HD isn't necessary? [Archive]

Zarxrax

18th February 2006, 01:06

In response to the HDMI stuff for PCs that will cause HD content to be downsampled to SD, you may remember the MPAA (I think) saying that most consumers will not be able to tell the difference anyway.

So I decided to test for myself, and I have come to the conclusion that HD on a PC is unnecessary.

Now I'm not trying to start a flame war or anything, but just consider it. Everyone is all excited about HD, eagerly testing H.264 codecs at HD resolutions. The resolution is so much higher, it MUST look way better, right?

WRONG.

I propose that for general purpose viewing on a pc at least, HD is a complete waste of both encoding time and filesize. I am not making any statement about viewing on an HDTV set, nor am I trying to make a blanket statement saying no one should ever encode HD resolution stuff for viewing on a PC.

All I am saying is, before you get caught up in the hype of HD, actually STOP and take a look and see the difference for yourself, before you just go wasting time and effort because you KNOW it looks so much better.

I said above that I have been testing, and I encourage you to do the same. Exactly what have I tested? On http://www.apple.com/trailers/ there are HD resolution movie trailers for download. They have both 720p and 1080p. Now, 1080p isnt a real HDTV standard resolution, but you can check those for yourself as well, if you really want to.

To test, I downloaded any 720p trailer, and loaded it through directshowsource in avisynth.
To compare it to Standard DVD resolution, I added a LanczosResize down to 720x480, then another lanczos resize back to the full resolution.

You can then compare both of these side by side in virtualdub or something.

By my eyes, I can BARELY see any difference at all! I was SHOCKED when I first tested this, because I really expected to see some difference! But no, I have to really strain and flip the images back and forth to actually see any difference. If I were actually watching the film and not straining to see a difference, I honestly wouldnt be able to see a difference.

The only parts where any difference was actually apparent was on disclaimer graphic at the beginning of the trailers. On the HD resolution trailers, these had JAGGY ALIASED EDGES, and I actually PREFERRED THE RESAMPLED VIDEO in this case!

Comments?

Guest

18th February 2006, 02:02

I tried it for some anime frames and the difference was obvious; the HD was much sharper. But I didn't use DirectShowSource().

Revgen

18th February 2006, 02:08

What kind of scenes did you watch?

Were they Low-motion or High-motion? High Detail or Low Detail?

How big is your monitor?

Is the footage your looking at 24fps film?

IMHO the only footage that looks worse at standard res down from Hi-def is high motion Sports and Nature ( Discovery Channel) footage. Sports and Nature footage tend to be highly detailed and fast moving hence retaining sharpness can be difficult for the sharpeners and the encoders.

Also, alot of Hi-Def footage isn't really optimized for Hi-def in the first place. Many TV stations are simply trying to comply with the standard without actually trying to spend resources to take advantage of it.

Also Apple isn't exactly the best place for hi-def footage.

Go to this site (http://www.fusionhdtv.co.kr/Eng/Download/Demo.aspx) and download one of the demos there. They usually have high motion nature scenes and other more detailed scenes.

EDIT:

I haven't looked at anime yet, but I'll take Neuron2's word that it probably looks less impressive at Standard Def.

Lil' Jer

18th February 2006, 02:31

The only parts where any difference was actually apparent was on disclaimer graphic at the beginning of the trailers. On the HD resolution trailers, these had JAGGY ALIASED EDGES, and I actually PREFERRED THE RESAMPLED VIDEO in this case!

Is that before or after you downsized and upsized?

And yes I have watched HD content on my PC and it looks much, much better than SD resolution stuff, but I also don't downsize and then reupscale it while watching. So, no, it's not pointless. OTOH I hope these next generation formats go down in flames and cost the studios tons of money so that maybe we can get a more consumer friendly format.

Zarxrax

18th February 2006, 02:43

@Revgen: How do you use the files? It doesnt work in media player classic. If I load it into dgindex I get the following error: "No Data. Check your PIDS."

