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High-order dither listening test
High-order dither listening test
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Old 9th October 2017, 07:31 PM   #1
MarcelvdG is offline MarcelvdG  Netherlands
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Default High-order dither listening test

It is usually assumed that triangular dither changes quantization distortion into something that's indistinguishable from additive noise, but as far as I know no-one has ever checked that with blind listening tests.

It shouldn't be difficult to create two versions of an audio file, one with triangular dither quantized to, say, 7 bits and one with 11th-order dither quantized to 8 bits (one bit more). The noise levels will then be exactly the same, but the 11th-order version has smaller quantization steps and is statistically closer to true additive noise; the first eleven moments of the error caused by dither and quantization are then independent of the signal, rather than only the first two moments.

Is anyone interested in blindly comparing such files?
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Old 9th October 2017, 08:10 PM   #2
Mooly is offline Mooly  United Kingdom
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High-order dither listening test
If you get no response we can move this over to 'Everything Else' which is where the majority of such threads seem to live... and they seem to get a fair response.
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Old 9th October 2017, 10:03 PM   #3
lms is offline lms  Micronesia
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interested
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Old 10th October 2017, 10:23 PM   #4
MarcelvdG is offline MarcelvdG  Netherlands
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Quote:
Originally Posted by Mooly View Post
If you get no response we can move this over to 'Everything Else' which is where the majority of such threads seem to live... and they seem to get a fair response.
I got only two responses so far including yours, so maybe moving it is a good idea.
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Old 10th October 2017, 11:34 PM   #5
jcx is offline jcx  United States
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Default there is this...

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Originally Posted by jcx View Post
Wannamaker is surprisingly readable for a PhD thesis -
http://www.digitalsignallabs.com/phd.pdf

but for the lazy:

Quote:
For audio signal processing purposes, there seems to be little point in rendering any moments of the total error other than the first and second independent of the input. Variations in higher moments are believed to be inaudible and this has been corroborated by a large number of psycho-acoustic tests conducted by the authors and others [13, 21]. These tests involved listening to a large variety of signals (sinusoids, sinusoidal chirps, slow ramps, various periodically switched inputs, piano and orchestral music, etc.) which had been requantized very coarsely (to 8 bits from 16) in order to render the requantization error essentially independent of low-level non-linearities in the digital-to-analogue conversion system through which the listening took place. In addition, the corresponding total error signals (output minus input) were used in listening tests in order to check for any audible dependences on the input. Using undithered quantizers resulted in clearly audible distortion and noise modulation in the output and error signals…
When 2RPDF [ triangle PDF ] dither was employed, no instance was found in which the error was audibly distinguishable from a steady white noise entirely unrelated with the input...
Admittedly, these tests were informal, and there remains a need for formal psychoacoustic tests of this sort involving many participants under carefully controlled conditions.

The use of of non-subtractive, iid 2RPDF [ triangle PDF ] dither is recommended for most audio applications requiring multi-bit quantization or requantization operations, since this type of dither renders the power spectrum of the total error independent of the input, while incurring the minimum increase in error variance.
Quote:
[13] Brinton, L.K., “Nonsubtractive Dither,” M.Sc. Thesis, Dept. of Elec. Eng.,
Univ. of Utah, Salt Lake City, UT (1984 Aug.).

[21] Wannamaker, R.A., “Dither and Noise Shaping in Audio Applications,”
M.Sc. Thesis, Dept. of Physics, Univ. of Waterloo, Waterloo, ON, Canada,
(1990 Dec.).

Last edited by jcx; 10th October 2017 at 11:51 PM.
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Old 11th October 2017, 07:55 PM   #6
MarcelvdG is offline MarcelvdG  Netherlands
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Thanks for the literature references! In the section that you quoted, the sentence "Admittedly, these tests were informal, and there remains a need for formal psychoacoustic tests of this sort involving many participants under carefully controlled conditions" seems a bit vague to me. Is there any information on whether the tests that they did were blind tests and whether there were subjects in the test who expected to be able to hear higher moments?
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Old 11th October 2017, 08:25 PM   #7
Mooly is offline Mooly  United Kingdom
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High-order dither listening test
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Originally Posted by MarcelvdG View Post
I got only two responses so far including yours, so maybe moving it is a good idea.
So lets see
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Old 1st November 2017, 12:20 PM   #8
PMA is offline PMA  Europe
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High-order dither listening test
Quote:
Originally Posted by MarcelvdG View Post

Is anyone interested in blindly comparing such files?
Sure! I am highly interested.
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Old 11th November 2017, 02:39 PM   #9
MarcelvdG is offline MarcelvdG  Netherlands
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OK, I've put two versions of a short fragment of I do like to be beside the seaside on WeTransfer:

WeTransfer

They'll be there until 18 November 2017.

If you think you hear a difference or that you might hear a difference, please do an ABX test using abx under Linux or the Foobar ABX plugin under Windows and report the results of all such trials in this thread.
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Old 11th November 2017, 03:18 PM   #10
PMA is offline PMA  Europe
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High-order dither listening test
Quote:
Originally Posted by MarcelvdG View Post
OK, I've put two versions of a short fragment of I do like to be beside the seaside on WeTransfer:

WeTransfer

They'll be there until 18 November 2017.

If you think you hear a difference or that you might hear a difference, please do an ABX test using abx under Linux or the Foobar ABX plugin under Windows and report the results of all such trials in this thread.
Marcel, have you checked (listened to) the files?? Something is going wrong, there is a noise like a hell in both of them. See spectrum.
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File Type: jpg silverysea.jpg (77.2 KB, 115 views)
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