720p or 1080i??

[DAVO]

I apologise if this has been discussed before as I'm sure it probably
has, but can someone please tell me if 1080i has more resolution than 720p?
I had a techie tell me because 720p is progressive scanning it is a better
option than the 1080i interlaced.

When I asked what did he mean by that, he said progressive scanning is like
doubling the resolution of interlaced meaning that 720p would need to have a
1440i to be equal. Is this correct?

DAVO

[Byron Forbes]

"DAVO" <davideo@hotmail.com> wrote in message
news:JqGVc.1825$D7.925@news-server.bigpond.net.au...
> I apologise if this has been discussed before as I'm sure it probably
> has, but can someone please tell me if 1080i has more resolution than
720p?
> I had a techie tell me because 720p is progressive scanning it is a better
> option than the 1080i interlaced.
>
> When I asked what did he mean by that, he said progressive scanning is
like
> doubling the resolution of interlaced meaning that 720p would need to have
a
> 1440i to be equal. Is this correct?
>

I'd say the difference between the 2 would be just about zero. What is
the screen being used anyway?

[schmegg]

There are plenty of experts about that know more about this than me - but theyre probably a little tired of answering these types of questions - so I'll give you my knowlege.

The number (1080/720/576) is the number of lines that make up the picture. Simplifying it a little (a lot) - you can say that this number represents the number of pixels vertically in the image. Therefore 720p is vertically roughly the same as the 1024x768 pixel mode on your PC. (720 pixels versus 768 pixels). Likewise, 1080i has 1080 lines (for our purposes 1080 pixels) so its roughly the same as the 1280x1024 pixel mode on your PC.

However - with TV the aspect ratio of the picture is 16:9 (not 4:3 like your PC) so the horizontal resolution (number of pixels horizontally) is greater.

I believe the digital TV standards are :-

1920x1080, 1280x720 & 720x576 - the bigger the numbers, the higher the resolution.

OK - that deals with the numbers (i hope).

The i and p describe how the image is drawn onto the screen. With a standard old PAL TV, the picture is 720x576i

This means the picture is 720x576 pixels in resolution and is rendered in "interlaced" mode. In interlaced mode, the TV will only draw half the lines that make-up the picture during each screen refresh (typically around 50 times a second - 50Hz). Then, on the following screen refresh, the TV draws the other half of the lines from the next frame of picture information. It does this by drawing the even numbered lines on the first refresh then the odd numbered lines on the second refresh. Hence the image is "interlaced" with the next frame of information. (I can imagine the experts cringe at this explanation - but read on)

With "progressive" scanning, the screen simply draws the full screen of lines from top to bottom during each screen refresh. With 576p therefore, there is no extra resolution to standard PAL (576i) but the picture will appear a little crisper due to the fact the picture information hasn't been interleaved with the adjacent frame (which will be a little different in most cases to the current frame due to movement, lighting changes etc). This makes progressive mode more attractive for some sports watchers as video of sport usually contains a lot of movement which causes (very slight) blurring on the image as the consecutive frames are interlaced together onto your screen.

So - if your still with me - this is what it all means.

1080i mode has the highest resolution but is interlaced.
720p mode has less resolution but is progressive.
576p mode is PAL resolution with progressive scanning.

What's the best I hear you say - well first of all there aren't (at the moment) too many TVs with a native screen resolution of 1920x1080. My 50" LCD Rearpro is 1280x720 native, which means when its displaying 1080i sources it will need to internally downscale the image from 1920x1080 to 1280x720 before it can display it. Therefore the BEST resolution I can achieve is 1280x720 - regardless of the source resolution. Your setup may very well be similar (almost all are at the moment, although 1920x1080 screens are now starting to become available - check your TV specs).

At the end of the day resolution is not the 'be all and end all' of a good picture. You should try to minimise the number of times your system rescales the image before it is displayed. In my case this means setting my settop box to output 720p which is the native resolution of my screen. This removes the necessity for the TV to rescale the image because it arrives at the TV inputs at the native screen resolution. If I set my HD box to output at 1080 then every time I recieve a broadcast in anything other than 1080 the box would first upscale the image to 1080 then send it to the TV which then would have to downscale it to 720 for display. All this image scaling is bad for image quality and should be avoided if possible.

If your HD box can be set to output the broadcast resolution (ie 1080 when broadcast is 1080, 576 when broadcast is 576), this is worth trying as then all the scaling will be done by your TV instead of your settop box. One of the scalers will probably give better results than the other - experiment, find the best one, and set up your system to use it.

When all is said and done all this stuff dosen't matter much at all. Its for the techies to argue about. What matters is how the picture looks!

When shopping for the best set of speakers - don't worry about brand names etc. Use your ears and buy what sounds best.
With HDTV setups the same applies - use your eyes! What looks good IS good!

Schmegg


I apologise if this has been discussed before as I'm sure it probably
has, but can someone please tell me if 1080i has more resolution than 720p?
I had a techie tell me because 720p is progressive scanning it is a better
option than the 1080i interlaced.

When I asked what did he mean by that, he said progressive scanning is like
doubling the resolution of interlaced meaning that 720p would need to have a
1440i to be equal. Is this correct?