@Lil' Jer: Resizing down and back up was to create a Standard Definition video. I was of course comparing this to the untouched HD video, which I noted had jaggy edges.

My observations were based solely on the trailers from Apple at this point, as I assumed them to be a reliable source for legitimate HD content. On the possibility that Apple's trailers are crap, my observations of HD may be flawed.

Revgen

18th February 2006, 02:59

While in DGindex

Go to Stream-->Detect PIDS: RAW

And select the "mpeg" pid and set it as your video stream, and set the "AC3" PID as your audio stream.

Don't worry if it gives a "GOP is not closed" error.

EDIT: The only player that can play these is VLC player. WMP has never worked for me either.

Lil' Jer

18th February 2006, 03:32

My observations were based solely on the trailers from Apple at this point, as I assumed them to be a reliable source for legitimate HD content. On the possibility that Apple's trailers are crap, my observations of HD may be flawed.

Your observations are very much flawed.

Zarxrax

18th February 2006, 03:37

Those samples give a much more apparent difference than the trailers from Apple did. I can actually visibly see a difference now. Its more noticable in some places than others. In some parts I can't tell a difference. I guess a lot of it depends on exactly what is being shown in the video.

Still, it's not a huge difference. Just a little added sharpness. Play around with some sharpeners on an SD video and you can start approaching the same quality, right?

I suppose what I'm seeing is just a point of diminishing returns right around DVD resolution. I remember back when it was commonplace to encode things at VCD resolution. Then when people moved up to say, 512x384, there was a big visual difference. There was much more detail. Then people started encoding using full DVD resolution. Yet again, lots more detail, very noticable difference.

But now, we jump up again, maybe even double from DVD resolution... and theres just not that same improvement.

If some HDMI device downsampled my resolution... I really WOUND'T be able to tell... except if I went and started comparing frame by frame.

Revgen

18th February 2006, 06:28

The difference also depends on your screen size. I have a 24 in. widescreen display and the difference is quite apparent. It may not be so on a 17in. or 19 in. display.

reepa

18th February 2006, 09:07

Now, 1080p isnt a real HDTV standard resolution

Yes it is. The problem with your comparison is that you use the 720p material. Of course the difference won't be as large if you use the lesser resolution. I don't understand why anyone would use 720p for films anyway when 1080p is available. Better to start with as much resolution as possible and let the codec remove some of it for you if necessary.

SeeMoreDigital

18th February 2006, 21:30

Well....

I have a high-def network capable stand-alone player that is connected to a high-def 42" plasma via HDMI and component

Even "superbit" std-def PAL DVD sources don't come close to well encoded high-def sources ;)

Zarxrax

18th February 2006, 23:36

Well, I said I don't know anything about how they might look on a real HDTV set or whatever, I'm just saying in comparison on a normal PC monitor. And I am comparing the full frame size in virtualdub, not looking at them full screen or anything, so monitor size isnt an issue.

Anyways, I've been scouring the net for all this HD content that will supposedly blow me away, and I still haven't found it. Nueron2 said that it was really noticable with anime, so I got ahold of few HD anime to see how they looked. On not a single one could I tell ANY difference between HD resolution and downsampled to standard resolution. I really kind of expected that, because anime isn't too detailed in the first place.

Maybe there is some certain anime that looks incredibly better in HD, but I just looked at 3 randomly chosen, and they certainly didn't show any improvements.

This leads me to my next observation.
In order to benefit from the additional resolution of HD, content will need to meet a lot of criteria.
1. It needs to be detailed enough in the first place to actually show improvement from added resolution.
2. Scenes need to be static. Motion in the scene introduces motion blur. No matter how high a resolution you use, if its blurred, its blurred, end of story. Sharpness and clarity could really have been improved a great deal if HD spec had doubled the framerate.
3. Material needs to be encoded with the utmost sharpness and clarity in order for the benefit to be there. I mean, if they release a blurry HD video... theres absolutely no improvement there. You might think "well duh", but just take a look at your own DVD collection right now. I have more DVDs than I can count that are blurry. I rarely ever make an encode without applying some sort of sharpener. I have no faith that content producers will make HD content any better. In fact, in a lot of cases I bet we will see people just upscaling regular content and calling it HD.

