Mastering HD PC Audio, Part 1

How many people are dissatisfied with DVD sound quality?

Sure, DVD standard definition picture quality leaves something to be desired on a 1080p monitor, but AC-3 through an S/PDIF cable into a nice home theater receiver and decent speakers seems perfectly good already.

I doubt a higher bit rate coder would make a perceptible difference to most ordinary listeners. The limit of human hearing is just over 20KHz (analog). For digital sampling, you multiply that by around 2.2. For example, phone transmissions are engineered for 3KHz analog and transported at 8KHz digital. So I think these 96KHz and 192KHz sampling rates are a waste. The standard 48KHz is more than adequate for the limits of human hearing.

And then there's the 24-bit sampling depth. There is no audio recording equipment on earth that can record that much dynamic range. And even if it could, nobody would want it. When the source audio track goes to near silent, many listeners will be annoyed. Most well engineered movie sound tracks always have something going (music, birds chirping, etc.) to keep the listener interested. So the dynamic range of most movies could probably be captured with around 12 bits. 16 bits is already more than adequate.

Then there's all the hoopla over compression algorithms. Many audio purists will dismiss any lossy compression algorithms without even giving it a proper listening test. The concept of audio compression goes like this: If you hear an alarm clock ticking, then the alarm bell rings, you don't need to encode the ticking when the alarm rings since no one will hear it. Double-blind listening tests have shown that many lossy encoded sound tracks can't be picked out even by audio mastering engineers (golden-ears people who do this for a living). Interestingly, it's often people with significant hearing loss that tend to pick out the lossy compression algorithms. If you can't hear the high frequencies of the alarm bell, then you'll notice the ticking has gone away.

I suspect all these new Dolby / DTS standards are mostly aimed at getting people to buy new home theater sound equipment. Remember that Dolby Labs & DTS both make a small royalty for each new receiver unit sold. Given that existing audio equipment can always use the core Dolby Digital track (without the higher bit rate extensions) over S/PDIF, I would welcome a Tom's listening review of these new sound schemes to see if there is any real difference.

Dear Dogman:
If you check out the quality sites that rate DVD audio, you'll see comments from people with very "good ears" that give Dolby TrueHD and DTS-HD Master Audio considerably higher ratings than they give to core Dolby Digital or DTS sound tracks. My own experience on my "less-than-state-of-the-art" but good quality audio gear (5.1 is as high as I go right now, because that's as many speaker as I've cared to purchase, position, and EQ for my home theater rig) confirms these confirms these other claims. I can hear more detail and richer sound when decoding DolbyTrue HD than I can when decoding normal Dolby Digital.
The sites that do a good job of rating Blu-ray DVD audio include Cinema Squid, www.highdefdigest.com (I cited a couple of their reviews in this story), www.blu-ray.com, www.soundandvisionmag.com, and www.hometheaterforum.com. A little digging can turn up loads of opinions around this subject matter, most of which leans in the direction that decoding the lossless codecs indeed requires new (and more expensive) gear, but is worth to those to whom such things matter.
HTH,
--Ed--

Hi Ed,

I really hope that you continue to do home theater articles for Tom's. This is, by far, the best article that I have ever seen Tom's publish on home theater. It sounds like a.) you really know your stuff, or b.) you took the time to thoroughly research the topic or c.) both. The in-depth info on the various HD audio formats is fantastic.

I hope that the part 2 article is just as in-depth, and I am hoping that you will at least partly cover the Asus Xonar AV1.

My personal preference is to have a stand-alone Blu-ray recorder, but in the US, those do not exist so far. I have heard rumors that Toshiba will release one later this year, however, if they do, it remains to be seen if it will record from an HDMI input. Perhaps the combination of the Xonar AV1 in a HTPC would provide an acceptable alternative.

Thanks again for the superb article.

Best Regards,
Matthew

Gee thanks Matthew. As far as your a-b-c list goes, it's mostly (b) with a growing amount of (a), hopefully heading toward (c)! I've had the good fortune to work with more accomplished home theater gurus including Mike Chin of SilentPCReview.com, and also Matt Wright (formerly of HTPCnews.com, now with missingremote.com), and to establish good relationships with home theater/audio experts at AMD, NVidia, and Intel. With a support network like that, I'm glad to dig into these topics for the readership, as much out of a desire to get out of home theater PCs what I think they should deliver, as out of plain orneriness (when it doesn't work that way) and curiousity (when it does).

And you're right: the only Blu-ray recorders I'm aware of that are currently available include $3,000+ models from Panasonic and Sony available only in Japan at present. It would be quite a coup for the HD DVD champion to be first to market in the US (or anywhere) with an affordable Blu-ray burner.

And yes, I do plan to touch on the Asus Xonar as well as some other upcoming products (most notably from Auzentech, a Korean-based outfit that plans to release direct HDMI 1.3a audio support later this year, and upcoming stuff from Nvidia that promises to do likewise). If anything, I hope you'll find Part 2 even *more* interesting than Part 1...

--Ed--