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Null test 88.2/24 and 44.1/16


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11 minutes ago, firedog said:

Thanks. Not surprising. On my present system I stopped worrying about recording format. I mostly buy what the original was recorded in, if it is available. But most important is a good recording. Redbook can sound perfectly satisfying, and I agree there are certainly lots of examples where the difference between it and Redbook are negligible, if they actually exist.
 

But there could still be reasons hi-res would sound better/different to some people, ranging from equipment sweet spots to filtering differences changing the sound slightly between Redbook and hi-res.
There may also be other examples where transients and detail are easier to hear on the high res, even though they are also audible on the Redbook. I've also a couple of times thought I heard "new" detail in a hi-res version, only to then find out it was also audible on the Redbook version. But I didn't notice it on the Redbook till I heard it first on the hi-res version, where it was more apparent, or should I say easier to pick out?
 

Anyway, as a cellist, check out the just released Yo Yo Ma recordings of the six Bach Cello Suites, called "Six Evolutions".

Yes, there is the issue of how DACs handle Redbook audio regarding the filter. So this little test doesn't address that particular question. But I imagine, if your DAC is well made, and it probably is, that is does a pretty stellar job at 44.1/16 bit audio.  For my own recordings, I often listen to them in the high res original versions. It's partly psychological for me! haha

 

I haven't heard the new recording of the Bach suites. That's his third recording of them, I believe. The suites are something that never completely settle in a cellist's interpretation.  They are always changing. I suppose that is why the album is called 'Six Evolututions'. It's a great title. Thanks for letting me know! 

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31 minutes ago, pkane2001 said:

 

Can you please share the audio files you used for this analysis? I’d like to run them through my own software to see if there’s anything interesting it can find.

Sure, they are uploading now to the cloud.

 

Can I send the link privately in a PM? 

 

 

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47 minutes ago, Jud said:

 

Insofar as the studio mics were able to capture it, and it wasn't removed by the ADC(s) during sigma-delta modulation or any downsampling.

Yes, I'm not saying the wav file has a perfect representation of the original source recorded.

 

I am comparing listening back to either the high res, original version vs the down sampled version.  

 

 

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1 hour ago, testikoff said:

Shouldn't the spectrum of null-test delta look something like that (well, mine does)?.. :)

 

delta_2488_1644_spectrum.thumb.jpg.60477e10f746b3bb0a8cec2836cf22c8.jpg

I think it depends on what is captured in the recording and the software. The program I used above is a picture of the whole jazz tune in time (at the bottom it shows the elapsed  time).

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20 minutes ago, Jud said:

 

Right, just wanting us to remember that A/D is the flip side of what goes on in a DAC - first converted from analog to digital with sigma-delta modulation, then (with most ADCs) converted to PCM at 352.8 or internally/externally downsampled to the more common resolutions, 192 or 176.4kHz or below.  So even the "hi res original" from the studio is almost always downsampled.

Got it! Thanks!

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2 hours ago, testikoff said:

What you posted is a spectrogram, not spectrum...

It's all I got. Sorry

 

Opening it up and looking at it closely again, everything except the high frequency content and perhaps the dither across the top looks to me to be -80db and lower, which is pretty quiet. And it all looks like random noise to me except, again, for the high frequencies at the top. 

 

 

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1 hour ago, pkane2001 said:

Here's what my own DeltaWave software as able to determine from about a 2.5 minutes extract from the middle of the recording.

 

The comparison is between the original 88.2Khz/24 bit recording and a downsampled version to 44.1Khz/16bit, then upsampled back to 88.2Khz/24 bit, as described by @bachish (thanks for the files!)

 

By the way, the recording sounds excellent! I also listened to the difference between the two files, which is primarily white noise. I was able to hear occasional notes come through buried in the noise, but only with software digital volume adjusted to about 70dB gain and my DAC set to 0dB (max volume).

 

The files were delivered with the upsampled version with inverted phase. Otherwise, the files match perfectly in level and phase, no phase offset or drift was found.

 

First, a comparison of the spectra of both waveforms. Original 88.2/24 is in blue:

 

image.thumb.png.13775eadc4a072b9cbbad47131105be6.png

 

The drop off do to downsampling/upsampling starts around 21800Hz at -92dB down. Here's the zoomed in portion where the cut-off starts. You can also see very tiny differences in level due to dither and computational error during resampling:

 

image.thumb.png.ae07d33c866488a256a0a6a4df1cd23a.png 

 

Now the actual waveforms overlaid on top each other:

 

image.thumb.png.1d267fca2e35d1f0360160160837aeb4.png

 

Stats below show excellent correlation between the two: 76dB correlated null and -75dB difference (rms).

