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Author Topic: Bitperfect / identical sound streams can sound different  (Read 32186 times)

glynor

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Re: Bitperfect / identical sound streams can sound different
« Reply #50 on: December 29, 2011, 12:38:04 pm »

In that case however, there is proof being racked up and it is scientific and undeniable.

The best comment along those lines I've ever read was from Penn Jillette (of Penn & Teller).  It was about religion versus science, so slightly different in scope (though "audiophile" in some circles is quite akin to a religion, where an idealized sonic perfection replaces god):

Quote
If every trace of any single religion died out and nothing were passed on, it would never be created exactly that way again. There might be some other nonsense in its place, but not that exact nonsense. If all of science were wiped out, it would still be true and someone would find a way to figure it all out again.

Not that exact nonsense indeed.
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MrC

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Re: Bitperfect / identical sound streams can sound different
« Reply #51 on: December 29, 2011, 01:10:40 pm »

Few things are harder to put up with than the annoyance of a good example -- Pudd'nhead Wilson's Calendar

;D
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mark_h

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Re: Bitperfect / identical sound streams can sound different
« Reply #52 on: December 29, 2011, 01:17:13 pm »

Not exactly. Engineers have always been able to make DACs etc with low jitter etc except that until recently they were expensive to produce. At this point they can be produced very cheaply. Manufacturing has caught up with technology. All but the most cheaply made cards have specs that are well below being audible.

That engineers have made DACs within their jitter tolerances is not in dispute.  The issue is that the audio/phile community were saying from the start that something was wrong with digital sound and it took some time for engineers to work out that jitter was one of the problems.  Nobody was talking about jitter when CD was released.  It took some time for the issues to be understood.  Had no issues been raised, the designs wouldn't still be the same 25 years after release.  This isn't the case.

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If in doubt look up any studies that have been done on what humans can detect (there have been some on jitter). Then compare that to the specs.  If you have something that contradicts what I have read point me towards it. I would be interested in reading it.

Perhaps YOU could point us at the studies that support your assertion?  Would save people time and we'd all be reading the same documents?



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MrC

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Re: Bitperfect / identical sound streams can sound different
« Reply #53 on: December 29, 2011, 01:26:15 pm »

Perhaps YOU could point us at the studies that support your assertion?  Would save people time and we'd all be reading the same documents?

See onus probandi.
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DarkPenguin

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Re: Bitperfect / identical sound streams can sound different
« Reply #54 on: December 29, 2011, 01:38:07 pm »

WAV's bitstream is more linear and has better continuity after quantization.

WAV and FLAC's bitstreams should be identical.  If they are not then there is an encoder or decoder bug and you should contact flac's author.
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InflatableMouse

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Re: Bitperfect / identical sound streams can sound different
« Reply #55 on: December 29, 2011, 04:00:26 pm »

I just smile when I read this thread.

The opening post doesn't even state a question but this is turning into a heated debate and ramping up views and replies like there is no tomorrow.

 ::)

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gvanbrunt

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Re: Bitperfect / identical sound streams can sound different
« Reply #56 on: December 29, 2011, 09:34:59 pm »

Quote
That engineers have made DACs within their jitter tolerances is not in dispute.  The issue is that the audio/phile community were saying from the start that something was wrong with digital sound and it took some time for engineers to work out that jitter was one of the problems.

Yes I agree that many argued that they didn't sound as good as vinyl on their Nakamichi Dragons and there were many ignorant people that claimed since it was digital it was perfect and should sound better. Back then the science on the matter wasn't as well known but WAS available. There were several manufactures who produced VERY expensive CD players for the audiophile market that were based on that knowledge that ENGINEERS designed. How do you think they designed them, guess work?

There were plenty of marketing guys etc saying CD's were perfect etc, and plenty of people claiming they knew that you could not tell the difference from vinyl etc. However neither group used what was widely known in the scientific and engineering community. Engineers always knew what was needed but made trades offs based on price. This was not something the audiophile community made them aware of. Advances in manufacturing have made this cheaper and that is the reason for the change.

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Perhaps YOU could point us at the studies that support your assertion?

