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Audibility of phase shifts and time delays
Reply #50
Let's see how this pans out in a simple experiment:


I like.

So are you saying that with a simple experiment you have overturned a major tenet on which MQA and other 'high res' systems claim superiority?

  • bandpass
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Audibility of phase shifts and time delays
Reply #51
Yes, please point  ‘temporal smearing’ proponents in the direction of my post.

I can't claim to be the first to have done something along these lines (axon described a similar experiment back in 2006), but I've done it in a way that is hopefully accessible to all and easily repeatable by anyone who wants to do so.

  • Woodinville
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Audibility of phase shifts and time delays
Reply #52
I forget which is which, but one of Proakis' books explains lots of ways to do pretty much infinitely variable sub-sample shift via interpolation by about 10 plus a 6 tap fixed-formula filter operating on the 10x filter response.
-----
J. D. (jj) Johnston

  • danadam
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Re: Audibility of phase shifts and time delays
Reply #53
I downloaded those files already a year ago, so I can't promise I'll try 3 samples delay any time soon. Probably in another year ;-)
Code: [Select]
foo_abx 2.0.2 report
foobar2000 v1.3.10
2017-11-22 02:35:21

File A: Impulses shift 0 samples 2klp norm 4416 .flac
SHA1: 8fc00a4bb6a1bb0a66ec5c83cfaa36f9d8fddd13
File B: Impulses shift 4 samples 2klp norm 4416 .flac
SHA1: 6133aaa124c97a3f768f3d9216af2eb07b7c0bf3

Output:
ASIO : ASIO4ALL v2
Crossfading: NO

02:35:21 : Test started.
02:38:48 : 01/01
02:39:48 : 02/02
02:40:31 : 03/03
02:42:31 : 04/04
02:44:00 : 05/05
02:44:54 : 06/06
02:47:26 : 07/07
02:49:35 : 08/08
02:56:36 : 09/09
02:57:49 : 10/10
02:59:46 : 11/11
03:01:23 : 12/12
03:03:16 : 13/13
03:04:04 : 14/14
03:07:30 : 15/15
03:07:30 : Test finished.

 ----------
Total: 15/15
Probability that you were guessing: 0.0%

 -- signature --
b76d1c64aff74736f104c5cd98c431b6c12b6dc8

  • danadam
  • [*]
Re: Audibility of phase shifts and time delays
Reply #54
And while I revived that old thread... the formula from the first page:
Code: [Select]
1/ ( 2 pi bandwidth number_of_levels)
I wanted to make sure I got it right. It is a bandwidth, not a sampling rate? And a number of levels of concrete signal, meaning that timing precision of a signal depends on its level? So for full scale 44/16 signal it is:
Code: [Select]
1 / ( 2 * pi * 22050 * 2^16)
Is that correct?

Also, is there any "citable" online source for this? (not that I don't believe it :-) )

  • splice
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Re: Audibility of phase shifts and time delays
Reply #55
I believe it's sample rate.
"The time resolution of a 16 bit, 44.1khz PCM channel is not limited to the 22.7µs time difference between samples. The actual minimum time resolution is equivalent to 1/(2pi * quantization levels * sample rate). For 16/44.1, that is 1/(2pi * 65536 * 44100), which is about 55 picoseconds. To put that in perspective, light travels less than an inch in that time. "
Regards,
   Don Hills
"People hear what they see." - Doris Day

  • saratoga
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Re: Audibility of phase shifts and time delays
Reply #56
I believe it is sample rate, although the difference is only a factor of 2.

The ability to introduce subsample shifts in noiseless waveforms is not very interesting, but volumes have been written on estimating shifts in noisy waveforms for radar, sonar, ultrasound, astronomy, interferometry and so on. There is probably a derivation of the noiseless case somewhere.

  • jsdyson
  • [*][*]
Re: Audibility of phase shifts and time delays
Reply #57
I have an anecdote -- not well tested, but something that SEEMS to be real to me:   when I was running tests on some software, I had the historical habit of using a low pass filter like this on SOX --- seemed to make the highs sound a little tighter but without significantly boosting the average HF content:  'lowpass -2 9k 1q lowpass -2 18k 1q'.   Sometimes, I'd use 15k instead of 18k depending upon material.   The slight tightening of the transients before loosing the HF further up seemed to help... but... I also noticed that some of the spatial perception was lost.   The rolloff or very slight 'ringing' -- actually manifest as a near flat response to the cutoff instead of some dB of loss -- seemed to have caused a SLIGHT loss of locality.  I am not one of the 'wine-taster' audio people -- and if I hadn't noticed this 'out of the blue' several times, I wouldn't be mentioning it.   So, I no longer use a gratuitous 'slightly peaky' rolloff to get a sharper sound without a very strong justification.  Now, if I want to SLIGHTLY brighten or smooth out some harsh HF edge, I might use such a filter, but not without carefully considered reason.

Re: Audibility of phase shifts and time delays
Reply #58
I have a license for iZotope RX which can shift channels by 0.1 increments of a sample. More than willing to use it to do some listening tests if anyone is interested.

The tool is called Azimuth adjustment.

  • bandpass
  • [*][*][*][*]
Re: Audibility of phase shifts and time delays
Reply #59
And while I revived that old thread... the formula from the first page:
Code: [Select]
1/ ( 2 pi bandwidth number_of_levels)
I wanted to make sure I got it right.
There’s a derivation of the formula here (with refinement in the following few posts).