Posted Fri Oct 16, 2009 at 11:50 AM 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
192 kHz Audio
Q: I have a first generation PS3 with an Onkyo TX-SR804 receiver taking audio through HDMI (decoded in the PS3). When I try to play the Dolby TrueHD 192 kHz 5.1 track on the 'Akira' Blu-ray, I only hear sound out of the front left and right speakers. If I change the audio to Bitstream to decode in the receiver, it comes in as 48 kHz (which I'm guessing is because my receiver is older and can't do Dolby TrueHD natively). I can't use a Toslink optical cable since the PS3 can't output 192 kHz 5.1 that way, only stereo. The 48 kHz 5.1 TrueHD track comes in fine, but the sound quality on the 192 kHz track is nothing short of incredible, so I'd really like to hear it. Is there anything I can do short of buying a new receiver?
A: The Japanese Dolby TrueHD track on 'Akira' presents a dilemma for many viewers. In their zeal to provide the Blu-ray disc with the best audio quality available, the disc authors failed to realize that not every A/V receiver can accept the full 192 kHz signal. Unfortunately, they neglected to provide a comparable losslessly-compressed option with a lower sampling rate. (At least, not for the original Japanese language track.) The options on the disc are either Japanese Dolby TrueHD 5.1 at 192 kHz or lossy Dolby Digital 5.1 at 48 kHz.
Although the PS3 can decode Dolby TrueHD 5.1 / 192 kHz to PCM, your receiver may not accept the full signal at that rate. It sounds like your receiver downgrades the signal it receives to 2.0 format.
By choosing "Bitstream" in the PS3 (original model), you are forcing the player to default to the standard Dolby Digital 5.1 track. Your PS3 can decode TrueHD internally, but can't transmit the raw bitstream. That's why you're seeing 48 kHz at the receiver, and hearing a significant downgrade in audio quality. You've not only reduced the sampling rate, you've also chosen the lossy audio track, which is from a different mix than the souped-up TrueHD track.
(Ironically, the 'Akira' Blu-ray does also contain another TrueHD 5.1 track at 48 kHz, but only for the English dub.)
What you need to do is this: With no disc in the player, go to the PS3's "Sound Settings" menu and de-select any audio option with a sampling rate of 192 kHz. This should force the PS3 to downsample the audio to the next highest rate (96 kHz). If your receiver can't accept that either, de-select 96 kHz as well, and the PS3 will downsample to 48 kHz.
Lossless Video Compression
Q: Much has been said about the advantages of lossless HD audio compression vs. lossy audio compression, but little is spoken about the potential advantages of lossless video quality. Would there be significant advantages in terms of video quality if media had the capacity to support lossless compression? Given current codecs/compression technologies, what kind of theoretical storage capacity would it take to store a movie using lossless compression and is that something you envision in the not too distant future? With future video formats, people often speak of increased lines of resolutions (2K, 4K, etc.), but few tend to address that today's video codecs are all lossy - just curious why?
A: The video compression formats in use on Blu-ray (MPEG-2, AVC/MPEG-4, and VC-1) are all lossy codecs, even at their highest bit rates. Lossless video compression would require an entirely different codec, such as the JPEG 2000 format used in digital cinema. Needless to say, it will also require significantly more disc storage space and a revision of the Blu-ray spec to accommodate the codec. I don't foresee this happening on Blu-ray anytime soon. Or, frankly, ever.
I also doubt that we will see a better disc format than Blu-ray in the future. All signs point to Blu-ray being the last physical media format for pre-recorded movies. Future distribution will continue to move toward internet downloads (with even heavier compression, unfortunately). Research currently being conducted into multiple-layered storage discs may be used for computer data applications, but not likely pre-recorded movies.
As I wrote in my Specs vs. Reality article a couple years ago, movie fans tend to get too caught up in the idea of higher bit rates or different compression formats being the most important criteria for good picture quality. In almost all cases, this is a fallacy. Unless the video compression is so poorly done that it results in distracting artifacts (which, admittedly, does happen sometimes, although honestly not as much as some people would have you believe), the resolution of the image and the quality of the video transfer are vastly more important.
Q: I recently started hearing about "clean power" and power conditioners. Is there such a thing as unclean power? How much does clean power impact home theater equipment. I have been looking at power conditioners, what should I be looking for in a power conditioner?
A: The notion of "dirty" power affecting a home theater first came into vogue through audiophile circles. Certain people insisted that replacing the electrical socket in their wall dramatically improved the clarity of the music they were listening to. This then led to super-expensive power cords that could carry the electrical signal better, and power conditioners designed to "clean" the electricity before it got to the CD player or stereo. Soon enough, the videophile ranks caught on and started seeing extraordinary improvements in picture quality as well.
In my opinion, this is almost entirely bunk. These dramatic improvements that people have convinced themselves that they're seeing or hearing are the result of placebo effect. They don't hold up to scientific measurement, or double-blind listening and viewing tests.
In my favorite article on the subject, a dyed-in-the-wool audiophile who was absolutely convinced that he could hear a difference in sound quality when using an expensive power cord sat down for a double-blind test and was utterly disabused of that belief.
Now, I'm not saying that there's no difference between "clean" or "dirty" power. I don't pretend to be an electrical engineer. I also don't mean to say that power conditioners serve no useful purpose. My own neighborhood used to regularly suffer from power brown-outs in the summer months when everyone ran their air conditioners. This would cause serious problems with my home theater equipment, until I added a power conditioner to stabilize the signal coming into my home.
However, in my experience, if you are otherwise receiving a steady power signal, fancy power cords and power conditioners will not improve your picture or sound quality to any discernable degree. A power conditioner can be a worthwhile addition to your home theater, but only if you understand its real purpose.
Some questions that the HD Advisor receives 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!
Computer/Multi-Media Speakers with a TV?
Q: I just bought a new HDTV for the living room. This is not being used for home theater purposes. This is just a general purpose TV, mainly so that my wife can watch 'The View' and 'Grey's Anatomy' in better quality. The picture is great, but the sound is tinny and awful. The speakers are far worse than the 20 year-old SDTV this set has replaced. Adding surround sound, even from HTIB speakers, is out of the question. My wife won't have speakers and wires running everywhere, and I have no room for a receiver. I've looked into soundbars, but haven't seen anything I liked. Again, a large bulky soundbar is something my wife won't approve. I was thinking of using a pair of small powered computer/multi-media speakers. Even if they don't give me full-range dynamics, they can't be any worse than what's built into this TV. However, most I've seen will only work with a computer. Are there any suitable for using with the analog L/R or Toslink output from this TV? (My wife needs to be able to control the volume using the regular TV remote.)
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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