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This topic comprises 3 pages: 1 2 3
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Author
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Topic: I have bought Gran Torino
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Julio Roberto
Jedi Master Film Handler
Posts: 938
From: Madrid, Madrid, Spain
Registered: Oct 2008
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posted 06-13-2009 10:09 PM
Ok, my 2 cents.
1) I don't see a difficulty obtaining a screen grab from a blu-ray disc that is not 100.00% representative of the EXACT information contained in that frame (i.e. not "degraded" in any form from what ANY non-defective blu-ray player, with any sort of "image enchancement turned off", would output to the TV). Protection can be stripped just about as easily as with DVD.
Be it an I-frame or any predictive or delta frame, they are all representative of 100.00% what any blu-ray compliant player (bug-free) would send to the TV over the HDMI (again, unless they are "enhancing" the picture additionally and colorspace convertions done right).
You of course could (and pbbly would) get "worse looking" non-I frames, but those are still the frames exactly pixel-by-pixel that are contained in the disc when you take a snapshot (screengrab) and not even necessarily worse than the I-frame (could actually be better looking if there is little motion, but usually not the case).
Not counting from gamma shifts from different monitors/TV's regulated to different "standards", and assuming both the person posting the screengrab and the blu-ray player in use performed the space color convertion correctly (to the final RGB result we are seeing), Mark should be seeing in his TV the exact same picture being seen in the screengrabs in that web page. Again, as long as his TV and monitor are both properly calibrated and actually capable of reproducing the range.
Note that blu-ray players do the 4:2:0-to-4:2:2 color space convertion themselves. Here is the first possibility for a blu-ray manufacturer to screw up, if I.E. they erroneously perform the convertion from 0 to 255 4:2:0 YCbCr to 601 4:2:2 instead of the 16-235 recorded in the disc to 601 4:2:2. It could crash blacks/whites when pushing an additional (and ficticious all-black and all white) 37 values into the space.
2) I don't agree with this.
quote: Bobby Henderson
The DVD format doesn't have the color fidelity and level of contrast that HD video on Blu-ray can show.
They both have the same color fidelity (8 bits YCrCb, 4:2:0) and level of contrast (again, 8 bits YCrCb ITU-R BT.601, or 219 levels per channel).
Actually, DVD offers slightly higher bandwidth-per-pixel ... but blu-ray offsets this by (normally) using more efficient codecs (than DVD's MPEG2-only choice).
Only real image advantage of blu-ray over DVD: much higher pixel count, possibility to use more efficient codecs at similar bit-rates (=less degrading due to compression).
But, of course, you can't use a DVD to compare it to a blu-ray because ... oh well, they may not even come from the same master or, at least, were authored (scaled, compressed, encrypted) separately.
3) I do agree it's hard to take a good photograph of a paused blu-ray frame from an HD TV ... and Mark did a fairly good job there(private plug off topic: I'm trying to buy a Canon 5D Mark II camera with the 24-105 lens official USA kit ... can't find it anywhere in stock for weeks, pls let me know if you see it)
4) Of course, no two blu-ray discs can possibly produce images that are any slightly different from each other (on the same equipment) due to "errors in pressing" or stuff like that. The only possibility is that they would come from two different masters, were each master took several hours/days to "build" (compress, encrypt) after any changes to the image "quality", even if only slight gamma changes, i.e. All discs MUST be 100.00% identical in the final result, or the encryption and compression wouldn't allow for (subtle) image changes at all. Either "massive" noticeable corruption (screen freezes, whole macroblocks shot to hell, etc) or 100.00% perfect. No in-between. Ever. For any reason.
The short answer: Mark, are you sure your TV is set to ITU-R BT.601 from the HDMI? Does your blu-ray player allow different color space convertions and, if so, have you chosen to respect the 601 convention and match it with the TV? (I.e. better no convertion at all than a double convertion before reaching RGB to the panel).
If so, and fiddling with the brightness/contrast in your TV doesn't reveal the near-black details that you can see on the screengrabs, then either your blu-ray player is screwing up somehow or your TV is just not capable of the full contrast range. Both things unlikely, but can't think of another reason. Certainly a "bad disc" can not be one of them. Unless, again, they came from different masters and WB is slipping the bad ones to unsuspecting customers or you actually purchased a badly re-authored chinese bootleg passing for the real thing or something like that.
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Bobby Henderson
"Ask me about Trajan."
Posts: 10973
From: Lawton, OK, USA
Registered: Apr 2001
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posted 06-14-2009 12:51 AM
quote: Julio Roberto
I don't see a difficulty obtaining a screen grab from a blu-ray disc that is not 100.00% representative of the EXACT information contained in that frame (i.e. not "degraded" in any form from what ANY non-defective blu-ray player, with any sort of "image enchancement turned off", would output to the TV). Protection can be stripped just about as easily as with DVD.
If copy protection measures for Blu-ray were anywhere near as easy to defeat as that of DVD you would see torrents of every Blu-ray release available for download. That isn't the case.
