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Ah, but converting 1080i60 to 1080p30 is quite a lot simpler than converting 1080i60 to 1080p60.
And there's no 720p60 HDV camera, but 720p30 HDV does indeed convert to 1080p30 very easily and looks great. I'd really say that if 720p30 doesn't scale well to 1080p30 on your projector, then it's scaler isn't that good. Getting rid of interlace should have been the first step to HD, not the last!! Graeme |
Graeme, that's post number 1000! do you win a prize or something?
Isn't there also the issue that interlacing leaves behind additional artefacts from the MPEG2 compression that otherwise would not be there? I've found de-interlacing Z1 footage to 25p oftenb leaves behind ugly little blotches that aren't necessarily there in CF25. I've tended to go back to CF 25 these days, despite the res drop because of this, in any "filmlook" situation. Ironically I find the artefacts worse in plain colour areas, rather than contrasty/detailly areas. |
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Dylan, I think I have to get to 1080p(osts) to get a prize!
MPEG2 compression is tough on interlace, but depending on the de-interlace algorithm I too find it can reveal artifacts that were less visible when interlaced - I don't think it creates them though. Ken, agreed that the 720p from the HD100 has more real detail than you get from the Z1/FX1. Graeme |
...now that's what I was hoping for when I posted that link- a real discussion. Now I can go back a reread it( the thread, except for the first page) and maybe learn something. thanks esp. to Douglas and Graeme for digging in and giving us more to think about . Kurth
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It's always a good discussion, and it's great that you're getting multiple educated points of view. Douglas really knows his stuff, and so do I, and that we disagree should be taken as that there's not a simple answer to the question, not that either of us is necessarily wrong. If our comments stop and make you think, then that's the best result by far :-)
Graeme |
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Additionally, had the Grand Alliance had their sh** together, we never would be hearing of 720p, as 720p was intended as an interim, and as history would have it, it will be indeed, an interim format, which is the main reason I'm mostly a 1080 guy. We do have 3 720 cams, we use them a lot, and have scaled them a lot. We first noticed problems on a 60" SXRD monitor at Government Expo, and one of our major clients needed vid for their tradeshow. They took the 720p acquired and delivered footage, viewed it on their Samsung 70", and told us they were unhappy. We reshot the same footage using 1080, and they were happy, and it ended up on 10 screens at CES in January. That whole real-world process is what caused us to dig in deeply, and really stretch what we could do, even buying two different 1080 displays and borrowing a Qualia projector to rip into the footage. (This client is seriously important to us, obviously) I will say that in the process, I've learned that scaling isn't as easy as one might think. While scaled vid looks great on displays smaller than 40", it exponentially increases in view-ability post 60", and gets worse when blown up with a large projector and screen. Especially look at the edges, which are somewhat hidden by bezels on many displays. Additionally, the discussion of "real" vs "perceived" becomes one of opinion, and at the end of the day, we're really stuck with that. "Really," what Panasonic has done with the HVX simply shows it can't work, on paper. But perceptually, it's a very good camcorder. so what is "real?" Given DSP on both mentioned camcorders, either one can be shown to best the other, depending on a number of variables. Like Graeme says, just the mere fact we can't agree on what we're seeing or doing, says a lot. I'll stick a dig in here though, and point out that what we see here on our screens, is identical what Poynton has written about in several papers and his "bible" of HD. I have to chuckle though, because when you see guys like Faroujda commenting that you can't deinterlace footage all that well selling deinterlacing devices, and you see Terranex, S&W, Miranda, etc all coming on with very well-made products...some manufacturer has an agenda in the industry. 1080 is the future, whether we need to debate semantics, processes, or actualities of the media conversions. |
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are we not kind of comparing different cameras here instead of really just the format?
