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Geoff Martin's tour of "Errors in digital audio"

oivavoi

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#1
The chief engineer at B&O, Geoff Martin, has recently finished writing a series of blog posts on "Typical errors in digital audio" over at his blog: http://www.tonmeister.ca/wordpress/

Very interesting stuff. According to him, streaming over wifi is much more error prone than commonly assumed, for example. What do you guys who possess more technical insight than me think?
 

Cosmik

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#2
Yes, I agree with him that there are many possible horrors lurking in the chain. With my system I have been almost paranoid about the issue of avoiding any form of re-sampling and have stripped it down to the bare ALSA bones - and if you write your own software you have an advantage in being able to check sample values as far as the DAC.
 

oivavoi

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#3
With my system I have been almost paranoid about the issue of avoiding any form of re-sampling and have stripped it down to the bare ALSA bones - and if you write your own software you have an advantage in being able to check sample values as far as the DAC.
For me, that sentence is the equivalent of saying "if you run faster than Usain Bolt"! But it's reassuring that you share some of his concerns, at least. I need to think about whether this has any implications for my own future setup(s).
 

restorer-john

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#4
Interesting article and blog. :)

I've tried all sorts of domestic streaming over the years and worked out a long time ago that it is full of uncorrectable errors and introduced errors, all of which manifest themselves very quickly.

Having various frequently used reference test CDs which much be absolutely pristine and unmarked, I figured, I'll throw them on my various network storage units, external HDDs etc and stream the test files (to preserve the discs from damage). It was a disaster from the first disc. The timing errors and lost packets, even across LAN, all types and speeds of WiFi, multiple routers over the years, made the files unusable for the purposes.

The issues simply are not noticeable in normal music listening. Clearly, music and human ears/brain are able to conceal and forgive single sample glitches and tiny timing errors that test equipment only serves to highlight.

IIRC, is was the high frequency, high level sines that were the most affected. It's been several years since my experiments, but the outcome was never to use network or WiFi (of any type) for distributing PCM audio @ 16/44. I would expect the problem would get exponentially worse as the bit depth and sampling rate went up.
 
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oivavoi

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#5
Interesting report, restorer-john!

What I can't work out from his blog, though, is whether these potential issues mostly apply to streaming of locally stored files, or whether it can also apply to streaming services like Tidal etc.
 

NorthSky

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#6
Why don't professional music recording engineers use analog tape recorders or direct to vinyl, it is much purer with lessor errors.
Is it a question of money that our quality music recordings are taking a beating, or something else more irritating.
 

Blumlein 88

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#7
I agree with much of it potentially. Haven't read all of his blogs. I've run into the long complex chain where something alters the bits in between when you didn't expect due to resampling. I'm mostly looking at you Windows OS. If only Amir had done a better job with audio in Windows. :p


A counterpoint of what's possible is this intercontinental audio test.
http://archimago.blogspot.com/2015/02/measurements-intercontinental-internet.html

I also don't do streaming from a NAS or such very often just from a standpoint of keeping it simple. I normally use an HD with music, connected to a PC that connects to a USB DAC.
 

Cosmik

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#8
Interesting article and blog. :)

I've tried all sorts of domestic streaming over the years and worked out a long time ago that it is full of uncorrectable errors and introduced errors, all of which manifest themselves very quickly.

Having various frequently used reference test CDs which much be absolutely pristine and unmarked, I figured, I'll throw them on my various network storage units, external HDDs etc and stream the test files (to preserve the discs from damage). It was a disaster from the first disc. The timing errors and lost packets, even across LAN, all types and speeds of WiFi, multiple routers over the years, made the files unusable for the purposes.

The issues simply are not noticeable in normal music listening. Clearly, music and human ears/brain are able to conceal and forgive single sample glitches and tiny timing errors that test equipment only serves to highlight.

IIRC, is was the high frequency, high level sines that were the most affected. It's been several years since my experiments, but the outcome was never to use network or WiFi (of any type) for distributing PCM audio @ 16/44. I would expect the problem would get exponentially worse as the bit depth and sampling rate went up.
Do you also get these issues with general network traffic - corrupted files, etc? It sounds strange to me...

While I can imagine all sorts of potential pitfalls in the rendering itself, moving bits around and getting them through to the other side generally isn't a problem with networked systems..?
 
