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Are CDs lossless?, Evolution of my are WAVs lossless thread
2Bdecided
post Aug 4 2003, 11:57
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QUOTE (Halcyon @ Aug 1 2003, 06:22 PM)
QUOTE
So, the differences due to different shaped ears are removed by the brain, allowing different people to hear, or at least experience, similar things for a given external sound source.


That is an interesting claim, but I cannot find scientific evidence to support your claim (there could easily be some, I'd like to know if there is). The whole hearing apparatus (including muscular coding in middle-ear and basilar membrane + hair cells in inner ear and neurochemical pathways to thalamus and onto cortex) does adapt to signals being fed to them (both over time and almost instanteneously)

This is not AFAIK the same as "remove the differences due to different shaped ears". Especially if we are talking about high level cognitive auditory perception, rather than low level auditory evoked potentials. Perception remains invariably a subjective experience, as you have stated.

Or have I completely misunderstood you (there's always that possibility) smile.gif

Well, I've confused myself now! What I was trying to say is that when you hear a sound from, say, 30 degrees, it has a huge notch at, say, 3kHz (I haven't got the data to hand - I'm guessing). You don't hear it and think "ooo - nasty notch there at 3kHz" - the sensation is decoded into a perception of a sound of a basically flat frequency response, located at 30 degrees.

Other people will have slightly different HRTFs (i.e. slightly different frequency response from different directions) - but they (probably) hear things in a similar manner to you. BUT if you listen via the wrong HRTFs, you will notice the weird frequency response.

As you say though - hearing is very adaptive. I think you could learn to hear properly via someone else's HRTFs over time.

IIRC there's useful stuff in:

D. W. Batteau, “The role of the pinna in human localization,” Proceedings of the
Royal Society of London, Series B, Vol. 168, pp. 158-180.

That's from the 1960s though. Don't know why the date has vanished in my reference database!


QUOTE
QUOTE

When you inject the source straight into the ear (e.g. using headphones, so bypassing the pinna, and hence HRTF), that's when it gets weird.


Err... how do you do that? With ordinary headphones you still get the coupling to head and pinnae and ear canal. Although you lose torso and head occlusion to some degree (depending on headphone construction), you don't "bypass HRTF".


But any pinna response you do get is wrong. For in-ear headphones (ear buds) it's absent. For circumaural headphones, the direction is wrong and the pinna is often squashed.

QUOTE
Even for canalphones (say Etymotics) the ear canal acts as a (somewhat closed) resonant chamber and as we know, the length of ear canal is not standard from human to human.

Did you mean something else (again)?


Don't think so. And though I disagree that your example is good for proving how differently we all hear, I totally agree that different people hear very differently. And HRTFs are maybe one reason why people disagree about the quality of various stereo Hi-Fi equipment. Because the stereo trick works differently for different people.

QUOTE
I have other comments to various other parts of your wonderful post (including direction discrimination and perception invariance), but have to leave my own comments truncated due real-life calling.


Yes - this thread is making me think, but I don't have time to reply to all of it!

Cheers,
David.

EDIT: P.S. - upNorth - no, I followed your argument, and I do agree with it up to a point. HRTFs seem to be a special case, where both the physical and neural processing is different from person to person, but the neural processing actually acts to cancel out the physical differences, and help us all to perceive similar things. There are examples of other aspects of hearing where we are all measurably different purely in the neural sense, so even given the same perfectly reproduced stimulus, we would hear different things. Measured masking is quite different from person to person.

This post has been edited by 2Bdecided: Aug 4 2003, 12:01
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2Bdecided
post Aug 4 2003, 12:13
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ScorLibran,

You're sure that something is lost in a digital system. Well, yes, but in an analogue system too!


Even in a near-perfect system, you have limited bandwidth, and a noise floor. You can't get away from noise completely, because even a resistor adds noise! Other electrical components are even worse. So any system, analogue or digital, will have noise. And the air moves at random anyway, so there's always some "noise", even in the quietest room.

As for bandwidth - well, the highest frequency you can store/process etc is not without limit. Most practical wires give up at some frequency. The air itself has its limits.

Accepting these limits, they are present in both analogue and digital systems. The difference with digital is that we can set them where we want them to be.