DAVO

[Winston [ausWY]]

A lot of film based 1080 content is actually broadcast in progressive but
tagged as interlaced, eg CSI: Miami, 2.5 Men, Smallville, Raymond, Gilmore
Girls, etc, etc. If you have a display that can do 1080p & can tell the
decoder not to deinterlace it (treat the image as progressive), then'll you
be able to see them in 1080p @ 25fps without interlacing artifacts. :)
That's how I watch HDTV on my computer ;).

"schmegg" <schmegg.1bcdia@no-mx.forums.eyo.com.au> wrote in message
news:schmegg.1bcdia@no-mx.forums.eyo.com.au...

> So - if your still with me - this is what it all means.
>
> 1080i mode has the highest resolution but is interlaced.
> 720p mode has less resolution but is progressive.
> 576p mode is PAL resolution with progressive scanning.

[schmegg]

Cool - didn't know that! (first day in the newsgroup and this is just the sort of stuff I was hoping to discover)

Regretably my PC card won't do this so I can't check it out. (TV is only 1280x720) Are there any TV screens that will do 1080p?

When you do get an properly interlaced 1080i broadcast, how does it look at 1080p?

And finally - sorry bout all the questions - what PC card do you use?

Thanks for the info ...
Schmegg.

']A lot of film based 1080 content is actually broadcast in progressive but
tagged as interlaced, eg CSI: Miami, 2.5 Men, Smallville, Raymond, Gilmore
Girls, etc, etc. If you have a display that can do 1080p & can tell the
decoder not to deinterlace it (treat the image as progressive), then'll you
be able to see them in 1080p @ 25fps without interlacing artifacts. :)
That's how I watch HDTV on my computer ;).

"schmegg" <schmegg.1bcdia@no-mx.forums.eyo.com.au> wrote in message
news:schmegg.1bcdia@no-mx.forums.eyo.com.au...

> So - if your still with me - this is what it all means.
>
> 1080i mode has the highest resolution but is interlaced.
> 720p mode has less resolution but is progressive.
> 576p mode is PAL resolution with progressive scanning.

[DAVO]

Thanks guys, in particular Schmegg for your concise description. My monitor
is an LG LCD KT17LZ21 AHPLKG and the set top box is a Panasonic TU HDT 104A.
I take Schmegg's point with regard to testing these things by the ear or
eyes and not by the specs, something I have been saying myself for years.
Recently I saw a Sharp Aquos 30" LCD and the picture quality blew me away as
did the bloody price.....$5,900 for 30 inches, but certainly the best HD
picture I have ever seen. If I can find a way of connecting my 17"w/s laptop
(Toshiba Satellite P20) to the STB I will even try that to get the best
picture quality. Once again, thanks.

DAVO

[Mike]

DAVO wrote:
> Thanks guys, in particular Schmegg for your concise description. My monitor
> is an LG LCD KT17LZ21 AHPLKG and the set top box is a Panasonic TU HDT 104A.

Your LCD, like most current HD displays, won't do more than 720p
resolution anyway. So there is no extra benefit from 1080i.
Its a bit academic since we don't broadcast 720p in Oz.

In a fast-moving scence, interlaced modes can trade resolution for
frame-rate. Thats one way to think of it.

> If I can find a way of connecting my 17"w/s laptop
> (Toshiba Satellite P20) to the STB I will even try that to get the best
> picture quality. Once again, thanks.

You could put a DVB receiver card in an old PC, and stream the digital
TV to your laptop over ethernet or fast wireless (802.11g).

[Mike]

Winston [ausWY] wrote:
> A lot of film based 1080 content is actually broadcast in progressive but

You mean "filmed" in progressive?

> tagged as interlaced, eg CSI: Miami, 2.5 Men, Smallville, Raymond, Gilmore
> Girls, etc, etc. If you have a display that can do 1080p & can tell the
> decoder not to deinterlace it (treat the image as progressive), then'll you

Interesting. I just had a look at a 1080i recording of Drew Carey, with
the deinterlacer off. And bugger me - no interlacing!
Thanks. I've been wasting my (cpu) time with the deinterlacer.

Thats surprising, because US TV uses 30Hz/60Hz, and even if shot on
progressive 30/60Hz there, it would be interlaced after conversion to
our 1080i 25/50.

Maybe they actually shoot it on film at 24fps? In which case, we see a
nice progressive image, but the yanks get 3:2 pulldown interlaced.

> be able to see them in 1080p @ 25fps without interlacing artifacts. :)

What sort of artifacts do you see? Is it trying do de-interlace fields
from different frames?

Mine doesn't seem any different if I try do de-interlace a progressive
frame. You might want a better filter.
Am using mplayer with -lavcdeint . Some other deinterlacing software
I've seen isnt as good.

> That's how I watch HDTV on my computer ;).

[Winston [ausWY]]

Here's Adam's explaination as mentioned in my previous message:

"Yes, the medium is interlaced, but what he means is that the source is
progressive and therefore you can "piece" together every two fields into a
single progressive frame and you will not get any interlacing artifacts
because both fields are from the same moment in time. For display purposes
this is the same thing as 25p if you are viewing on a progressive display,
ie. you are getting a full progressive frame for each full frame of the
original source (film). The fact that the actual broadcast medium is
interlaced (50i) in this case, is irrelevant, as what you are seeing is 25p.

