Should we define SVCD as 480i x 480 for clarity ?

[SingSing]

There are many posts here about interlace vs Progressive.

DVD can be flim, ntsc, interlace, and progressive in mpeg2.
SVCD is in 480 x 480, NTSC or NTSC flim rate mpeg2.
To me, NTSC means interlace, thus SVCD can be defined as 480ix 480.

I also like to know does a progressive player plays SVCD with better quality with those Fancy built in Chip sets, as they upconvert the 480i
contents in DVD ?

[Nelson37]

Don't know about the expensive Fouradja(?) chips, but

SVCD can be progressive as well as interlaced. Typically a film-rate SVCD is progressive, although not necessarily. I believe all PAL SVCD are progressive, though I am NTSC so I'm not positive.

Defining an SVCD as 480x480p or 480x480i would probably be useful, but would most likely not be used. Look at how many people use the designation XVCD or XSVCD, without stating a bitrate or resolution.

[SingSing]

I grow up in a PAL country, then end up in a NTSC country.

I used to think interlace is a NTSC only things. Is it true most of the PAL brocast material is non-interlace ( the old name for progressive ) ?

I remember DVD2AVI tell me most DVD disc in USA is interlaced, and in flim rate.

Oh, I saw how NBA and other US sportcast in NTSC get mangled into PAL TV : They are stretched to fit. It is really awful to watch paper doll like NBA players shooting hoops.

[epo]

Nearly all PAL film broadcasts are progressive. All true video is interlaced.

[SingSing]

1. Does this means all PAL brocast over tha air are progressive ?

2. That all the material are upconvert to progressive in the TV station, so all the PAL TV set can be progressive ?

3. All PAL DVD players are progressive ?

4. If I play a PAL DVD, and show it on a NTSC TV, then the DVD player has to downconvert ?

If there are all true, then all these interlace artifact is only messing up US consumers.

[bugster]

3. All PAL DVD players are progressive ?

Definatley not. In fact AFAIK, there are only a couple of DVD players on the market that will output PAL progressive and they are VERY top of the range types. In contrast there are quite a few NTSC progressive players available.

The best (most economic?) way to currently get PAL progressive output is to use a PC with DVI output to a projector with DVI inputs. Only for the real home cinema enthusiast I think!

[SingSing]

So, standard PAL TV and broadcast must be interlaced.

Should we refered PAL SVCD as 480 x 576i ?
and NTSC SVCD as 480 x 480i ?

[epo]

Ofc all of PAL broadcast is interlaced. (I didn't think, it can be questioned). What I meant was, what you see after capture/on TV screen and in what way it can be encoded. I don't see, why PAL SVCD can't be 480x576p, while I see, why NTSC can't be 480x480p (without pulldown)

[SingSing]

All NTSC TV are interlaced, thus all TV Broadcast are interlace.

It is very unlikely that PAL TV can be interlace and progressive, and switched according to broadcast type.

[adam]

Regardless of what format you are using (DVD or SVCD) both pal and ntsc can be either progressive or interlaced. So there is no reason, nor any possible way to adobt a general naming policy to designate whether NTSC/PAL, SVCD/DVDs are interlaced or progressive. If you want to add i or p to your resolution in your post to clarify the nature of your source then sure that may help people in solving your problem, but its hardly necessary.

To answer your other question, a progressive scan dvd player simply bypasses the pulldown flags on a DVD or SVCD. Most commercial dvds, both pal and ntsc, store the movie as 24fps progressive. The stream will then have a pulldown flag which instructs the dvd player to perform a telecine on the footage as it plays. NTSC DVDs undergo the 3:2 pulldown which both interlaces and repeats fields to bring the framerate up to 29.97fps. Pal dvds undergo the 2:2 pulldown which both interlaces it and speeds it up to 25fps without adding any new frames. A progressive scan dvd player bypasses this flag and plays the movie as it is stored, at 24fps progressive frames which is ideal for the progressive scan of HDTVs. You can accomplish the exact thing simply by removing the pulldown flags manually before authoring the SVCD/DVD but technically it will no longer comply with its respective standard (NTSC or PAL.) I'm sure a progressive scan dvd player does more than this also to better handle the progressive image, this is just the main function.

Most NTSC dvds are authored like this for quality reasons, because it saves you %20 of your bitrate because the extra frames are extrapolated during playback instead of actually having to be encoded, which obviously uses up bitrate. For pal dvds I suppose it is just cheaper and easier to include the pulldown flag rather than do a hard telecine.

There are however some dvds which do not use pulldown flags and which store the movie as interlaced 25fps or 29.97fps, or they may be a hybrid of both interlaced and progressive footage. For ntsc, this usually only occurs with anime or tv shows. For pal I guess this would occur if the movie was filmed using a PAL camera which captures in 25fps (yes those do exist.) Still, production studios can do whatever they want. It seems sometimes they hard telecine a movie for no good reason.

The above descriptions are just the conventional way of storing video on a SVCD or DVD, but there are others as well. As I said, PAL video can be stored as 24fps progressive and played back at 25fps interlaced, or it can be stored as either 25fps interlaced or progressive.

NTSC is typically either stored as 24fps progressive and played back at 29.97fps interlaced or it is stored as 29.97fps interlaced but you could also store the material as 29.97fps progressive if you combined the fields or only selected every other field. Obviously this is not ideal but the standard does support it.

[hp_lovecraft]

Most commercial dvds, both pal and ntsc, store the movie as 24fps progressive.

Can you name any?

As far as I know, 99.99% of all NTSC DVDs (movies) are 24fps interlaced, according to avsforum and hometheaterforum. The only 24fps progressive stuff I've ever seen was on TEST DVDs.