The only true way to test the formats is to take a scene from the same camera but in both formats. I know this is impossible right now. One thing I have done however is made a scene in 3D Studio Max to match a real world setting. I then rendered at 720p and 1080i with the intent of converting both to 1080p. The 720 was slightly softer but had much less artifacts. The scene I rendered had many thin line objects such as power lines and low angle edges. One thing that was hard for me to test however is the interlace filtering that interlace cameras always have. Any filtering of the image I did quickly killed any extra detail the 1080i had over the 720p. I know this isn't a god test in terms of what cameras do but it does tell me what can be done with raw images of certain resolutions and aspect ratios. My outcome is that 720p is softer but much cleaner. I personally would rather have a slightly softer image but with no missing thin details or aliased edges. I personally think people are looking for way too much detail. Who really wants to see every single blemish and imperfection? Douglas what cameras were you using for your client that were shown on those 60" displays? Perhaps it was more of a certain look to the 1080i cameras and really nothing to do with the 720p format. You can take 4 different 1080i cameras and they look all look very different. The JVC HD100 for example does have a slightly more smooth filmic look to it which some people who are used to the crispness of video might not like. It doesn't mean it has less detail but just a different look and style. If you used a highend 2/3" 1080i camera compared to a prosumer 1/3" 720p camera well no kidding there was a boost in detail between the two images. If you used a HD100 compared to a Z1 I cannot see any way on how there could be more detail. Considering a lot of people think a progressive scan SD DVD is HD on a 60" HDTV I think it is going to be a long time before people start choosing a 1080 image over a 720 image (if somebody didn't just try selling them the numbers first) The are only two areas where I consider 1080i HDV to have an advantage. 1. smoother motion at 60/50 fields per second. Hopefully this will change when we get 720p 60p. 2. Even though 1080i has more compression per pixel the compression artifacts are not blown up as much. Mpeg2 artifacts at 720p can show up more when scaled up to 1080p. For those interested on the points of Graeme and Douglas you should check out Steve Mullen's view on 720p HDV vs. 1080i HDV. Most of his tests show many 1080i cameras to have less detail than the 720p from the HD100. |
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http://www.dv.com/ titled "Four Affordable HD Camcorders Compared" under "Top Stories on DV.com". This article leaves me with no dillusions that when converting to a 1080p image, 720p JVC HD100 would produce a better image than the interlaced Sony's. |
While it might not leave you with any delusions about converting, I don't see the relevance. They didn't didn't convert anything in the shootout test to be viewed on scaled or native monitors. Additionally, I believe enough murkiness has been thrown over that particular test to cause it to not be of merit.
Additionally, the conversion is heavily dependent on the algorithm used for the conversion. What may convert well from one system won't convert well for another. For instance, Graeme brought up using a polynomial set. Polynomials are generally not usable for video because it's not consistent with the limited range of video. There are many variables, and many theorems about how this could, should, would be and *is* done. How many taps? From where is the output sample value derived? 8 bits? 10 bits? 12 bits processing? How far is it oversampled? Looking at a res chart and not being disillusioned about scaling values is like looking at a gas tank and suggesting you know how fast the car can go. |
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I think it is possible to say three things: 1/ 1080 is better than 720 2/ Progressive is better than interlace. 3/ 50fps gives better motion rendition than 25fps The obvious conclusion from that is the best format (given a good enough front end) must be 1080p/50, and I don't think anyone seriously can disagree with that. The problem is that that is a huge challenge for todays technology, and that necessitates making a compromise with at least one of those points. (At present.) The big debate is normally whether to accept going down to 720, OR accepting the problems of interlace. Which is the least bad compromise - 1080i or 720p. That's why I'm surprised the third option isn't more discussed of in these forums - 1080p/25, which is what I believe most top end TV drama etc is being shot in currently (for delivery psf). It keeps the undeniable advantages of 1080 resolution and progressive scan, and for drama many producers actually like the temporal look - "film like". Assuming you have a camera front end that can deliver the goods. |
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What it means in practice is that the same transmission structure is used for both psf and i, and whether the origination is interlace or progressive can be chosen on a programme by programme basis, such as interlace for sport and progressive for drama (for delivery psf). I'd be interested what Graeme thinks of this? |
PSf is exactly as you describe David, a way of trasmitting progressive video carried in an interlaced video carrier. It's not any form of de-interlacing.
