Picture Quality and underallocation of space on DVD
11-11-03, 06:54 PM
#1
DVD Talk Hall of Fame
Thread Starter
Picture Quality and underallocation of space on DVD
Inspired by the recent Superbit thread....
I am seeing this trend more and more, especially with MGM new and catalog releases. Often there is so much unused space, it is absurd. DVD5 holds 4.38 GB, and many new releases only utilize 3 to 3.2 GB of that space. DVD9 holds 8.3 GB and often in the frenzy to cram as many (often 'fluff") extras and advertisements as possible, the main movie bitrate suffers and it is only 3.5 to 4 GB in size. Ex: almost all of the MGM Midnight movies are only 3 to 3.5 GB where easilly they could have allocated many more bits which would only improve picture quality. The WILLARD release is RSDL and crammed with extras, yet the movie itself registers a pitiful 2.8 GB, where > 8 GB could have been used to maximize picture quality.
Is this undersizing an intentional marketing scheme in order for us to be "wanting something more" and baiting us for a double/triple dip later on? Is it DVD authoring houses being lazy and not doing things optimally?
Is it a surreptitious way for the studios and authoring houses to cut corners and save a buck without the masses really noticing? A sort of thinking that "They won't care, they'll never notice"? I realize DVD authoring is an art, and bitrate isn't everything, but, all other variables being equal, can anyone tell me a reason why more bits dosen't amount to better picture quality?
I am seeing this trend more and more, especially with MGM new and catalog releases. Often there is so much unused space, it is absurd. DVD5 holds 4.38 GB, and many new releases only utilize 3 to 3.2 GB of that space. DVD9 holds 8.3 GB and often in the frenzy to cram as many (often 'fluff") extras and advertisements as possible, the main movie bitrate suffers and it is only 3.5 to 4 GB in size. Ex: almost all of the MGM Midnight movies are only 3 to 3.5 GB where easilly they could have allocated many more bits which would only improve picture quality. The WILLARD release is RSDL and crammed with extras, yet the movie itself registers a pitiful 2.8 GB, where > 8 GB could have been used to maximize picture quality.
Is this undersizing an intentional marketing scheme in order for us to be "wanting something more" and baiting us for a double/triple dip later on? Is it DVD authoring houses being lazy and not doing things optimally?
Is it a surreptitious way for the studios and authoring houses to cut corners and save a buck without the masses really noticing? A sort of thinking that "They won't care, they'll never notice"? I realize DVD authoring is an art, and bitrate isn't everything, but, all other variables being equal, can anyone tell me a reason why more bits dosen't amount to better picture quality?
Last edited by zyzzle; 11-11-03 at 06:57 PM.
11-11-03, 07:56 PM
#4
DVD Talk Gold Edition
On the other hand, there has been discs that have too much: DTS track, extras, etc. and the picture quality has been compromised. I personally don't mind seeing some underallocation - better than the opposite. At least you know they are playing it safe.
11-11-03, 08:10 PM
#5
DVD Talk Hall of Fame
Thread Starter
Yes, the logical reason would be that they want to double-dip with the Superbit release. However, even some Superbits are undersized. Granted, if the movie is short enough (ie, < 100 min), accounting for DVD's max. compression rate of 9.8 mbit/sec, the movie could still be undersized. In such cases, movie could be 'pegged' at bitrate = 9.8 mbit/sec (Constant Bitrate) for its entirity and still be under 7 - 7.5 GB.
Yes, there is a notion of playing it safe. But, those figures I quoted above are the *complete* movie with Dolby 5.1 and Commentary tracks included. Even with these, which naturally add bitrate, allocation of space is woefully mismanaged.
Blue Underground is a company which seems to "get it right" almost every time, and I commend their authoring and compression people. They take the extra effort to ensure the extra bits are there in most of their titles. Result, some astonishing transfers with better picture quality. And, guess what? Their releases on average, are not any more expensive than MGMs or Warner's.
Yes, there is a notion of playing it safe. But, those figures I quoted above are the *complete* movie with Dolby 5.1 and Commentary tracks included. Even with these, which naturally add bitrate, allocation of space is woefully mismanaged.