Finding documentation to back up my claims is easy: pick up any recent book on the science and they will support my claims. Actually you can pick up some over 30 years old and they say the same thing. A quick google or a look on Amazon will find you plenty. The reason I asked for assertion on your points is because I've NEVER seen even one that supports your claims. Prove me wrong. I have nothing to lose and everything to gain by it.

As for my original request why is it every time one of us "non believers" asks for an impartial ABX test an audiophile never steps up to the plate?

As I mentioned I have personal experience where experts were/are wrong and have based their ideas on flawed  science (or none at all) and it was ordinary sick people that banded together that forced further study and broke new ground in how things actually work. In their case they provided statistical and empirical evidence that showed what they claimed was true. Science was able to use that to find out why. Many have benefited from what happened.

In this case, I'm asking for that statistical or empirical evidence in the form of an ABX test of WAV vs FLAC. If this can be heard, it can be proven. It isn't even hard to do. You pick a WAV and FLAC file that we here can verify null and then ABX to your hearts content. When you've had all the practice you can stand and still claim you can hear the difference I'll let a few experts know. I guarantee you they will flock to your location to see this in person as it turns everything they know on their head and would love to be the first to get a paper out on it.

Looking forward to being proven wrong...
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gvanbrunt

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Re: Bitperfect / identical sound streams can sound different
« Reply #57 on: December 30, 2011, 12:16:26 am »

I didn't like leaving the request to support my assertions go with a reply to Google it. So here is one article. There are older ones, but I thought it would be good to provide more recent research. I can provide more if you need them:

[6] Eric Benjamin and Benjamin Gannon - "Theoretical and Audible Effects of Jitter on Digital Audio Quality", AES, 1998

Since I have provided one, perhaps you can provide some data that shows that the average person (or even someone with golden ears) can perceive the difference in the jitter in a high end DAC and a newer Soundblaster card.
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mark_h

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Re: Bitperfect / identical sound streams can sound different
« Reply #58 on: December 30, 2011, 02:20:01 am »

However neither group used what was widely known in the scientific and engineering community. Engineers always knew what was needed but made trades offs based on price. This was not something the audiophile community made them aware of.

Citations, please.

Quote
Finding documentation to back up my claims is easy: pick up any recent book on the science and they will support my claims. Actually you can pick up some over 30 years old and they say the same thing. A quick google or a look on Amazon will find you plenty.

As for my original request why is it every time one of us "non believers" asks for an impartial ABX test an audiophile never steps up to the plate?

Never?  I'll do it [jitter testing, not WAV vs FLAC]?  But even if I fail, it doesn't disprove the claims, it just proves that *I* cannot hear the difference (and I actually believe I can to certain levels of jitter).  

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mark_h

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Re: Bitperfect / identical sound streams can sound different
« Reply #59 on: December 30, 2011, 02:22:19 am »

I didn't like leaving the request to support my assertions go with a reply to Google it. So here is one article. There are older ones, but I thought it would be good to provide more recent research. I can provide more if you need them:

[6] Eric Benjamin and Benjamin Gannon - "Theoretical and Audible Effects of Jitter on Digital Audio Quality", AES, 1998

Thanks. 

Quote
Since I have provided one, perhaps you can provide some data that shows that the average person (or even someone with golden ears) can perceive the difference in the jitter in a high end DAC and a newer Soundblaster card.

Has such a test even been documented?  

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mark_h

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Re: Bitperfect / identical sound streams can sound different
« Reply #60 on: December 30, 2011, 02:27:51 am »

In this case, I'm asking for that statistical or empirical evidence in the form of an ABX test of WAV vs FLAC. If this can be heard, it can be proven. It isn't even hard to do. You pick a WAV and FLAC file that we here can verify null and then ABX to your hearts content. When you've had all the practice you can stand and still claim you can hear the difference I'll let a few experts know. I guarantee you they will flock to your location to see this in person as it turns everything they know on their head and would love to be the first to get a paper out on it.

Looking forward to being proven wrong...

On this, we agree.

But certainly in the early iterations of the Squeezebox there were firmwares where the FLAC->WAV conversion did cause audible issues, but that was resolved as far as I know years ago.  Sometimes when people claim there is an issue, there really is.  And when we all agree that there shouldn't be, it warrants further investigation, as per your medical issue.