The Canon doesn't shoot Psf. It shoots a so called "24f" mode which to me looks like 48i roughly de-interlaced. David, you're right that if you want a filmish look, 25p, or 30p is just fine, but no affordable HDV camera shoots those rates other than the JVC with it's 720p30. All the 1080i cameras have fake progressive modes, some better than others, but all faked from interlaced chips. Even thinking that 1080i will deinterlace to 1080p and give a result approaching real 1080p forgets that 1080i has about 30% less vertical detail than 1080p, and even best de-interlacers don't put that back in. People say you can think of 1080i60 say as 540p60, but really it's more like vertically wobbled 378p60. The faked progressive modes on the 1080i cameras turn of interlace filtering, so you can get 540p, but only at rates up to 540p30, not 540p60. And although I like the 24p/25p film look rates, I really like the 50p and 60p rates also. They have a certain luxuriousness to them that's very apealing, and a certain creamyness that 50i / 60i lacks. David, you're list is correct - P is better than I, 1080 is better than 720, 50fps is beter than 25fps, but.... 1080i only has the SAME vertical resolution as 720p due to the interlace factor, so, if you were to rate formats in terms of qualtiy based upon that list you have to take that into account. From what Sony were describing to me, the new XDCAM HD will shoot 50p or 60p, but at (perhaps less than) half vertical resolution. They couldn't tell me if interlace filtering can be turned off. Basically, in overcrank you get 540p, probably embedded in 1080i. Nothing is ever simple..... Graeme |
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Graeme |
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I was also only thinking of transmission formats from a broadcast perspective, and here think 1080 i or psf has a lot to commend it for the present time. That is not the same as saying any individual camera using any recording format is better than another solely because of that. Format comparisons need to be divorced from camera comparisons, and vice versa. |
Douglas- ( alittle off topic ) you reminded me of checking out www.pixelmonger.com to see if Mr. Billups has updated his site. The man is in serious need of a webmaster. He's about 3 years ( light years in todays market ) behind. Maybe he's working too much ! It was a relevant source. Now it should be in the Smithsonian. Kurth
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Kurth, I get to see/listen to Scott once a year at NAB...maybe I should mention his website, but chances are (knowing the kind of guy he is) he won't care. It's not really part of his very focused world. |
Speaking of the Canon H1 and all of these formats, has anyone made a deck that will work with all of them yet?
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Figured I'd finally jump in here -
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I'm not an engineer - and there are a ton of people in here smarter than I, But I probably speak for a good slice of the pro-sumer camera buying contingent. I think and make buying purchases in laymens terms and what my eye sees is most important. IMHO - 720 sucks on a 1080 monitor. As stated by someone else: "720 was designed as an interium format" - I.E. MEDIUM DEFINITION (in the JVC HD100 case - NO I don't loathe the Varicam - I was simply speaking of the "Small Four" Indie HD cameras). I'm not concerned with the specs - I know what I see (obviously, this is completely arbitrary. During my interview with FresHDV, my opinions were requested, remember). Your creative process/ workflow could be way different from mine. Keep in mind, I believe the JVC HD100 to be a fine camera - the image does look great coming out of the viewfinder. There is no perfect Indie HD camera on the market. However, I do think everyone who buys a JVC now for the progressive feature, and those who pay a premium to work with the hassles of P2 are going to be pissed off in 18 - 24 months when cheaper and easier 1080p is avaiable. Progressive is better - just not how its currently packaged for Indie HD users. |
How about somebody setting up a double blind viewing test?
Do one test on a 1080p display, and another on a 720p display. I figure these two are likely to dominate viewers' homes for the forseeable future. Niether the participants nor the administrator know the sources, and participants only compare two pictures at a time, only identifying a preference. A wide variety of equipment could be used to create the sources, with identical shots. The beauty of such a system is that NOBODY can bring any prejudices to the table. I remember Stereo Review doing such tests years ago on CD players (then new), and various audio amps - tube and transistor. Niether the "golden ears" nor the "techno-nerds" could pick consistent differences. Speakers seemed to be the only big variable. |
Well looks like we've come full circle . Welcome Josh . I hope you didn't mind me starting this diatribe on dvinfo. Thanks for stepping in with your two cents. I , for one, enjoyed how you phrased the situation . Keep it up .Kurth
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Are we talking 720p from the HD100 here? I think we are making the mistake as I tried pointing out of thinking of 720p as only what you get from the HD100. While I think the HD100 is a great HD camera for the price I do admit it isn't as good as 720p could be. How does Varicam footage look on a 1080p display? How about good 1080p 30p/24p down converted to 720p and then shown on a 1080p display? I know this point doesn't really matter since really the only way to shoot 720p is to use the HD100 or the Varicam. My point however is I think we are all thinking in terms of what the camera is doing to base what the format is like which is wrong. DV from a 1/3" camera and a 2/3" camera can be very different even though they use the exact same 4:1:1 DV format. Trying to compare 720p from one camera to 1080i from another is useless. There are many aspects that go into how the image looks other than resolution. Some people may not like the look of the JVC but then again there are some that love it. The only real way to ever compare 720p to 1080i and get a fair test is for both formats to come from the same source.