The reason? One would think that it doesnt matter since the DVD mpeg2 decoder can convert progressive -> interlaced, and interlaced -> progressive in "film mode", without any loss of quality....

But the problem is that a 24fps progressive image converted to interlace by the DVD player has worse artifacts on an interlace TV, especially combing, flicker, moire, jaggies, etc...

So, studios will convert the 24fps to interlaced, then run vertical filters. The vertical filters acount for a 10% loss of visible resolution, but helps hide the interlace artifacts. Then, edge enhancement is applied to artificially add the detail back in, then is encoded to mpeg2.



nick

[SingSing]

That is also my take, that most DVD movie are interlaced and flim rate.
I am going home to look at them.

Is there a tool that can tell us quickly ?

[adam]

hp_lovecraft: Yes you are correct but this is just a technicality and as far as the user is concerned, it really makes no difference.

The movie is stored as an interlaced sequence but with progressive frames, and the frames are all that really count.

A source picture is a contiguous rectangular array of pixels. A picture may be a complete frame of video ("frame picture") or one of the interlaced fields from an interlaced source ("field picture").

In a progressive sequence, all pictures are frame pictures

In an interlaced sequence, any frame may be coded as a frame picture or as two field pictures

MPEG-2 progressive_sequence is not allowed, but interlaced sequences can contain progressive pictures and progressive macroblocks...

Most film source is encoded progressive; most video sources are encoded interlaced. These may be mixed on the same disc, such as an interlaced logo followed by a progressive movie.

The material on a DVD is stored as an interlaced sequence, but only frame pictures are used, so whenever you actually work with the material ie: editing/transcoding, you are still only getting the full frames, not fields. For all intents and purposes, it may as well be a progressive sequence. I never really understood why the sequence had to be interlaced, I assumed it was either a limitation of the DVD standard or the mpeg2 standard, but your explanation sounds good to me.

Incidentally, excluding anime and some tv shows, if you use forced film on about %99 of commercial ntsc dvds and then view the output you will have progressive frames which you can then encode progressively if you choose to do so.

[hp_lovecraft]

Yes you are correct but this is just a technicality and as far as the user is concerned, it really makes no difference.
The movie is stored as an interlaced sequence but with progressive frames, and the frames are all that really count

I agree for the most part- THe only exception would be alot of 'cheap' progressive players that do the 3-2 pulldown BEFORE combining the frames into a progressive image. In this case, the cadence is incorrect, and the original frames are not resolved. Another problem is DVD with incorrect progressive flags, so your system switches from "film" progressive to "adaptive/video/etc" progressiv, and again the frames are not correctly resolved.

I don't mean to complicate the issue. Its just one of those DVD pet peeves where DVD spec allows for the image to be stored as "true" progressive, but doest. Perhaps improving quality for cheaper TVs, but robbing quality for high-end TVs.

Well, its probobly moot anyway for SVCD, since I can author them any way I want. Adding the 'i' to 480x480 would probobly be meaningless anyway, like you said, since the frames are still technically stored as progressive for film.

NIck

[SingSing]

Do you implied all flim rate Video are progressive ?

[SingSing]

Nearly all PAL film broadcasts are progressive. All true video is interlaced.

PAL broadcast have to be interlace, because the rate is 25fps, and the line frequnecy is 50 Hz, thus 2 screen per frame. That's also why NTSC based on 60 Hz and produced 29.92 fps.

Even when morden electronics does not depends on line frequency, the old legacy relation still hold.

[adam]

Do you implied all flim rate Video are progressive ?

Yes. If it is stored as film on the DVD than it should have progressive frames. Dvd production studios can always make mistakes, but it really makes no sense to store a movie as true interlaced film because it will look much worse on progressive scan playback devices, ie: HDTV and pc monitors.

[SingSing]

TV is synchronous at line frequency. I.e. 60 Hz and 50Hz.
NTSC and PAL movies playback at 29.97 and 25 fps.

For interlaced NTSC material, it show one field at first 1/60 second, then show the other field in the second 1/60 second.

Progressive NTSC is still playback at 29.97 fps. If it is stored as two halves and construct into one progressive frame, then this implied we are watching two identical frames repeatively on a 60Hz TV.

[adam]

TV is synchronous at line frequency. I.e. 60 Hz and 50Hz.
NTSC and PAL movies playback at 29.97 and 25 fps.

For interlaced NTSC material, it show one field at first 1/60 second, then show the other field in the second 1/60 second.

Progressive NTSC is still playback at 29.97 fps. If it is stored as two halves and construct into one progressive frame, then this implied we are watching two identical frames repeatively on a 60Hz TV.

No. For NTSC, you have ~30 frames per second. Each frame is made up of two fields, that's 60 fields. 60 fields at 60 Hz, what's the problem?

The frames are stored progressively but are interlaced during playback, that's part of what the 3:2 pulldown flag instructs the dvd player to do.

[SingSing]

Thanks for information that applied to interlaced TV.

But don't (480P) progressive TV displays both fields as a complete frame every time ? Do them refresh only 1/30 instead of 1/60 second ?

[adam]

Progressive tv's use what's called line doubling to prevent the flickering that you would normally get if you displayed progressive frames at that low of an fps.

[SingSing]

Yes.

Since line doubling put the full 525 lines on screen, and thus have to show the screen twice to meet the 60 per second refresh rate to work with our eyes. That is what I was worried about.

Recently, there is a lot of new chips trying their best to put two color video dots on the same exact location on screen. The HDTV and digital video engineers are not able to meet specification with jittering of clock due to many layers of clock (video rate ) change, with the increase demand of flexibility demands on TV sets.

Showing two pictures twice itself can add another form of image distortion.