Blue Underground is a company which seems to "get it right" almost every time, and I commend their authoring and compression people. They take the extra effort to ensure the extra bits are there in most of their titles. Result, some astonishing transfers with better picture quality. And, guess what? Their releases on average, are not any more expensive than MGMs or Warner's.
11-11-03, 11:34 PM
#6
DVD Talk Legend
The DVD File did an excellent article a few years ago about compression that gives some insight as to why there may be some underallocation of the space. It doesn't exactly answer your question, but it does show that it's not so simple to use every last bit available:
With The Beyond, the profile showed that some sequences with rapid movement needed more bits. Using the flexibility of the Minerva, Malooly set an input at the beginning of a sequence that needed to be adjusted, and an outpoint at the end. But more than just raising and lowering bit rates, how they are adjusted is an additional factor that must be weighed. A "flat bit rate" adjustment could be made, allotting a set rate for the entire sequence, or a more complex procedure of raising the bit rate levels proportionally. Both are supported by the Minerva. To help clarify, Malooly offers an example. "If the first 2 seconds of a sequence were encoded at 5mps , but the remaining 10 seconds at 6mps, if I raise the bit rate for the entire sequence by 1mps, the first 2 seconds would then increase to 6mps, and the remaining 10 to 7mps."
But bits you add to one sequence have to be taken away from another. Depending on the software, when one part of a sequence is granted more bits, it is taken away from the entire rest of the sequence uniformly. However, some programs allow bits to be pulled from selected segments as well. Malooly also "locks off" difficult sequences when he has completed a particularly demanding tweak. Thus, any future bit rate redistributions will not ruin all the hard work a locked off sequence required.
And sometimes, it is also valuable not to go too far in the other direction, and "over manage." The focus of a tweak can be as exacting as a single frame, but the effort to go and adjust bit rate for such a short sequence is often counterproductive. "You can physically go down to one frame, but most sequences contain long passages of extended motion, so very small segments don't usually benefit much from such micromanagement." It is also possible to be left with unused space, and not utilize it in the final encoding. "Surprisingly, sometimes projects have lots of space leftover" he relates, yet some clients still don't take advantage of the extra space. "Though sometimes it just isn't worth it, because if you struggle to use every last bit, it won't add up to any appreciable difference in the quality of the final product."
But bits you add to one sequence have to be taken away from another. Depending on the software, when one part of a sequence is granted more bits, it is taken away from the entire rest of the sequence uniformly. However, some programs allow bits to be pulled from selected segments as well. Malooly also "locks off" difficult sequences when he has completed a particularly demanding tweak. Thus, any future bit rate redistributions will not ruin all the hard work a locked off sequence required.
And sometimes, it is also valuable not to go too far in the other direction, and "over manage." The focus of a tweak can be as exacting as a single frame, but the effort to go and adjust bit rate for such a short sequence is often counterproductive. "You can physically go down to one frame, but most sequences contain long passages of extended motion, so very small segments don't usually benefit much from such micromanagement." It is also possible to be left with unused space, and not utilize it in the final encoding. "Surprisingly, sometimes projects have lots of space leftover" he relates, yet some clients still don't take advantage of the extra space. "Though sometimes it just isn't worth it, because if you struggle to use every last bit, it won't add up to any appreciable difference in the quality of the final product."
11-12-03, 12:40 AM
#8
DVD Talk Hall of Fame
Thread Starter
That answers my question almost perfectly, Drexl! This article is one of the most informative and unbiased that I've ever read on the subject of DVD compression. It was so insightful. (Incidently, I forgot to mention that I have found Anchor Bay is another company which takes time on its transfers to allocate bits correctly and makes the most use of the available space.) This just goes to show that that art of being a DVD Compressionist is underappreciated. It is the "final link" and I think many companies should consider hiring superior compressionists and spend a little extra money there where the results will be so tangible onscreen.
Thanks for digging that up, Drexl!
Thanks for digging that up, Drexl!
