HD Interlaced vs Progressive

[Cheesus]

I understand, from what I've been reading, that progressive HD needs more bandwidth than interlaced material, I just don't get why.
Doesn't progressive material just get the whole frame scanned twice whilst interlaced gets both fields scanned over the same period of time? Obviously progressive is twice the size then (two whole frames getting scanned as opposed to two halves of a frame) but why can't the monitor just store the frame and scan it twice? Or the frame could be buffered in the player and just repeated twice. Or any other number of solutions.
Am I completely missing the point?
Maybe it's a data reading speed problem.

Anyone care to elaborate?
Cheers

[Cheesus]

Hi Foxyshadis

But it's just repeat information, the same frame played twice, there is no need to store the information twice or output twice, just tell the device to repeat the frame.

I'm also talking about film sources too where temporal resolution of interlaced material doesn't come into play. Sorry, I didn't make that clear.

[foxyshadis]

I trashed my reply when I realized I really wasn't sure what you were asking and got all confused, sorry you ended up replying anyway. ^^;

Anyway, 60p isn't always 24p upsampled. If the source is 24p film, the codec will just treat the next frame or two after every frame as a duplicate, then there's no penalty of course. (Barring certain minor motion estimation problems that causes.) But real 60p video actually is 60 different frames a second, there are no repeats, and I'm sure that's what your sources meant. Basically, for bitrate 24p telecine < 30p < 30i (aka 60i) < 60p.

[Cheesus]

Is this what they're talking about when they say Blu-ray is 1080p as opposed to HD DVD being 1080i? The Sony camp are making a big deal out of saying Blu-ray is 1080p.

The whole point of making DVD's or HiDef DVD's is to show films on though, which surely have a 24 fps source and consequently repeat frames. Where would you get a 60p source?

[communist]

The whole point of making DVD's or HiDef DVD's is to show films on though, which surely have a 24 fps source and consequently repeat frames.
FILM NTSC DVDs have a frame rate of 29.976, they get to this fps by telecining the original 24fps stream of a film source, if done properly its just a flag in the MPEG stream and costs about nothing bitrate wise.

Where would you get a 60p source?
From HD broadcast cameras for ex.? Though I guess they mostly do 60 fields per second.

[Cheesus]

Thanks Communist. I'm from PAL land but do understand the 3:2 pulldown etc which is why I still can't see why producing 1080p is any more difficult than 1080i from a film source.
Blu-ray apparently can do 1080p (even though it's not even out) HD DVD at the moment can only do 1080i.
I suspect that it has to do with progressive needing higher transfer rates and Blu-ray being able to handle this and HD-DVD not but am still at a loss as to why there needs to be a higher bit rate involved for progressive.

[Manao]

Cheesus : to match 1080i motion fluidity, you'd need to use 1080p50. Hence, you'd encode twice the amount of frames of the 1080i video, in order to achieve the same fluidity. You encode more data -> you need a higher bitrate ( not twice that bitrate though, still the data is more coherent temporally, and since interlaced video are inherently harder to encode than progressive one ( at the same framerate ) )

[Cheesus]

Ah ha. So they don't repeat frames.
Surely this is only relevent to broadcast material though as feature films are still only 24 fps?

[Doom9]

For movie content, there's effectively no reason to go interlaced. Encoding a standard 24fps Hollywood movie, or today's TV series which are almost always shot on film as well unless we're talking very low budget productions by irreputable studios, all 1080i means is that a progressive 24 fps source is telecined to get 59.97 fields per second (or 29.97 fps interlaced as I prefer to say). Such content is perfectly restoreable to its original form.

Where it begins to differ is when we're dealing with content that was shot interlaced. News and sports programming is unfortunately still shot interlaced.. so they effectively "close the shutter" 59.97 times per second, but instead of transmitting the entire picture each time the shutter closes, they only transmit every second line, thus effectively reducing the vertical resolution by two. And there you have your 1080i content that is different. If you transmit every single line, naturally that's more data and requires more bandwidth and since bandwidth is limited, it would result in a degraded picture as compared to the 1080i one (that's not taking into account that on today's progressive displays - plasma, projectors, LCDS - you get degradation from the display trying to deinterlace the interlaced signal).