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Sure 720p is an "interim" format - but what is it the part-way stage to? It's the partway stage to 1080p. Back when, 1080p60 was not a reality. There's still no commericial camera out there that can shoot 1080p60. Ok, easier target, 1080p30 or 1080p25 or 1080p24 - sure you can shoot that today, the most affordable being the Sony HDCAMs. They will do real 1080p at these rates, real progressive, really nice, but not affordable. No HDV cam (ie affordable HD) does real 1080p at any frame rate. The HVX200 does 1080p, but only at 1080i resolution. (XDCAM HD is on the horizon - no 60p, no specs on resolution of the 1080p30) But for ages we've been able to shoot 720p at any frame rate - 24p, 30p, 60p. 1080i is NOT an interim format. It's a dead end. Interlace is as dead as SD. 1080i is not going anywhere and it's not a part-way solution to 1080p. The number "1080" might be the same, but interlace is so radically different to progressive, it's not an interim solution. So yes, 720p is interim, but in the best sense that if you want 1080p60 tomorrow, 720p60 is the best format to shoot now, not 1080i60. If you just want the lower frame rates, 720p30 raised to 1080p30 will give a very equivalent visual quality to 1080i60 de-interlaced to 1080p30, but you need less system requirements while editing. So is 720p "Medium definition" - yes, compared to 1080p it is. Is 1080i "Medium definition" - yes, compared to 1080p it is. Remember the interlace filtering reduces 1080i's resolution to about that of 720p vertically, and that's not just on motion - that's everything. Things in motion are reduced to 50% of 70%, about 35%. Interlace is very 1940s. Quote:
The EBU also thinks along similar lines: http://www.ebu.ch/en/technical/trev/trev_300-wood.pdf There's some very good points in there: Given that all modern TVs are inherently progressive, given that good de-interlacing is hard, it makes sense to have a few, expensive, really good de-interlacers in the broadcast chain, before transmission, rather than fit a multitude of inferior de-interlacers to every HD TV - this, of course, necessitates broadcasting HD in only progressive not interlaced. There is a compression quality efficiency of 720p50 over 1080i50 that allows you to deliver better images at 720p50 than 1080i50 for smaller bandwidth. "It is relatively easy to convert a progressive delivered image to an interlaced form, but it's much more difficult to convert an interlaced image to progressive form to suit it to thenew displays." "all the arguments we have found support broadcasting a signal that does not need de-interlacing." There's a lot of good meat in that article - take a read - it's enlightening. Graeme |
Again...it's not being defined as acquisition vs display....
no point in continuing to talk about 1080p 60, because it's not relative to *this* market here and now. Not at all. Sure, the HVX "records" 1080p60, but I fall back on my earlier question...if I record VHS to HDCAM, is my video now 3:1:1 uncompressed, 1920 x 1080 HD? |
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The viewing distance is uncannily accurate in my own case, but since that document was written many people within the industry have been taken by surprise by the rate at which screen sizes have leapt up, and the sweet spot for displays in UK stores is probably already at 42", with a fair number of 50" - and that's before HD broadcasting has even started! If the document was being written today, it would probably foresee the vast majority as being in the 37"-42" range, with a significant percentage going up to 50". Referring to the chart (fig 4) then a significant percentage of observers now find an advantage in 1080 resolutions, and this is part of the "what if" conclusions on page 8, (though at the time closer viewing distances seemed more likely than bigger screens). I do note they then conclude that 1080p would be more suitable than 720p, and presume this includes 1080p/25 for appropiate programming? |
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Yes, screens get bigger, but UK homes do not. I find it very cramped to now visit the UK after living in Canada. Most homes in the UK don't have enough room for an old 27" never mind a 50" widescreen monster set.