Correct dither ensures that nothing is lost in the amplitude domain, and the number of bits sets the noise floor at any level we wish. Correct application of the nyquist theorem ensures that nothing is lost in the frequency domain below any frequency limit we wish to enforce.

Obviously beyond the limits we set, we are losing something. But in an analogue system, we also lose something - usually, a lot more.

Please have a read through the threads in the FAQ - they really contain some great information - you don't have to bow to anyone's superior knowledge - you can read about it yourself and understand what really happens when a signal is digitised.

EDIT: as to your actual point about lossless, I think Pio2001 already answered it perfectly. Of course, you are right - we just have to be careful about using the word - lossless compared to what?


Cheers,
David.

This post has been edited by 2Bdecided: Aug 4 2003, 12:16
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2Bdecided
post Aug 4 2003, 12:20
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QUOTE (Pio2001 @ Aug 2 2003, 03:03 PM)
However, I'll take you point of view into account and move this into the off-topic section.
This way, there will be no point anymore in saying that "this thread is unuseful".

Pio,

I know you got onto Budhist philosophy, but this thead doesn't seem to be that far off topic.

We've carefully defined what "lossless" means, and that it must have a "to" and a "from" to make any sense as a concept.

We've touched on digital sampling vs analogue again, but that hardly makes it off topic.

The interested posters have apparently (or have stated that) they've ignored the supposedly of topic stuff.

Seems like a typical HA thread to me! Can't you move it back?

Cheers,
David.

P.S. So a CD is lossless, in the sense that it delivers 16-bit 44.1kHz digital audio data losslessly from the recording studio to the consumer. Most basically, from the ADC of the artist to the DAC of the listener, though there are other more complex paths.
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ScorLibran
post Aug 5 2003, 06:13
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QUOTE (2Bdecided @ Aug 4 2003, 07:13 AM)
Obviously beyond the limits we set, we are losing something. But in an analogue system, we also lose something - usually, a lot more.

Please have a read through the threads in the FAQ - they really contain some great information - you don't have to bow to anyone's superior knowledge - you can read about it yourself and understand what really happens when a signal is digitised.

EDIT: as to your actual point about lossless, I think Pio2001 already answered it perfectly. Of course, you are right - we just have to be careful about using the word - lossless compared to what?

I had assumed that lossless capture would not be (currently) possible in either model, but I had thought that analog would have at least a better chance in theory since the source audio is itself analog by its continuity...though infinite in many ways, hence prohibiting lossless recording. I stand corrected, though, as I guess analog would have more limitations and require even more boundaries to be imposed for capture. And after all, an analog recording is just data, too, and therefore cannot infinitely capture source (live) audio.

I did spend quite a bit of time in the FAQs, as well as learning from you and Pio2001 and some others, and following the links in this thread. I've done some analog and more digital recording and encoding for several years, but never *really* started getting into the science of all of it until now. And there is a lot more to it than I thought! I'm making it a point to listen/read and learn as much as possible, as most or all of my postings on this matter tend to be either observations and questions, or general statements of philosophy.

And beyond just reading and learning, the only real position I came into this thread with was believing the term lossless as being absolute in nature, and requiring (as you point out) qualification to be used correctly.

Thanks to you guys, maybe I'll actually feel knowledgable about this stuff someday!
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keLston
post Aug 7 2003, 23:22
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Thanks for all the replies, it will take a bit for me to read through all the info (and I will), but there really is no need for the "elitist" attitude portrayed here. I asked a question simply to satisfy my own personal curiosity. I'm not trying to bash a compression standard, or any audio format.

I figured simply that, there are plenty of people paying hundreds of thousands of dollars on stereo equipment, so I figure why not question the media that you're playing as opposed to wondering if it's your 10 foot stretch of copper that you paid 1000/foot for was the reason your music isn't as good as it was performed live?

I'm not trying to be an elitist myself, as I know my computer isn't exactly the most pure "source". But I just wanted information, don't bash me for that.
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buzzy
post Sep 15 2003, 14:53
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In the interest of some kind of resolution on a practical level ... is it fair to say that there is some slight compromise made with 16-bit 44.1khz audio, but that the compromise is one that almost everybody is willing to accept in the broader marketplace? (And that $ spent to increase the resolution at playback are better spent elsewhere in the whole chain of what happens between when it's captured and when it hits your ear?)