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mark_h

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Re: Bitperfect / identical sound streams can sound different
« Reply #61 on: December 30, 2011, 02:49:35 am »

Another comment to make here:

Of course it MAY NOT be jitter causing issues.  It may not be WAV vs FLAC.  It could well be something else in the audio chain.  It MAY BE that whatever word is used to explain the problem is a misnomer for the phenomenon and that it is being incorrectly used, perhaps through lack of understanding of the subject.   As you pointed out, most audiophiles are not engineers and so may be misusing the word, grasping for something to help explain what they hear...

The point I'm remaking, is the one above.  When there should be no audible differences, but enough people claim the opposite, it warrants investigation to see if there is a reason why...


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mark_h

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Re: Bitperfect / identical sound streams can sound different
« Reply #62 on: December 30, 2011, 03:16:18 am »

I didn't like leaving the request to support my assertions go with a reply to Google it. So here is one article. There are older ones, but I thought it would be good to provide more recent research. I can provide more if you need them:

[6] Eric Benjamin and Benjamin Gannon - "Theoretical and Audible Effects of Jitter on Digital Audio Quality", AES, 1998

I cannot access this without paying for it, which I am not about to do...

Bob Katz, eminent Mastering Engineer, had this to say, in 2007, on the subject:

"I have participated in a number of blind (and double-blind) listening tests that clearly indicate that a CD which is pressed from a "jittery" source sounds worse than one made from a less jittery source. In one test, a CD plant pressed a number of test CDs, simply marked "A" or "B". No one outside of the plant knew which was "A" and which "B." All listeners preferred the pressing marked "A," as closer to the master, and sonically superior to "B." Not to prolong the suspense, disc "A" was glass mastered from PCM-1630, disc "B" from a CDR.

Full article, with interesting statements such as:

"The AES/EBU (and S/PDIF) interface carries an embedded clock signal. The designers of the interface did not anticipate (my emphasis) that it could cause a subtle amount of jitter due to the nature of the preamble in the AES/EBU signal. The result is a small amount of program-dependent jitter which often sounds like an intermodulation, a high-frequency edge added to the music."

http://www.digido.com/jitter.html

So it seems it's not just audiophiles talking about jitter and it's negative effects...
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Vincent Kars

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Re: Bitperfect / identical sound streams can sound different
« Reply #63 on: December 30, 2011, 04:33:18 am »

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windowsx

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Re: Bitperfect / identical sound streams can sound different
« Reply #64 on: December 30, 2011, 07:55:34 am »

I'm assuming that you verified that both of these signals nulled with each other to verify that they are the same before your A/B comparison? They are both lossless which means output would be exactly the same. If there is a difference it would be the ENCODER that is making the difference and not the format. It is possible that an encoder is not doing is job properly or was setup incorrectly to do a comparison.

I use dbpoweramp to convert FLAC to wav to play in J River so I believe it's quite reliable encoder.

WAV and FLAC's bitstreams should be identical.  If they are not then there is an encoder or decoder bug and you should contact flac's author.

You can try comparing the same file between ASIO without memory playback to WASAPI (Event Style) with memory playback. They both are bit-perfect so the graph after quantization should be identical and you can hear no difference if your theory is true.

It seems that JPlay took step further demonstrating different memory access pattern (River/Beach) can cause different in sound. You can get JPlay 4.1 trial to test with J River and see if the claim is true or not. I don't think it'll take more than 15 minutes to download jplay to test with J River and see if there's any significant changes you can perceive or not. I'm not trying to promote jplay or anything but that existance itself can prove that bit-perfect doesn't mean you can always get the exact same thing. If you can or can't hear any difference between JPlay and default J River output engine, report in here.
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Vincent Kars

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Re: Bitperfect / identical sound streams can sound different
« Reply #65 on: December 30, 2011, 08:52:25 am »

I don’t think anybody in the known will argue that there are differences at bit level.
Numerous test has been done and all yield the same result: WAV and FLAC are identical at bit level.
The most convincing test imho has been done by Barry Diament, he recorded the SPDIF out when playing FLAC and WAV. This is exactly what is send to the DAC and of course, at bit level both are identical.
http://www.computeraudiophile.com/content/first-test-and-some-food-audio-thought

As both FLAC and WAV are converted to “raw” PCM and PCM= sample + time step a possible explanation might be that there are differences due to the differences in amount of processing required. This will translate into different levels of RFI, EMI or ripples on the power rail. In turn this might disturb the clock driving the DA.
If this is true the difference is not due to the file format but due to the DA (the sound card) being very susceptible to its environment. As the sound quality fluctuates with system load, the card is obvious not up to its job. I call this a system error.

