Posted Fri Jul 16, 2010 at 12:11 PM PDT 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
Dolby ProLogic II vs. DTS Neo:6
Q: Since the last HD Advisor column dealt with surround formats, I thought I would keep it in the same vein: What has your experience been with Dolby ProLogic II Cinema vs. DTS NEO:6 Cinema? Do you have a preference? There are still several movies on premium cable channels that are in HD but only output in digital stereo.
A: As I mentioned in last week's column, Dolby ProLogic II is an audio decoding process that will take a 2-channel sound signal and convert it to multi-channel format through the use of matrixing techniques. Specifically, ProLogic II will convert a 2-channel signal to 5.1 channels. ProLogic IIx will convert up to 7.1 channels, and the new ProLogic IIz will add height channels on top of that (for a 9.1 configuration).
But Dolby isn't the only company that offers this feature. Competing programs are built into most A/V receivers on the market. As you mention, one of the most ubiquitous and notable is DTS Neo:6. Another common alternative is SRS Circle Surround II.
In essence, these products do the same thing as ProLogic II. They convert a 2-channel audio signal to multi-channel format. (DTS Neo:6 can convert to 6.1 configuration.) However, each program uses unique algorithms that will deliver different results in regard to how directional steering is handled. For example, ProLogic II sends all movie dialogue to the front center channel, and has a centered focus for sound effects that aren't specifically mixed with steering cues. DTS Neo:6 tends to spread the sounds out a bit more.
Which is considered "better" than another is largely a matter of subjective preference. If your receiver offers more than one, try them all and see which you like. My own Denon receiver includes Dolby ProLogic IIx and DTS Neo:6. I've tested them, and came to the conclusion that I personally prefer ProLogic IIx. Its steering sounds the most natural and organic to me, while Neo:6 sounds a little forced and artificial. Your mileage may vary.
Also in Dolby's favor is the fact that ProLogic IIx can be applied to any audio input signal at all, from 2 channels to 7.1. It works on any audio codec, whether Dolby, DTS, or raw PCM. This makes it ideal to leave set as a default. I know that whatever audio source I feed into the receiver, ProLogic IIx will take care of it and deliver results to my liking, without needing me to manually adjust any settings. Neo:6, on the other hand, only works with 2-channel sources.
Blu-ray Disc Space Usage
Q: I've been looking at disc space usage of various films, and it seems many Blu-ray discs are authored with a lot of space left unused on the disc. Would it not be better to encode the film and features at a higher bit rate and make use of this unused space? Is there a reason why this isn't done?
A: Oh, how I wish that Blu-ray players were never built with bit rate meters, Blu-ray software in computers didn't display these stats, and people would stop obsessing over things like bit rate or space usage!
Yes, boiled down to its absolute most basic and simplistic concept, more disc space used means less compression used, and less compression is theoretically better than more compression. However, the real world factors that come into play during movie encoding and disc authoring are much more complex than that.
As I argued in my Specs vs. Reality article a couple years ago, bit rate and disc storage are just numbers on a screen. They tell you nothing about how a movie actually looks or sounds during playback. The AVC/MPEG-4 and VC-1 codecs used for Blu-ray video are incredibly efficient compression formats. They're specifically designed to maintain high visual fidelity even at low bit rates. Further, the number of bits needed for any given scene in any given movie will vary wildly depending on the complexity of the visual content in each frame. The skill of the compressionist and the quality of the work is always more important than the bit rate used, which is little more than an arbitrary number. It tells you nothing about the video or what was needed to compress it.
No, this doesn't mean that I think all Blu-rays are encoded flawlessly. That isn't the case at all. Studios have been known to let sloppy work slip through. However, we must judge the quality of each disc based on how it actually looks, not based on how many bits the file uses. It's equally possible to create a lousy video image with a high bit rate, or a great image with a low bit rate. Both have been done many times over on Blu-ray already. Watching the bit rate stats go up and down simply isn't an accurate measure of picture quality.
In other words, watch the movie, not the bit rate meter.
As for why a studio would want to compress a movie down to a smaller file size when the disc has extra space left over, you must consider that the studio may plan to use the file for other purposes than just Blu-ray, such as digital downloads. A smaller file size may be needed for that, and it's less expensive for the studio to encode the movie once for multiple purposes than to encode it separately for each use. Does this excuse a studio from using a sub-standard encode with visible compression errors on a Blu-ray disc? Not at all. I just want people to learn to judge that based on what they actually see when watching the movie, not based on the arbitrary and misleading numbers displayed on the bit rate readout.