 

Spectrum of the difference of the two files. Well below -115dB in the audible range:

image.thumb.png.e6d29c86a9040cad7b4572a1d2a97ce1.png

 

Spectrogram of the original 88.2/24 file:

image.thumb.png.c7427bca258964c7cf6828b07de551eb.png

 

And spectrogram of the downsampled/upsampled file:

image.thumb.png.ed0642a997f6523c701b117e0ff7324c.png

 

Spectrogram of the differences of the two files:

image.thumb.png.b3e006b88ca1daea9950489267d388d4.png

 

Interesting results in the cepstrum analysis of the two files:

 

image.thumb.png.9b40bc21674c10c90d957dd397038638.png

 

This shows that the downsampled/resampled file has some ringing/aliasing going on at a number of frequencies that are not present in the original 88.2/24 bit file. Probably the side-effect of the resampling process and filtering applied. I tried to label the main ones. Note that the vertical value (Y axis) is a correlation coefficient. It's an indication of how strong the ringing is in the measured file, while the X coordinate is the frequency at which this ringing was detected.

 

While the artifacts of the resampling process are visible in the Cepstrum plot, they are not at all noticeable in any of the measurements or in listening to the differences between the two files.

 

 

 

 

After I posted, I was looking again at your analysis and a couple questions occurred to me. 

 

In the Cepstrum plot, the y axis - I'm curious what measurement that is.  Just trying to get a handle on just how loud the ringing is. You mention the level is pretty low, I realize. 

 

In the 'Spectrum of the difference of the two files. Well below -115dB in the audible range' the left side of the graph looks like the noise shaping of the dither applied, which would make sense.  So essentially, that graph is showing that the difference between the two files is primarily in the dithering and the high frequency content from the original file. Am I reading that correctly?

 

Thanks!

 

 

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3 hours ago, Jud said:

 

If you were trying to hear noise, that's correct. But we're trying to hear music. :) How much very low level musical detail is the noise masking?  (Maybe none, considering the noise level of a typical listening room, but it's the way of conceptualizing noise and masking that I'm thinking of.)

I think when talking about noise in these files, we need to realize that -100db is the equivalent to 0.001 % distortion in audio equipment.  Highly unlikely we would hear this. 

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8 hours ago, pkane2001 said:

 

Cepstrum attempts to find repeating patterns in the frequency domain. The Y axis in the plot is a correlation coefficient. All it's saying is that a relatively higher value has a relatively greater amount of ringing (i.e., the pattern is better defined). It doesn't say anything about the level of ringing.  Since it does point to specific frequencies, it might be interesting to see if the magnitude can somehow be dug up from the signal and noise in the frequency domain. Not sure that's possible, but I'll think about it some more :)

 

 

Right. Most of the differences are well below -115dB in the frequency domain. But, that represents an average over the measured period. For a time version of the difference plot, here is what it looks like in the time domain:

 

image.thumb.png.4e47cb5f3a0be4754592c21ce68aadfd.png

 

You can see some peaks rising to about 0.02. In dB terms, that represents about -34dB level. But that's just a few peaks. Most of the difference is well below -100dB level. By the way, this is the waveform I listened to to hear the difference. Most of it sounds like noise, with a few very occasional notes coming through. Probably corresponding to some of the peaks in the above plot. So, there is some difference between the files, they are not a perfect match, but they are very, very close.

 

Here's that same difference plot but with all the frequencies above 20KHz removed:

image.thumb.png.8d1b09b2c281a7b0cd5f1aafe5dc566a.png

OK, thank you for the more detailed information. It would  be interesting to fine tune the conversion settings to see if those larger spikes couldn't be tamed. 

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4 hours ago, crenca said:

Interesting.  When the OP transmitted these files to Paul over the Internet, was the EM/RF "noise" of your computer, your ethernet cables and switches/routers, etc. taken into account?  Would "audiophile" networking equipment made any difference to any computational analysis?  What if you retransmitted these files several times and due to the differing paths these filed traveled over the Internet backbone (as any tracert will tell you), an analysis was done to see the effects these differing routes had?

