What is High Resolution Audio?

Posted by: Simon-in-Suffolk on 14 January 2016

I was reading a thought provoking article by Bob Stuat at the AES on what constitutes high resolution audio. Here is my summary of his article.

Firstly he makes a good comment, that in hi res audio we tend to borrow many metaphors and adjectives from the visual world such as focus, transparency and definition, where he maintains hires audio should be natural, resembling real life, and sounds should have clear depth and positioning and seperate readily into perceptual streams, particularly where environmental effects cause multiple arrivals to our ears providing temporal resolution of sound structures which is akin to spatial resolution in vision. I agree with this observation..

Stuart then goes onto define high res audio without falling into the traps of limiting to the narrow definitions of digital audio Nyquist sample frequency and bit depths.. So in the analogue world, assuming high definition equates to natural sounding, then referring to the research by JW Oppenheimer and others that hearing is not bound by pitch perception (approx 18kHz) but our brains appear to exploit population coding, and can approach a temporal resolution of 8 υS. This implies a Gaussian bandwidth of about 44kHz .

Next Stuart introduces encoding and replay systems ... Still all in analogue. He suggests that in a typical recording and replay environment it could be appropriate to consider 8 cascade stages .. Now each stage impacts the bandwidth on the other, so with 8 cascaded interfaces so as to protect the bandwidth of 44 kHz through the cascade, each stage should more likely have a bandwidth of 100 kHz.

Now any of these of stages could be digital and then Nyquist and bit depths comes in to play .. So here we can see at least 96kHz  and upto 200 kHz (192kHz) given the cascaded bandwidth issues to fully capture 8uS spatial awareness. But referencing papers by M.S. Lewicki, and Jackson, Capp and Stuart, he states evidence shows with current digital sampling technology and hardware through decimation and interpolation that the results above 96kHz sample rate are very much diminished and that 96kHz would preserve most of the spectral content.

Now Stuart talks about bit depth of sampled audio. The increased bit depth above 16 bit give diminishing returns, and P.B. Fellgett's research into the thermal noise limit of a microphone shows that the fundamental limit of a microphone can be bound by a 17.5bit 192 kHz LPCM channel, therefore there is often little justification for using more than 18 bits.

Therefore to summarise  Stuat effectively suggests that Hi Res audio should capture as close as possible the 8uS temporal resolution and offer at least 18 bit LPCM dynamic range. (So with digital audio at least 96kHz sample rate with 18 bit sample length - or more likely the excessive 24 bit)

Stuart then talks about air temperature, air flow and shape of recording and listening rooms, as these will modify the audio .. But that's another story.

So food for thought, and nice to have a view that is more from a science/engineering perspective rather than the marketing room. I recommend this paper to AES members on this forum rather than rely on my paraphrasing .. J. Audio Eng Soc Vol 63 No 10   2015 Oct.

Simon

 

 

 

 

Posted on: 14 February 2016 by bicela

Simon, given a like to your post.

Posted on: 14 February 2016 by Darke Bear

High Definition or Resolution is where everything is done right at all stages of capture and reproduction.
I think the illusion is that if you have the final format that has higher sample-rate and bit-depth then all will be better - this is assumed to be true when it is just one factor.

I'd like the real drop in quality presently accepted and normal to be addressed, which is in the mastering equipment capability, quality and decisions made by those using it.
The final format by comparison is not setting the limits.

DB.

 

Posted on: 14 February 2016 by J.N.
Simon-in-Suffolk posted:

Nah John, vinyl is light years from Hidefinition in its true sense.. i.e. matching reality. Vinyl is about sounding pleasing and attractive. 

True hi definition audio is really more about virtual reality and less about music.

I would argue the point that musically speaking I feel hidef could be largely irrelevant.

But of course we shouldn't get hung up thinking hidef is associated with 'Sample rate'. That really is a very simplistic proxy that in my experience fails to match true hi definition. Hidef is about accuracy - not how the sound is reproduced, encoded, or conveyed.

I can't help feeling for many people so called 'hidef' is simply a euphemism for recording and mastering quality. 