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DonH56

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#9
I've had many problems trying to stream from my NAS to my SONOS:Connect over WiFi. Very unreliable, partly because the WiFi itself is not all that reliable. However, even after getting the network much better (range extender and some router settings), music streaming is still a PITA. My normal network connections seem to be OK, so maybe it is some sort of setup issue, but I am not (and do not wish to be) a network expert. I am planning to purchase or build'ish some sort of local streamer with local storage to drive my processor. Really wish the processor or SONOS would let me plug in a USB drive but such is not the case, alas, and most "good" streamers seem around the $1k mark. I am thinking Raspberry Pi instead but need to settle on an app for the library.
 

Guermantes

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#10
I am using an RPi3 with a locally attached 3TB drive for music files and a Topping D30 for the DAC. The software I'm using is moOde by Tim Curtis which is very actively supported and updated. It uses the ubiquitous MPD for library management which I find a little quirky when it comes to searching for music. MoOde is generally run headless with control via a web browser on another networked device such as a smartphone, tablet, etc. In this setup, the network is only used for control and not for streaming media.

I see that the DietPi distribution has support for installing JRiver which may be a superior library app to MPD, though I don't know how responsive it is on RPi.
 

garbulky

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#11
Yes, I agree with him that there are many possible horrors lurking in the chain. With my system I have been almost paranoid about the issue of avoiding any form of re-sampling and have stripped it down to the bare ALSA bones - and if you write your own software you have an advantage in being able to check sample values as far as the DAC.
ALSA? Whats that?
 

Jinjuku

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#13
The chief engineer at B&O, Geoff Martin, has recently finished writing a series of blog posts on "Typical errors in digital audio" over at his blog: http://www.tonmeister.ca/wordpress/

Very interesting stuff. According to him, streaming over wifi is much more error prone than commonly assumed, for example. What do you guys who possess more technical insight than me think?
I think WiFi, like any other connection technology can either be setup correctly or incorrectly.

I think that he has two NAS units with NAS side streaming applications that would backup the reasons I render music local to the DAC (I.E. client side rendering).

I think I don't know anything about how he has stuff setup and that's a problem. I quote:

"Do not bother contacting me to ask which “commercially-available system/device” I measured and in which I found these errors. I’m not doing this to get anyone in trouble. I’m just doing this to try to illustrate common errors that I see often when I evaluate and test audio devices."
 

restorer-john

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#14
Do you also get these issues with general network traffic - corrupted files, etc? It sounds strange to me...
No problems whatsoever with general network traffic or corrupt anything. All my movies are streamed via wifi on 150-300Mbs to a Dell Zino HTPC and they are fine for general, non critical enjoyment- SPDIF out to a standalone Rotel D/A, amp and speakers. I've been networking since windows3.11 and wifi since 8021.1b and have a houseful of computers running everything from win95 to 10 to various Linux/Ubuntu boxes. They all play together happily.

I haven't revisited network storage for my test discs for a few years now, so I might break out my unused Synology 5 bay NAS as my current router I think tops out at 600Mbs over n+ or something and seems to be rock solid.

Another reason it didn't really work for me was the RFI from WiFi cards near my test gear causing trouble, so I just pulled the pin and went back to a single box CD player for the specialized test signals needed for CD player testing and ultra low distortion signals for amps etc. I've always kept my HiFi gear and computer gear completely separate and apart from a few forays into HTPCs it's remained that way for ages.

I think it would be very interesting to see the results of say J-tests over WiFi from a NAS-Router-PC-D/A vs PC straight to D/A...
 

svart-hvitt

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#15
I think Geoff Martin’s article raises more questions than it provides answers or understanding.

His remarks remind me of those who say that for example an IMac 5k sounds better than a Mac mini, cfr. @watchnerd ‘s comment from Dec 27 in this link
https://www.audiosciencereview.com/...-a-new-daw-streamer-pc.2114/page-6#post-71388

It also reminds me of those who claim better sound after upgrading clocks or even stacking digital filter boxes.

I will not claim that @watchnerd and others must be wrong. However, it would be clarifying if Geoff Martin and other engineers could provide more practical, tangible advise on what works better in digital audio. Otherwise, such articles just contribute to FUD.
 
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