As far as there being some compromise - whether it's reproducing some specific note or passage, or the dynamic range, or the spatial effects - it does seem like there are probably some tiny ways in which a very high end, but still real-world listening space could do better than CD audio. Though some of the encoding schemes for noise reduction or multi-channel effects in a two channel system may address those somewhat. (I'm not referring to air pressure, the theoretically infinite number of samples one might need, or other such topics.)

As far as what most people who actually buy music are willing to spend money on - it seems unlikely DVD-A and SACD will gain much market share. Most audiophile formats seem not to survive. And right now, it's hard to make a real case that they represent higher fidelity, until such a time as studio recordings are actually made contemplating those formats as the primary form the music will be released in.

It's probably apocryphal, but at some level isn't there some fundamental truth to the idea that the CD audio format was designed to fit a symphony within the limitations of the physical format as it existed 20+ years back? It seems almost a given that there is some more-than-theoretical but also more-than-acceptable compromise in the CD audio format.
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2Bdecided
post Sep 15 2003, 16:50
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buzzy,

I think most of your points/questions have been answered in this (and similar) threads - see the FAQ for threads on whether CD is good enough, whether DVD-A or SACD are better etc etc.


Jo Public just bought a 5.1 system. CDs only play in stereo, or with crappy simulated echo coming from the back channels. DVD-As (with most people using the DVD-V layer!!!) play with proper sound coming from all speakers. And they're new, so they must be better! And they've got pictures and lyrics on-discs too! Wow - I'll buy the DVD-A instead of the CD!

(I'm sure that's what the record companies are hoping, and I'm sure they'll make it happen with marketing, re-issues etc etc).

Cheers,
David.
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buzzy
post Sep 15 2003, 20:17
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Really? I'd take the other bet. DVD-A and (especially) SACD will go the way of quadrophonic sound. The industry is having a hard time getting people to part with their $ now for CDs. In a world where most people don't even buy music; FM, TV and mp3 are good enough; and video games and DVDs are competing for dollars - I don't see the economics of the new formats working out in a way that gets any meaningful share of the market.

(Though this topic isn't about whether special effects can wow some people into buying them, or whether we'll buy live shows or video compilations with an audio track attached ... that's already happening to some degree, look at all the video releases; but people aren't buying those for the audio quality, and don't understand what they're getting anyway.)

Not to mention the point that it's a fair bet the recordings weren't made with the new formats in mind; if not, it's often just a gimmick when the issue is fidelity to the original.

This post has been edited by buzzy: Sep 15 2003, 20:20
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fewtch
post Sep 15 2003, 21:24
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QUOTE (ScorLibran @ Aug 4 2003, 10:13 PM)
And after all, an analog recording is just data, too, and therefore cannot infinitely capture source (live) audio.

IMO, an analogue signal is data only if you mentally model or envision it as data (was it Pio who said LP's have "13 bits" of resolution?). This is getting a little into the area of philosophy, but before digital came along nobody ever would have said that an analog format 'has xxx bits of resolution' or called it 'data'. It's probably handy to call it that now, when/where it helps create a common frame of reference for discussion, but there's nothing strictly factual about it... just thought that might be worth mentioning.

Anyway, it's probably safe to say that 'infinite capture' of anything is impossible -- the concept of infinity may be useful in mathematics, but doesn't seem useful to me in practical matters (no offense to any mathematicians here wink.gif).

This post has been edited by fewtch: Sep 15 2003, 21:48


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mithrandir
post Sep 16 2003, 01:37
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The community's energy is better spent getting sound engineers to produce cleaner, less distorted masters than worrying about whether 44.1KHz 16-bit 2-channel digital is sufficient. The container/format isn't the problem, it's the data that's stamped to it. You can get orgasmically fantastic audio from Red Book CD, but only if you put some heart and soul into its creation. The industry seems more intent in flaunting new, costlier formats to get everybody to rebuy their collections all over again.
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Pio2001
post Sep 16 2003, 22:26
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FPS discussion splitted : http://www.hydrogenaudio.org/forums/index....howtopic=13310&
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