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Audio player, equalizer, resampling measurements

post #1 of 15
Thread Starter 

Hey guys,

 

in the course of developing an equalizer I wondered how well some of the built-in EQs in common audio players perform.

 

So I decided to do some measurements.

In fact, I now have a measurement setup that allows me to capture any sound that goes through Windows' audio subsystem right before it's passed to the soundcard. Therefore, I can also measure, e.g., how well an audio player, or even DirectSound itself, handles situations where resampling or quantization (24-bit file played in a 16-bit format) is needed, or look at digital volume controls, or any DSP that can be used in a player, or ...

 

I'll mostly be using RMAA to analyze the results, even if it's just the frequency response I'm looking at.

TODO: short RMAA description

 

As a reference, here are the untouched test files in the formats 44.1/16, 44.1/24 and 96/24:

 

rmaa-ideal.png

 

 = Flat frequency response, low noise levels, distortion and crosstalk (as far as each format allows).

 

 

 

Equalizers

So let's take a look at some EQs. Test file is in the format 44.1/16. The target is a simple peaking filter, with -5 dB at 500 Hz.

Versions used: foobar2000 v1.1.1, Winamp v5.6, iTunes v10.1.0.56

 

eq-table1.png

 

As can be seen in the table above, other than frequency response neither EQ really degrades audio quality. Winamp's seems to be the worst however, but see for yourself:

 

eq-fr1.png

 

The first (white) one shows how it should look like. It's a smooth curve and at 500 Hz we're down exactly 5 dB.

 

 

The second (green) EQ is the one that comes with fb2k. While each band can be controlled with a 1 dB precision, which is nice, the result looks like the Stiegl beer logo - stepped, the opposite of smooth and not musical.

Here's the configuration of the EQ for reference:

 

fb-eq.png

 

So if you can use alternatives my suggestion is to use them instead of the built-in EQ.

 

 

The third (cyan) one shows winamp's default built-in EQ. The number of bands is very limited and I never liked the interface and the result is very inaccurate. Just look at the configuration and compare it to the measurement above:

 

winamp-eq.png

 

The result looks nothing like the curve in the user interface. At 600 Hz we're down over 8 dB, but I configured -4.8 dB (the closest possible to -5 dB it seems, which is also weird). 

Maybe with some (a lot of) tweaking you can get this EQ to do what you want, but I'd look for an alternative instead.

 

 

The fourth (purple) EQ is the one built into itunes. In the frequency response you can see why I don't like built-in graphic EQs. It's hard to predict what happens between the bands and how wide each band really is.

Besides, I couldn't find any indicator of how many dB I'm down at the sliders in the user interface:

 

itunes-eq.png

 

At least there are gridlines in 3 dB steps. Nevertheless, this EQ also needs some tweaking to really get what you want, if that is even possible considering the limited number of bands.

 

 

Here's the second batch of EQ measurements.

Versions used: Winamp sane as above, Electri-Q - posihfopit edition v1.0

 

eq-table2.png

 

This time the target curve is at the end, so that it's on top in the graphs. Let's take a look at the frequency responses:

 

eq-fr2.png

 

For the first (white) curve I used the same band-EQ configuration as described above ('built-in default EQ / winamp') but I set the EQ-type from 'Winamp-4Front-Equalizer' to 'Constant-Q-Equalizer' in the options. While the curve itself is ugly and looks a bit like the one from itunes above, it's an improvement compared to winamp's default EQ

 

 

The second (green) EQ is from AiXcoustic's and is called Electri-Q - posihfopit edition (freeware). I used it as winamp DSP plugin here, but there's also a VST version.

Electri-Q offers a lot of options and also different modes. We're looking at the mode 'analog' here.

In the frequency response graph the analog curve is hidden by the next curve (mode 'digital'). Since it's a parametric EQ, and not a band-EQ, the results look promising for the first time. In fact, the curve's very close to the target. Here's a screenshot of the configuration for reference:

 

winamp-electriq-eq.png

 

If you've taken a closer look at the RMAA comparison/results table above, you can see that something weird seems to be going on with distortion levels. Here's the explanation from the Electri-Q manual: "The algorithm ‘Analog’ is based on a real analog circuit and thus it delivers a subtle  warmth.  Its  counterpart  is  the  algorithm  ‘Digital’  which  delivers  a more transparent sound."

 

So how does this 'warmth' / distortion look like? See for yourself:

 

eq-thd2.png

 

Here we can see a 1 kHz sine wave and the noise floor - and the distortion (green spikes) the 'analog' mode creates. But the strange thing here is that there are no even order harmonics (2 kHz, 4 kHz etc.). All I see is odd order harmonics. I'm not sure which 'warm' sounding analogue circuit would produce something like that.