Simon

 

 

My post was of course somewhat tongue-in-cheek Simon; and like Gary, I can attest to the ownership of some very good sounding older CD's.

The point I was trying to make is that Hi-Def recording/mastering (as well as it could be done at the time) used to come as standard. With newly recorded popular music; 'crap' is the norm, and we get ripped off to pay more for supposed high fidelity recording/mastering.

I've heard nothing labelled hi-def in mainstream music (i.e. the stuff we actually want to enjoy as music, as opposed to a manufactured audiophile orgasm) which sounds better than many examples of optimal 16/44 digital transcription from the 1980's.

And ............. I still hear a perceived dynamic slam from some really well-recorded vinyl, which digital stuff just cannot seem to match. As you say; 'connecting' with the music transcends bit rates.

Gary has a theory about modern mixing desks being part of the problem, and I think he's right. There is just too much digital hash swirling around and muddying the water. According to Greg Milner in the excellent 'Perfecting Sound Forever' (a book which every audiophile should own), we arguably hit the peak with 16 track analogue multi-track recording.

John.

Posted on: 14 February 2016 by Simon-in-Suffolk

John, indeed. However I am curious about mastering quality styles... about five to six years I had severeal new releases that were markedly distorted and clipped, but lately I haven't noticed any such major disasters.

I also tend to look at the engineer who has done the mastering, especially for favourite artists.. in popular music there are definitely some good names out there and equally some names to be avoided. Of course with such music the recorded master is seen as part of the final recording and often/usually has direction from the artist or the label. Reading the tweeter feeds and blogs of renown mastering engineers can be enlightening....

However the mastering/recording traits that irritate me are over compressed and clipped vocals... I was always taught this was a symptom of bad microphone technique... but Ho hum.. recordings from artists like Adele seem to exhibit this badly. The other trait common right now is eq compressed baselines.. often going into soft clipping... this can sound great with ear buds or car stereo... but over the top and poorly mastered on a good audio system.. 

BTW I don't think is the mixing desks that are to blame, even lo-fi bedroom desks can sound good... it's the various software audio processors in the DAW that are used that can, in my experience, tend to dumb down the sound and turn it into a digital soup.

I think modern mixing desks and digital recorders are often a major advancement on the old noisy analogue 16 track desks and recorders.... 

But of course as I think we all mostly agree this has nothing to do with hidef.

Simon

 

 

 

 

Posted on: 14 February 2016 by joerand

Eloquently stated Simon!

So often modern bass is compressed to a degree that it becomes more of a sound effect than anything having to do with musical sound quality. Perhaps, in part, an artifact of the trend towards musical listening on home theater systems or on ear buds as you suggested.

Got a sub woofer? We'll make the walls shake. No sub woofer? We can still make things vibrate. Guttural replay of bass notes that sound nothing like a struck string on the bass guitar from which they originated. No degree of hi res will correct that kind of mixing/mastering. The masses seem to demand bass in quantity rather than quality.

Posted on: 15 February 2016 by Innocent Bystander
Simon-in-Suffolk posted:

I also tend to look at the engineer who has done the mastering, especially for favourite artists.. in popular music there are definitely some good names out there and equally some names to be avoided. Of course with such music the recorded master is seen as part of the final recording and often/usually has direction from the artist or the label. Reading the tweeter feeds and blogs of renown mastering engineers can be enlightening....

However the mastering/recording traits that irritate me are over compressed and clipped vocals... I was always taught this was a symptom of bad microphone technique... but Ho hum.. recordings from artists like Adele seem to exhibit this badly. The other trait common right now is eq compressed baselines.. often going into soft clipping... this can sound great with ear buds or car stereo... but over the top and poorly mastered on a good audio system.. 

joerand posted:

Eloquently stated Simon!

So often modern bass is compressed to a degree that it becomes more of a sound effect than anything having to do with musical sound quality. Perhaps, in part, an artifact of the trend towards musical listening on home theater systems or on ear buds as you suggested.

Got a sub woofer? We'll make the walls shake. No sub woofer? We can still make things vibrate. Guttural replay of bass notes that sound nothing like a struck string on the bass guitar from which they originated. No degree of hi res will correct that kind of mixing/mastering. The masses seem to demand bass in quantity rather than quality.