Of course if you are watching a program which is based upon source material
that is truly interlaced, ie. each field is from a successive moment in
time, then the above does not apply, however a progressive display device
will still attempt to deinterlace this material (since it can't natively
display interlace) -- but it won't be artifact free and won't correspond to
original film frames (interlaced material does not originate from film
anyway, but video).

Adam "

"Winston [ausWY]" <me@privacy.net> wrote in message
news:rg0Wc.3104$D7.1431@news-server.bigpond.net.au...
> AJL, all Australian 1080 transmissions are all indeed broadcast as 1080
with
> 50 interlaced fields per second. As you know, in order to acheive the full
> 50 fields per second, half of the fields are 1/50th of a second later,
> however, with film, 1/50th of a second later is the same, since the image
> only changed every 1/25th of a second, thus, you CAN view it as
progressive
> without any deinterlacing, if you don't believe me I can show you
> screenshots from the 9HD Demo where 50i HD is used and interlacing lines
can
> be seen, but where it is film based such as CSI there are no interlacing
> artifacts. Here's one of my earlier attempts at explaining this:
>
> Video has 50 frames per second, however there's only room for 25 frames
per
> second, interlaction puts two of those frames into one single frame by
using
> the odd fields for one 1/50th of a second frame and the even one for the
> frame proceeding immediately afterwards (or the other way around), since
> film is [sped up to] 25 frames per second and there's room for two fields,
> the next 1/50th frame would be the same since there are only 25 frames,
thus
> both the even and odd fields of the source is shown in that single frame
> making it progressive at 25fps.... I'm not really good at explaining these
> things, so have a look at these two screenshots, the one
> [http://img1.imageshack.us/files1/hd_50.JPG] is from HD video, and the one
> [http://img1.imageshack.us/files1/hd_25.JPG] is HD film, the screenshots
> have not been deinterlaced in anyway and as you can clearly see [when
viewed
> in full size] where the content is 50fps [HD content taken from video],
> there are interlaction artifacts but where the source material is 25fps
> [from film] there are no interlace artifacts whatsoever.
>
> There are 25 frames per second in the broadcast, interlacing (kinda of
like
> compression) allows for 50 frames to be shown by putting two 1/50th second
> frames into 1/25th second frame, since film is broadcast as 25fps (shot in
> 24fps), it doubles up, any given film frame is shown on two 50fps
interlaced
> frames, 1/50th of the second shows its odd fields, and the other 1/50th of
> the second shows its even fields, these two fields are the put together
onto
> the same 25fps HD 'interlaced' frame, since their from the same moment in
> time, there are no interlaction artifacts allowing for me to watch 1088p
on
> monitor . Now all I need is for someone good at explaining things to back
me
> up and make sense out of what I just said, though I quite like Adam's
> explanation. Also note a fair bit of 9 and 10's station graphics and IDs
> are made in 25fps.
>
> Winston,
>
> *Both captures taken direct off the Channel 9 HD stream Sydney using a
DVB-t
> card, resized to 1920x1080 with out deinterlacing, original frame size
> 1440x1088.
>
> "AJL" <someone@microsoft.com> wrote in message
> news:OWJVc.2045$D7.1797@news-server.bigpond.net.au...
> > Sshmegg is dead right in his first post, but Winston - what a lot of
> rubbish
> > re movies and 1080p in regard to HD DVB transmission. No network tx's
> > 1080p, only 1080i or 576p. Further the hdtv standard for interchange
is
> > 1080i, ie eg vtr tape & how the signals move around on the cables within
a
> > tv station. - so event if the Tanberg coders could handle it (which they
> > dont) the signal to the copers off tape or server is 1080i. . The
reason
> > 1080p is not used for tx is that hdtv crt sets cannot deal with the
freq.
> > (the scanning coils in domestic tube tv's would ppack it in) & of course
> the
> > only quality displays (grade A &B professional) are crt). Sorry to
> > disappoint all the plasma & crt folks - they have very poor colourimatry
> due
> > to the plasma tecnology not being a true 'black body source') - despite
> > their cost. The DVB TX stardard does include 720p & yes the second gen.
> > hdtv boxes will handle it, but no network is tx it to date
>
>

[Winston [ausWY]]

AJL, all Australian 1080 transmissions are all indeed broadcast as 1080 with
50 interlaced fields per second. As you know, in order to acheive the full
50 fields per second, half of the fields are 1/50th of a second later,
however, with film, 1/50th of a second later is the same, since the image
only changed every 1/25th of a second, thus, you CAN view it as progressive
without any deinterlacing, if you don't believe me I can show you
screenshots from the 9HD Demo where 50i HD is used and interlacing lines can
be seen, but where it is film based such as CSI there are no interlacing
artifacts. Here's one of my earlier attempts at explaining this:

Video has 50 frames per second, however there's only room for 25 frames per
second, interlaction puts two of those frames into one single frame by using
the odd fields for one 1/50th of a second frame and the even one for the
frame proceeding immediately afterwards (or the other way around), since
film is [sped up to] 25 frames per second and there's room for two fields,
the next 1/50th frame would be the same since there are only 25 frames, thus
both the even and odd fields of the source is shown in that single frame
making it progressive at 25fps.... I'm not really good at explaining these
things, so have a look at these two screenshots, the one
[http://img1.imageshack.us/files1/hd_50.JPG] is from HD video, and the one
[http://img1.imageshack.us/files1/hd_25.JPG] is HD film, the screenshots
have not been deinterlaced in anyway and as you can clearly see [when viewed
in full size] where the content is 50fps [HD content taken from video],
there are interlaction artifacts but where the source material is 25fps
[from film] there are no interlace artifacts whatsoever.

