Posted Fri Feb 5, 2010 at 12:00 PM PST by Joshua Zyber
Editor's Note: Each Friday, High-Def Digest's own HD Advisor will answer a new round of questions from our readers. If you have home theater questions you need answered, send an email to [email protected]
Answers by Joshua Zyber
21:9 Enhancement on Blu-ray?
Q: Last week, you mentioned Phillips new 21:9 aspect ratio TV. Its benefit allows you to watch 'scope' movies (2.35:1) with no black bars on the screen. You've also been referring to the problems associated with CIH (Constant Image Height) in that zooming is required to fill the entire screen area, because Blu-rays waste part of their resolution on letterbox bars. So my question is, why not encode the wider 'scope' movies anamorphically to Blu-ray? As you've said "all high-definition Blu-ray content has the same inherent aspect ratio of 16:9 (1.78:1)" and so only movies and TV shows that are truly 16:9 will utilize all the 1920x1080 pixels. As "a 2.35:1 movie only uses approximately 1920x815 of those pixels," about 265 lines are wasted. Would an anamorphic Blu-ray help alleviate this problem or is this even possible?
A: Many 2.35:1 Constant Image Height users wish that the Blu-ray format had been designed with some form of 21:9 anamorphic enhancement, much as DVD was designed with 16:9 anamorphic enhancement. That would allow 2.35:1 aspect ratio movies to utilize all (or nearly all) of the pixel resolution in a 1920x1080 Blu-ray frame, rather than the approximately 1920x815 pixels they utilize now. Unfortunately, the Blu-ray format designers did not have the foresight to plan for that in advance. The format spec has no provision for non-square pixels or anamorphic enhancement.
More to the point, the format spec has no provision to down-convert a 21:9 enhanced image to standard 16:9 proportions. It actually wouldn't take much effort for a movie studio to issue a disc enhanced for 21:9 displays. All the studio would have to do is master the movie with an anamorphically stretched transfer and press that onto a disc. However, if they were to do this, viewers with traditional 16:9 HD displays would see a vertically stretched picture on their screens. As would any 2.35:1 CIH viewer who uses the "Zoom Method" rather than an anamorphic lens in front of their projector.
The DVD format was released during a period of transition from old-fashioned 4:3 televisions to widescreen 16:9 TVs. The format was designed to accommodate both display aspect ratios. If a viewer doesn't own a 16:9 TV, the DVD player will downconvert the picture to 4:3 letterbox shape. Unfortunately, Blu-ray was designed with only the 16:9 aspect ratio in mind. A Blu-ray player cannot downconvert a 21:9 enhanced image to the equivalent 16:9 letterbox shape.
Although it could theoretically be possible to upgrade existing Blu-ray players to support 21:9 enhancement (and downconversion to 16:9) with a firmware update, the likelihood of doing so is virtually nil. For one thing, it would require every Blu-ray player manufacturer to provide updates for every single Blu-ray player, even discontinued models. It would also require that every Blu-ray owner out there actually follow-through and update his or her player's firmware.
Failing that, the movie studios would by necessity be forced to issue separate 16:9 and 21:9 versions of each movie, one for general audiences and one for the CIH niche. They'd have to label and package them separately, and provide sufficient promotion to educate buyers as to which version would be more appropriate to purchase.
In short, adding 21:9 enhancement this late in the game would be a marketing nightmare for both Blu-ray hardware and software providers. As much as I might personally benefit from this, I don't foresee it happening. Maybe on the next video format down the road?
Lossless Audio Bit Rates
Q: We are told that DTS-HD Master Audio and Dolby TrueHD are bit-for-bit identical to the studio master. The signal is compressed, and then reconfigured at the audio stage. I do not understand then why the bit rates vary massively from 2 Mbps to 13 Mbps (the highest I have seen on a Blu-ray) and up to a possible 40Mbps. I understand the logic of having as high a possible bit rate for video.
A: The Dolby TrueHD and DTS-HD Master Audio formats are both lossless compression codecs. As you note, they are each bit-for-bit identical to the studio master. However, they utilize different compression algorithms to accomplish that goal. That's why their bit rates can vary so drastically.
The important thing to note here is that, regardless of how they perform their compression, these two formats are both lossless. Once decoded, they each provide an exact replica of the source originally fed into them. Therefore, the bit rate numbers you see on your player's display are completely irrelevant. Lossless is lossless, no matter how it's achieved. A higher bit rate will not give you a soundtrack that's more lossless than another.
Bit rate numbers are only relevant when discussing lossy compression formats, such as the standard Dolby Digital and DTS used on DVD. Even then, Dolby and DTS use different lossy algorithms. You may compare the bit rates of one Dolby Digital track to another Dolby Digital track, or one DTS track to another DTS track. But you cannot directly compare the bit rates of a Dolby track to a DTS track, because those numbers simply do not mean the same thing.
Bit rate numbers are just statistics. They really tell you nothing about how a disc looks or sounds during actual playback. I've long argued that home theater viewers would all be better off to ignore bit rates entirely, and focus instead on judging how a disc really looks and sounds.