I suspect the masses just want to hear the bass, being an important part of the music they listen to - otherwise they might notbthink the music is good, so not buy it  - and this approach is deemed to be the best (=simplest/cheapest) way to make it audible on tin-pot systems. Instead the industry should be trying to educate people that they need better system - even better earbuds costing just a few 10s of £ can make a big difference, but few peopl of the iPod generation seem to bother - or perhaps have any idea there can be a difference.

and sadly, most music I want is available only with whatever engineer mixed it, with no choice, so to have the music means having its imperfections.

Posted on: 15 February 2016 by Simon-in-Suffolk

and arguably it was this person, Joe Meek,

who pioneered mastering, mixing and processing techniques for music to suit mass cheap audio replay equipment in the early 1960s

Simon

 

Posted on: 15 February 2016 by J.N.

With current digital recordings, small indie labels seem generally to produce a better (or certainly more audiophile) sound. The result of a less complex recording/mastering process? Dunno. It takes a major label to really screw things up.

There are fortunately, flashes of light in the gloom. Steve Hoffman and Steven Wilson are two names which spring to mind as engineers who can produce a good uncompressed, dynamic, detailed and transparent sound. SW has properly remastered some old prog rock classics to great effect, so it can be done. His 'new music' recording and mastering is good too.

Many of you here will have heard Bowie's swan-song 'Blackstar'. Tony Visconti has excellent credentials, so why has he produced this (technically) truly terrible epitaph to the great Mr David Jones? Mass-market demand I guess.

I was producing a better sound than that, when I made home recordings on a 4 track Tascam 144 about thirty years ago - as indeed did Springsteen with 'Nebraska'.

The sound quality of 'Crime of the Century' (on vinyl or digital) from over forty years ago can still make the hairs on the back of my neck stand up. I don't hear that sort of insight into the depths of the recording on any new material.

Something has been lost, but what is it? Perhaps (as Simon alludes), there is a positive human connection and reaction to analogue tape-hiss and vinyl surface noise. Steven Wilson states on the sleeve notes of his superb remastering of 'Aqualung' that he recognises that tape hiss is intrinsic to the sound of the original recording, so he has the good sense to leave it in. Attempts to fully digitally de-noise old analogue recordings most definitely chuck out the baby with the bath-water.

We must try to meet up at our esteemed dealership sometime, Simon. Drop me an email.

John.

 

Posted on: 15 February 2016 by Huge

What is High Resolution Audio?

A technology with great potential that's frequently messed up by humans!

To err is human; to mess up exactly the same way 10,000 times in one second takes a computer.
The two most common elements in the solar system are hydrogen and human stupidity.

Posted on: 15 February 2016 by Darke Bear

I don't think it has anything to do with including tape-hiss, or for that matter pitting Vinyl 'clicks' as some do for effect onto modern recordings to give them that 'something' which has been, at least subliminally recognised, as lost on many (but certainly not all) modern releases on any media - Vinyl, CD or 'HiDef'.

On the poor recordings - leaving aside the obvious poor ideas in action of compression and tweaking the vocalists to be 'in-tune' - I hear not so much a random noise-floor increase, as an increase in both harmonic and inter-modulation distortion sitting over everything like a clinging cloud that in itself sets the floor of the dynamic range perceived. What is actually causing this I do not know - poor electronics, noise from digital clocks - but it is there and obvious.

As to Steve Hoffman's stuff - I see why people like what he does, but I've hated everything I've heard he has done to date on vocals in the mix. It sounds, to me, like he uses a combination of aggressive noise-coring and response tweaks that make instruments sound impressive but ruin - for me - the vocals and strip them of anything but shallow emotions - no depth at all remains.

But there are some very good, unfortunately rare, modern digital recordings about that seem to have steered fairly clear of whatever infects most nowadays.

DB.

Posted on: 15 February 2016 by J.N.

I accept that enjoying the sound of vinyl is illogical - it being fraught with the extant and inevitable technical compromises of the medium. Surface noise is never completely absent, so why do so many of us still enjoy it?