There are 25 frames per second in the broadcast, interlacing (kinda of like
compression) allows for 50 frames to be shown by putting two 1/50th second
frames into 1/25th second frame, since film is broadcast as 25fps (shot in
24fps), it doubles up, any given film frame is shown on two 50fps interlaced
frames, 1/50th of the second shows its odd fields, and the other 1/50th of
the second shows its even fields, these two fields are the put together onto
the same 25fps HD 'interlaced' frame, since their from the same moment in
time, there are no interlaction artifacts allowing for me to watch 1088p on
monitor . Now all I need is for someone good at explaining things to back me
up and make sense out of what I just said, though I quite like Adam's
explanation. Also note a fair bit of 9 and 10's station graphics and IDs
are made in 25fps.

Winston,

*Both captures taken direct off the Channel 9 HD stream Sydney using a DVB-t
card, resized to 1920x1080 with out deinterlacing, original frame size
1440x1088.

"AJL" <someone@microsoft.com> wrote in message
news:OWJVc.2045$D7.1797@news-server.bigpond.net.au...
> Sshmegg is dead right in his first post, but Winston - what a lot of
rubbish
> re movies and 1080p in regard to HD DVB transmission. No network tx's
> 1080p, only 1080i or 576p. Further the hdtv standard for interchange is
> 1080i, ie eg vtr tape & how the signals move around on the cables within a
> tv station. - so event if the Tanberg coders could handle it (which they
> dont) the signal to the copers off tape or server is 1080i. . The reason
> 1080p is not used for tx is that hdtv crt sets cannot deal with the freq.
> (the scanning coils in domestic tube tv's would ppack it in) & of course
the
> only quality displays (grade A &B professional) are crt). Sorry to
> disappoint all the plasma & crt folks - they have very poor colourimatry
due
> to the plasma tecnology not being a true 'black body source') - despite
> their cost. The DVB TX stardard does include 720p & yes the second gen.
> hdtv boxes will handle it, but no network is tx it to date

[AJL]

Hi again Winston & Adam, I still maintain it is interlaced - not
progressive, what you are saying is that when the film is scanned, there
was no movement due to the 25fps capture, thus less artifacts between the
lines - the question for debate is whether it is visible or not... Any still
image can benefit from this of course, but I take your point - however the
issue is actually one of motion blur, that is because of the 25p shutter
speed, I would suggest the diff, you see from film source material is motion
blur & he non linear nature of film colour & contrast - not the interlace
artifacts. You are oversimplifying the situation believe me.

