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Author Topic: Parametric EQ channel mixing problem  (Read 399 times)

justsomeguy

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Parametric EQ channel mixing problem
« on: January 22, 2021, 05:27:51 pm »

I seem to have found a problem with mixing channels in the parametric eq. If I set it up like in the screenshot below and play a test file that simply alternates white noise between the left and right channels every 5 seconds the resulting sound is white noise being played from both the left and right channels at the same time when the sound should actually be the same as the original audio (alternating between the left and right every 5 seconds).
Playing the audio with these settings disabled produces the expected alternating left right whitenoise.

Here's a link to the test audio file I used. https://drive.google.com/file/d/1jt-oxTNbCIPSr5xSBTYHl3TjJU0t_kGL/view?usp=sharing
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justsomeguy

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Re: Parametric EQ channel mixing problem
« Reply #1 on: January 22, 2021, 05:46:15 pm »

So it actually seems like what is happening in this case is the white noise is on say the right channel and the left is silent. Now I subtract the right(noise) from the left(silient) the left actually goes "negative"/now has the white noise but 180 out of phase with the right. I'm thinking that's what is happening? Would/Should this be the expected behavior?

What I was trying to accomplish ultimately was separate out the differences between the left and right channels and only sounds unique to that channel play in that channel. Basically removing anything identical between the left/right channels.
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mattkhan

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Re: Parametric EQ channel mixing problem
« Reply #2 on: January 23, 2021, 02:44:05 am »

Copy is "add A to B" which leaves A is left intact so you are doing

U1=L
U2=R
U1=U1-R
U2=U2-L
L=L+U1
R=R+U2

which means

L=L+(L-R)
R=R+(R-L)

i.e. use move instead copy in that 1st step as that blanks out the original channel

I don't understand what you're trying to do though, if the track simply alternates between channels then there is nothing to diff as it's silence vs some sound at all times. Is the intent to compare the blocks of actual sound? if so, you'd need to edit the file separately (e.g. in a tool like audacity) to align the channels and then play it back in MC (or add enough delay in MC to do a sample perfect alignment, might be tricky to get right0.
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justsomeguy

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Re: Parametric EQ channel mixing problem
« Reply #3 on: January 23, 2021, 04:38:27 am »

From what it says in the parametric eq copy actually should overwrite the destination, move should also overwrite but "empty" the source as well. There is a separate ADD option for combining the source into the destination.

The sound file I'm using is only for testing out why I wasn't hearing the expected result when playing normal music files. It just gave me a way of feeding a known repeatable source of different combination of left/right mixing to easily see if it was doing what I was expecting. I'm simply trying to loosely mimic MC's built in JRSS mixing. JRSS uses two different ways of mixing internally that's not selectable by the user. MC chooses which to use based on media type. Music gets on type of mixing and tv/movies get a different type of mixing. I prefer the mixing it uses for movies/tv and would like to use it for music as well but again it isn't user selectable. So I'm attempting to try and closely replicate it through the eq as much as possible. Also just out of curiosity I want to see if it's possible.
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mattkhan

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Re: Parametric EQ channel mixing problem
« Reply #4 on: January 23, 2021, 04:59:33 am »

Ah yes sorry, misread that completely!

You could direct the output to a wav file for easier analysis rather than relying on hearing. You can then compare against similar results of operations done offline.
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