It's not just a nostalgia thing either. After a vinyl playing session, my digital alternatives have a frustrating flatness and lack of apparent 'realism' and insight into their sound. Now; of course not everybody hears this or 'gets' vinyl, so I suppose we are back to personal perception and not fully understanding the mental process of enjoying music replay in the home.

John.

Posted on: 15 February 2016 by Jan-Erik Nordoen
Darke Bear posted:

What I do find is that the same issue of a CD is in fact totally different depending on what pressing plant issued it in many cases.

Reading this reminds me of Barry Diament's similar findings and his observation that when ripped to a computer, the SQ differences from different plants' pressings largely disappeared (link below).

How much of the difference is in the mastering vs the pressing ?

https://forums.naimaudio.com/to...79#33245103025701379

Posted on: 15 February 2016 by George F

Barry’s Post:

 
I've always felt that what is "good", "better" or "best" depends entirely on exactly what one seeks.
The goal might truth to the source or it might be what someone may just like.  Personally, I think both are equally valid as I'd never argue with whatever brings anyone their listening pleasure.
 
But if the goal is truth to the source, my experience has been that well ripped files (in raw PCM format such as .aif or .wav) invariably are truer to the CD master than any CD pressing played back via any transport.
 
Ever since I created my first CD master, early in 1983, and heard the results that came back from the replication facility, I realized that CDs made at different plants (and often on different lines at the same plant) all sound different from each other and *none* sounds indistinguishable from the master used to make it.  The differences, in my experience, range from subtle to not-at-all subtle, with focus and fine detail being lost to varying degrees.
 
I've always found a slow-burned CD-R to get closer to , if still not indistinguishable from, the CD master.  But when any decent pressing is properly extracted to hard drive (in raw PCM format such as .aif or .wav), I've found the differences go away.  This is what has me so excited about playback from the computer: for the very first time in my experience, the listener can get the sound of the master, unaltered.
 
I had a related experience not too long ago when comparing an SHM pressing with its plain vanilla counterpart, both created from the same CD master.  At first, when listening via my transport, I was certain I was hearing two different masterings, so different did the drums, cymbals and piano sound.  I would have bet money I was hearing two different EQs created by two different engineers.  I thought it was a trick to make SHM, which I took to be just another way of pressing a CD, sound better than it really was.  Much to my surprise, when I extracted both the SHM and CD versions to computer hard drive and played them from there, they were indistinguishable.  
 
What accounts for the differences?  I'm can only speculate.  Playback from the disc involves several processes.  The player must track the spiral of pits, maintain focus on the laser, read the pits, decode the 8:14 modulation by which the binary data is encoded to create the nine different length pits on a CD, perform any necessary error correction, and convert the binary stream to analog audio, all in real time.  While playback from hard drive in a computer certainly involves some processes too, it seems to me there is less to do overall and my experience has been when there is less to do, better results are achieved.  Again, just speculation on my part.  (I'm always open to learning something new.)  What I do know is that I've never heard CD playback from any transport/DAC combination, regardless of price that sounds indistinguishable from listening to the CD master, while playback from the computer routinely does sound indistinguishable from the master.
 
So again, if someone feels playback from the CD is "better", I wouldn't argue.  They may simply like the resulting sound.  But my ears tell me it doesn't sound the same as the master sent to the replication facility by the mastering house.  Me?  I'd rather hear the sound of the master.  
Just my perspective, of course.
 
Best regards,
Barry
 
___________________
 

This seems like the best of cases for preferring playing ripped files from a CD rather than playing directly on any CD player. 

I came to that conclusion as long aho as 2002 using Sonic Foundry as the ripping engine creating WAV files. No automatic tagging of course, but it was useful for editing some private recordings I was sorting out at that time.

I converted fully to using a computer playing ripped CDs back in 2010, by which time tagging had become much easier.

ATB from George

 
Posted on: 15 February 2016 by J.N.

I think Barry makes a very pertinent point. 'Better' is kinda irrelevant. It's all about what connects us individually with the music, the most convincingly. The myriad of loudspeaker choice and selection is a good example of that. I think CD players have to some extent, 'a sound' in some ways reminiscent of the vinyl analogue era and that's why I've yet to hear a streaming alternative which I prefer.