 

Another thing that can be seen here is that Constant-Q EQ from winamp adds small amounts of noise. Similar amounts of noise can be observed if the 'eco' option in Electri-Q is enabled ('eco' like economic, reduces CPU usage).

 

 

The third (cyan) curve shows Electri-Q again, but this time in 'digital' mode. This mode doesn't produce harmonic distortion (purposely). As can be seen above, the results are the closest to the target so far.

 

 

 

 

 

Resampling

Back with an update, resampler measurements!

As starting point, I generated a dithered 24-bit, 44.1 kHz file with sine waves at frequencies 60, 600 and 6000 Hz:

 

resampling-start.png

 

 

Then I converted this with foobar2000's built-in resampler (PPHS) in ultra mode to 24-bit, 96 kHz with this ok result:

 

resampler-pphs.png

 

I repeated this (resampling from 44.1 to 96 kHz), but this time with the SoX resampler plugin (quality: very high) for foobar2000 which improved results further:

 

resampling-sox.png

 

 

I couldn't measure the DirectSound resampler properly, but if you use quality resamplers like above to convert your audio to the format that is configured for your playback device, DirectSound/KMixer or the sound driver doesn't need to do any format conversions.

 

 

 

Any comments, wishes or suggestions? All welcome.

 

(Please note that this post is a work in progress. I'll add further measurements over time.)


Edited by xnor - 10/9/12 at 10:49am
post #2 of 15
Thread Starter 

double post / reserved


Edited by xnor - 12/5/10 at 2:25am
post #3 of 15

Very nice...

post #4 of 15

Never mind. Stupid question. I thought there was some way to bypass having to do all that..


Edited by Aurvergne - 12/4/10 at 11:19pm
post #5 of 15

I did same measures few years ago after finding the uncommon type of EQ build-in in fb2k.

At that time, I decided to switch to use VST EQ plug-ins through DSP addon with fb2k. For Winamp, there's already Aixcoustic Creations Electri-Q which is a native Winamp DSP plug-in.

 

If you're starting to program (another) EQ for any of those playback software you mentioned in your post, just be sure not to prepare another 7 to 10 (fixed) band one.

 

jiitee

post #6 of 15
Thread Starter 
Quote:
Originally Posted by jiiteepee View Post

I did same measures few years ago after finding the uncommon type of EQ build-in in fb2k.

At that time, I decided to switch to use VST EQ plug-ins through DSP addon with fb2k. For Winamp, there's already Aixcoustic Creations Electri-Q which is a native Winamp DSP plug-in.

 

If you're starting to program (another) EQ for any of those playback software you mentioned in your post, just be sure not to prepare another 7 to 10 (fixed) band one.

 

jiitee


I know that there are several DSP/VST plugins and I used some of those too in the past. I'm measuring Electri-Q atm, results will show up in the first post soon. ;)

post #7 of 15
Thread Starter 

Just added Constant-Q (also a winamp built-in) and Electri-Q posihfopit (modes 'analog' and 'digital').


Edited by xnor - 12/5/10 at 11:28am
post #8 of 15

For questions regarding Electri-Q posihfopit you might get "exact" answers by posting either

@ AIXcoustic Creations Forum or

@ KVR's subforum 'DSP and Plug-In developement' since, Christian (W. Budde, developer) posts there every now and then, when he has time for that.

 

jiitee

post #9 of 15
Thread Starter 

 

Update: added resampler measurements

post #10 of 15

Very usefull and informative, thank you xnor!

post #11 of 15
Awsome thread, xnor!!!!
post #12 of 15

I'm glad this thread got bumped, this is some great info.

post #13 of 15

So Electi-Q in digital mode is the best equalizer so far? Or are there better equalizers out there? (for use with f2k, preferably)

 

edit. Just noticed xnor was banned. That's really a shame. He's was great user, very knowledgeable when it comes to audio science/engineering and was always posting useful stuff, just like this thread.


Edited by Okamoto - 3/9/14 at 11:58pm
post #14 of 15
Quote:
Originally Posted by Okamoto View Post
 

So Electi-Q in digital mode is the best equalizer so far? Or are there better equalizers out there? (for use with f2k, preferably)

 

...

 

Depends on what do you mean by better ... features or accuracy. Most of those parametric ones which I have checked (tens) are excellent. Graphic EQs are a different story... .

KVR database is one good place to look from http://www.kvraudio.com/q.php?search=1&q=EQ

post #15 of 15
Quote:
Originally Posted by jiiteepee View Post
 

 

Depends on what do you mean by better ... features or accuracy. Most of those parametric ones which I have checked (tens) are excellent. Graphic EQs are a different story... .

KVR database is one good place to look from http://www.kvraudio.com/q.php?search=1&q=EQ


In terms of accuracy. Based on xnor's measurements, it seems I wouldn't need anything besides Electri-Q, but maybe I'm wrong.


Thanks for the link, by the way. Very interesting site.

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