To sum it up, all the "real" HD content that I have seen so far really offers no real added clarity over a downsampled version. The only difference I have seen was in the videos revgen pointed me to. These videos are designed to showcase what HD is capable of... in other words, those videos are "as good as it gets". I wasn't impressed. If thats the best, you can bet most content wont approach it.

Now I do think there can be some clarity difference on a device like a large screen HDTV, I don't deny that. It's just the differences between a large TV set and a computer monitor. After all, when you stretch some small resolution across a 50 inch set, something's gotta give.

My main point though, for those who have been reading all my stupid rant...
We will soon be hit by HD-DVD discs and Blu-Ray, telling us we need to buy all our movies again to get better quality. I'm thinking it will be a waste of money in many cases, because if you are like me and don't have a large HDTV set, you wont see any improvement.

SeeMoreDigital

19th February 2006, 00:58

Zarxrax

19th February 2006, 01:45

If we take the average resolution of a 4:3 PC monitor as being 1024x768 pixels, when you play/display a 1920x1080 video on such a monitor, only 1024x576 pixels will make up that image....

So no.... you would not see much difference between a std-def image and a hi-def image :eek:

That does not mean there "is" no difference!

I respectfully suggest you either purchase a higher resolution PC monitor (preferably 16:9) or go-see a proper HDTV demonstration before making such sweeping statements!

Cheers

You are not understanding what I am saying.
I am NOT resizing the image to full screen, I am viewing the FULL image. You can view the full image by not having it all visible on your screen at the same time. I can view a 32,000x24,000 pixel image in photoshop if I want, at full resolution. I can't see it all at the same time, but I can still see the full resolution.

Zarxrax

19th February 2006, 01:58

By the way, here are some actual screenshots to back up my words. One is an untouched HD source, the other has been downsampled to dvd resolution and then sized back up to HD. See if you can tell which is which. Then honestly tell me the difference was obvious.

http://zarxrax.kicks-ass.net/hdtest/hdtest1a.png
http://zarxrax.kicks-ass.net/hdtest/hdtest1b.png

http://zarxrax.kicks-ass.net/hdtest/4a.png
http://zarxrax.kicks-ass.net/hdtest/4b.png

I'm not saying HD doesn't have some potential. But when I take about 6 RANDOM samples of HD content that is out there intended to be consumed by the masses, and they all look similar, it doesnt really matter what HD is capable of, this is what the current state of HD *actually is*.

Mug Funky

19th February 2006, 03:23

IMHO high-def only makes a difference on certain stuff. there's not much point watching the news in HDTV, and some movies you can safely do without, but there's stuff out there that actually needs it. many films are shot with subtleties in the background that get lost on SD sizes - even if background objects are defined, they don't stand out enough to be noticed the way they were intended to. many 70mm movies are like this - they're shot with wider angles and from further away to enhance the spectacle.

of course, these movies would only be done justice when projected on a huge screen. a 68cm TV, even a HD capable one, will not be the same.

it's probably worth it for the 1% of films out there that need it :) i can't see anime needing HDTV unless it's studio ghibli with a massive budget.

but yeah, a lot of the time all you get is extra grain. 16m in SD is grainy as hell, but you should see it in HDV 25mbit - about 4 film grains per DCT block is not a good thing at all, but at least noise reduction is more effective with less obvious artefacts when you scale it down to SD. a grainy blockfest in HD can look superb in SD after a few of fizick's filters have been run on it.

DigitAl56K

19th February 2006, 04:12

In response to the HDMI stuff for PCs that will cause HD content to be downsampled to SD, you may remember the MPAA (I think) saying that most consumers will not be able to tell the difference anyway.

So I decided to test for myself, and I have come to the conclusion that HD on a PC is unnecessary.

You are smoking crack. I work with HD and SD video daily, and when I have a good HD source, the difference blows me away.