Both Gordon Rankin and a Linn engineer tried to measure this without success
http://thewelltemperedcomputer.com/KB/WAV-FLAC.htm

Buffer management, smooth processing as Matt calls it on this forum, memory access patterns in JPlay might be another explanation. However this is in general used as an explanation why different media players with all DSP off still can sound different.
Can’t conjecture up something why this will make WAV and FLAC sound different.

Anyway, perceived differences between lossless uncompressed and lossless compressed formats remains a bit of a mystery.
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DarkPenguin

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Re: Bitperfect / identical sound streams can sound different
« Reply #66 on: December 30, 2011, 10:24:45 am »

You can try comparing the same file between ASIO without memory playback to WASAPI (Event Style) with memory playback. They both are bit-perfect so the graph after quantization should be identical and you can hear no difference if your theory is true.
That's output.  That has nothing to do with flac v wav.
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gvanbrunt

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Re: Bitperfect / identical sound streams can sound different
« Reply #67 on: December 30, 2011, 10:53:27 am »

Quote
Quote
However neither group used what was widely known in the scientific and engineering community. Engineers always knew what was needed but made trades offs based on price. This was not something the audiophile community made them aware of.

Citations, please.

That is a little silly. The fact that jitter has been listed as spec on CD players since the 80's means they knew it was important. And since there were many DACs with low jitter etc they obviously knew how to make them. The fact that they were not cheap proves my point.


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Of course it MAY NOT be jitter causing issues.  It may not be WAV vs FLAC.  It could well be something else in the audio chain.  It MAY BE that whatever word is used to explain the problem is a misnomer for the phenomenon and that it is being incorrectly used, perhaps through lack of understanding of the subject.   As you pointed out, most audiophiles are not engineers and so may be misusing the word, grasping for something to help explain what they hear...

Finally an "audiophile" with some sense of logic. I mean that with the most respect, it isn't often things are constructive in these kinds of conversations. As I pointed out, I would love to be proven wrong as that will increase knowledge and lead to better equipment for all of us. Things have to start somewhere. The start is proving you can hear a difference and that is done with an ABX test.

The reason for most of skepticism of audiophiles is that they can spend unreal amounts of money on equipment, yet never even verify themselves if the investment is worth it? Without an ABX test you cannot. Even worse, they then proceed to come up with wild explanations for their assertions and some magazine does testing on it etc.  But never an ABX test to prove they can hear it in the first place. Why not? That is doing science in reverse and proves nothing.

Quote
Quote
Since I have provided one, perhaps you can provide some data that shows that the average person (or even someone with golden ears) can perceive the difference in the jitter in a high end DAC and a newer Soundblaster card.
Has such a test even been documented? 

As far as I know, no it hasn't yet. I've seen many audiophiles claim they can and many others say it is not possible. The skeptics already have science and specs on their side saying it can't be done, so it's up to audiophiles to prove they can. I would love to see it put to an actual test. That would be a great starting point.


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Vincent Kars

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Re: Bitperfect / identical sound streams can sound different
« Reply #68 on: December 30, 2011, 12:37:52 pm »

There is a intriguing post by C.R.Helmrich: http://www.hydrogenaudio.org/forums/index.php?showtopic=73686&pid=649256&st=50&#entry649256
 
Indeed, tiny details are best remembered by our short time memory. That is why he uses loops of 2 sec.
Makes me wonder if ABX simply exceeds the capabilities of our short time memory and as a consequence yields to many false negatives.

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windowsx

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Re: Bitperfect / identical sound streams can sound different
« Reply #69 on: December 30, 2011, 01:29:30 pm »

That's output.  That has nothing to do with flac v wav.