Video to Film Back to Video Transfers
Q: Why is that when the time comes to do a home video transfer (be it DVD or Blu-ray) of a movie shot on video, such as 'Paranormal Activity', 'Jackass: The Movie', 'The Blair Witch Project', etc., that the studio doesn't use the original materials for the transfer? What I mean is, they shoot a film like 'Paranormal Activity' and 'The Blair Witch Project' on video because that medium captures how they want the movie to look. When it goes to theaters, they have to transfer the video to film. So, when it then gets released on video, why do they not use the original, and in many cases much clearer video elements? Films like 'Jackass', 'Paranormal Activity', 'Blair Witch' and '28 Weeks Later' look terrible on DVD. The video to film process causes the source material to lose color, and detail. When you watch deleted scenes on many of these discs, the scenes are usually in their original digital video state and look much better than the actual movie itself.
A: This often depends on the specifics of each movie's production and the stylistic decisions made by the filmmakers. There aren't blanket rules that we can mandate for how movies such as these should be transferred to home video. When you mention that the behind-the-scenes footage (transferred directly from video) for some of these movies sometimes looks clearer than the movies themselves, you assume that it was the intent of the filmmakers to present you with a crystal clear image. That isn't always the case.
For example, I'm going to assume that you meant to say '28 Days Later' above. (The sequel, '28 Weeks Later', was shot on 16mm film.) '28 Days Later' is notoriously one of the worst-looking Blu-rays on the market. Much of that is deliberate. Almost the entire movie was shot on standard-definition video, using a consumer camera set for a mode that barely records 240 lines of resolution. Directly Danny Boyle wanted the movie to look as gritty, grainy, and just plain ugly as possible. That's the aesthetic of the piece. By the time he made that movie, Boyle was already an accomplished director with several hit films under his belt. If he'd wanted to make a high-gloss production, he easily could have. Even with the camera he chose to use, he could have set it for another mode that would have recorded a better-looking image. He didn't want that. The very final scene in the movie was shot on 35mm film in order to provide a dramatic contrast between the end of the movie and everything that preceded it.
Likewise, 'The Blair Witch Project' was shot with a mix of SD video and 16mm film. One of the characters in the movie shoots his POV footage with a video camcorder, and the other with a film camera. There's meant to be a contrast between how good one looks and how poor the other does as the scenes alternate between characters.
In both of these examples, the video footage was transferred to film and then back to video again in order to maintain that contrast with the better-looking footage shot natively on film.
This isn't the case for every movie shot on video. Although movies such as 'Zodiac' and 'The Curious Case of Benjamin Button' were shot on video, they were intended to have a very slick and polished appearance, with as much clarity as possible. When these movies were brought to Blu-ray, they were transferred directly from the original video files without any film step in between.
The HD Advisor knows many things, but he doesn't know everything. Some questions are best answered with a consensus of opinions from our readers. If you can help to answer the following question, please post your response in our forum thread linked at the end of this article. Your advice and opinions matter too!
Blu-ray Lens & Disc Cleaners
Q: I haven't been able to find a Blu-ray lens cleaner. When you ask people that work at electronics stores (and supposedly have some appropriate knowledge), they look at you funny. I have one for DVDs and CDs, but I know that Blu-ray players have 2 lasers...red and blue. Don't I need a different lens cleaner for Blu-ray? Also, I'm looking for a good automated Blu-ray disc cleaner. I've been told you should clean them radially (from inside out) rather than in a circular fashion. The problem is that all the automated cleaners I've seen (and own) seem to clean in a circle. Can you provide some guidance?
JZ: It's been a while, but I mentioned way back in an early column that I usually advise against using abrasive lens cleaners. They may do more harm than good. In most cases, there's almost never a need to clean the internals of a DVD or Blu-ray player unless you've had catastrophic playback errors.
With that said, assuming you still want one anyway, I'm honestly not sure whether you'd need a separate cleaning disc for the Blu-ray laser. I'm inclined to think you wouldn't. But if some of our readers are more familiar with this topic, please let us know in the forum thread linked at the end of this article.
Likewise, I've never bothered to use automated disc cleaners. The protective coating on Blu-ray discs makes them pretty easy to clean by simply wiping with a lint-free cloth. Since I don't do a lot of renting, I've never had much of a problem with dirty discs. I'll admit this may be more of an issue for renters. So I'll leave the recommendations for lens cleaners to our other readers who may have more experience in this area.
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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