To test, I downloaded any 720p trailer, and loaded it through directshowsource in avisynth.
To compare it to Standard DVD resolution, I added a LanczosResize down to 720x480, then another lanczos resize back to the full resolution.

So what you're saying there is that you totally destroyed the benefit of the HD video by subsampling it, and based on that you found HD and SD to be comparable. Good plan there. Food for thought: What you did to the HD source is exactly the same as what the studios do to film when they make a DVD - therefore you just compared two things that had been processed similarly. Did you expect to see a difference?

That's also exactly the opposite of what is going to happen on your PC: The SD version will get enlarged, and the HD version will either be enlarged or downsampled slightly - though certainly not down to SD resolution. Try taking the DVD clip and blowing it up to the HD resolution with either a bilinear or bicubic resample (because your graphics card isn't going to do Lanczos for you ;)) then see which looks better.

The only parts where any difference was actually apparent was on disclaimer graphic at the beginning of the trailers. On the HD resolution trailers, these had JAGGY ALIASED EDGES, and I actually PREFERRED THE RESAMPLED VIDEO in this case!

Maybe the encoder is not so good (I've noticed some encoders have aliasing problems), or maybe the source looked this way. You softened the picture by resampling it. That doesn't make SD better.

Q: If HD is no better than SD, then why go HD at all?
A: HD is much better than SD, and this HDMI story is totally weak.

MfA

19th February 2006, 04:38

He did the downsize+upsize himself to know exactly how it was done, for the reason you mentioned, he still compared that against the HD original ...

DigitAl56K

19th February 2006, 04:58

He did the downsize+upsize himself to know exactly how it was done, for the reason you mentioned, he still compared that against the HD original ...

Not how I read it: What would be the point of downsizing the HD if you're going to compare against the original HD?

"To test, I downloaded any 720p trailer, and loaded it through directshowsource in avisynth.
To compare it to Standard DVD resolution, I added a LanczosResize down to 720x480, then another lanczos resize back to the full resolution."

To me that reads "I downsampled the HD, then I upsampled it again".

Here is a quick AVS script I hacked together if you want to compare an SD clip against an HD version using the type of resize your graphics card is going to do (if you're lucky..):

HDClip=AVISource("Clip_HD.avi")
SDClip=AVISource("Clip_SD.avi")
SDClipResized = SDClip.BicubicResize(HDClip.width, (HDClip.width / SDClip.width) * SDClip.height)

vdiff = HDClip.height - SDClipResized.height
Vborder = vdiff > 0 ? vdiff / 2 : 0
vcrop = vdiff < 0 ? vdiff / -2 : 0

StackVertical(HDClip.crop(0,HDClip.height/4,0,HDClip.height/-4), \
SDClipResized.AddBorders(0, vborder, 0, vborder, $000000).crop(0,(HDClip.height / 4) + vcrop, 0, (HDClip.height / -4) - vcrop))

It's not pretty, but it does the job.

MfA

19th February 2006, 05:04

To me that reads "I downsampled the HD, then I upsampled it again".
You read that right, he did this to get a "Standard DVD resolution" version for comparison ... rather than having to dig out an actual DVD version. Because as you say :

"What you did to the HD source is exactly the same as what the studios do to film when they make a DVD"

DigitAl56K

19th February 2006, 05:13

If that's the case then I apologise to Zarxrax, and bow to his evil genious ;)

But you still have to encode it to MPEG-2 at typical DVD data rates, which means further degredation.

MfA

19th February 2006, 05:20

Yeah, didn't say it was a completely valid way to perform the comparison :)

Revgen

19th February 2006, 09:00

@Zarxrax

I looked at the .png's and I honestly don't agree with you when it comes to the anime image. The drawn lines of the characters are noticeably blurred and less sharp.

However, the film shot does indeed look the same. However I'm not surprised, since I mentioned earlier that only sports and nature footage really benefit from hi-def.

The video's from the dvico website prove that. And of course you've admitted that much.

