Question about stereo upmixing

[NekoAlosama]

All of the audio content I listen to only uses 2 channels, but I would still like to use all of the BRIR .wav's instead of just the A-30 and A30 .wav's for stereo content. However, this project doesn't have a suggestion for how to upmix stereo for this purpose. I have been able to find an idea from HeSuVi (Copy: L=0.5*L R=0.5*R C=0.2*L+0.2*R SUB=0.0 RL=0.3*L+-0.2*R RR=-0.2*L+0.3*R SL=0.45*L+-0.25*R SR=-0.25*L+0.45*R, though I just multiplied all of the values by 2 to result in Copy: C=0.4*L+0.4*R SUB=0 RL=0.6*L+-0.4*R RR=-0.4*L+0.6*R SL=0.9*L+-0.5*R SR=-0.5*L+0.9*R), but I don't know if this makes sense/is valid for this purpose, nor do I know if this specific upmix is for narrow 7.1 or wide 7.1.

Here is what my current configuration looks like:

[NekoAlosama]

@ShanonPearce

[ShanonPearce]

I think the above method of copying the L and R channels to the additional channels should work well. I did some brief testing and tried to modify the values and came up with below. I also added a very slight delay to the rear channels which should help give a more surround image.

You can try adding this config before the 7.1 BRIR convolution step and adjusting the gains/delays to your preference. Stereo_upmix.txt

[NekoAlosama]

@ShanonPearce Definitely seems the values for the upmix requires some experimentation, so I'll look around for anything that claims to be better with good reasoning. The small delay for the rear channels makes sense, though I don't know if the BRIR .wav's already incorporate this. A 4 sample delay also seems to be quite low, to the point that it might not even be noticable (I cannot access my computer at this time), since 4 samples should just be about 0.0000907 seconds worth.

[NekoAlosama]

A 4 sample delay also seems to be quite low, to the point that it might not even be noticable (I cannot access my computer at this time), since 4 samples should just be about 0.0000907 seconds worth.

Nope, it is noticeable. Don't know what would be the best value to put here though.

[NekoAlosama]

I've now switched from 7.1W_Config_32_Seminar_Room_Surrey to 7.1W_Config_18_Conference_Room_Pos_2 (then 7.1W_Config_03_Control_Room_7 since this one doesn't have reduced reverberation) after noticing the different azimuth ranges. I originally chose the former since it has the lowest deviation from its estimated critical distance (1.5m source distance vs 1.55 critical distance estimate), but RL and RR both have the +/-90 .wav's, making the seemingly-7.1-wide stereo upmix values make less sense in my opinion.

[ShanonPearce]

That's understandable considering some rooms have limited azimuth ranges (rooms 08, 09, 12, 13, 14 & 17) which will limit the surround effect. The BRIR convolution configs for those rooms will just take the largest available azimuth for the rear channels.

[NekoAlosama]

@ShanonPearce After thinking about it for a bit, I feel like this issue have been resolved in #2 because a person can just use ASH and HeSuVi with the Upmix Stereo option ticked.