AJL
"Winston [ausWY]" <me@privacy.net> wrote in message
news:wj0Wc.3109$D7.2557@news-server.bigpond.net.au...
> Here's Adam's explaination as mentioned in my previous message:
>
> "Yes, the medium is interlaced, but what he means is that the source is
> progressive and therefore you can "piece" together every two fields into a
> single progressive frame and you will not get any interlacing artifacts
> because both fields are from the same moment in time. For display purposes
> this is the same thing as 25p if you are viewing on a progressive display,
> ie. you are getting a full progressive frame for each full frame of the
> original source (film). The fact that the actual broadcast medium is
> interlaced (50i) in this case, is irrelevant, as what you are seeing is
25p.
>
> Of course if you are watching a program which is based upon source
material
> that is truly interlaced, ie. each field is from a successive moment in
> time, then the above does not apply, however a progressive display device
> will still attempt to deinterlace this material (since it can't natively
> display interlace) -- but it won't be artifact free and won't correspond
to
> original film frames (interlaced material does not originate from film
> anyway, but video).
>
> Adam "
>
> "Winston [ausWY]" <me@privacy.net> wrote in message
> news:rg0Wc.3104$D7.1431@news-server.bigpond.net.au...
> > AJL, all Australian 1080 transmissions are all indeed broadcast as 1080
> with
> > 50 interlaced fields per second. As you know, in order to acheive the
full
> > 50 fields per second, half of the fields are 1/50th of a second later,
> > however, with film, 1/50th of a second later is the same, since the
image
> > only changed every 1/25th of a second, thus, you CAN view it as
> progressive
> > without any deinterlacing, if you don't believe me I can show you
> > screenshots from the 9HD Demo where 50i HD is used and interlacing lines
> can
> > be seen, but where it is film based such as CSI there are no interlacing
> > artifacts. Here's one of my earlier attempts at explaining this:
> >
> > Video has 50 frames per second, however there's only room for 25 frames
> per
> > second, interlaction puts two of those frames into one single frame by
> using
> > the odd fields for one 1/50th of a second frame and the even one for the
> > frame proceeding immediately afterwards (or the other way around), since
> > film is [sped up to] 25 frames per second and there's room for two
fields,
> > the next 1/50th frame would be the same since there are only 25 frames,
> thus
> > both the even and odd fields of the source is shown in that single frame
> > making it progressive at 25fps.... I'm not really good at explaining
these
> > things, so have a look at these two screenshots, the one
> > [http://img1.imageshack.us/files1/hd_50.JPG] is from HD video, and the
one
> > [http://img1.imageshack.us/files1/hd_25.JPG] is HD film, the screenshots
> > have not been deinterlaced in anyway and as you can clearly see [when
> viewed
> > in full size] where the content is 50fps [HD content taken from video],
> > there are interlaction artifacts but where the source material is 25fps
> > [from film] there are no interlace artifacts whatsoever.
> >
> > There are 25 frames per second in the broadcast, interlacing (kinda of
> like
> > compression) allows for 50 frames to be shown by putting two 1/50th
second
> > frames into 1/25th second frame, since film is broadcast as 25fps (shot
in
> > 24fps), it doubles up, any given film frame is shown on two 50fps
> interlaced
> > frames, 1/50th of the second shows its odd fields, and the other 1/50th
of
> > the second shows its even fields, these two fields are the put together
> onto
> > the same 25fps HD 'interlaced' frame, since their from the same moment
in
> > time, there are no interlaction artifacts allowing for me to watch 1088p
> on
> > monitor . Now all I need is for someone good at explaining things to
back
> me
> > up and make sense out of what I just said, though I quite like Adam's
> > explanation. Also note a fair bit of 9 and 10's station graphics and
IDs
> > are made in 25fps.
> >
> > Winston,
> >
> > *Both captures taken direct off the Channel 9 HD stream Sydney using a
> DVB-t
> > card, resized to 1920x1080 with out deinterlacing, original frame size
> > 1440x1088.
> >
> > "AJL" <someone@microsoft.com> wrote in message
> > news:OWJVc.2045$D7.1797@news-server.bigpond.net.au...
> > > Sshmegg is dead right in his first post, but Winston - what a lot of
> > rubbish
> > > re movies and 1080p in regard to HD DVB transmission. No network tx's
> > > 1080p, only 1080i or 576p. Further the hdtv standard for interchange
> is
> > > 1080i, ie eg vtr tape & how the signals move around on the cables
within
> a
> > > tv station. - so event if the Tanberg coders could handle it (which
they
> > > dont) the signal to the copers off tape or server is 1080i. . The
> reason
> > > 1080p is not used for tx is that hdtv crt sets cannot deal with the
> freq.
> > > (the scanning coils in domestic tube tv's would ppack it in) & of
course
> > the
> > > only quality displays (grade A &B professional) are crt). Sorry to
> > > disappoint all the plasma & crt folks - they have very poor
colourimatry
> > due
> > > to the plasma tecnology not being a true 'black body source') -
despite
> > > their cost. The DVB TX stardard does include 720p & yes the second
gen.
> > > hdtv boxes will handle it, but no network is tx it to date
> >
> >
>
>

[Stephen Neal]

"Winston [ausWY]" <me@privacy.net> wrote in message
news:MMIVc.1970$D7.1805@news-server.bigpond.net.au...
> A lot of film based 1080 content is actually broadcast in progressive but
> tagged as interlaced, eg CSI: Miami, 2.5 Men, Smallville, Raymond, Gilmore
> Girls, etc, etc. If you have a display that can do 1080p & can tell the
> decoder not to deinterlace it (treat the image as progressive), then'll
you
> be able to see them in 1080p @ 25fps without interlacing artifacts. :)
> That's how I watch HDTV on my computer ;).

That isn't completely the case. Although the stuff may be shot 1920x1080/24p
(and shown 1080/50i in Aus and 1080/60i with 3:2 pulldown in the US) it is
likely to have been slightly vertically pre-filtered as all progressive
material needs to be when converted to interlaced format. This is to reduce
the vertical flicker on fine detail an interlaced scanning system
introduces.

Although there is no motion between fields in the 50i transmission and thus
a 25p stream can be reconstructed, the 1080/25p stuff you are watching is
likely to be not quite as sharp as the 1080/24p (or 25p) material as
originally shot - the vertical pre-filtering required for interlace sees to
this.

Steve

[Stephen Neal]

"Mike" <mike.n@nospam-westnet.com.au> wrote in message
news:4128109e@quokka.wn.com.au...
> Winston [ausWY] wrote:
> > A lot of film based 1080 content is actually broadcast in progressive
but
>
> You mean "filmed" in progressive?
>
> > tagged as interlaced, eg CSI: Miami, 2.5 Men, Smallville, Raymond,
Gilmore
> > Girls, etc, etc. If you have a display that can do 1080p & can tell the
> > decoder not to deinterlace it (treat the image as progressive), then'll
you
>
> Interesting. I just had a look at a 1080i recording of Drew Carey, with
> the deinterlacer off. And bugger me - no interlacing!
> Thanks. I've been wasting my (cpu) time with the deinterlacer.
>
> Thats surprising, because US TV uses 30Hz/60Hz, and even if shot on
> progressive 30/60Hz there, it would be interlaced after conversion to
> our 1080i 25/50.
>
> Maybe they actually shoot it on film at 24fps? In which case, we see a
> nice progressive image, but the yanks get 3:2 pulldown interlaced.