However many people enjoy watching sports and recording the games. I don't believe it's fair for people like myself to have to deal with HDCP crap and lower the resolution just to watch.

The MPAA may be correct when it comes to movies, but once sports fans (who are very vocal about what they don't like) start having to deal with HDCP and the obvious quality loss associated with it, there will be hell to pay. The NFL, NBA, NHL and their broadcast partners will inevitably follow in the MPAA's HDCP footsteps and it will make sports fans angry. I wouldn't surprised if this anger comes back to bite the MPAA and HDCP on the heels.

foxyshadis

19th February 2006, 09:09

It's funny that the push for uptake is mostly centering around film and film-like tv, when the cinema experience doesn't deliver much better than DVD, since sports is the only popular program that really gets revolutionized. I wonder how much BS will surround the HD movie upgrade commercials.

Doobie

19th February 2006, 14:52

Of course, we don't neeeeed HD. We don't even neeeed TV and video to start with. In most cases, I'm even happy with sub-DVD resolution DVD rips. There's nothing about my regular TV's resolution that compels me to run out and buy a HDTV.

On the other hand, a visually grand movie looks ordinary on TV, but in the theater, it is awesome. I want HD. Don't be a crackerhead, it's easy too see and appreciate the improved detail and sharpness of higher resolutions.

I'll just wait until prices come down more, technology/protection bumps are ironed out, and high quantities of HD material appears.

In 30 years, we will debate debate with a future luddite guy who insists that we don't need 3D HDTV. And, what happened to the dullard who insisted that VCRs are good enough and DVD isn't needed?

Qjimbo

19th February 2006, 15:33

Yeah, it's like saying you don't "need" 192kHz audio, which is true in cases where the DVDA or SACD disc has used the CD master which have the brickwall at 22.05kHz, I guess this is a similar thing. As for HD, I was blown away by numerous HD trailers compared with their SD counterparts, but I have a 19" monitor which means you can see the differences clearly. Thats the only major reason I can see for HD, the fact TVs are getting bigger and bigger means that SD content looks worse and worse.

Wilbert

19th February 2006, 16:12

People, be nice to each other, and don't make personal insults.

*.mp4 guy

20th February 2006, 04:40

Terminator III is being aired on CBS in HD as I type this, I also have the DVD sitting around somewhere. If anyone is interested I could post some comparative scrrenshots (although it won't be perfectly frame accurate unless someone else wants to do it).

MrTroy

25th March 2006, 19:44

To compare it to Standard DVD resolution, I added a LanczosResize down to 720x480, then another lanczos resize back to the full resolution.
Can I be the first to point out that you're *NOT* comparing it to DVD quality this way? DVD uses 4:2:0 chroma, while your video is 4:2:2. The correct way would be:

DirectShowSource("video.mov")
LanczosResize(720,480)
ConvertToYV12()
LanczosResize(1280,720)
ConvertToYV16()

zambelli

25th March 2006, 23:41

Your test methodology is completely wrong. No wonder you're not impressed with HD.

If you want to do a fair comparison, resize the SD content up to HD size and then compare them. Use the Interleave() function in Avisynth to combine the videos into a single video where HD frames alternate with SD frames. Then frame step through the video and you'll see the difference.

Wilbert

25th March 2006, 23:49

Your test methodology is completely wrong. No wonder you're not impressed with HD.
No, it's good (not perfect but good). Read MfA his comments.

zambelli

26th March 2006, 01:14

No, it's good (not perfect but good). Read MfA his comments.
I understand that he didn't have the SD source so he "faked" it by downsizing the HD trailer. That still doesn't make it a good approach!

For a start, DVDs are MPEG-2 compressed at SD resolutions. Yes, the HD trailers are compressed too, but any loss of detail due to compression of the HD video is probably lost or at least significantly reduced when you scale it down to SD resolution. So essentially, he's comparing uncompressed SD video generated from a high definition source to a compressed HD video. If he had compressed the "fake SD" video with MPEG-2 and THEN compared it to the MPEG-4 HD trailer - that'd make more sense.

