Setting up a low pass filter in OBS Classic

OBS Classic does not have built in support for audio filters so you need to set up the audio processing outside OBS and add some virtual audio devices in Windows to get the processed audio in OBS. There's a (much simpler) version of this for OBS Studio at https://pastebin.com/WT2jQ6av



1) install VB-Cable

Download from https://www.vb-audio.com/Cable/index.htm and run the setup, choosing the appropriate one between 32 and 64 bit versions. If you can see "CABLE Input" in playback tab in windows sound settings and "CABLE Output" in recording tab, you're good.

2) download Reaper VST plugins

Download from https://www.reaper.fm/reaplugs/ again choosing the appropriate installer and run it.

3) download VSTHost

Download either vsthostx86.zip or vsthostx64.zip from http://www.hermannseib.com/english/vsthost.htm and extract the package somewhere. You might also want to save the manual (vsthost.pdf) somewhere.

4) setup OBS

Go to Settings -> Audio and change Microphone/Auxiliary Audio Device to CABLE Output instead of your microphone, then preview stream and move the OBS window somewhere out of the way but so that you can see the microphone signal level (which should be 0 right now since there isn't anything coming through the virtual cable yet)

5) setup VSTHost

Run vsthost.exe from where you installed it. Go to Devices -> Wave, set MME: [your microphone] as the Input port, MME: CABLE as Output port, and Buffer to 70 samples. Smaller buffer means smaller delay but I guess it also makes the audio more prone to stuttering if there are issues? I didn't test myself beyond getting this working in the first place, but some forum post I got this from said they were using the lowest setting and didn't have issues.

6) setup the Reaper finite impulse response plugin in VSTHost

Select File -> New Plugin..., navigate to where you installed the Reaper plugins (should be C:\Program Files\VSTPlugins\ReaPlugs) and select reafir-standalone.dll. VSTHost should display another box and a bunch of lines, and OBS should start displaying audio input. Press the round white button at the top of newly created box saying Reafir-standalone. This should show you the actual plugin control panel. Put some audio on in the source and you should see the signal in the editor in yellow. To check that the filter works, select Mode: Gate and try dragging the Gate floor slider, which should make the signal stronger or weaker, leaving the original as a shadow.

7) configure the low pass filter

Configure the parameters like this: https://www.dropbox.com/s/xuufub8l06fklzs/reafir.png

The CRT hum is roughly 15 kHz so put the gate somewhere around 14.x kHz. One of the points should be at 0 dB (I didn't see a way to set it exactly and dragging it with mouse might put it at -0.02 dB or something) and the other one at the bottom. If you cross them over the line flips so it doesn't really matter which circle you drag first and at which level, just make sure the end result is as in the reference image (red line low on the left and high on the right, signal unmodified on the left and disappearing on the right).

8) save the VSTHost settings

Honestly I still don't understand how this part works. Go to File -> Use bank..., select bank 0, and create the file somewhere. I *think* this should make it so that the program remembers your filter pipeline (which in this case is just a simple input -> equalizer -> output), but won't remember the plugin settings? Then you can select the equalizer and go to PlugIn -> Save Bank and save that separately somewhere. What seems to happen for me at this point is when I close VSTHost and reopen it, all the settings are restored. Then when I close and reopen it *again*, the filter pipeline is restored but the equalizer is back to the default settings. Then when I do PlugIn -> Load Bank... everything's correct again, gets restored on the next restart and lost on the restart after that and what the fuck seriously

9) recap

At this point the situation should be:
-OBS is configured to use the virtual audio cable instead of the microphone directly, and will not have microphone signal without VSTHost open
-Opening VSTHost should bring up the settings created earlier, unless it craps out and reverts the equalizer settings to not doing anything and you need to reload them through PlugIn -> Load Bank...