Why HDTV has interlace?

[AlexeyS]

I think new HDTV is the video format which could kill interlace and NTSC/PAL. But we can see that NTSC and PAL is still there. Camcorder's HDV video format has interlace...

Why interlace and NTSC/PAL difference were not killed? :confused:

[nexx]

I had hoped somebody had answered this by now as I am interested too.
My understanding is that 1080i exists because of technical and bandwith limitations that could not support full 50/60fps 1920x1080.

There is however 720p (which personally I prefer for non-film material). I'll let somebody else argue which is better :)

[scharfis_brain]

1920x1080i shows clearly MORE image information than 1280x720p with video content

at least in static areas you'll get the double resolution compared to 720p

and when there become Mocomped deinterlacers built into HDTV sets available, even motion areas will returned to full 1080p resolution.

btw.: I've read that the YUV 4:2:0 chroma of 720p is 'interlaced', though!
progressive luma with bobbing chroma, to achieve near to YUY2 chroma quality

[Wilbert]

btw.: I've read that the YUV 4:2:0 chroma of 720p is 'interlaced', though!
Where did you read this?

[scharfis_brain]

I've read it in this book:
Charles Poynton: Digital Video And Hdtv Algorithms And Interfaces

here an image of page 100:
http://home.arcor.de/scharfis_brain/samples/yuv4-2-0p.png

Sorry I was confused. 480p chroma subsampling is not used for 720p signals

[SeeMoreDigital]

Until everybody in the world has "progressive" capable display equipment, we will not see the end of interlaced content... Especially for broadcast TV :eek:

Technically, it should be possible to broadcast PAL/SECAM content with 25 progressive frames. And construct suitable receivers to puke out either an 25p signal - for progressive display owners and/or an 50i signal - for interlaced display owners. But I doubt this will happen, as I think we are more likely to get 50p instead :angry:


Cheers

[Sulik]

The primary reason is simple: it's just more efficient to compress 1080@30i than 1080@60p (almost half the data rate), with little drawbacks (the loss of vertical resolution only applies to fast moving areas).

[Latexxx]

Dodge this.

http://img273.echo.cx/img273/8052/untitled8ks.png
http://www.ebu.ch/en/technical/trev/trev_300-wood.pdf

1080i is waste of bandwith and waste of processing power. 720p is enough for 50" screens for over half of the population, requires less bandwith and is easier/cheaper to process at the receiver (no deinterlacing, conversion to interlaced sd is trivial). I don't claim that more resolution isn't required but I can't see any reason to add analog and destructive compression to digital images. Instead of, I'd like to see 720p adopted today and 1080p in a time frame of ten years.

Thanks to ImageShack for Free Image Hosting (http://www.imageshack.us)

[scharfis_brain]

for film-content, 1080i behaves like 1080p. for both, 50 as well as 59.94 Hz TV-Systems.
only video-contents like sports, news and TV-Shows will get a slight loss due to interlace. Films will retain the full progressive 1080 lines.


also both, 720p and 1080i, are very easily to convert to 480/576i.

[Latexxx]

for film-content, 1080i behaves like 1080p. for both, 50 as well as 59.94 Hz TV-Systems.
only video-contents like sports, news and TV-Shows will get a slight loss due to interlace. Films will retain the full progressive 1080 lines.
Except that your tv will deinterlace your already progressive content with some cheapo filter which craps the quality. :p Of course it's different thing if you capture using a PC.

[scharfis_brain]

uhm, digitally steered (DVI / HDCP) connections should be (I am not sure) able to carry a interlaced/progressive frame flag that is coded into the mpeg-stream...

1080i can contain dynamic progressive frames like SDTV DVB already does.

also newer TVs (SDTV) implement 2:2 Pulldown and 3:2 Pulldown (IVTC) so no unnesesary deinterlace gets applied..

[Latexxx]

Don't they interlace movies in America to get rid of the chip munk mode introduced by direct conversion to 30/60 Hz?
As you said, 1080i works for progressive content in Europe but makes no sense for new productions because displays of today are progressive.

