# Exported "stereo" impulse response only contains one channel



## MaximalC (Aug 1, 2013)

When exporting an impulse response WAV from REW, I'm finding that the resulting file only contains a single channel of audio. I checked the "stereo" button and selected the appropriate filter for the left channel and the right channel, but the resulting wave consists only of a single channel. I've tried this at all three bit depths and got the same result.

Can anyone else who has tried exporting a stereo impulses response confirm that the created file truly is stereo? I've been using one in foobar for months, only to realize that both speakers are being equalized with the same filter. I managed to correct the problem by simply pairing two separate impulses to opposing channels in my audio editor, but it would be nice if I could skip this step altogether. I'm also wondering if this is simply a bug in REW that has gone unnoticed, or something I'm doing wrong.

Thanks in advance.


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## EarlK (Jan 1, 2010)

MaximalC said:


> When exporting an impulse response WAV from REW, I'm finding that the resulting file only contains a single channel of audio. I checked the "stereo" button and selected the appropriate filter for the left channel and the right channel, but the resulting wave consists only of a single channel. I've tried this at all three bit depths and got the same result.
> 
> Can anyone else who has tried exporting a stereo impulses response confirm that the created file truly is stereo? I've been using one in foobar for months, only to realize that both speakers are being equalized with the same filter. I managed to correct the problem by simply pairing two separate impulses to opposing channels in my audio editor, but it would be nice if I could skip this step altogether. I'm also wondering if this is simply a bug in REW that has gone unnoticed, or something I'm doing wrong.
> 
> Thanks in advance.


I confirm that REW will export stereo correction ( EQ ) filters ( in the wave format ) .

I just created 2 test filters ( trace1 = Lchnl = +20db at 1K , trace2 = Rchnl = -20db at 1K ) and exported these as a stereo wave filter .

This test filter was convolved by jRiver's Media Center using its built-in convolver . The "source" was a pink noise file that was played back ( by MC ) , & then that "noise" was viewed ( in mono one channel at a time ) within the softwares ( dsp-based ) RTA window . I verified that the appropriate 1K ( boost or cut ) was visibly present. I could have accomplished this audibly, using either headphones or my playback system ( with less db boost for the sake of safety ) .

*FYI :*

REW stores a ( mono ) correction filter along with each associated trace ( file ) once one runs the EQ module & hits "Save Filters" . 

- Each trace's unique correction EQ is view-able ( upon closing & reloading the trace ) assuming it was saved before moving onto something else ( such as a different trace ) .

- When working with a larger file that houses multiple traces, each trace is best thought of as a separate "instance" ( for EQing purposes ) .

- IME, one should make sure each trace ( file ) has had a unique EQ-correction filter saved as one goes through their work-flow ( before moving to another trace ) .

- I believe the "cleanest" way to do this is to work with single trace files while one is EQing . 
- Two single traces can eventually be loaded/merged & opened ( for the sole purpose of exporting both EQ filters as a stereo set ) .
- ie; This problem might have been simply a file management & house-keeping issue ( "one hand not knowing what the other is up to" , etc. etc. ) . 


:sn:


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## MaximalC (Aug 1, 2013)

Thanks, Earl. So if I'm understanding you correctly, the two separate traces need to be merged into a single file in order to export a stereo impulse response? I had both traces open simultaneously, but they were not merged, so perhaps that is the shortcoming. It is a little confusing as the dialog allowed me to select each of the two traces when exporting even though they had not been merged. I shall give merging a try then.


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## EarlK (Jan 1, 2010)

MaximalC said:


> Thanks, Earl. So if I'm understanding you correctly, the two separate traces need to be merged into a single file in order to export a stereo impulse response? I had both traces open simultaneously, but they were not merged, so perhaps that is the shortcoming. It is a little confusing as the dialog allowed me to select each of the two traces when exporting even though they had not been merged. I shall give merging a try then.


Had you previously made sure to "Save Filter" for each of these "Auto-EQed" correction filters ?

I always export from within a ( saved ) file that holds both traces .

:sn:


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## MaximalC (Aug 1, 2013)

In retrospect, I'm realizing my original question is missing an important piece of information. There are actually two different impulse response export types: "Export Impulse Response as WAV" and "Export Filters Impulse Response as WAV". I can successfully do the first (which I believed is the measured response), but am still unsuccessfully do the second (the filter's response). I even merged the left and right measurements into a joint file (as suggested above) and have the EQ filters saved (which I also had done originally), and the result is the same: exporting the filter response as a stereo WAV results in a mono WAV file.

Seeing as how nobody as seems to be having the same issue, I may just have to be content to do a little post-processing to achieve the desired result.


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## EarlK (Jan 1, 2010)

MaximalC said:


> In retrospect, I'm realizing my original question is missing an important piece of information. There are actually two different impulse response export types: "Export Impulse Response as WAV" and "Export Filters Impulse Response as WAV". I can successfully do the first (which I believed is the measured response), but am still unsuccessfully do the second (the filter's response). I even merged the left and right measurements into a joint file (as suggested above) and have the EQ filters saved (which I also had done originally), and the result is the same: exporting the filter response as a stereo WAV results in a mono WAV file.
> 
> Seeing as how nobody as seems to be having the same issue, I may just have to be content to do a little post-processing to achieve the desired result.



Are you sure REW is generating a ( single chnl ) mono WAV file ( & not a dual chnl type that uses a single filter set ) ? Granted, this is a subtle , but important difference ( for trouble-shooting purposes by the developer ) .

Anyways ( English language parsing aside ) , Java ( the software engine used by REW ) & the Mac OS are very unhappy marriage partners , you aren't by chance running REW on a Mac are you ?

For instance , I get some very goofy ( REW ) errors when I view ( on my Mac Mini, running OS 10.4.11 ) the previously mentioned filters ( which were created on a PC running on XP Pro, SP3 ) .

:sn:

EDIT ; oops,,, I see you mentioned convolving in *Foobar2000*  ( which is a Windows-only player ) , so I must assume you're running a PC .


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## jtalden (Mar 12, 2009)

Is the OP running REW 5.01 Beta 17?

I think there was a problem with the very early versions? I may be wrong about that. I didn't review the release notes to be sure.


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## EarlK (Jan 1, 2010)

jtalden said:


> Is the OP running REW 5.01 Beta 17?
> 
> I think there was a problem with the very early versions? I may be wrong about that. I didn't review the release notes to be sure.


The release notes ( for the Beta version ) made my eyes glaze over / I couldn't spot anything obvious .

I don't know what version of REW is being run here ( or which OS, for that matter ) / these days I simply assume a bunch of givens ( like OS & up-to-date REW versions ) . 

I've discovered the fun of "guessing" ( mind-reading ) / which has it's own intangible benefits . ;>) 

:sn:


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## jtalden (Mar 12, 2009)




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## MaximalC (Aug 1, 2013)

I'm running one of the v5.00 builds on WinXP SP3. For some reason I thought I had the most recent version installed, but clearly I do not. I shall certainly try updating and see how far that gets me. Thanks for the heads-up.

From the v5.01 Beta 1 change log:
"Bug fix: Exporting filter impulse response as WAV always exported the set from the currently selected measurement regardless of the selection made in the export dialog."


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## MaximalC (Aug 1, 2013)

Updated to the most recent beta and filter export worked like a charm. Anyone interested in exporting filter impulse responses as WAVs should absolutely be using REW v5.01.


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