Sorry for the confusion. Back then someone claimed that both WAV and FLAC's bitstream are identical so I'm demonstrating ASIO and WASAPI which both have bit-perfect so bitstream will be identical too in the same principles. If the claim of identical bitstream will produce exact same sound, ASIO and WASAPI shall make no difference too like FLAC  and WAV comparison due to logic followed by his claim.

The difference between flac and wav on output is flac has one more stage for uncompressing bitstream packet data making the process chain little longer than wav causing more induced jitter in bitstream. I know using jitter word in explanation sounds too skeptical and popular words to draw some cash from audiophiles but only possibility I can give for explanation now is "continuity of bitstream". You can try Fidelizer to test more and judge it yourself whether you can hear what I claim or not.
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DarkPenguin

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Re: Bitperfect / identical sound streams can sound different
« Reply #70 on: December 30, 2011, 02:29:01 pm »

Sorry for the confusion. Back then someone claimed that both WAV and FLAC's bitstream are identical so I'm demonstrating ASIO and WASAPI which both have bit-perfect so bitstream will be identical too in the same principles. If the claim of identical bitstream will produce exact same sound, ASIO and WASAPI shall make no difference too like FLAC  and WAV comparison due to logic followed by his claim.

The difference between flac and wav on output is flac has one more stage for uncompressing bitstream packet data making the process chain little longer than wav causing more induced jitter in bitstream. I know using jitter word in explanation sounds too skeptical and popular words to draw some cash from audiophiles but only possibility I can give for explanation now is "continuity of bitstream". You can try Fidelizer to test more and judge it yourself whether you can hear what I claim or not.
That makes more sense to me.

How you get things out to whatever DAC is more of an adventure than people generally think.
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windowsx

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Re: Bitperfect / identical sound streams can sound different
« Reply #71 on: December 30, 2011, 02:53:57 pm »

I used to take computer audio seriously enough to spend over $10k on research just to get the best SQ out from PC. But now I don't really care that much about it anymore. I'm just sharing my experiences during my crazy trips. What the real adventure is how good the song is produced. ;D
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gvanbrunt

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Re: Bitperfect / identical sound streams can sound different
« Reply #72 on: December 31, 2011, 12:08:43 am »

Quote
Makes me wonder if ABX simply exceeds the capabilities of our short time memory and as a consequence yields to many false negatives.

That wouldn't be a false negative. It would be proof that they can't tell the difference and that all that science on memory and hearing is correct. No matter how golden ones ears are, you can't get around the basic wiring of the brain. There are limitations in what we can remember, how much of a sound we can hear at once, and the fact that the brain automatically interpolates what it thinks should be there. And that isn't even touching on personal bias which is impossible to get past without double blind testing.

However ABX isn't about telling A apart from B. It's about which you prefer. If you prefer one over the other, after repeated testing the preference is clearly shown. That is unless they really can't tell the difference and there is no preference.
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Listener

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Re: Bitperfect / identical sound streams can sound different
« Reply #73 on: December 31, 2011, 01:15:42 am »

The best comment along those lines I've ever read was from Penn Jillette (of Penn & Teller).  It was about religion versus science, so slightly different in scope (though "audiophile" in some circles is quite akin to a religion, where an idealized sonic perfection replaces god):

Not that exact nonsense indeed.

Fine quote.

I remember related observations by Thomas Kuhn in "The Structure of Scientific Revolutions".

The Amazing Randi has interesting observations about spoon-benders, paranormal behavior researchers and pseudo-science in general.

Here is my synthesis:

 A paradigm shift is successful if after a few years, the  field validates and incorporates the new ideas and moves on to other concerns.  If the same ideas remain asserted but never proved and are not widely accepted, the paradigm shift has not succeeded.  Randi notes that pseudo-science does not advance.

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If marking the edges of CDs had really produced a difference, all those people who professed belief would still be marking their CDs or doing something else based on that finding.

Bill


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mark_h

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Re: Bitperfect / identical sound streams can sound different
« Reply #74 on: December 31, 2011, 03:55:39 am »

The reason for most of skepticism of audiophiles is that they can spend unreal amounts of money on equipment, yet never even verify themselves if the investment is worth it? Without an ABX test you cannot.