Yep - a lot of US HD drama is shot at 24p rather than 30p or 60i. This
means it is usually shown with 3:2 pulldown to 60i in the US, but sped up to
25p for the 50Hz territories. This means there is no 3:2 pulldown removal,
and no motion between fields to worry about with de-interlacing.
>
> > be able to see them in 1080p @ 25fps without interlacing artifacts. :)
>
> What sort of artifacts do you see? Is it trying do de-interlace fields
> from different frames?
>

The above statement isn't quite true. Whilst the 50i material will have no
interlacing MOTION artefacts (and thus not require de-interlacing) , it is
likely to still have a lower vertical resolution when compared to the 24 or
25p source - as the conversion from 25p to 50i may well introduce a vertical
pre-filtering to reduce interline flicker for interlaced viewers. This
could be considered a different interlace artefact ? (Unless the 24p/25p
stuff is prefiltered prior to interlace conversion anyway - which I doubt?)

Steve

[Stephen Neal]

"Winston [ausWY]" <me@privacy.net> wrote in message
news:rg0Wc.3104$D7.1431@news-server.bigpond.net.au...
> AJL, all Australian 1080 transmissions are all indeed broadcast as 1080
with
> 50 interlaced fields per second. As you know, in order to acheive the full
> 50 fields per second, half of the fields are 1/50th of a second later,
> however, with film, 1/50th of a second later is the same, since the image
> only changed every 1/25th of a second, thus, you CAN view it as
progressive
> without any deinterlacing, if you don't believe me I can show you
> screenshots from the 9HD Demo where 50i HD is used and interlacing lines
can
> be seen, but where it is film based such as CSI there are no interlacing
> artifacts. Here's one of my earlier attempts at explaining this:

This is true - there may be no motion artefacts present in progressive
material carried over an interlaced transmission path (and in fact some HD
post production systems exploit this) However because the progressive
material has been converted to interlaced format - for broadcast and display
on interlaced displays - it is likely to have been vertically prefilted to
reduce the interline twitter (25Hz flicker caused by high frequency vertical
detail flickering between fields) that would be introduced with fully sharp
progressive sources. This pre-filtering means that a 25p signal
reconstructed from a 25p source carried over a 50i broadcast channel is
likely to be softer than the 25p source vertically. It will still be good -
but not as good.

As a rule of thumb the Kell factor for interlaced scanning and display is
around 70-75% - this is the pre-filtering/vertical resolution reduction
required compared to a progressive system with the same number of scanning
lines. In other words a 1080/50i stream has the same approximate vertical
resolution as a 750-800/50p system. This is pretty close to 720p - which is
why so many people say 1080/50i and 720/50p are the same in resolution
terms. Of course 1080i runs at either 1920x1080 or 1440x1080, whilst 720p
runs at 1280x720 - so the horizontal resolution of the best 1080 stuff is
much greater than that of 720p - but at 1440 (as used in Aus I believe) they
are more closely matched. As both are running at 50 picture refreshes a
second they have identical motion capture characteristics - though fast
motion is captured with greater clarity in 720/50p (as each 1/50th second
image is a full 720 line resolution, whereas a 1080/50i 1/50th second
capture is only 540 lines - as it is a field based system)

Modern Plasma, LCD and DLP devices are inherently progressive in their
display - so a 1080/50i feed has to be converted to a progressive format via
de-interlacing (which can be a quality loss area - though is unlikely to be
a major issue when showing 50i material sourced from 25p progressive source
material - where there is no motion between fields to cope with) whereas
720/50p stuff could be displayed progressively (and scaled to fit the
display resolution with no de-interlacing processing required). Most HD
direct-view CRTs (and CRT 3 tube projectors) can display interlaced material
in interlaced format.

Steve

[Winston [ausWY]]

Hi,

I am simply stating that film based content can be viewed without running it
through any deinterlacing without having interlacing artifacts. Yes, it does
suffer from more motion blurring than what 50i would get, but that is simply
the nature of the format. The only thing I'm saying is that 25fps sourced
1080i content can be viewed in a progressive way without deinterlacing with
PAL, or can be viewed as progressive in NTSC after 3:2 pulldown.