So the bottom line is: for material shot on film, 24 fps should be used and it could be up to the player to decide what to do with it. If it feeds a digital display, it should just display the content as is. If it's an interlaced display or the output you're using is only capable of transmitting an interlaced signal, the player can perform telecine (for NTSC) or basic field separation (for PAL) on the fly and do the PAL speedup on the fly as well.

So say after me: movie good, TV bad.

[MrTroy]

Blu-ray apparently can do 1080p (even though it's not even out) HD DVD at the moment can only do 1080i.
Both Blu-ray Disc and HD DVD are 1080p capable. The first batch of HD DVD's to be released in the US will indeed be 1080p.
I guess you are talking about the first Toshiba player, which indeed can't output 1080p.

[Cheesus]

Thanks. That's what I thought and explained very well.
So why isn't HD DVD doing 1080p then? Or does it? I'm sure I read it was only doing 1080i. There doesn't really seem to be a reason why it can't do 1080p hence my confusion.

Edit
I've just read your reply Mr Troy so that clears that up. Any reason for it not being able to do 1080p?

[Latexxx]

Thanks. That's what I thought and explained very well.
So why isn't HD DVD doing 1080p then? Or does it? I'm sure I read it was only doing 1080i. There doesn't really seem to be a reason why it can't do 1080p hence my confusion.

For progressive movie content 1080i is 1080p.

[zambelli]

The entire 1080i vs 1080p issue is mostly a decoder issue anyway. Film content itself will nearly always be encoded at 24p because that's the optimal way to encode film content. So the real difference between HD-DVD and BluRay ends up being whether one decodes that 24p at 60Hz, or something divisible by 24p, such as 24Hz, 48Hz or 72Hz. The latter would seem to be a non-factor for most people since, alas, their displays are probably 60Hz or 50Hz anyway.

[Revgen]

Actually, Mitsubishi has released 1080p HDTV's recently in the US. I saw a model at Fry's.

[SeeMoreDigital]

I think you'll find that most if not all 1920x1080 panels can cope with 1080 progressive sources. As Zambelli mentioned it's more likely to be a decoder issue....

If you connect a 1920x1080 display to an PC and play true 1980x1080 progressive sources, the panel should be able to display the content progressively!


Cheers

[niknik]

More so, with the endless delays, and lack of a 1080p "standard", every day they lose more ppl to the "PC" media center.

Not that I can afford a 1080p display right now. But I wouldn't buy one until they get their act together.

[scharfis_brain]

just get displays with builtin 2:2 and 3:2 Pulldown.
then you get a TRUE progressive image with 24fps, 25fps and 30fps videos in 50i and 60i HD transmissions.

Of course 50fps and 60fps will stay interlaced.

[*.mp4 guy]

More so, with the endless delays, and lack of a 1080p "standard", every day they lose more ppl to the "PC" media center.

Not that I can afford a 1080p display right now. But I wouldn't buy one until they get their act together.

Building on your point 1080P capable pc monitors are available and quite reasonably priced (flay screen crt) too, compared to all the hidef displays on the market. Most of them have very nice pictures, much better then lcd's are capable of, and they will all last much longer then plasma screens. I don't see why anyone would wan't to treverse the minefield of standards that has plagued anything "HiDef" when pc monitors and projectors work so well doing the same job.

[SeeMoreDigital]

Building on your point 1080P capable pc monitors are available and quite reasonably priced (flay screen crt) too, compared to all the hidef displays on the market. Most of them have very nice pictures, much better then lcd's are capable of, and they will all last much longer then plasma screens. Depending on where you are in the world Samsung have released an 32" CRT HDTV... It has a very shallow depth and is reasonably priced: -

http://www.engadget.com/2006/03/13/samsungs-new-ctv-32z30-32-inch-crt/


Cheers

[jstelly]

I think the main roadblock right now is that HDMI lacks the bandwidth to do 1080/60p. That doesn't make sense to me, because if the source is 1080/24p, why not send 1080/24p over the wire, and let the decoder on the TV handle framerate conversion?