The amount spent should not impact the impartiality of the observer if objectivity is the goal...

With regards testing, many of the desired results require lab equipment.  It's unreasonable to expect the majority of interested parties to have access to such kit.  Which leaves general testing.  And the thing is, it's not always easy to ABX in any useful way, which is perhaps why people don't do it as much as they should.  Memory is a terrible thing to rely on when testing, and tests usually involve playing tracks, pausing, connecting new bits of kit, playing the same track and then trying to make judgements.  Almost a pointless exercise, IMO, because your (lack of) memory, even over these short terms causes problems.

When I test I try to set up parallel systems so that I can instantly switch between components being tested LIVE meaning that any differences are immediately obvious and don't rely on memory at all.  I also never use full tracks; you simply cannot remember things you heard a minute ago in these situations. I use short samples, at most a few seconds long, containing single components of music that allow me to test specific aspects of replay.  I then repeat these samples over and over and over until I'm utterly focussed on what I'm hearing and ONLY THEN do I switch to the parallel system - memory is not required - any differences are immediately apparent.  And the results from samples tend to then scale up - that is, the best sounding samples lead to the best sounding music.

Clearly my sympathies lay with the audiophiles.  My goal is the absolute best music reproduction I can create within my budget.  Ideally that system is created using objectively tested kit, but where testing is unavailable I am open minded enough to listen to both sides of the commentary without automatically dismissing either and confident enough in my ability to listen objectively that, where possible, I then test things myself using my method above.  If some bit of kit sounds better to me, even if objective data backing up my observations is unavailable, I will adopt it; it would seem silly not to...

Yes, of course, there is much nonsense out there; subjectivity often trumps objectivity.  But to automatically dismiss audiophile commentary seems rather short sighted.

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mark_h

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Re: Bitperfect / identical sound streams can sound different
« Reply #75 on: December 31, 2011, 08:49:05 am »

There is a intriguing post by C.R.Helmrich: http://www.hydrogenaudio.org/forums/index.php?showtopic=73686&pid=649256&st=50&#entry649256
 
Indeed, tiny details are best remembered by our short time memory. That is why he uses loops of 2 sec.

Interesting. As above, I do exactly the same for that reason.  I wasn't aware of anybody else testing in the same way! :D
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MarkGrigsby

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Re: Bitperfect / identical sound streams can sound different
« Reply #76 on: January 02, 2012, 06:12:06 pm »

I'm also having an unexpected audio difference between two outputs I'd expect to be identical - would appreciate any ideas...

I used to have my PC connected to the Denon 3310 via Optical output, and always had great sound.  A few days ago I switched to an HDMI connection, and immediately noticed something lacking in my audio files.  I 'proved' my point by doing a blind test with my wife who typically says 'it all sounds the same', and she specifically noticed the lack of low-end in the HDMI output.

As far as I can tell, all settings are the same.  I was testing high bitrate MP3 files, using WASAPI event-style on both, and even the same 'device' setting on the amp (switching between optical and HDMI inputs).  I know the sound driver differs (Realtek for optical, ATI for HDMI), but could that really make the difference?  According to the amp, the bit-depth of the PCM stream is the same on both, and of course MC would decode the MP3 the same, so can there be something at the driver level degrading the HDMI sound?
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Listener

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Re: Bitperfect / identical sound streams can sound different
« Reply #77 on: January 02, 2012, 06:20:33 pm »

I'm also having an unexpected audio difference between two outputs I'd expect to be identical - would appreciate any ideas...

I used to have my PC connected to the Denon 3310 via Optical output, and always had great sound.  A few days ago I switched to an HDMI connection, and immediately noticed something lacking in my audio files.  I 'proved' my point by doing a blind test with my wife who typically says 'it all sounds the same', and she specifically noticed the lack of low-end in the HDMI output.
...
According to the amp, the bit-depth of the PCM stream is the same on both, and of course MC would decode the MP3 the same, so can there be something at the driver level degrading the HDMI sound?

HDMI is notorious for high levels of jitter.  Much higher than the usual for SPDIF or async mode USB. At such high levels, jitter probably produces quite audible differences.