Reading fig 4 is interesting. It's showing that 720p meets mosts people's needs for most TV sizes at the average viewing distance. However, it's a chart of horizontal, not vertical resolution. I guess that's to keep the interlace factor out of the equation. You can think of 1080i having a vertical resolution somewhere between 378 lines and 756 lines, depending on content and movement. Something else I found interesting: "If the three colour primary points are not spatially coincident (as they are not in practice), it may be that to fully exploit a given signal resolution, a higher resolution panel is needed to avoid spatial aliasing effects. In other words, it may be that a 1080p panel is needed in order to fully use the 720p delivery format." Graeme |
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Bottom line is, manufacturers prefer to build bigger displays, many people tend to want bigger displays, and at the end of the day (currently) more bigger than smaller displays have been sold. So perspective is very relevant to the discussion. If we're talking 46" and smaller, there is little reason to talk about any of this, right? Because at 32ppi and square pixels, 46" is native scale for 720 |
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With a view to buying a new screen I measured up at home and found the viewing distance was pretty well 2.6-2.7metres, almost exactly the figure the BBC research used for their tests. Currently I watch a 32" widescreen CRT TV, and that seems more or less "right". That follows on from a 36" 4:3 TV which was a mistake - too big - though the problem was it's height and bulk rather than screen size. I feel the limiting factor has been not screen size, but the size of the piece of furniture. Many stores here recently were giving away brochures which would unfold and could be used to give an idea of how varying screen sizes would look in your home. My conclusion was that for a screen flat on the wall 42" was a bit too small, and anything over 50" would be oppressive. Now that 50" prices are falling and becoming acceptable, this is probably what we'll get within the next year. The big difference will be losing that piece of furniture in the corner of the room,and even a much bigger screen on the wall will give us more space. I suspect this is why rear projection TVs, even DLP ones, haven't made much of a mark here. The real importance of the BBC research - and it's relevance to the rest of the world outside of Europe - is that it primarily deals with angle of view and resolution of the eye, and screen size etc is secondary to that. I can well believe US and Canadian room sizes are bigger than the UK, and viewing distances and screen sizes are correspondingly bigger. I suspect that means similar angles of view in all these countries. What figure 4 shows is that whilst 720p was acceptable for envisaged screen sizes and angles of view at the time of writing, then for the situation now around half will appreciate something better. |
And to go to anything better than 720p means going to 1080p, not 1080i, and not 1080psf where progressive is broadcast as interlace, and such progressive for broadcast is often filtered vertically as 1080i is, so you don't get the full vertical resolution 1080p is capable of.