Regarding the screen grabs, NO, there is NO way to get all of the information of a film frame in a frame grab from a movie on Blu-ray because each frame doesn't have all of the data there in the first place. If Blu-ray was based on a compression system like JPEG2000 for digital cinema then there would be a discrete, seperate picture file for each film frame. Blu-ray does not have that. There is a hell of a lot of shorthand going on to get video compression levels squeezed down to levels more severe than 100:1. The only way to truly see all the detail in a Blu-ray movie is by watching the movie playing in motion.
quote: Julio Roberto
They both have the same color fidelity (8 bits YCrCb, 4:2:0) and level of contrast (again, 8 bits YCrCb ITU-R BT.601, or 219 levels per channel).
Movies on DVD are muted down for NTSC color levels for display on standard definition television sets. I have rougly a dozen movies on both DVD and Blu-ray. The quality of color and contrast levels on the Blu-ray versions are clearly superior to their DVD counterparts. If the two formats were really operating at the same color and constrast depths the only difference I would see between the two formats is a sharper picture in the Blu-ray version. That's clearly not the case.
quote: Julio Roberto
I do agree it's hard to take a good photograph of a paused blu-ray frame from an HD TV ... and Mark did a fairly good job there(private plug off topic: I'm trying to buy a Canon 5D Mark II camera with the 24-105 lens official USA kit ... can't find it anywhere in stock for weeks, pls let me know if you see it
The only way I've been able to get a decent photograph of a TV set showing a still Blu-ray image is by closing down the aperture and taking a somewhat underexposed image -that way the highlights and such on the TV screen aren't all blown out to hell. You also have to experiment with different white balance levels because the photo of the TV screen will try to shift to blue.
The EOS 5D Mark II should be more readily available. I've been considering buying one of those camera bodies as well. Stores like B&H Photo have the camera body listed as back-ordered. Best Buy is actually selling it with a 18 months 0% interest financing deal -but I would probably buy it cash up front from B&H or Adorama.
More likely, I'm going to buy a 580EX II external flash in the short term. There's a $50 instant rebate for it valid until July. I want to put together a good remote lighting kit with two or three external flashes and umbrella setups and maybe even add a ring light eventually. But the 5D Mark II would be really nice. I bought my L-series lenses for a camera body like that.
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Julio Roberto
Jedi Master Film Handler
Posts: 938
From: Madrid, Madrid, Spain
Registered: Oct 2008
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posted 06-14-2009 07:54 AM
quote: Bobby Henderson
If copy protection measures for Blu-ray were anywhere near as easy to defeat as that of DVD you would see torrents of every Blu-ray release available for download. That isn't the case.
We are not going to encourage piracy, so I won't post any links to the utilities to decrypt them, but you must not be looking around too hard .... as blu-ray pirate downloads of plenty of movies abound ... They are not sooooo popular as they often require upwards of 22GB, which is a bit too much "bandwidth" for most people to spend on a single movie. But still, you easily find hundreds.
quote: Bobby Henderson
Regarding the screen grabs, NO, there is NO way to get all of the information of a film frame in a frame grab from a movie on Blu-ray because each frame doesn't have all of the data there in the first place.
I never said that. I said that a screengrab of a blu-ray disc is 100% representative of the information in said disc (i.e. it doesn't add any "distortions" or it's particularly hard to get a screengrab), other than colour space convertions and further compressions to the desired format (i.e. as a jpeg image to post on a web site).
What I said is that: A) It's easy to get a screengrab of a blu-ray movie B) This screengrab is easily perfectly representative of what the blu-ray disc MUST (on non buggy equipment and decent TV's) look like, no matter what frame it is ... it's what you should be seeing in the TV screen.
Of course, what was in the original film may have nothing to do with what was decided to put in the blu-disc ... as just about anything can be done to the image during mastering.
The fact that the image compression is of an inter-frame nature and not only intra-frame does NOT necessarily (although it often does) mean that the frames are going to be of inferior quality and, regardless, not to any "noticeable" extend.
What's more. Intra-frame only schemes can be (and always are) MUCH worse at the same bandwidth, so they ALWAYS require more ("wasted") bandwidth to produce THE SAME (not necessarily "superior") results. Only advantage is the ability to move on demand to a particular frame without potentially having to decode a whole group of them to get at it.
It is not correct that the information is "not there" in a delta frame. Given enough bandwith, it ****IS**** there 100.00% period, just it used fewer bits to encode since it saved from repeating the *EXACT SAME* INFORMATION that was in some previous (or forward) frame.
It all comes down to bandwidth. Say with M-JPEG and 100mbs you could get the SAME (approximate to say 99%) result than with a similar scheme (say MPEG2) but that makes use of inter-frame redundancies at, say, 75mbs. They would BOTH produce ALL frames, I-frames or any predictive delta frames, exactly the same (to say within 99.99%) while one of them use (say) 25% less bandwith (and more processing power) than the other.
If you give the same bandwidth X to two similar codecs, an intra frame only and a similar one but also inter-frame, like a M-jpeg codec vs a MPEG2 codec, the MPEG2 would look CLOSER to the original source ("better") in ALL frames, including predictive frames, than the M-jpeg version as a general rule (there could be a couple of frames here and there that the MPEG2 codec decided weren't so visually relevant and allocated a too-low amount of bandwidth for them and may look better in the M-JPEG version).