“I am amazed that anybody would consider launching new services based on interlace. I have spent all of my life working on conversion from interlace to progressive. Now that I have sold my successful company, I can tell you the truth: interlace to progressive does not work!”.

This remark was followed by a spontaneous round of applause from the audience. When the person was asked to give his name, he replied “Yves Faroudja”
http://www.ebu.ch/trev_301-editorial.html

Ever heard of Faroudja converters/filters?

[scharfis_brain]

Don't they interlace movies in America to get rid of the chip munk mode introduced by direct conversion to 30/60 Hz?

No, they transmit 24p encoded content with Pulldown flags.
the receiver will blow it up to 60 hertz, if the display needs it...

As you said, 1080i works for progressive content in Europe but makes no sense for new productions because displays of today are progressive.

I didn't say that new production with 1080i are nonsense.

Ever heard of Faroudja converters/filters?

for sure!
Tdeint from tritical with those parameters:
tdeint(mode=1,type=3,full=false)

comes very close to Faroudja's results, inclusive fieldmatching and EDI

I can tell you the truth: interlace to progressive does not work!

That's a bit rude for my taste.
A am working with deinterlacers for some years now and also do some script based experiments like mvbob(), which does a *really* good job for i to p, because it is motion compensated.

for sure there are some flaws, because 50% of information is missed, but 90% of its information is recoverable with motion compensation and EDI techniques...

http://www.ebu.ch/trev_301-editorial.html :
If you look carefully at interlaced pictures, you will see “inter-line twitter” which reduces the subjective vertical resolution: many tests indicate that, in subjective terms, 1080i and 720p deliver the SAME vertical resolution.

uhm yeah, with stupid displays, this will happen.
but displays with pulldown and/or (at least) motion adaptive deinterlacing won't show flicker, so the relolution will not get reduced, meaning 1080i has more than twice the resolution than 720p

[SeeMoreDigital]

As I mentioned earlier, PAL HDTV could prove to be quite a different animal to NTSC HDTV.

For a start we don't need to bother with pull down flags. We have power that runs at 50Hz (which is perfect for 50 fields interlaced content). And technically it should be possible to broadcast 720p at 25fps instead of 50fps, as our PAL progressive displays can accurately display 25p images.

Who knows, it might even be possible for us guys in Euroland to have 1080p running at 25fps.... Now wouldn't that be a first?


Cheers

[scharfis_brain]

as I said earlier, 1080i @50Hz runs as 1080p @25Hz if the video content (FILMs) allows it.

it is similar to DVB-S and DVB-T, where the encoding dynamically (framewise!) switches between interlaced and progressive depending on the underlying content.

[Latexxx]

As you said, 1080i works for progressive content in Europe but makes no sense for new productions because displays of today are progressive.

I didn't say that new production with 1080i are nonsense.
The "but" is there to indicate that the rest is my own opinion.

[Latexxx]

For a start we don't need to bother with pull down flags. We have power that runs at 50Hz (which is perfect for 50 fields interlaced content). And technically it should be possible to broadcast 720p at 25fps instead of 50fps, as our PAL progressive displays can accurately display 25p images.

Who knows, it might even be possible for us guys in Euroland to have 1080p running at 25fps.... Now wouldn't that be a first?
ETSI TS 101 154 V1.7.1 (2005-06) ("Digital Video Broadcasting (DVB); Implementation guidelines for the use of Video and Audio Coding in Broadcasting Applications based on the MPEG-2 Transport Stream") specifies all scenarios you just mentioned as mandatory.

[Kika]

Who knows, it might even be possible for us guys in Euroland to have 1080p running at 25fps

But that's what we had and have now (sometimes). If the content is FILM, it is only encoded and flagged as interlaced, but the picture structure IS progressive - so, in fact, wie have 1080p25. I have two films from the german Broadcasters Pro7 and Sat1 (Pride and Nibelungen), both of them are progressive. So where's (and what's) the problem?
I prefer 1080i, because it is able to do it both: interlaced and progressive. Oh, by the way, 720p50 needs nearly the same bitrate than 1080i25...