Monty Python's The Meaning of Blu-ray
Q: In your site's review of the 'Monty Python's The Meaning of Life' HD DVD, you say that the film had an underwhelming transfer. Is this movie available on Blu-ray yet? If it is, is it the same underwhelming transfer? Should I wait for a better transfer if it isn't any good?
A: 'Monty Python's The Meaning of Life' is one of many catalog titles that Universal Studios issued on HD DVD but has not yet brought to Blu-ray. During the format war, the studio was eager to crank out as many movies as it could on HD DVD. Unfortunately, many of those catalog titles sold very poorly. Now that the format war is over, the studio has been hesitant to release poor-selling titles on Blu-ray.
Of those movies that Universal has released on both formats, in almost every case, the Blu-ray contains an identical video transfer to the prior HD DVD, for better or worse. When the studio finally gets around to issuing 'The Meaning of Life' on Blu-ray, I'd expect it to look identical (or nearly identical) to the HD DVD.
Universal is notorious for making very little effort to restore or remaster its older movies for Blu-ray (or HD DVD). The studio generally just recycles old video masters first prepared for DVD, even when those masters are not up to modern standards. This no doubt plays a part in why the HD DVD edition of 'The Meaning of Life' was so underwhelming. However, it must also be noted that all of the 'Monty Python' movies were made very cheaply and often with rather poor production values. Even if the studio took the effort to give the movie a full-blown restoration, there's a limit to how good it can look.
Two weeks ago, our HD Advisor column focused on the issue of 3-D. One reader sent a detailed response to address and clarify some of the points in that article. It's a good read and makes some important points. I'll add some footnotes at the end.
Feedback: I work in the entertainment industry and have an intimate knowledge of stereoscopic 3-D exhibition technologies. As such, I thought it may be worthwhile to give my two cents on some of the statements in the recent HD Advisor column.
"Most 3-D movies have been shot either with two side-by-side cameras or one camera with two lenses. (Modern 3-D movies use the latter process.)"
This is not quite accurate. Current 3-D films are produced in one of three ways: 1) computer animation; 2) dimensionalizaton; or 3) live-action capture. The first production method is the most straightforward given that most animated films are modeled in three dimensions to begin with. For these films, production studios effectively place "virtual cameras" at the appropriate locations to render the right-eye and left-eye views. The second production method involves capturing a film in 2-D and then applying a series of production and post-production tools to effectively convert the 2-D material into 3-D. There hasn't yet been an entire feature film that has been dimensionalized.(1) However, this process is used for particular shots in live-action films that are challenging to capture with the current generation of acquisition rigs. In addition, this process is what will inevitably be used to convert catalog titles to 3-D.
The third and final production method uses live-action capture. Current live-action acquisition rigs use either side-by-side camera rigs, or a beamsplitting rig whereby the acquiring cameras are at a 90-degree angle (i.e. one camera shoots straight ahead, the second shoots toward the floor). Each of these forms of rigs has pros and cons. They are used on a shot-by-shot basis depending on the required inter-axial spacing (the space between each optical center). The single camera with dual lens concept has been shown by Panasonic and a handful of other companies, however these are not being used in production to my knowledge. (2)
"The brief 3-D revival of the 1980s used a single-projector process called 'over and under,'...however, it also effectively reduced the resolution of each picture by half."
It is worth noting that Technicolor has developed and is currently selling to exhibitors a high-quality variant of the over/under solution. The notion that the over/under (or the side/side) format "reduces the resolution of the picture" is not entirely accurate. The "resolution" on film depends on the acquisition method of the feature in addition to how it is taken back out to final deliverables. The short answer is that using modern post-production workflows, each image in an over/under format can have the same "resolution" as an equivalent digital cinema projected image. In fact there are relatively standard methods that would allow for "higher resolution" images than their digital equivalents. I use the phrase resolution in quotes with film as it is an analog format so the notion of pixels/dots doesn't apply. However, there are general metrics of equivalence. (3)
"Some of the brand names you might encounter are RealD, Dolby 3D Digital Cinema, XpanD, or Tru3D. Each is slightly different than the others, but the basic underlying principle is the same. Digital 3-D uses a single projector with a liquid crystal screen in front of the lens that alternately projects the left eye and right eye imagery. Viewers wear polarized glasses again to sort out the views."
Both accurate and inaccurate. The liquid crystal screen in front of the lens (i.e. Z-screen) is specific to the RealD digital 3-D solution, which also uses passive polarized glasses. XpanD uses active glasses to shutter between eyes (much like the presumed forthcoming home theatre standard) that is synced via an IR emitter. Dolby 3D is an entirely different animal altogether. Crudely, it is anaglyph on steroids with proprietary passive glasses. Dolby uses advanced color filtration to differentiate the right-eye and left-eye images, however keeps the entire spectrum of colors. Effectively, each eye has its own specific color spectrum, that when projected together exhibits the entire spectrum. Tru3D, Disney Digital 3-D, and a few others are nothing more than rebranding of the aforementioned digital 3-D solutions.
