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6th January 2010, 15:45 | #41 | Link | |
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That's just when things aren't moving though. When things move at a multiple of 1 pel per field in the vertical direction even the best deinterlacers being used at the moment are not going to be able to make something sharp out of the result ... the object becomes identical (ignoring the shift) in both fields, all the image data for half the lines in every frame is simply gone, interpolation will have to do. So in that case the effective resolution becomes 50% ... but it's aliased, so it's actually a little worse than 50%. Which is why you really don't want to do high movement video with interlacing (sports mostly, since action movies are of course shot with flicker cam, making interlacing moot). Last edited by MfA; 6th January 2010 at 22:56. |
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8th January 2010, 01:39 | #42 | Link | ||
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http://www.camcorderinfo.com/content...erformance.htm Quote:
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8th January 2010, 07:04 | #43 | Link |
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Not exactly, because generally we don't use brickwall filters in video filtering ... just for instance a simple 1/4, 1/2, 1/4 filter will let such high frequency line patterns through attenuated. You can't exactly say it leaves resolution intact though.
PS. if you are going to ignore my argument of vertical resolution in the presence of vertical motion don't quote it ... |
8th January 2010, 08:54 | #44 | Link | |
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8th January 2010, 09:11 | #45 | Link | |||
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A tent filter will still have considerable attenuation above its cutoff frequency. If the measurement technique is good, then quoted line-pairs (or whatever) should be representative of the real frequency response, should it not? Quote:
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-k Last edited by knutinh; 8th January 2010 at 09:15. |
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8th January 2010, 10:09 | #46 | Link |
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No, it's not representative of the frequency response because in and of themselves you can't determine how fast the fall off (ie. how blurry vs ringy it is) is from a single data point.
I never said you didn't supply URLs ... hell the more the merrier, let me do one too. It's from EBU which has been doubted in this thread, but even if you doubt them there is the zinger from Faroudja (yes, that one) ... “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!”. |
8th January 2010, 10:24 | #47 | Link | |||
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Ringing is first and foremost an issue in high-order filtering including negative coefficients, I think. Do you see much ringing in 2-3tap decimation/interpolation filters? A system with flat and wide passband should be relatively unblurry. The degree of blurryness should be relatively well predicted from the "single datapoint" of passbandwidth? Quote:
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8th January 2010, 10:49 | #48 | Link | |||
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It would seem that their "video sharpness" test does in fact factor in temporal aspects such as interlacing/deinterlacing, temporal lossy compression etc (my assumption was wrong. Always delightful to improve understanding): Quote:
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8th January 2010, 11:02 | #49 | Link | |
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Lots of movement and/or lots of fine detail isn't a fundamental problem - the fundamental unrecoverable problem is the specific combination of fine detail and specific movement, as you illustrated. Where there's movement + fine detail that is recoverable, it's often argued that it doesn't matter so much if the display can't recover it because we're less sensitive to detail when the image is moving. It's not true for eye-tracked motion however - but then most modern displays are already a disaster for eye-tracked motion anyway, so it matters less. Cheers, David. |
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8th January 2010, 11:19 | #50 | Link | |
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Sorry, I got you and 2B mixed up ... thought you were arguing in favour of making interlacing a standard in a time period when progressive displays already ruled the roost (the US had a decent excuse since they started so much earlier). |
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8th January 2010, 11:32 | #51 | Link |
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Getting better all the time though. As long as we are going to put ever more computing power and algorithms into something I'd rather have it go into better motion compensated framerate conversion than better deinterlacing. With 240 Hz displays with 2 msec gray-gray I'd guess the display technology is pretty close to where no further improvements in smoothness can be perceived ... assuming good content to actually drive it at 240 Hz (where the computing power and algorithms come in).
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8th January 2010, 11:39 | #52 | Link | |
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8th January 2010, 12:01 | #53 | Link |
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Bitwise yes, moneywise no ... the costs added on display devices for the extra necessary gates to decode high fps streams is problematic (progressive vs. interlaced, when EBU was deciding things, was already not a big deal in any part of the chain). When H.265 is being hammered out and almost all displays are 144 Hz+ to begin with, HD slowmo cameras ubiquitous and transistors cheaper than ever I would definitely want to see high fps modes being a fundamental part.
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31st March 2010, 15:40 | #54 | Link | ||
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31st March 2010, 18:13 | #56 | Link |
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You doubt, that's okay. But that's guessing only.
Also note that it's not necessarily x264's interlaced mode being "so bad", but potentially it's non-interlaced mode being "much more efficient". Last edited by lovelove; 31st March 2010 at 18:21. |
31st March 2010, 20:16 | #57 | Link |
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lovelove : Deinterlacing != bobbing. The quote from mewiki is misleading. If you deinterlace an interlaced source, you lose information (since you halves the motion). So saying it's more efficient is misleading, because the efficiency doesn't consider the lost information. What the quote wants to say is that, if you take an interlaced video, encode it with some bitrate X, and measure the PSNR, you'll get a (far lower) PSNR than if you deinterlace, encode it at the same bitrate X, and measure PSNR (against the deinterlaced version, of course). You're actually comparing apples and oranges when you do that, but it's an easy mistake to conclude that it's more efficient.
Furthermore, x264 is a very efficient encoder, but when encoding interlaced content, it's lacking some major tools (either field picture support, or adaptive mbaff, or both) that seriously hampers it in regards to the concurrence. That doesn't mean it will be worse, but it does mean there is a lot of room (from 0.5 to 2dB, depending on the sequence) for improvement in x264 when it comes to interlacing.
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31st March 2010, 20:45 | #58 | Link | |||
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31st March 2010, 21:36 | #59 | Link |
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bobbing == Deinterlace(parity=alternating)
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1st April 2010, 07:07 | #60 | Link |
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I think we can agree that on this forum, when somebody says he "deinterlaced a video", nobody will assume he bob-deinterlaced it, just that he took a 50i/60i video and made it 25p/30p. Bobbing has become more than a deinterlacing method, it has become the process of taking a 50i/60i video and making it 50p/60p (see the number of avisynth filters with 'bob' in their name, and look at what they do).
If I talk of PSNR, it's because as of now, we still haven't a way to measure quality. If you prefer, I could have said the quantizer would be lower on the deinterlaced encoding. I still stand by my interpretation of mewiki's quote (it's easy for a guy writing a documentation to get carried on and make a mistake) Finally, all the broadcast encoders support one or both of the tools x264 lacks. I'm pretty sure mainconcept's does to.
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content, deinterlace, interlaced, progressive, quality |
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