OP
- Thread Starter
- #21
None of the articles I referenced were journal papers. They were all conference papers where peer review is optional.
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Understanding Jitter in Digital Audio: Measurements and Listening Tests
- Thread starter amirm
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OP
- Thread Starter
- #23
Thanks for watching. I was somewhat unhappy with the video at the end, worrying it went into the weeds too much.
maxwell3e10
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Thanks for the overview. I didn't quite follow the purpose of 250 Hz modulation of the square wave in J-test file. Is it modulating the amplitude, frequency or phase of the 12 kHz square wave? Using a square wave as the main signal makes intuitive sense since the transitions are sharper. An interesting comparison would be an FFT in the presence of jitter for a sine wave signal, square wave signal, and square wave with 250 Hz modulation.
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One source of jitter with an SPDIF connection that really isn't an issue with other connections is when the bits in use flip. Back when the papers were written the SPDIF was pretty much the only game in town for consumers. I think it was called logic modulation. Anyway the addition of that small squarewave, its amplitude was only 1 LSB (I think), cause zero and ones to flip at the most extreme way. All of them going from zero to nearly all ones which created the most extreme possible modulation. Also if you were using a 16 bit multi-bit DAC you were also flipping all of its bits which meant switching from most current thru the DAC to least and back again in these multi-bit ladder DACs. So causing this extreme exercise of possible jitter infiltration was the purpose of the square wave at 250 hz. BTW, this is for 48 khz, it is 229.6875 hz for 44,100 hz rates. The small wave should be the sample rate divided by 192.
I'm not an expert. Don't think anything here is wrong, but if so Amir or someone can correct it.
dougi
Addicted to Fun and Learning
From the J Dunn paper/s I believe the 250 Hz (for 48 kHz sampling) is supposed to help identify interface data dependent jitter susceptibility as opposed to random jitter. I did a comparison of my two USB interfaces on the weekend. An older USB on my Marantz NA7004 showed the 250 Hz products, hence susceptible, but my iFi nano-ISD did not, so not susceptible.
OP
- Thread Starter
- #27
It is changing the amplitude by 1 bit.
The Capstan
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This is E X C E L L E N T ! ! ! Thanks Amir. Well done!
A digital audio signal is, in the grand world of communications, a low bandwith signal tough. Still the cables should be following standards of shielding and lenghts, but the phenomenon you describe won’t happen in audio. there might be bit flips, if noise is too high or there is too much lenght before a repeating amp impacted the amplitude, those are extreme case, but there is not a cable used in digital audio that doesn’t have a 384k bandwidth, no other digital techniques needed beside respecting the protocols standards.
I didn’t watch the video I admit, but more generally, an audio precision analyser is not the right tool to explain jitter. It can show it’s effect. An eye diagram on a scope show jitter. But in all cases, In audio, you don’t need bit flips for jitter to have an effect, all the samples decoded can be right, but if they are converted at a fluctuating rate, the resulted analog signal is distorted.
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That is correct. It was designed to provoke data-dependent modulation of the recovered S/PDIF clock, a common issue with older receivers. This is obviously not a problem with asynchronous USB interfaces. However, toggling (almost) all the bits at the same time can still have unwanted effects through various mechanisms, not necessarily involving clock jitter.
What is a “predatory journal”? I don’t think we have those in biology.
Gotcha! I never tried to publish without going through peer review before. Wouldn’t have even thought about it in my academic days.
What other journal for publishing peer reviewed audio science and engineering research has a higher impact factor? Also, Impact factors can be misleading sometimes....
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I don't know about impact factor, but on audio topics, I'd trust papers published by IEEE more than anything from the AES.
The key difference between IEEE and AES is that you don't need to have any academic degree to publish in AES. All you have to do is to become a member by paying the membership fee. AES basically welcomes ignorance... The interesting fact is that even well respected audio engineers like Bruno Putzeys don't have any major IEEE publications (Bruno Putzeys is features as co author in only two IEEE papers, and about 10 AES papers).
audio_tony
Addicted to Fun and Learning
@amirm In the video you indicated that when plugging in the USB connection jitter increased, I believe you said due to noise from the port.
Can an earth loop be ruled out here then? Because I've seen the same behaviour caused by a ground loop.
I don't believe that USB ports are noisy as a rule - it always seems to be ground induced noise.
Can an earth loop be ruled out here then? Because I've seen the same behaviour caused by a ground loop.
I don't believe that USB ports are noisy as a rule - it always seems to be ground induced noise.
The thing is, beside the impact factor, what do you find erroneous with his research and experiments? Sure it’s open to discussion, that’s one men finding. But, hey, it’s audio reproduction folks, not the formula of the Covid vaccine. we have to put things in perspective, not everything is a major scientific breaktrough, that deserve an article in science publications and peer review. You can take it for what it is and if some bits of it is inexact or not fully complete you can of course flag it. But blanket statements to the effect that it can’t be trusted is not really helping. Some people do research, and it helps the state of the art. If we need a comitee to confirm every times someone want to spread knowledge and studies, we wouldn’t have the advancement we have with audio fidelity products. It still better to use this as a reference than a youtube video...
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I've done both neither charged any publication fees. My AES conference presentation was rejected as a journal article, the circuit presented eventually became a multi-million dollar product that is still in production 30yrs. later. It also got me an invitation from the LIGO team to visit their facility in appreciation for the socket it filled (as well as Bruce Hofer of AP). BTW there have been plenty of dropout presenters in the IEEE.
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OP
- Thread Starter
- #39
Where are you reading the requirement for a degree for IEEE? As far as I know, they accept equivalent work experience in lieu of a degree.
As to AES membership, you have to have three sponsors to get accepted as a member. It is not as simple as just paying the money.
I personally don't like IEEE because they take free papers from authors and then charge an arm and a leg for access to them. They think everyone is a major corporation and can pay their fees.
As do most of the academic publishers, sadly. Personally, I have access to IEEE but not AES.
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