Of course, take into account the compression that's applied in broadcast, you'll get, given the low bandwidth allotted to HD broadcasts, a better picture with 720p anyway. There's no point in HD if all it does is increase the number of nasty artifacts you see. Graeme |
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I'll bow out of the discussion as it's getting rather stale, as we're discussing things that are not changeable by any of us and playing ring around the rosie with opinions. My apologies for having kept my end of it up this long. Might as well be discussing how soon we'll be at war with Iran. so as my final comments.... We shoot both formats here. We have everything from the bottom end HD camcorders to full-time access to an LDK 5000. (Grass Valley's international service center is here, and their director of service for the US is one of my closest fishing buddies) For what we shoot, and for what our clients money for the most part, 1080i is the best we can offer them affordably. Motocross looks terrible acquired at 30p in any flavor. Same goes for lacrosse, and especially same for the high motion military stuff (like when helicopters are brought in to catch Mars rovers parachuting to earth) On the other hand, we've used the JVC HD100U on two corporate projects, and have been very, very happy with the results. We're also very impressed with JVC's BR 50 upscale of DVX originated footage. I also believe that there is a lot of ignorance about conversion quality, and the quality of the tools used to make those conversions. As an example, FCP and Adobe PP2.0 can't scale to save their a$$. Premiere 1.5 does a pretty good job. I'd wager that roughly 8-10 hours a day of my daily life involves downconverting, with maybe 10 hours per week in upconverting depending on the client, so I'm pretty comfortable with most of the tools, having experimented with virtually all of them in hardware and software. Sony Vegas, Algolith, and Red Giant are all wonderful software tools. I use Vegas most of the time, but occasionally use Algolith if I end up working AE. I might not be able to get as deeply into the math as some folks can. But I'm not by any stretch blind, we own several different HD displays and two projectors here, and have a fairly critical client list, two of whom offer HD authoring tools. If we were putting out the "lesser grade" that some folks call 1080i, or 1080p30 converted, or in a couple cases, 1080i converted to 1080p60, then believe me, both of those software companies would be crawling up our rectums. Especially our client in Germany, who is likely the best known h.264 company on the planet next to Quicktime's new, but slightly inferior QT wrapping of .264. When we ship them HDCAM, we've yet to have a complaint. We haven't shot anything for them in HDCAM, but that's how we deliver. Prior to that, it was all the loaner 5000, or our older 700. Cost went down with the HDV cams, client is pleased with that, because they also feel quality didn't coincidentally go down. We're happy, they're happy, they've noticed issues (made up in their minds or not) with 720p, and they've specifically asked for 1080i converted to 1080p30 or 1080p60 (in one case only) based on what we've sent them, all footage from all three HDV cameras available as of December 05 (not including the A1u) We're likely moving to the XDCAM HD platform for most of our work, I've had quite a bit of time with the 350 thus far, and am disgustingly impressed. We'll likely go with the 350 with the Fuji 38 lens for a main cam as soon as they start shipping. |
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Which means the comparison between 720p and 1080i in this market is primarily one of temporal vs. spatial resolution. 720p30 gives twice the spatial resolution while 1080i gives twice the temporal resolution. While 720p may convert better spatially to 1080p than 1080i does, 1080i should likewise convert better to 720p60 than 720p30 will, at least if motion is a concern. If you can accept the P2 workflow then the HVX at 720p60 may be the best of both worlds (assuming the CCDs are capable of maxing the spatial resolution of the format) until 1080p60 becomes practical. Otherwise the better format is the one which best fits your subject - 720p for dramatic, scripted, static or controlled motion shots vs. 1080i for sports, action, reality/documentary, etc. |
hey guys - great points made by all. thanks. It reads to me that Graemes' view is theoritically correct , and many here are indebted to him for his theorical knowledge. Douglas' point is based on real world equipment and it's limitations. Obviously his clients are his judge but there's no sustitute for handson experience. Most here will never have the opportunity to use 1/4 of the equipment he uses.
What we see now with the available cheap hd equipment is they're all performing more or less equally. Maybe the next generation will get closer to perfection , i.e. 1080/60p. I guess what I liked about Joshs' article was that all of the cameras have achilles heels and no one should feel they need to go out and get the next best toy to shoot good video. I think alot of sony owners felt that canon, jvc , and panasonic were being touted as being sooo much better that the sony hdvs' were passe' and they needed to figure out how to raise 10k or just go back to shooting dv. The truth is last week I saw a mint arriflex bl with 10-100 zeiss and internal lightmeter sell for 1200 bucks. That's what these small, cheap hd cameras have done. I mean , who in their right mind would want to still pay $50 a footage/minute ? Now we can start filming instead of butting heads over formats and quality. Until the xdcams define the next gen we're all more or less in the same boat- 720p,108060i are just splittin' videohairs. thanks esp. to Douglas and Graeme for turning this thread around- Kurth |
"last week I saw a mint arriflex bl with 10-100 zeiss....who in their right mind would want to still pay $50 a footage/minute ?"
well i'm in that $$ per foot area ... i looked/tested the 4 hand size HD camera's ... i wanted to BUY/spend but my wallet didn't jump out of my pocket .. i thought they were all OK ..but OK isn't good enough at this time ... so for short project, rented a spring wound 16mm bolex - scanned ( not telecined) at 2k res -now in post ... |
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