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Topic: J-Test? (Read 7219 times) previous topic - next topic
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J-Test?

I've heard about J-Test in several websites but I can never find a J-Test audio file to perform the test. However I found this paper and I made some J-Test files by following the instructions in part 2.6 of the paper.

I don't know if my files are correct or not so I uploaded them here, could anyone help me to examine them?
http://www.hydrogenaud.io/forums/index.php...ost&id=8270

jtest1648.wav and jtest2448.wav are the final mixdown files, other three files are the low level square waves and the 12khz tone.

And how should I perform the test? Is it similar to RMAA - either make an analog loopback recording or record from another source?

Thank you very much.

J-Test?

Reply #1
I don't know if my files are correct or not so I uploaded them here, could anyone help me to examine them?

I only looked at jtest2448. The frequency of the low-level LF signal seems to be wrong. That needn't be a problem, but it differs from the description in Dunn's paper.

J-Test?

Reply #2
I've heard about J-Test in several websites but I can never find a J-Test audio file to perform the test. However I found this paper and I made some J-Test files by following the instructions in part 2.6 of the paper.

I don't know if my files are correct or not so I uploaded them here, could anyone help me to examine them?
http://www.hydrogenaud.io/forums/index.php...ost&id=8270

jtest1648.wav and jtest2448.wav are the final mixdown files, other three files are the low level square waves and the 12khz tone.

And how should I perform the test? Is it similar to RMAA - either make an analog loopback recording or record from another source?

Thank you very much.



Kicking around the web there are two little command line programs that generate what is supposed to be a bit-for-bit proper Jtest files with 44 and 48 KHz sampling.

I think that doubling the sample rate in the .wav file header from 48 to 96 without upsampling will result in a proper 24/96 file. If that is a problem for someone, I can upload one of those, too.

I upuloaded them to the uploads forum here: Link to uploads forum post  with the programs and data

J-Test?

Reply #3
Thanks pelmazo and Arnold. The low level portions of my files are really different from the ones that Arnold provided.

J-Test?

Reply #4
Thanks pelmazo and Arnold. The low level portions of my files are really different from the ones that Arnold provided.


I think that is a critical difference, and my investigations suggest that the files I uploaded are accurate representations of what Dunn intended and created for this test. If that is not so, I'd like to know that they are wrong and the reasons why.

Compact form of the files here:

Zip file of FLAC files of all 3 .WAV files.

These files compress like crazy because they are so redundant!

J-Test?

Reply #5
My files are created by the tone generator of Adobe Audition 1.5. After some inspections I find that the low level square wave files I generated do not always have 96 0s and 96 -1s. Sometimes they are 95 or 97.

J-Test?

Reply #6
My files are created by the tone generator of Adobe Audition 1.5. After some inspections I find that the low level square wave files I generated do not always have 96 0s and 96 -1s. Sometimes they are 95 or 97.


Are you generating a 16 or 32 bit file?

Also, it may not be clear from the documentation at hand, but the file is supposed to be undithered.

J-Test?

Reply #7
My files are created by the tone generator of Adobe Audition 1.5. After some inspections I find that the low level square wave files I generated do not always have 96 0s and 96 -1s. Sometimes they are 95 or 97.


Are you generating a 16 or 32 bit file?

Also, it may not be clear from the documentation at hand, but the file is supposed to be undithered.

You can refer to the link in my first post, the low level square waves are included in the 7z archive. They are all created in 32-bit and undithered, otherwise the 7z file will not be so small (only 17KB for 50 seconds) because random values are hard to compress.

EDIT: I've posted my waveform creation parameter here:
http://www.hydrogenaud.io/forums/index.php...st&p=896070

J-Test?

Reply #8
My files are created by the tone generator of Adobe Audition 1.5. After some inspections I find that the low level square wave files I generated do not always have 96 0s and 96 -1s. Sometimes they are 95 or 97.


Are you generating a 16 or 32 bit file?

Also, it may not be clear from the documentation at hand, but the file is supposed to be undithered.

You can refer to the link in my first post, the low level square waves are included in the 7z archive. They are all created in 32-bit and undithered, otherwise the 7z file will not be so small (only 17KB for 50 seconds) because random values are hard to compress.

EDIT: I've posted my waveform creation parameter here:
http://www.hydrogenaud.io/forums/index.php...st&p=896070


I have to admit that over a decade ago I attempted the same thing - I tried to create a J-test file with CEP 2.1 and failed. Eventually I found the solution that I have provided you with and moved on.

I question the relevance of the J-test file for technical testing because I can't figure out how to interpret results obtained with it in terms of standard psychoacoustic thresholds. Regrettably Julian Dunn passed away in 2003 at a relatively young age without IMO shedding much light on theses issues.  The J-test often produces jitter sidebands that appear to be significantly greater than those that are produced with steady sine waves of the same fundamental frequency.  Why this is and whether it is significant seems elusive.

Julian Dunn Obituary

 
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