"AJL" <someone@microsoft.com> wrote in message
news:Hr1Wc.3205$D7.3078@news-server.bigpond.net.au...
> Hi again Winston & Adam, I still maintain it is interlaced - not
> progressive, what you are saying is that when the film is scanned, there
> was no movement due to the 25fps capture, thus less artifacts between the
> lines - the question for debate is whether it is visible or not... Any
still
> image can benefit from this of course, but I take your point - however the
> issue is actually one of motion blur, that is because of the 25p shutter
> speed, I would suggest the diff, you see from film source material is
motion
> blur & he non linear nature of film colour & contrast - not the interlace
> artifacts. You are oversimplifying the situation believe me.
>
> AJL
> "Winston [ausWY]" <me@privacy.net> wrote in message
> news:wj0Wc.3109$D7.2557@news-server.bigpond.net.au...
> > Here's Adam's explaination as mentioned in my previous message:
> >
> > "Yes, the medium is interlaced, but what he means is that the source is
> > progressive and therefore you can "piece" together every two fields into
a
> > single progressive frame and you will not get any interlacing artifacts
> > because both fields are from the same moment in time. For display
purposes
> > this is the same thing as 25p if you are viewing on a progressive
display,
> > ie. you are getting a full progressive frame for each full frame of the
> > original source (film). The fact that the actual broadcast medium is
> > interlaced (50i) in this case, is irrelevant, as what you are seeing is
> 25p.
> >
> > Of course if you are watching a program which is based upon source
> material
> > that is truly interlaced, ie. each field is from a successive moment in
> > time, then the above does not apply, however a progressive display
device
> > will still attempt to deinterlace this material (since it can't natively
> > display interlace) -- but it won't be artifact free and won't correspond
> to
> > original film frames (interlaced material does not originate from film
> > anyway, but video).
> >
> > Adam "
> >
> > "Winston [ausWY]" <me@privacy.net> wrote in message
> > news:rg0Wc.3104$D7.1431@news-server.bigpond.net.au...
> > > AJL, all Australian 1080 transmissions are all indeed broadcast as
1080
> > with
> > > 50 interlaced fields per second. As you know, in order to acheive the
> full
> > > 50 fields per second, half of the fields are 1/50th of a second later,
> > > however, with film, 1/50th of a second later is the same, since the
> image
> > > only changed every 1/25th of a second, thus, you CAN view it as
> > progressive
> > > without any deinterlacing, if you don't believe me I can show you
> > > screenshots from the 9HD Demo where 50i HD is used and interlacing
lines
> > can
> > > be seen, but where it is film based such as CSI there are no
interlacing
> > > artifacts. Here's one of my earlier attempts at explaining this:
> > >
> > > Video has 50 frames per second, however there's only room for 25
frames
> > per
> > > second, interlaction puts two of those frames into one single frame by
> > using
> > > the odd fields for one 1/50th of a second frame and the even one for
the
> > > frame proceeding immediately afterwards (or the other way around),
since
> > > film is [sped up to] 25 frames per second and there's room for two
> fields,
> > > the next 1/50th frame would be the same since there are only 25
frames,
> > thus
> > > both the even and odd fields of the source is shown in that single
frame
> > > making it progressive at 25fps.... I'm not really good at explaining
> these
> > > things, so have a look at these two screenshots, the one
> > > [http://img1.imageshack.us/files1/hd_50.JPG] is from HD video, and the
> one
> > > [http://img1.imageshack.us/files1/hd_25.JPG] is HD film, the
screenshots
> > > have not been deinterlaced in anyway and as you can clearly see [when
> > viewed
> > > in full size] where the content is 50fps [HD content taken from
video],
> > > there are interlaction artifacts but where the source material is
25fps
> > > [from film] there are no interlace artifacts whatsoever.
> > >
> > > There are 25 frames per second in the broadcast, interlacing (kinda of
> > like
> > > compression) allows for 50 frames to be shown by putting two 1/50th
> second
> > > frames into 1/25th second frame, since film is broadcast as 25fps
(shot
> in
> > > 24fps), it doubles up, any given film frame is shown on two 50fps
> > interlaced
> > > frames, 1/50th of the second shows its odd fields, and the other
1/50th
> of
> > > the second shows its even fields, these two fields are the put
together
> > onto
> > > the same 25fps HD 'interlaced' frame, since their from the same moment
> in
> > > time, there are no interlaction artifacts allowing for me to watch
1088p
> > on
> > > monitor . Now all I need is for someone good at explaining things to
> back
> > me
> > > up and make sense out of what I just said, though I quite like Adam's
> > > explanation. Also note a fair bit of 9 and 10's station graphics and
> IDs
> > > are made in 25fps.
> > >
> > > Winston,
> > >
> > > *Both captures taken direct off the Channel 9 HD stream Sydney using a
> > DVB-t
> > > card, resized to 1920x1080 with out deinterlacing, original frame size
> > > 1440x1088.
> > >
> > > "AJL" <someone@microsoft.com> wrote in message
> > > news:OWJVc.2045$D7.1797@news-server.bigpond.net.au...
> > > > Sshmegg is dead right in his first post, but Winston - what a lot of
> > > rubbish
> > > > re movies and 1080p in regard to HD DVB transmission. No network
tx's
> > > > 1080p, only 1080i or 576p. Further the hdtv standard for
interchange
> > is
> > > > 1080i, ie eg vtr tape & how the signals move around on the cables
> within
> > a
> > > > tv station. - so event if the Tanberg coders could handle it (which
> they
> > > > dont) the signal to the copers off tape or server is 1080i. . The
> > reason
> > > > 1080p is not used for tx is that hdtv crt sets cannot deal with the
> > freq.
> > > > (the scanning coils in domestic tube tv's would ppack it in) & of
> course
> > > the
> > > > only quality displays (grade A &B professional) are crt). Sorry to
> > > > disappoint all the plasma & crt folks - they have very poor
> colourimatry
> > > due
> > > > to the plasma tecnology not being a true 'black body source') -
> despite
> > > > their cost. The DVB TX stardard does include 720p & yes the second
> gen.
> > > > hdtv boxes will handle it, but no network is tx it to date
> > >
> > >
> >
> >
>
>

[DAVO]

"Mike" <mike.n@nospam-westnet.com.au> wrote in message
news:412808be$1@quokka.wn.com.au...
> DAVO wrote:
> > Thanks guys, in particular Schmegg for your concise description. My
monitor
> > is an LG LCD KT17LZ21 AHPLKG and the set top box is a Panasonic TU HDT
104A.
>
> Your LCD, like most current HD displays, won't do more than 720p
> resolution anyway. So there is no extra benefit from 1080i.
> Its a bit academic since we don't broadcast 720p in Oz.
>
> In a fast-moving scence, interlaced modes can trade resolution for
> frame-rate. Thats one way to think of it.