John.

Posted on: 15 February 2016 by EJS
George Fredrik Fiske posted:

With classical music the situation has parallels. Some of the very earliest CDs are still superb, and some remasterings have less than stellar quality, but about 1993 EMI set about an approach which has a great deal to commend it for their classic remastering of analogue recording from tape and 78 metal master parts.

They used the higher resolution of 24 bit with 96 K sampling for the initial transfers, and this was subsequently the basis of a Red Book standard master. They had specially made equipment installed for this process, and subsequent CD re-issues of analogue recordings really showed the highest imaginable production standards and quality. 

These restorations are still frequently made the basis of subsequent re-issues, and I doubt that much more could be achieved with the old recordings. 

I think that new recordings of classical music are astonishingly good. In recent times many companies have moved back to the simpler microphone set-up, resulting in coherent sounding recordings that work well in stereo or mono. 

But I do understand from a certain amount of experience of friends who bring popular music recordings here to have a listen on a highly resolving system that in the popular field, new recordings and re-issues are frequently worse than older CD re-issues and first releases of previous decades. Really that is deplorable, but nowadays most popular music is actually designed for iThingies, and the workplace or car radios. 

The quality of pop music recordings reflects the market for pop music, and it is hardly a consideration at all, how these recordings do sound on very fine replay.

There is nothing to indicate that this situation is going to change.

ATB from George

George, if you are referring to the ART process followed by EMI in their Great Recordings of the Century series, I respectfully disagree that it had a great deal to recommend it - aggressive noise shaping, spotlighting frequency bands (e.g. to bring a cello forward) and extreme frequency attenuation killed the life out of many rather good recordings - from Rostropovich's Dvorak cello concerto to Fürtwängler's Tristan and Giulini's Don Giovanni. The only series that got it right, in my humble opinion, was DG's the Originals series. These remasterings focused on fidelity to the source, often at the expense of increasing the noise rather than suppressing it. 

However I do agree with the rest of your post

EJ

Posted on: 15 February 2016 by George F

Dear EJ,

I briefly owned the Furtwangler London made recording of Tristan, and I could not make much of it either on CD or before that LPs. 

Sometimes the basic recording is not all that fine. An example from Giulini is the Verdi Requiem recording for EMI, which has basic overload distortion in it. No remastering can completely disguise that. 

But I do agree that some old recordings - from EMI, and I would certainly add to this DG - sound just as bad as could be feared. Not helped much by the most advanced of remastering techniques. 

On the other hand every EMI restoration done for Klemperer seems remarkably successful. The system that EMI used was first devised for the complete Electrical Recordings of Sir Edward Elgar, on nine CDs in 1992/3, and this is an exemplar of how it should be done. I knew the original 78s, and the 1950s to 1970s LP transfers. The LPs reduced the surface noise, but brought problems all their own, such as difficult tracking, while the CD Edition really showed how marvellous the originals were. Some of the old LP transfers hinted that much might be possible! 

But yes there are duff restorations from all the majors, and the only company I can think of who seemed to have a Saintly record of restoring records was the late lamented Philips!

ATB from George

 

Posted on: 15 February 2016 by tonym

The big problem in all this is the vast majority of people, even those with a great love of music, couldn't really give a damn about the quality of recordings because most have never picked up the deficiencies using the equipment they're most likely to own.

We can wring our hands and obsess about this, but if we're not careful we can miss out on good music. Being pragmatic, I've learned to see past the lousy recordings, but still take most pleasure in the many old excellent recordings I own, and quite a few new ones. I'm also a fan of Steven Wilson remastering and when comparing his work to the original recordings his versions have always won out to my ears.

 

Posted on: 15 February 2016 by Tony2011
tonym posted:

The big problem in all this is the vast majority of people, even those with a great love of music, couldn't really give a damn about the quality of recordings because most have never picked up the deficiencies using the equipment they're most likely to own.

We can wring our hands and obsess about this, but if we're not careful we can miss out on good music. Being pragmatic, I've learned to see past the lousy recordings, but still take most pleasure in the many old excellent recordings I own, and quite a few new ones. I'm also a fan of Steven Wilson remastering and when comparing his work to the original recordings his versions have always won out to my ears.

