much simpler. How many established standards and
practices do you think it would be wise to abandon all in one go?

Rod.

In article , Roderick
Stewart writes

Would you suggest the same policy for gamma correction? As it's a
pre-distortion applied in the camera to compensate for the
characteristics of a CRT, we shouldn't, in theory, need it in a flat
panel broadcasting world, and doing without would make post-production
colour correction much simpler.

Whilst gamma was originally intended to compensate for the response
characteristics of a typical CRT, by one of those amazing coincidences
it is almost exactly the correct function to compensate for the
perceptual response of the human eye - the eye is close to the inverse
response of the CRT.

Without gamma we need about 18-bits of linear intensity coded video to
produce the same dynamic range that an 8-bit gamma 2.2 picture is
capable of producing (ignoring the contrast limitations of the display
itself. Even then, most of the data that 18-bit signal will carry is
redundant, particularly in the mid tones and highlight regions, because
we only need the full precision of that bit depth in the shadows.

In other words, if gamma was not already in use, we would need to invent
something very similar to it even for linear response displays unless we
were to adopt very high bit video encoding.

See http://www.poynton.com/notes/colour_.../GammaFAQ.html

So, whilst your claim that in theory we don't need gamma is correct,
without gamma we would have to use something much more cumbersome, and
it certainly wouldn't make post production or colour correction any more
simpler.
--
Kennedy
Yes, Socrates himself is particularly missed;
A lovely little thinker, but a bugger when he's ****ed.
Python Philosophers (replace 'nospam' with 'kennedym' when replying)

Kennedy McEwen wrote in
:


Whilst gamma was originally intended to compensate for the response
characteristics of a typical CRT, by one of those amazing coincidences
it is almost exactly the correct function to compensate for the
perceptual response of the human eye - the eye is close to the inverse
response of the CRT.

I was brought up in them days, even to messing with the transfer
characteristic of image orthicons

snip explanatio

but what I don't understand is why flat screens seem so black crushed.

(which is a bit of a laugh because my Philips abortion, among it's other
lacks, can't get anywhwere near black anyway)

But on the grey backgound, I seem to be totally unable to get anything
between alleged black and low mid tones.

Is this a funtion of all LCDs? and will it always be.

IOW, I guess I'm asking if future pictures will always be as bad?

mike

"rookie" wrote in message
...

"Brian McIlwrath" wrote in message
...
Adrian wrote:

: I won't be buying one that is less than 1920x1080

You will have a long wait!

This September, Philips will be releasing their 1920x1080 "True HD"
sets.
Check out the 37PF9830 for example. Around 4000 euro retail here on
the continent.

Link please

I can only find 37PF9830 on the Philips Netherlands site, but the
details are in Dutch, and the translation engines don't work for
Dutch/English.

I tried the search in the French and German sites, (that do work in
the language translators) but they just return 'no results'.

Roger

On 22 Aug 2005 10:52:27 GMT, mike ring
wrote:

Kennedy McEwen wrote in
:


Whilst gamma was originally intended to compensate for the response
characteristics of a typical CRT, by one of those amazing coincidences
it is almost exactly the correct function to compensate for the
perceptual response of the human eye - the eye is close to the inverse
response of the CRT.

I was brought up in them days, even to messing with the transfer
characteristic of image orthicons

snip explanatio

but what I don't understand is why flat screens seem so black crushed.


I have a feeling that it's probably marketing. If you look at the
default settings for most modern TVs the contrast is way too high and
the brightness too low giving a nastyy combination of crushed blacks
and blown out highlights, however it gives an initial impression of
sharp bright pictures to the uncritical eye. CF the Sony Trinitron
effect; when Sony introduced the Trinitron most ordinary viewers said
that the picture was better than normal TVs, because the tube could
give a brighter image. In other respects, like resolution the average
Trinitron was worse than a standard dotty shadowmask.

A couple of years ago I bought a projector. The factory setup gives
terrible black crushing; in order to get a decent picture you have to
get into the menus and tweak the gamma to the opposite end of the
range from the factory setting. Again I assume it was set like that to
give an initial impression of sharp contrasty pictures.

(which is a bit of a laugh because my Philips abortion, among it's other
lacks, can't get anywhwere near black anyway)

But on the grey backgound, I seem to be totally unable to get anything
between alleged black and low mid tones.

Is this a funtion of all LCDs? and will it always be.

IOW, I guess I'm asking if future pictures will always be as bad?

I haven't seen a good flat panel display yet, but they do seem to be
improving, and I would expect them to eventually get to an acceptable
quality level.

Bill

In article , Kennedy McEwen wrote:
Would you suggest the same policy for gamma correction? As it's a
pre-distortion applied in the camera to compensate for the
characteristics of a CRT, we shouldn't, in theory, need it in a flat
panel broadcasting world, and doing without would make post-production
colour correction much simpler.

Whilst gamma was originally intended to compensate for the response
characteristics of a typical CRT, by one of those amazing coincidences
it is almost exactly the correct function to compensate for the
perceptual response of the human eye - the eye is close to the inverse
response of the CRT.

If what you say were true, i.e. if our eyes really did correct for the
CRT's characteristic, why would it be necessary also to include electronic
correction for it in the camera? That would be two lots of correction,
wouldn't it?

Actually my previous posting was intended to highlight the unwisdom of
abandoning technical standards in broadcasting just because of the
invention of one new piece of equipment. A system such as broadcasting
that involves a lot of equipment owned by a lot of people needs standards
that will not be changed overnight, even if it a better system might
hypothetically have resulted from scrapping the entire system and starting
again. Interlace, gamma correction, and various other technical features
of television have been used for about seventy years and are now in use in
millions of items of equipment all over the world, so that changing any of
them would have enormous financial consequences and incur widespread
conmfusion. Look at he number of wrongly adjusted TV pictures resulting
from the simple decision to change something no more complicated or
obscure than its shape, something that you would think anyone could see
and understand easily.

Rod.