Hi Mike, thanks for your input. Please excuse my ignorance here but I am now
somewhat totally confused by your statement above. The STB has done a test
scan of the monitor and it says it is capable of 576i, 576p, 720p and 1080i.
When tuned to WIN HD, the monitor says it is receiving and reproducing it in
1080i. FWIW, the loop WIN are playing is just unbelievable quality. 7HD is
coming through in 720p (according to the onscreen info on the monitor). We
are not yet receiving Southern Cross 10 in HD, only SD.
>
> > If I can find a way of connecting my 17"w/s laptop
> > (Toshiba Satellite P20) to the STB I will even try that to get the best
> > picture quality. Once again, thanks.
>
> You could put a DVB receiver card in an old PC, and stream the digital
> TV to your laptop over ethernet or fast wireless (802.11g).

I think I can understand what you are saying here and I will explore that
option but will it give me better results than the LG?

DAVO

[AJL]

Hi Winston, Mike, Steve, Schmegg and Davo,

I think we are all in a sort of techno agreement here - I am impressed and
delighted that Davo's original question has delivered such a great
discussion trail re: HD - it is great to have a spirited q&a on the issue.
and I, for one, now understand Winston's viewpoint and while I still
disagree with the interlaced progressive argument, I see that the end result
of the film transfer if at 25 fps is 'progressive like' in that the limited
artefacts created by the separate fields being shot at different times is
reduced, however the reduction in resolution is of course the downside.
This argument can go on for some time depending on the content - what I
think we all might agree on is that 1080p50 should be the standard and that
720p50 is the next best progressive standard if you are displaying on a
plasma or lcd screen / projector. Of the current supported standards, the
purists argue however that 1080i50 is the best for HD sport- so the argument
can go on forever - content dependent I guess.

It is interesting because Thompson and Sony are now developing cameras with
1080p switchable capability.




"Stephen Neal" <stephen.neal@nospam.as-directed.com> wrote in message
news:cgafks$98e$1$8300dec7@news.demon.co.uk...
>
> "Winston [ausWY]" <me@privacy.net> wrote in message
> news:MMIVc.1970$D7.1805@news-server.bigpond.net.au...
> > A lot of film based 1080 content is actually broadcast in progressive
but
> > tagged as interlaced, eg CSI: Miami, 2.5 Men, Smallville, Raymond,
Gilmore
> > Girls, etc, etc. If you have a display that can do 1080p & can tell the
> > decoder not to deinterlace it (treat the image as progressive), then'll
> you
> > be able to see them in 1080p @ 25fps without interlacing artifacts. :)
> > That's how I watch HDTV on my computer ;).
>
> That isn't completely the case. Although the stuff may be shot
1920x1080/24p
> (and shown 1080/50i in Aus and 1080/60i with 3:2 pulldown in the US) it is
> likely to have been slightly vertically pre-filtered as all progressive
> material needs to be when converted to interlaced format. This is to
reduce
> the vertical flicker on fine detail an interlaced scanning system
> introduces.
>
> Although there is no motion between fields in the 50i transmission and
thus
> a 25p stream can be reconstructed, the 1080/25p stuff you are watching is
> likely to be not quite as sharp as the 1080/24p (or 25p) material as
> originally shot - the vertical pre-filtering required for interlace sees
to
> this.
>
> Steve
>
>

[stephen neal]

"AJL" <someone@microsoft.com> wrote in message news:<HWjWc.4025$D7.267@news-server.bigpond.net.au>...
[snip]

> It is interesting because Thompson and Sony are now developing cameras with
> 1080p switchable capability.
>

They are past the development stages.

Most high-end Sony cameras will shoot at 50i/60i/24p/25/30p I believe
- one of the major benefits of a standard 1920x1080 image format is
that it is easier to build multi-standard cameras. (576 vs 480 was the
problem in SD)

The BBC series Rockface was shot 1080/25p native - Sony have a system
called segmented fields for recording the progressive signal using
(slightly modified) 50i equipment.

In fact isn't Home and Away shot 1080/25p, and downconverted to
576/25p for post production using 50i kit (but avoiding any vertical
processing that could reduce the resolution to that of interlaced)
before being upconverted to 576/50p (by un-subtle frame-doubling
rather than interpolation?) for transmission?

However if you mean cameras running 1080/50p rather than 24/25/30p
then I think this is more experimental.

Of course there is always the Arri / Quantel / NAC Tornado cam - which
is HD and runs at 1000fps progressive!?

Steve

[DAVO]

SNIP

> Of course there is always the Arri / Quantel / NAC Tornado cam - which
> is HD and runs at 1000fps progressive!?

Now that's what I would call a camera!

DAVO

[DAVO]

7HD is
> coming through in 720p (according to the onscreen info on the monitor).

Sorry guys, this is what I mean by becoming confused as I can't even see the
numbers properly as it should read 576p NOT 720p which I guess would have to
be another story. Wouldn't 1080i be far superior to 576p? It sure looks that
way here.

DAVO