 

Sorry, but I own original copies of  King Crimson  and Jethro  Tull original albums and to my ears the remasters are nothing short of sonic murder! Sorry, Tony.

Posted on: 15 February 2016 by Simon-in-Suffolk
tonym posted:

The big problem in all this is the vast majority of people, even those with a great love of music, couldn't really give a damn about the quality of recordings because most have never picked up the deficiencies using the equipment they're most likely to own. 

Really? I think we tend to think in our hifi bubble we are the only sub group that cares about audio quality - in my experience quality is important for many if not most - certainly with the younger generations - however what they consider a quality replay system may sound quite different from what many of us on this forum might consider. Question is who is right? I suspect both groups are.. after all recorded music and replay is a compromise and is subjective...

Posted on: 15 February 2016 by tonym

Each to heir own - I've also got the original, first pressing vinyls of Aqualung, ITCOTCK, Lizard, etc. etc., and much as I love vinyl, the recordings were never up to much.

Posted on: 15 February 2016 by Tony2011

We agree to disagree. Good taste in music though...

Best

Tony

Posted on: 15 February 2016 by tonym
Simon-in-Suffolk posted:
tonym posted:

The big problem in all this is the vast majority of people, even those with a great love of music, couldn't really give a damn about the quality of recordings because most have never picked up the deficiencies using the equipment they're most likely to own. 

Really? I think we tend to think in our hifi bubble we are the only sub group that cares about audio quality - in my experience quality is important for many if not most - certainly with the younger generations - however what they consider a quality replay system may sound quite different from what many of us on this forum might consider. Question is who is right? I suspect we both are.. after all recorded music and replay is a compromise and is subjective...

Personally, I've yet to meet anyone, outside of hi-fi buddies, who've expressed any interest in the quality of recordings. 

Posted on: 15 February 2016 by J.N.
Tony2011 posted:
 
 

Sorry, but I own original copies of  King Crimson  and Jethro  Tull original albums and to my ears the remasters are nothing short of sonic murder! Sorry, Tony.

Are you including the Steven Wilson remasters in that statement Tony? Generally; I would agree with you on the subject of subsequent remasters, but I think SW has done a superb job on vinyl and digital with 'Aqualung', 'Benefit' and 'TAAB', though some say that Peter Mew screwed up the mastering of the vinyl on the latter. I like his work on two 'Yes' albums and 'In the Land of Grey and Pink' too.

I suppose it comes with the territory of being an audiophile, but unlike Tony M, I can't listen seriously to poor new recordings/masterings. The latest Richard Thompson studio album is an example of that. It's a real shame because the music is great, so I save it for the iPod/iPhone/car etc.

Daft? Maybe; but I haven't spent all that money on a Maserati to run it (badly) on paraffin.

It's another interesting facet of our individual listening mechanisms that some of us seem to be able to get past crappy SQ and into the music, more than others.

John.

Posted on: 15 February 2016 by Tony2011

John,

I was referring to Mr Wilson's remasters. I never forgave him for what he did to KC's Red. I did give him the benefit of the doubt and did listen to his remasters of ITOTCK, Benefit, Aqualung on vinyl, cd and Tidal HF. I just can't swallow a single track the  guy touches. I haven't listened to any Yes so cannot comment on them. Some people love  it. As Tony says: each to their own. But I do wonder sometimes if it is just me.

Just my personal opinion. 

Tony

Posted on: 15 February 2016 by joerand
J.N. posted:

I accept that enjoying the sound of vinyl is illogical - it being fraught with the extant and inevitable technical compromises of the medium. Surface noise is never completely absent, so why do so many of us still enjoy it?

With vinyl there is literally physical contact in the replay chain between the music on the LP and the stylus. Humans crave physical contact - it's stimulating. There's no physical contact in digital replay.

Then there's the notion that humans inherently accept or expect imperfection in their everyday lives. The less flawed, more sterile listening environment of digital replay may create some subconscious discomfort - at least for those of us that grew up in the analog era.