The Truth About 'HD Audio'
"HD" Audio?
You know there’s trouble on the HD road ahead when Windex pitches a new formulation prefixed with the letters “HD”. And how about the marketing gurus at Kodak pitching “HD” photographic prints to counter the proliferation of digital photos, is this progress? Amidst the push for HDTV and heavy marketing of iBiquity’s so-called “HD Radio”, it should come as no surprise that the Consumer Electronics Association has rolled out a campaign to recognize and promote the improvement of reproduced music for consumers…AND that they’ve decided to call it “HD Audio”. It’s not high resolution anymore…a description that is more in keeping with existing verbiage. The audio community has jumped on the “HD” bandwagon.
First, let me state right out front that I am a huge advocate of advancing the quality of recorded audio. It’s easy to dismiss the fidelity of MP3 audio files, but I go further and dismiss the quality of compact discs for releasing original HD recordings. CDs lack the bit depth, sample rate and multi-channel capabilities to adequately reproduce recordings that are conceived and realized in real high definition surround. My high performance label, AIX Records, is probably unique in that we only release on DVDs and soon as HD digital downloads via iTrax.com.
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 introduce 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 Runco VX-2c 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 new Niveus K2 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’ll be celebrating the 25th anniversary of the venerable 12 cm compact disc later this year. “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 recent EHX show in Florida, 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 800D 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 50 titles and 800 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…a media server. Imagine it… instead of having 10,000 songs at your fingertips; you have 500 HD Audio tracks. On the horizon is headphone technology that will bring the surround experience to private listening... we’re getting there. Just don’t settle for less than real HD Audio.
Special thanks to Mark Waldrep, Ph.D.
Founder and Chief Engineer of AIX Records
Recent Forum Posts:
'Linear and non-linear distortion mechanisms within digital audio FIR low pass filters used for decimation and interpolation have been described...The typical cosinusoidal passband ripple characteristic has been analysed to estimate the time-dispersion characteristics of the filter to signals within the audio band. This analysis is used to show significant differences in the pre and post-echo performance between the example filters.
Susceptibility of the filters to overshoot has been illustrated and the effect of compromises in stopband performance close to the folding frequency are discussed.
Filters designed for the higher sampling frequency of 96kHz are used to show how all these distortion mechanisms can be reduced by filters of similar computational requirements but with a more relaxed transition region. This results in either reduced ripple (and hence pre-echo) amplitude or in a lower time displacement for the echo.
In both cases the effect is likely to be a reduction in the audibility of the echo. A direct effect of the higher sampling rate is that for an identical filter design the time displacements will scale inversely with sample rate. Hence an improvement can be made just from raising the sample rate - even for those who cannot hear above 20kHz.
More work is required to evaluate the limits on the perception of the echo effects described here. This should cover both the audibility of echoes and their effect on the localisation of sound sources...The effects described here indicate that it may be difficult to distinguish any beneficial effects of an increase in sampling frequency from the different filter behaviour. This should be considered when making comparisons between different rates.'
http://www.nanophon.com/audio/antialia.pdf [nanophon.com]
Dunn, J. (1998). "The benefits of 96 kHz sampling rate formats for those who cannot hear above 20 kHz", Preprint 4734, presented at the 104th AES Convention, May 1998.
Locke6854;262081
... current cds dont sound like live instruments.
And that is because a mic didn't capture all the soundfiled? Wasn't mic-ed properly? Sample high enough with equally high bit rate? Poor mastering?
I bet you don't remember long ago when they experimented with placing a speaker where a player was and let the speaker reproduce his instrument and swap back and forth, behind and acoustic curtain. Yep, no one could tell which was paling when.
Or, when John Dunlavy demonstrated his speakers with live sound. Yep, under his controlled conditions, it was another one of those misses.
I'd like to see a fair comparison between that HD recordings and the same mic being parallel fed to a lower sampling rate, or, even lower sampling from that HD recording. I bet it would be an interesting or not, outcome.
How is that HD different from a DVD-A recording? Certainly not the sampling and bit depth. Maybe, most likely, nothing.
When you walk by a bar and hear music playing, can you tell if its live music or a dj/recording? Most people can. Thats not to say that restaurants/bars/clubs have great audio systems.
The simple fact is we're trying to REPRODUCE sound. And it really doesnt matter how much you spend on your audio equipment, current cds dont sound like live instruments.
On a side, when I say "live" I'm obviously not referring to a "live" recorded cd, with a usually muffled far-away sound, and an audience cheer drowning out the instruments.
Not everyone has an ear that can tell the difference. Most of my friends can't tell the difference between mp3s or cds, but mp3 compression drives me crazy.
I think of it as a curse. Being an audio/videophile, and letting black levels, color banding, equalization, bass response etc bother you... I dont even like watching movies at other's houses because I'll be tempted to fiddle with their settings.
In that case, what is wrong with DVD-A? Or is that yesterdays marketing title and a new one is needed in light of the HD TV and HD soundtracks on it?
If CD quality in stereo is sufficient in its current implentation for the majority of readers then it would seem the development of audio engineering techniques, recording equipment and consumer delivery formats were perfected 30 years ago.
While some still prefer 2 ch, it was well known back in the 1930s that at least 3ch up front is needed and the advancements in multi channel has shown that is what is needed to better reproduce a live performance. So, that is not the issue here but the marketing of 'HD' that seems to be what D-A is about, or that ultrasonic is indeed audible and enhances the recorded music. That latter has not yet been demonstrated contrary to claims otherwise.
I still believe that there is room for improvement and I'm encouraging the record industry to move to greater fidelity not less...which has sadly been the state of affairs over the past decade or so.
That will be a tough sell considering that most of today's CDs are compressed to the hilt with hardly any dynamic range in there. Classical is a very small market share.
Perhaps what is needed is a better capture of the soundfield? Better mic locations? Better mastering folks?
..I'll be happy to report on the research that is presented.
Yes, please, we would like to hear what went on, what was presented, etc.
lowmagnet;261436
What's the point of HD if our hearing is to inferior to hear it.
Marketing
The latest and greatest out there must be better
While those higher data rates may be beneficial in the mastering process, it is highly questionable for the home marketplace.