I just picked up a Toshiba that has 1080p display support, but has no digital input that can accept 1080p (1080i is the best you can do). It's unclear if the firewire port will accept 1080p but I don't have a 1080p source to check. Despite that seemingly serious limitation that's common on today's 1080p TVs and even though I'm normally very picky / aware of deinterlacing artifacts, I don't notice those things on the 1080i cable channels I watch. So it seems to be doing a good job of deinterlacing and cleaning up the signal, and I've got no regrets about not waiting for sets that can accept 1080p digital inputs.

[niknik]

Also (and it's only my oppinion), I don't think I'd want a 1080p display on anything less than a 50".

I am amazed at how it looks in 720p... 1080 will be even better.

[petermarina]

I think the main roadblock right now is that HDMI lacks the bandwidth to do 1080/60p. That doesn't make sense to me, because if the source is 1080/24p, why not send 1080/24p over the wire, and let the decoder on the TV handle framerate conversion?

I was wundering that my self. Does anyone have an answer?

[Kika]

In PAL-Land, that's no problem. After a PAL-SpeedUp to 25 fps on Film-Source, 1080i is progressive.
In NTSC-Country, they missed a big chance to get rid with those old problem (23.976/29.97, Pulldown and so on). But even PAL-Country missed that chance, it's still mandatory to do the SpeedUp. That's silly, because it should not be a problem to build Panels with to cabablity to show the true framerates.

[Blue_MiSfit]

HD on CRT really is the way to go... My 21" Trinitron does 1920x1440 at 72 hz and 1280x960@96hz... PERFECT for 1080p and 720p- the only way to go IMHO... If I saw that 32" CRT HDTV was out in shops at that price I would buy one in a second.

Still, my client's 150" DLP @ 1080 is really, really, really, really nice. Showtime HD off Comcast is....... Absurd :) If only I could crack his box and get a working firewire port on that sucker, pristine HD transport streams here I come... Oh well :)

I just really get angry when people still use interlaced video. I simply dont understand why companies still develop interlaced products. What advantages does interlaced have over progressive??? Was interlacing not implimented to conserve bandwidth on early analog TV systems where they could increase frequency easily, but not bandwidth per "pulse" (sorry I'm not really sure what the correct terminology is). This seems like a non issue today..

Oh well, just ranting. HD is great....

~misfit

[Kika]

I think, most people don't understand what the little "i" means in the digital world.

For true Film-Source, 50(60)p is crazy, 25(24)i can handle it perfectly - no interlacing, no problems (only stupid decoders). On Source like that, there's no true difference between 25(24)p or 25(24)i.
720p50 is a lot more complicated than 1080i25 (25 fps, 50 fields per seconds).

BTW: My Samsung SyncMaster ist able to handle true 1920x1080 at 75 or 100 Hz = perfect Picture, even is the Source is true interlaced.

[Blue_MiSfit]

Kika,

try setting your monitor's refresh rate to an even multiple of your source frame rate, this has noticeably improved motion, whereas before I noticed jitters occasionally (similar to enabling vsync in games)

In case you are wondering, why I do 1920x1440, is simply to still have a usable 4:3 desktop while watching HD.

[reepa]

I think the main roadblock right now is that HDMI lacks the bandwidth to do 1080/60p.

According to hdmi.org, HDMI can do 1080/60p just fine.

What types of video does HDMI support?
HDMI has the capacity to support existing high-definition video formats (720p, 1080i, and 1080p/60). It also has the flexibility to support enhanced definition formats such as 480p, as well as standard definition formats such as NTSC or PAL.

[Kika]

try setting your monitor's refresh rate to an even multiple of your source frame rate, this has noticeably improved motion, whereas before I noticed jitters occasionally

I'm in PAL-Country, so 75 or 100 Hz are perfect. ;)
And my LCD-TV has the same technology for progressive scan and Upscaling/Scaling than my Denon 2910.