A second, and much more important point: sharpening. LanczosResize() sharpens the video. It sharpens it when scaling down, and it sharpens it again when scaling up. It's a completely unfair comparison because you're not comparing the optical resolution of one source to another - you're comparing the optical resolution of a postprocessed source to another.

It's like slowing down one AMD Athlon64 to 800 MHz and comparing it to another Athlon64 running at full 2400 MHz, and then saying: "Look, a Pentium III 800 MHz computer isn't THAT much slower than an Athlon64 2400 MHz!"

siddharthagandhi

26th March 2006, 16:54

Wilbert

26th March 2006, 17:40

For a start, DVDs are MPEG-2 compressed at SD resolutions. Yes, the HD trailers are compressed too, but any loss of detail due to compression of the HD video is probably lost or at least significantly reduced when you scale it down to SD resolution. So essentially, he's comparing uncompressed SD video generated from a high definition source to a compressed HD video. If he had compressed the "fake SD" video with MPEG-2 and THEN compared it to the MPEG-4 HD trailer - that'd make more sense.
Sure.

A second, and much more important point: sharpening. LanczosResize() sharpens the video. It sharpens it when scaling down, and it sharpens it again when scaling up. It's a completely unfair comparison because you're not comparing the optical resolution of one source to another - you're comparing the optical resolution of a postprocessed source to another.
I agree that Lanczos might not be the most suitable resizer for this purpose. But of course any resizer sharpens or softens the image. The dvd footage is also resampled from a higher resolution, and thus sharpened/softened depending on which resampler is used.

xyloy

26th March 2006, 18:11

I agree with Doobie. We don't even need HDTV...SD looks perfectly fine to me on my TV. We're all spoiled brats. We are never happy with what we have, we just want more, more and more.

"I got a 62 inch TV man!"
"Oh yea, I got a 78 inch."
"Screw you all, i got a 105 inch"
:D That's a good point! ;-)

But I think the difference between HD and SD can be compared with the difference between watching a movie in a theatre, and after on a damn 4:3 TV... Even if the DVD image is perfectly clean, the visual experience is definitely not the same.

siddharthagandhi

26th March 2006, 19:08

Anyways, whoever sits in front of the TV or computer all day doesnt have a life. So you shouldnt that concerned about your visual experience for an hour or two a day. Plus, its the content that makes the show, not the sorround sound 7.1 Dolby Digital n Sony HDTV 1080p widescreen 1000 inch tv.

smok3

26th March 2006, 20:07

its the content that makes the show, not the sorround sound 7.1 Dolby Digital n Sony HDTV 1080p widescreen 1000 inch tv. yes and no, form will/may introduce the certain meaning and in some cases it is essential.

btw, i do belive that hd is good - especially rather cheap hdv and similar hd cameras will make a really nice 'longtail' graph in the near future; or in other words f*** hollywood - and big names certainly know that, thats why there are all the delays with this BR and HDDVD; they really cannot affort to get it wrong this time.

as for the end users (consumers); they may have really 2 many options to pick from (quality wise/content wise, distribution wise, ect.) - simple example would be my 'videospam@gmail account' which allready functions as sort of a reality tv RSS feed ;) - not that i really ever wanted that....

zambelli

27th March 2006, 01:33

But of course any resizer sharpens or softens the image. The dvd footage is also resampled from a higher resolution, and thus sharpened/softened depending on which resampler is used.
Sure, but in addition to that he's also scaling up and sharpening again. Most displays don't have scalers that sharpen as much as Lanczos does. Bilinear or Bicubic would be a more realistic comparison.

Soulhunter

3rd April 2006, 00:37

Imo Zarxrax thesis is correct, at least to some extend! The thing is that most of the current HD content doesnt contain as much details as it could/should (wrong processing, low bitrates and codecs which tend to smooth) If you use a HQ source (5MPix or above, which should be close enough to the quality of a master, no?) and downsize it to 720p (http://img87.imageshack.us/img87/1002/sourceto720p6nm.jpg) and compare it to a "downsized to D1 -> upsized to 720p (http://img87.imageshack.us/img87/5587/sourcetod1to720p0ah.jpg)" version (all via lanczos) the difference is much more visible, huh!?