The "master" of a film is not its 12bits YXZ MJ2 Dcinema version, and this is not where the blu-ray and DVD masters come from. It's the original DI, pbbly as 10-bits log uncompressed (or losslessly compressed) DPX files.
The 5D Mark II body is available in most places, but the KIT that comes with the 24-105 lens is what has been out of stock forever ![[Frown]](frown.gif) Thankfully, just found a place that received them Friday, so hopefully I'll get one next week.
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Julio Roberto
Jedi Master Film Handler
Posts: 938
From: Madrid, Madrid, Spain
Registered: Oct 2008
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posted 06-15-2009 07:46 PM
quote: Bobby Henderson
Most movies on Blu-ray take up more than 22GB of disc space.
Perhaps I didn't use the correct expression. By "upwards of 22GB" I meant that most pirated blu-ray rips on torrent sites are 22GB and up, all the way to ~50GB. Just check your favourite torrent site, type blu-ray and sort by size. You'll see plenty of movies. Yes, I have downloaded one or two and some of the Imax transfers.
Bobby, why do you have such a hard time believing that blu-ray decryption is perfectly possible? Oh, well, since its a commercial product that has many legit uses in many countries to enable fair-use policies, here it is:
http://www.slysoft.com/en/anydvdhd.html
quote:
Features Blu-Ray
Same features as regular AnyDVD
Removes encryption (AACS) from Blu-ray Discs.
Removes BD+ copy protection from Blu-ray Discs.
Removes region codes from Blu-ray Discs.
Watch movies over digital display connection, without HDCP-compliant graphics card and without HDCP-compliant display.
The "must have" utility for the serious home theater enthusiast using a media center / home theater PC.
Provides its own Universal Disk Format (UDF) reader, no need to install 3rd party filesystem. Discs which cannot be read by Windows can be copied using the AnyDVD ripper.
If the use of such a thing is illegal in your country, then I encourage you to not buy it. You could donwload a trial copy a check it out yourself. Again, as long as laws in your country permit copy protection circunvention and fair use of copied derivatives of copyrighted material on different supports.
And yes, it's as easy and automatic as it is with DVD, thus plenty of REAL, not-from-HDTV transmission or reconverted analog-to-digital abound on the internet. Why would you do such a thing when there is available in the market an automatic, easy to use blu-ray disc decrypter that even works on (99.9% of) BD 2+ discs? Hardly a handful of discs can't currently be decrypted and that's only because some glitch in them or weird interaction with the current version of the decrypter triggers a bug somewhere that prevents it. All other 99.9% of the blu-ray discs that have ever been marketed have been able to be ripped to totally unprotected copies into a hard drive (and thus torrent sites) for about 2 years now, IIRC (not sure of the timeframe, but certainly well over a year).
I see now what you mean by a single screengrab not being totally representative of the overall blu-disc and I agree. I missunderstood you and thought that you meant that a screengrab was "distorted" and thus not the way it should've looked when playing back the disc. My argument was that THAT frame in the screengrab was basically 100% representative of what you would be seeing in your TV when THAT frame hit the screen. Obviously frames before and after that one could look something radically different, but this would be most unusual.
Thus, the screengrabs posted of Torino showed like it was mastered with the levels on a very shallow curve in highlights and shadows and steep in midtones, obviously on purpose for the look of the film. But it also showed that the shadow detail WAS there, while Mark didn't seem to be getting it on his screen.
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Julio Roberto
Jedi Master Film Handler
Posts: 938
From: Madrid, Madrid, Spain
Registered: Oct 2008
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posted 06-16-2009 08:02 PM
For blu-ray reproduction, it should've been 16-235. Also, if your TV happens to have a setting as well as to what to expect from HDMI, set it also to 601 16-235 (it should do it by itself, but WTF knows with some manufacturers or perhaps may have manual override settings for pro's who know what they are doing).
Doing that, which is what should've happened by default, you avoid a double color space convertion that can't bring but problems, like what you were experiencing.
quote: Chris Slycord
No one is saying "blu-ray decryption is impossible." What he was saying is that it HAS NOT HAPPENED
Errr ... you may want to rephrase that if we are talking about subtleties as blu-ray decryption happens every single time someone plays a disc (or a decryption utility recovers the plain unprotected video stream).
Chris: I'm not familiar with the crack (or just plain hack) of the AACS on blu-rays or the (I imagine virtual machine) for the BD+ copy protection circunvention. It definitevely works and there are definitevely tons of (real) pir*ated blu-ray movies floating around, just like DVD(R) ones.
Of course, many of the (serious) encryption system have NOT been "cracked" per se, but in many cases, like this one, their implementation has been rendered useless due to fully exploitable vulnerabilities.
Of course, if someone really wanted and had some resources (say around $200k), they could also obtain a 1:1 digital copy of a DCinema uncompressed video stream ... But much cheaper and good enough for the criminals just to stick an HD camera and tape the whole thing and then strip the watermarks, I'm sure.
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