What is HD-Audio?
by Mark Waldrep
It seems everywhere you look there's increased interest in "high-definition or high-resolution" audio. Artists like Neil Young, a longtime advocate for better sounc has even announced a new hardware and software initiative that he calls Pono and Apple is rumored to be readying their iTunes delivery system to accept 96 kHz/24-bit music masters from record labels and aggregators. There are an increasing number of so-called HD download sites that make available music files at 96 or even 192 kHz and 24-bits (AIX Records has its own with iTrax.com). There are working groups and committees within NARAS (the Grammy people), the AES (Audio Engineering Society) and CEA (Consumer Electronics Association) looking into raising the fidelity of both downloaded AND streamed music. I'm a member of all of those committes and I can tell you that the new interest in quality is very refreshing after over a decade of terrible sounding music BUT we are a long way from agreeing on a strategy or even a definition for HD-Audio. Let me share some of my thoughts on the subject.
First, let me state right out front that I am a huge advocate of advancing the quality of recorded audio. I have no interest in the "resurgence" of vinyl and even analog tape as consumer delivery formats. It's quite true that many engineers and audiophiles look longingly back 20 years or more to the so-called "golden age" of music recording and reproduction, they're entranced by sonic familiarity and equipment nostalgia rather than a true interest in the improvement of fidelity and the elevation of a recorded musical experience. I have no argument with fans of vinyl or tape or XRCDs or K2 mastering or any of the other format. They are certainly allowed to favor a particular tonal "color" over another but that doesn't mean that their preferred flavor becomes the pinnacle of recording technology or musical involvement.
I first heard about HD Audio from a friend that forwarded an email that explained that the CEA was going to hold a press event to introduced the concept at a press event in Las Vegas the Saturday prior to the CES 2007 show. I applaud the folks at CEA for recognizing that audio is important and for their efforts to bring awareness to the general press. They also attempted to highlight those audio companies that provide products that are capable of delivering audio that is, “better than Red Book” or “greater than 44.1/16 bit.” There were a number of companies in January sporting the “We Support HD Audio” sticker including Esoteric and Thiel Loudspeakers, but not nearly enough. The high performance audio division of the CEA and the marketplace are still firmly grounded in vinyl and compact discs…because those are the formats that have all of the content.
Reading the CEA’s definition of “better than Red Book” or “greater than 44.1/16 bit” got me thinking about the vagueness of their definition and the inexactness of the whole area of HD. Just what does this mean? As a new member of the CEA, I shot an email off to the person organizing the press event asking for some clarification. I wanted to know if an analog recording from 1953 transferred to digital PCM at 96 kHz/24-bits would quality for “HD Audio” status. The answer was yes because the sample rate and word size of the new copy are “greater then 44.1/16 bit”. Wait a minute! Following this logic, any recording from any era that is re-recorded into a 96 kHz/24-bit DAW [digital audio workstation] qualifies. Does that make any sense at all?
When trying to explain this to groups gathered to hear real HD surround music tracks [captured from microphones in front of living musicians], I’ve found the following analogy to be helpful. Imagine I’ve unearthed a box of 8mm home movies taken of the Waldrep family Christmas in 1958 [shades of Clark W. Griswald in Christmas Vacation] and want to experience them on my new HD projector. So I take them to the top of the line Hollywood HD Post house and have them telecined [converted from film to video] to an HD CAM tape at 1920 x 1080. Upon my return home, I immediately playback this “HD” file on my HD media server to my 136” Stewart Filmscreen GrayHawk screen. Am I experiencing HD 1080P video? Or am I seeing everything that was on the 8mm original and nothing more? Transferring any older recording medium to a new HD "bucket" can only deliver as much quality as the original source. The same is true of audio recast in 96 kHz/24-bits or even higher. The fidelity of the original analog tape or vinyl master is reproduced at home with the same fidelity as the engineers and artist heard in the studio…but it is not magically transformed into HD. We need another name for "studio master reproduction." Those who argue that the repurposed playback is "HD" would have you believe that the recording technology that we had in 1966 was HD. It was really good…maybe capable of 60-72 dB of dynamic range and 20-18 kHz of frequency response. But new HD recording equipment has the potential to go way beyond those standards.
The same holds true for anything recorded in standard definition digital audio. The Red Book standard provides the exact specifications for CD players and the discs that play in them. We just celebrated the 30th anniversary of the venerable 12 cm compact disc in October. "CD-Quality" cannot accommodate HD Audio content. It is not, as one digital download site states, "perfect audio". It is limited to 44.1 kHz/16-bit PCM, 2-channel stereo. This translates to 20-20 kHz and 96 dB [optimistically]. Real life music exceeds these limits. So in order to experience real HD Audio, the source recording has to be made with HD recording equipment AND the musicians need to be present to record their performance. Anything else should not be construed as HD.
Add 5.1 surround sound mixes in real HD Audio and you can experience audio fidelity that is immediately perceivable as better than MP3s, CDs, Dolby Digital, DTS and HD Radio [which is closer to MP3 quality…not "HD"]. At the EHX show in Long Beach, I had the unique opportunity to playback an award-winning AIX Records track through a really great surround sound system. We had Boulder 2060 power, B&W 803D speakers and Audience AU 24 cables all fed from an Inteset “Maximus” media server. I was able to do an A-B comparison of the track “Mosaic” from Laurence Juber’s Guitar Noir DVD-Audio/Video project at CD standard 44.1 kHz/16-bit PCM and then at real HD, 96 kHz/24-bit PCM. Same track, same levels, same system…but the assembled group of average listeners could tell the difference! There is room for improvement in reproduced audio especially the stuff that is over processed, compressed and hyped for radio play. There is room for more channels, higher sample rates and longer word lengths. There’s even room for alternative recording schemes. But the entire industry has got to get behind the notion that sound quality counts and can be part of a solution to the gradual demise of the recording industry as we know it.
DVD-Audio and SACD didn’t capture the imagination of the music buying public. As the developer of over 70 titles and 1000 tracks in real HD Audio, you might think that I’m unenthusiastic about the prospects for my catalog. Not in the least. The world of media servers capable of storing and delivering HD Audio content in 5.1 surround sound is upon us. After all what is an iPod anyway but a media server? Imagine it, instead of having 10,000 songs at your fingertips; you have 500 HD Audio tracks. We now have headphone technology that can bring the surround experience to private listening, we’re getting there. Just don’t settle for less than real HD Audio.