Vincent may be able to provide links to test results.

Bill
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MarkGrigsby

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Re: Bitperfect / identical sound streams can sound different
« Reply #78 on: January 02, 2012, 06:29:51 pm »

Thanks for the quick reply!  Are bitstreamed formats such as DD, DTS-HDMA etc more immune since the amp does the decoding of the original untouched stream?
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Vincent Kars

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Re: Bitperfect / identical sound streams can sound different
« Reply #79 on: January 03, 2012, 01:01:41 am »

No, the audio part of HMDI can be very high on jitter.
Using 2 different digital connections, the bits might be identical, the timing can (and will) differ.

http://thewelltemperedcomputer.com/HW/Connect/HDMI_connect.htm
http://www.avsforum.com/avs-vb/showthread.php?p=17504717#post17504717

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flac.rules

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Re: Bitperfect / identical sound streams can sound different
« Reply #80 on: January 03, 2012, 03:35:18 am »

No, the audio part of HMDI can be very high on jitter.
Using 2 different digital connections, the bits might be identical, the timing can (and will) differ.

http://thewelltemperedcomputer.com/HW/Connect/HDMI_connect.htm
http://www.avsforum.com/avs-vb/showthread.php?p=17504717#post17504717



None of the links answer his question, seeing that as the stream must be read, then decoded into audio by he receiver. As a brand new audio stream based on what earlier is a data stream, won't the jitter of the HDMI-interface be irrelevant?
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Vincent Kars

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Re: Bitperfect / identical sound streams can sound different
« Reply #81 on: January 03, 2012, 04:13:41 am »

The audio stream over HDMI is digital anyway, be it PCM, DD, DTS.
In all cases the conversion to analog is done by the receiver.
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flac.rules

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Re: Bitperfect / identical sound streams can sound different
« Reply #82 on: January 03, 2012, 04:30:06 pm »

The audio stream over HDMI is digital anyway, be it PCM, DD, DTS.
In all cases the conversion to analog is done by the receiver.

Of course, but when you decode a format, won't you have to buffer the indata, decode it, to lpcm and then send it to the DAC? Won't this part of the chain remove any possible jitterproblems added by the hdmi-interface?
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gvanbrunt

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Re: Bitperfect / identical sound streams can sound different
« Reply #83 on: January 03, 2012, 05:08:23 pm »

Quote
Of course, but when you decode a format, won't you have to buffer the indata, decode it, to lpcm and then send it to the DAC? Won't this part of the chain remove any possible jitterproblems added by the hdmi-interface?

The DAC (in the receiver in this case) will remove jitter if it is half way decent. That is what the clock signal is for. Also jitter does not produce a "lack of low end". That is not the cause.

However there are many different things "in between" the source (MC?) and the jacks. Drivers, filters etc. They all could have something to do with it. I would look there.
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flac.rules

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Re: Bitperfect / identical sound streams can sound different
« Reply #84 on: January 03, 2012, 05:14:40 pm »

The DAC (in the receiver in this case) will remove jitter if it is half way decent. That is what the clock signal is for. Also jitter does not produce a "lack of low end". That is not the cause.

However there are many different things "in between" the source (MC?) and the jacks. Drivers, filters etc. They all could have something to do with it. I would look there.
So any well designed DAC buffers the dataflow and reclocks it for the conversion process? I am very interested in the details if you have them.
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gvanbrunt

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Re: Bitperfect / identical sound streams can sound different
« Reply #85 on: January 03, 2012, 05:28:36 pm »

Sorry don't have the exact details, but yes buffering and reclocking\syncing is part of the job. There is plenty of information on the net though. Probably a ton right in the HDMI spec if you can dig it up somewhere.
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pcstockton

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Re: Bitperfect / identical sound streams can sound different
« Reply #86 on: January 03, 2012, 06:46:16 pm »

So any well designed DAC buffers the dataflow and reclocks it for the conversion process? I am very interested in the details if you have them.

Here is some reading on a DAC I would call well designed.  It has much value for understanding the processes in general.

http://www.naimaudio.com/userfiles/modules/attachment/naim_dac_august_2009.pdf

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