[bob0r]

Kinda relative question:

A source 1080i or 1080p, 2 hours video, would be around ~18-20GB, correct?

If correct Then, HDVD = 15GB, BD = 25GB per layer.
Dual layer would doubles sizes, but i would guess is very expensive to burn in the future.
(2 hour HDVD-DL would fit on 1 BD, extras removed)

So to come back a bit on topic, 1080i and 1080p would be around the same size, correct?

[*.mp4 guy]

So to come back a bit on topic, 1080i and 1080p would be around the same size, correct?

If they are both being used to store the same framerate 1080P would be smaller (or better quality) because encoders do better on progressive content.

A perfect ATSC 1080i transmission of a 2 hour movie would be 17.166GB

[siddharthagandhi]

That means you're saying that the transmission uses a bitrate of approximately 16-20 mbps (I calculated). Thats a little high for HD isnt it? Isn't 8 mbps a bitrate that can be used for HD?

[niknik]

It would depend on the codec... for h264, 8Mbps may be enough; but on Mpeg2, 16-25Mbps are pretty common.

[siddharthagandhi]

Lol well what would you expect with MPEG-2...

How about VC-1...what sort of bitrate would that have relative to AVC and MPEG-2

[zambelli]

These are the specs for the first 3 HD-DVD American releases:

Last Samurai:
VC-1: 1080P, 18 Mbps avg, 24 Mbps peak
Dolby Digital-Plus: English 5.1, 640 Kbps 16 bit/48 kHz

Phantom:
VC-1: 1080P, 15 Mbps avg, 21 Mbps peak
Dolby True HD: English 5.1, 1.6 Mbps average and 3 Mbps peak, 16 bit/48 kHz
Dolby Digital-Plus: English 5.1, 640 Kbps 16 bit/48 kHz

Serenity:
VC-1: 1080p, 16 Mbps avg, 24 Mbps peak
Dolby Digital Plus: English 5.1, 1.5 Mbps, 16 bit/48 kHz


These bitrates might go down a little as encoders get better, but Special Edition releases (i.e. Superbit) might choose to go higher instead of lower anyway.

You have to keep in mind that the goal here is transparency. You're not really supposed to notice a difference between the uncompressed source and the encoded HD-DVD version. The 8Mbps 1080p stuff you guys talk about is definitely not transparent - at least not consistently so, anyway.

[Revgen]

I disagree.

I watched a Boston Red Sox vs. Toronto Blue Jays game that was simulcasted in both 1080i (INHD) and 720P (ESPNHD) on my 24in. Dell monitor, and the 1080i version looked noticably sharper. I'm not sure what the bitrate was on both broadcasts, but the result was a sharper image for the higher resolution despite the interlacing.

[SeeMoreDigital]

Hi Zambelli,

Do you know what the "horizonatal" resolution is for those three VC1 releases. And whether the vertical resolution includes "hard encoded" black mattes?


Cheers

[*.mp4 guy]

isn't 8 mbps a bitrate that can be used for HD?
8 Isn't neer enough, You seem to be forgetting that the closer to lossless you get the less of an advantage new formats have. Mpeg2 and AVC hit transparency at similar bitrates, but AVC keeps quality better as bitrates decreases, so you can have something almost transparent at half the rate of a transparent mpeg2, but to get full transparency you need almost as much bitrate, especially on grainy sources like hidef films.

[niknik]

Hi Zambelli,
Do you know what the "horizonatal" resolution is for those three VC1 releases. And whether the vertical resolution includes "hard encoded" black mattes?


The battle for anamorphic HD begins. ;)

[zambelli]

Do you know what the "horizonatal" resolution is for those three VC1 releases. And whether the vertical resolution includes "hard encoded" black mattes?
1920x1080, AFAIK. I don't think the HD-DVD spec allows for cropping, so I think it's a given that you'll have black mattes on all titles with AR > 1.78.