EDIT: Before someone complains that the "downsized to D1 -> upsized to 720p" sample has too much aliasing, I also made a alternative version with softer resizing (http://img125.imageshack.us/img125/4885/sourcetod1to720pb0uv.jpg)which results in less aliasing but blurs more...

Bye

zambelli

3rd April 2006, 01:49

all via lanczos
Once again... Lanczos sharpens more than the scalers typically found in video cards and displays. The fact that you're sharpening on the way down and then sharpening on the way back up pretty much invalidates this comparison, IMHO, because you aren't just scaling the image - you're post-processing it, too.

A better test, IMHO: take a nice, detailed picture with a 3-4 megapixel digital camera. Raw format if possible, or at least with low JPEG compression. Make two copies. Resize the 1st to 720p using Bicubic resizing. Resize the other to 480p using Bicubic, then back to 720p using Bilinear. Compare now.

It's a better test because:
1) We started from the same high resolution master.
2) We used the same Bicubic scaling algorithm to produce both 720p and 480p images - one that's close to what most editors and encoders use.
3) The Bilinear resize of 480p to 720p is a more accurate representation of what an average renderer or display would use.

When comparing the images, remember to look for extra detail in tiny objects, especially the ones far away.

Soulhunter

3rd April 2006, 02:25

Where you got that Lanczos sharpens the image? Lanczos is a sharp resampling method (means, it produces a sharper picture than bilinear or bicubic resampling) but it wont sharpen the image! Its the opposite, it blurs the image, like all resizers (well, except pixel doubling or stuff like EDI) do (thats what interpolation does, blurring pixels together, no?). It keeps more of the sources sharpens than bicubic or bilinear, yes, but it doesnt sharpen/enhance) the image! If lanczos would sharpen the image a "downsized->upsized" version should be less compressible than the source, but its up to 10% more compressible after the two (or even six) lanczos resizes! Anyway, here is a compare closer to your instruction: 5MPix source downsized to 720p via bicubic resampling (http://img125.imageshack.us/img125/9943/720pbicubic2wv.jpg) / 5MPix source downsized to D1 and upsized to 720p via bicubic (http://img131.imageshack.us/img131/8964/576720bicubic1gp.jpg) <- Note: I used PAL D1 resolution not NTSC D1, and I used bicubic for the upsampling as renderers use bicubic (or something close to it) and not bilinear to my knowledge! Well, imo the result is somewhere between the lanczos and the soft-resize sample (which used 3 instead of 1 lanczos downsizing steps <- proofs again that lanczos doesnt sharpen but blurs)

Bye

milldakill

3rd April 2006, 09:37

I have also noticed this. I think the issue is that resolution is not the end all be all determination of picture quality. A clean encode free of articacts at DVD resolution and above is probably the most important factor and I can only hope that HD-DVD stuff will be cleaner than DVD.

zambelli

3rd April 2006, 21:44

Where you got that Lanczos sharpen the image?
From just about every text describing Lanczos resizing methods.

From Avisynth's documentations, for starters:
"LanczosResize is an alternative to BicubicResize with high values of c about 0.6 ... 0.75 which produces quite strong sharpening."

Lanczos is a sharp resampling method (means, it produces a sharper picture than bilinear or bicubic resampling) but it wont sharpen the image!
If LanczosResize doesn't sharpen, how come min/max luma values increase in a Lanczos resized image?

You can see for yourself:
original = AVISource("foo.avi")
video1 = original.ColorYUV(analyze=true)
video2 = original.BilinearResize(x,y).ColorYUV(analyze=true)
video3 = original.BicubicResize(x,y).ColorYUV(analyze=true)
video4 = original.LanczosResize(x,y).original.ColorYUV(analyze=true)
return Interleave(video1,video2,video3,video4)

You can run that on something simple like ColorBars and see for yourself. The min/max luma values will increase with each resizing method, which is a clear sign of sharpening.