 

Along these lines, what would happen if you took these files and transmitted them back and forth from your computer to an external HD connected via USB, say 1000, or 10,000, or 10,000,000 times?  How would this computational analysis be effected, and would it matter if your USB connections used "Audiophile" USB cables, USB decrapifiers, and differing USB design implementations?

I have to admit, you did make me chuckle. Point well made, though, in a somewhat smart @$$ way. Haha

 

 

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4 hours ago, Jud said:

 

Following up on this -

 

Here are some recordings available from NativeDSD, and you can filter your search to come up with only those albums/tracks available in DSD256: https://www.nativedsd.com/new_browse

 

@bachish, @pkane2001, I don't know whether you're able to do the same analysis with one of these tracks, but it would be interesting to see whether a recording that presumably had experienced less processing would show any greater difference to a 44.1kHz resolution downsampled file than the 88.2kHz original you used before.

 

It would be interesting to try it with DSD. DSDis a different way to capture the analog signal (super high sample rates at 1 bit) so the math would be different. 

 

My understanding is that, unlike the past, editing can be done in DSD without converting it to PCM. 

 

Unfortunately, I dont have any DSD software. Otherwise, I would be curious to at least try a null test.

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4 hours ago, Jud said:

 

I don't care.  :) 

 

I'm just interested in the very nice analysis these two kind folks have done, and looking forward to anything further they're able to do along the same lines.  But to save these people the trouble, if you have got a link to the types of measurements they've done, comparing a DSD256 recording and a 44.1kHz downsampled version, that would be great.  If including DSD is a problem, there are the 2L comparison tracks that would enable comparative measurements of 352.8 and 44.1kHz files: http://www.2l.no/hires/index.html?

 

Thank you, Jud! Interesting. I'll have to check these out. Thanks. 

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59 minutes ago, mansr said:

Creating the DSD stream requires some additional maths, the sigma-delta modulator, but once that is done, the analysis is no different from regular PCM. 

 

Some software can do simple operations like splicing without converting the whole stream to PCM and back. Mixing, or even a simple volume adjustment, is impossible to do directly in DSD.

 

That's not possible. Each sample in a DSD stream can have one of two values, 1 or -1. The difference between two such samples can have four values. You can compute the difference, but it won't be DSD.

Ok good info. 

 

For a test betwen DSD and 44/16 I was thinking one could convert DSD to PCM 96/32 then downsample and dither to 44/16 and back up again to 96/32 and finally to DSD and see how it compared to the original file. 

 

My hypothesis is...it probably would compare quite well to the original in the audible range much like this test did.

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7 hours ago, Jud said:

 

There are a few folks in recording circles who fuss about such things, but they are definitely outliers. 

 

Ok, interesting. I suppose it isn't too hard to test. I could take an original recording that is on the SD card in my field recorder that hasn't been transfered yet, upload it to the computer, load it into programs and export over and over, transfer between external hard drives, many times, and upload and download from OneDrive several times. 

 

I could then take it, flip the phase and load it into my DAW and load, just one time, the original from the SD card into the DAW and see if they null. Would be interesting.

 

 

 

 

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4 hours ago, cookiemarenco said:

 

We have a "Test your systems" page for free downloads.  One song, 4 formats.  It's free.  The source file is DSD256 recorded to DSD256 and no conversion to PCM / DXD for the DSD256.  The other DSD, WAV, FLAC files were made from the DSD256.

 

Here's the link at Blue Coast Music

https://bluecoastmusic.com/free-downloads

 

I recorded it so I'm familiar with the processes used if you have any questions.

BTW..  we have found ways to keep the editing process in DSD on the Pyramix.  It involves mixing through an analog mixing console.  Sounds great.

 

Enjoy!

Cookie Marenco

founder and producer

Blue Coast Records (produces and owns music) and Music (store for all high resolution labels)

https://bluecoastmusic.com/

 

 

 

 

Thank you, Cookie! I'll check it out 

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6 minutes ago, Jud said:

 

And/or you could ask Cookie.  :) 

 

Whether I agree with what she thinks on various matters (bearing in mind she's an experienced producer, I'm just some guy), I really like the quality of the recordings she produces. 

Yes, I'm sure she does excellent work. I'm definitely going to take a listen.

 

You mean ask her to do the test or ask her opinion?

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