additional option to set the upper frequency boundary for the spectrum analyzer

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Caelin1
Posts: 57
Joined: Wed Jun 12, 2019 8:41 pm
Location: United States

additional option to set the upper frequency boundary for the spectrum analyzer

Post by Caelin1 » Wed Feb 05, 2020 7:40 pm

I know how to adjust the logarithmic scale but how do I adjust the linear? Picture attached to show why I want to adjust it.
Screenshot_20200205-133946_Neutron.jpg
Screenshot_20200205-133946_Neutron.jpg (169.84 KiB) Viewed 3465 times

blaubär
Posts: 3313
Joined: Tue Apr 02, 2019 6:48 am

Re: How to adjust linear scale spectrum analyzer?

Post by blaubär » Wed Feb 05, 2020 8:25 pm

There's a similar topic here : https://neutronmp.com/forum/viewtopic.php?f=3&t=3404
The point is : this is perfectly normal. How to test this ?
1. Feed pink noise, the logarithmic spectrum should be flat

Screenshot_20200205-212823_Neutron-360x374.jpg
Screenshot_20200205-212823_Neutron-360x374.jpg (25.42 KiB) Viewed 3458 times
2. Feed white noise, the linear spectrum should be flat

Screenshot_20200205-212800_Neutron-360x391.jpg
Screenshot_20200205-212800_Neutron-360x391.jpg (37.4 KiB) Viewed 3459 times

So why the peak in your example at lower frequencies in the linear spectrum ? Because music isn't like white noise, rather like pink one :D. We humans hear logarithmically, so neutron's spectrum has been scaled in a way that music that sounds normal to humans would scale well on the logarithmic spectrum, not the linear one.

blaubär
Posts: 3313
Joined: Tue Apr 02, 2019 6:48 am

Re: How to adjust linear scale spectrum analyzer?

Post by blaubär » Wed Feb 05, 2020 9:16 pm

And as to manually scaling the spectrum : currently there's no option for that afaik

blaubär
Posts: 3313
Joined: Tue Apr 02, 2019 6:48 am

Re: How to adjust linear scale spectrum analyzer?

Post by blaubär » Thu Feb 06, 2020 11:36 am

also see here :
blaubär wrote:
Thu Dec 12, 2019 6:44 pm
I just noticed that, too. But I think this is just an effect of scaling. When you switch from the default logarithmic to linear, then the width of the lower octaves shrink, so the height has to grow so that the area = width * height stay the sames. Now if one would scale everything down so that the height stays the same in the lowest octave then we wouldn't see anything in the highest octave (which is the full right half of the screen in the linear spectrum) at all. Ahem ... clear what I mean ?

Caelin1
Posts: 57
Joined: Wed Jun 12, 2019 8:41 pm
Location: United States

Re: How to adjust linear scale spectrum analyzer?

Post by Caelin1 » Fri Feb 07, 2020 9:26 pm

I recently got a new phone and before transferring neutrons data to my hard drive, I saw that the linear scale was much thinner with respect to the x-axis. There's gotta be a way to change it.

See here I was able to make the x-axis much shorter:
20200207_152239.jpg
20200207_152239.jpg (204.54 KiB) Viewed 3438 times

To do that I first backed up the NeutronMP folder to my SD card and then deleted the one on my hard drive. After restarting my phone, I booted Neutron up and checked out the spectrum analyzer and it was not the same width as it had been before when I took the screenshot in my first post. How the heck do I change it? I actually think I'd like the linear more than the log base whatever analyzer.

blaubär
Posts: 3313
Joined: Tue Apr 02, 2019 6:48 am

Re: How to adjust linear scale spectrum analyzer?

Post by blaubär » Sat Feb 08, 2020 4:59 am

You mean the high maximum frequency that the x-axis shows in your first screenshot ? The spectrum is taken after the DSP ( digital signal processor ), before the data are transferred to the DAC ( digital analog converter ). You had either played high-res-audio or activated oversampling or simply chosen a high sampling rate for transfer to the DAC. If you're interested in the background see https://whatis.techtarget.com/definitio ... st-Theorem . In short : the maximum frequency in a digital signal equals half the sampling rate.

blaubär
Posts: 3313
Joined: Tue Apr 02, 2019 6:48 am

Re: How to adjust linear scale spectrum analyzer?

Post by blaubär » Sat Feb 08, 2020 7:52 am

So, should we treat this as a feature request : an additional option to set the upper frequency boundary for the spectrum analyzer ?

Screenshot_20200208-085142_Neutron-360x279.jpg
Screenshot_20200208-085142_Neutron-360x279.jpg (20.7 KiB) Viewed 3427 times

blaubär
Posts: 3313
Joined: Tue Apr 02, 2019 6:48 am

additional option to set the upper frequency boundary for the spectrum analyzer

Post by blaubär » Sat Feb 08, 2020 9:40 am

Situation : the spectrum analyzer currently shows the full frequency range from zero to the maximum possible value (half the sampling rate).

Problem : the range above 20 kHz isn't really that interesting, the sampling rate may be that high only due to oversampling or upsampling, not because there is high-res-audio-input containing frequencies above 20 kHz. In the logarithmic view that doesn't matter much, but using the linear scale you won't see much of the interesting frequency range below 20 kHz.

Proposal : add an additional option to limit the upper frequency boundary shown by the spectrum analyzer, either as a checkbox (fixed limit 20 kHz) or a slider (variable limit from zero to half the maximum possible sampling rate). As a default it should be enabled resp. enabled to 20 kHz, as most users probably would expect it to be that way. I'd expect the use cases where upper frequencies matter to be rather limited.

WitzyZed
Posts: 211
Joined: Fri Nov 22, 2019 8:49 pm

Re: additional option to set the upper frequency boundary for the spectrum analyzer

Post by WitzyZed » Sun Feb 09, 2020 2:20 pm

+1 this feature would be very welcomed.

I have to enable x2 oversampling quite often on my FiiO X5iii, as for whatever reason 44.1 & 48 kHz sample rate files (when played natively w/o oversampling) make the spectrum analyzer stutter (low frame rate). Anything 88.2 kHz and above shows smoothly always.

This is odd as when playing same 44.1 & 48 kHz files over Bluetooth connections, the frame rate becomes smooth again.

So the option to reduce the upper frequency limit would restore the smoothness to the ideal spectrum analyzer window size.

blaubär
Posts: 3313
Joined: Tue Apr 02, 2019 6:48 am

Re: additional option to set the upper frequency boundary for the spectrum analyzer

Post by blaubär » Fri Apr 10, 2020 6:27 pm

I just found that we already have a slider in the eq settings that sets the lower boundary :

Screenshot_20200410-202234_Neutron_copy_310x64.jpg
Screenshot_20200410-202234_Neutron_copy_310x64.jpg (5.42 KiB) Viewed 3007 times
So the proposed additional slider for the upper limit might be put below.

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