If lanczos would sharpen the image a "downsized->upsized" version should be less compressible than the source, but its up to 10% more compressible after the two (or even six) lanczos resizes!
That's just incorrect. Compressability is impoved when quantized image information is removed or simplified. If you resize the image to a size smaller than the original, you're removing image information. Even if you blow it back up and interpolate the missing pixels, you have't actually reconstructed any of the destroyed information so of course the new image will be easier to compress. Sharpening doesn't even enter into it at that point.

Soulhunter

3rd April 2006, 22:18

Compressability is impoved when quantized image information is removed or simplified. If you resize the image to a size smaller than the original, you're removing image information... [snip]Quantizing the image = Removing details = Making the image more blurry, not sharper! The thing is that the interpolation overall etas more detail than the highpassing/ringing adds (at least for normal movie content, for images of GUIs or Colobars where you mainly have ultra-high next to ultra-low frequencys its a different story). So, at the end the final result is less detailed (more blurry), not sharper... that was my point! Its like: Imagine you'd write a filter which first applys a mild sharpening and then a blur which not only cancels all of the sharpening but also make the image less sharp than it originally was, would you describe the output of this filter as blurred or sharpened!?

Bye

zambelli

4th April 2006, 00:53

Its like: Imagine you'd write a filter which first applys a mild sharpening and then a blur which not only cancels all of the sharpening but also make the image less sharp than it originally was, would you describe the output of this filter as blurred or sharpened!?
Look, any resizing requires some form of interpolation - creating pixels which didn't previously exist. If you're aggressively creating pixels with the goal of more sharply delineating high contrasting areas - then you're sharpening the image, in my opinion. You seem to assume that "sharpening" means "adding more detail". That's not the definition of sharpening. You can throw away information and still "sharpen" the image.

Anyway, we're getting off track here. I originally objected to Lanczos because I think it doesn't represent the scaling that's done in most renderers and display devices. I think that still holds true.

Soulhunter

4th April 2006, 01:09

Look, any resizing requires some form of interpolation - creating pixels which didn't previously exist. If you're aggressively creating pixels with the goal of more sharply delineating high contrasting areas - then you're sharpening the image, in my opinion. You seem to assume that "sharpening" means "adding more detail". That's not the definition of sharpening. You can throw away information and still "sharpen" the image.Depends on the definition of detail again... My definition: Detail = High frequency parts of a image (texture and edges) and as sharpening amps the high frequencys, sharpening means a enhancement of details!

Anyway, we're getting off track here. I originally objected to Lanczos because I think it doesn't represent the scaling that's done in most renderers and display devices. I think that still holds true.
Ditto! Tho its a interesting topic for itself, huh? Anyway, as I posted samples of both, lanczos and bicubic resizing, ppl can make their own pick! Imo both demonstrate that the current HD content (or lets say, most of it) is far away from being "perfect" ^^

Bye

IgorC

4th April 2006, 04:12

If bring some parallel thougts between DVDaudio and DVDvideo in my opinion first few years HD-DVD will be poorly popular between people who cares about excelent quality of video.

There are enough nubmer of dvd-audio titles but only audiofils care about it. While most of people are looking just for mobile decisions with lossy solution like MP3. High contrast, isn't it? DVD-audio 4.3 gb & MP3 128 kbits - 50 mb per album. 80x difference.

Nocturno

5th April 2006, 20:20

imho we do need HD , and the sooner the better, i observe macroblocks in our cable transmissions on a daily basis, the digital signal offerd here is just the same crappy source digitised. i watch 1080i movies and documentary's through my pc on my tv at 1024x768 at the difference is shocking.
even if you play the same movie from dvd the difference is still shocking. the HD version of pulp fiction is like watching a completely different movie than the dvd version. no kidding!
the amount of detail is stunning, facehairs etc, the colours amazing. do we need HD? definately. but on your pc? well that depends on the size and resolution of your screen i suppose.