The commonality between all single-projector digital 3-D solutions is that they effectively show images in rapid succession to create the 3-D effect. These images are projected at 48fps (24fps per eye) then often "triple-flashed" to minimize flicker that can lead to eye fatigue (as such most digital presentations are technically at 144fps in sequential order: L1 R1 L1 R1 L1 R1 L2 R2 etc). IMAX has both analog and digital 3-D projection methodologies, the former using 70mm film, the latter using dual digital projectors. It's also worth noting that the majority of the installed projectors aren't actually projecting a full 2K resolution image due to the need for "triple-flashing". The current generation of DLP projectors, however, are capable of "triple-flashing" in full resolution.
"Older 3-D HDTVs use the simultaneous method. In this, the left and right images are combined into a single 1080p frame, such that the pixels alternate between the left and right views in a "checkerboard" pattern. The downside to this is that it means the individual 1080p images are each reduced to 540p resolution. These checkerboard HDTVs may still function with the new 3-D standards with the help of a convertor box (Mitsubishi has already announced one), but the picture you watch won't be true high definition."
Generally correct, however it is worth noting that each of these "older" 3-D-ready TVs has its own method for squeezing the information into a full 1080p frame. Some use checkerboard, some side-by-side, some over/under. However, the point does remain the same here, which is that the spatial resolution is halved.
"The new frame-sequential high-def 3-D standard will require that both the left eye and right eye images each be displayed at the original 24 Hz or 60 Hz rate. That means that the Blu-ray player will transmit either a 48 Hz or 120 Hz output signal. Because your TV was not built to accept either of those frame rates, it cannot display the 3-D image."
Correct. Fundamentally, the challenge with existing home theatre equipment is the generally unsupported 1080p48 signal. HDMI 1.3 has the requisite bandwidth, technically, but there is an implementation issue that HDMI 1.4 is currently set to address. In addition, while the signal will be 1080p48 (or 1080i96...same data rate) the television will need to effectively "flash" the data multiple times to present a quality 3-D experience that minimizes eye fatigue, headaches, etc. While that isn't an issue for Blu-ray players and HDMI, it is a challenge for TV manufacturers that don't currently offer televisions with the requisite internal bandwidth. In the example of digital cinema, the projectors are effectively exhibiting 1080p144.
"From my understanding, the Sony CineAlta does not actually display 3-D content at 4k resolution. A traditional 2k RealD theater will project the left eye and right eye information sequentially, much like an interlaced TV. Each eye's view is a full 2k resolution, one alternating with the other in series. However, the CineAlta projects both 2k views simultaneously to create its 3-D effect. Technically, the content still only has a resolution of 2k, even though the projector is using its full 4k panel."
Correct...subject to my comment above that many RealD and other digital 3-D theatres don't even exhibit a full 2K image.
There are several anecdotal assessments by forum users that RealD is brighter or dimmer than Dolby, than 2-D, etc. The fact is that virtually all 3-D projection (and certainly any single-projector 3-D projection) is dimmer than 2-D projection. 2-D film is supposed to be projected at 16ftL (this is without film in the gate), 2-D digital at 14ftL. 3-D digital is similarly supposed to be projected at around 4.5ftL. The most important thing, however, is that while these are the "supposed to" figures, reality is often lower across the board for varying reasons (age of lamp, frequency of maintenance, alignment of lamphouse, etc.). The studios do create different versions of their content to compensate for this (i.e. 2-D digital is color timed at 14ftL, 3-D is color timed at 4.5ftL).
JZ: This is valuable information, and I stand corrected on a few of the statements I made in my last column. Here are some of my follow-up notes:
1) Actually, 'The Nightmare Before Christmas' was photographed entirely in 2-D, and then years later processed into 3-D for a new theatrical run. That 3-D version of the movie has been re-released several times since. Also, Tim Burton's new 'Alice in Wonderland' was likewise photographed in 2-D but later dimensionalized into 3-D. It was not a native 3-D production.
2) Looking into this further, I find that your explanation is more accurate than mine. However, that dual-lens Panasonic camera will be released imminently.
3) We may be arguing semantics here with regard to the definition of the word "resolution." It's true that film is an analog medium that cannot be measured in terms of pixel resolution. 35mm film is also generally accepted to have a higher effective resolution than HD video. I understand your point that it's (at least theoretically) possible for the over/under or side/side methods of 3-D to produce a better quality image than digital 3-D methods, if we can incorporate modern production workflows.
With that said, I remain skeptical that a new implementation of 35mm 3-D will really be a viable alternative to digital 3-D. The dupe film prints distributed to movie theaters are usually several generations removed from the source, and are rarely capable of delivering all the detail captured by the original photography. It's been estimated that many typical 35mm theaters project an image with barely better effective resolution than a DVD (albeit on a much larger screen than any of us have at home). Considering that the over/under and side/side 3-D prints only utilize half of the 35mm frame for each eye's view, I have a hard time believing that the 3-D image projected from 35mm will hold a candle to digital or IMAX 3-D. I don't think you were necessarily claiming otherwise, but it's worth noting for our readers that the theoretical possibilities for these formats may not play out so well in practical real-world application.
Check back soon for another round of answers. Keep those questions coming.
Joshua Zyber's opinions are his own and do not necessarily reflect those of this site, its owners or employees.
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