Spatial sound calculates diff incorrectly (swaps left and right)

[strowk]

In these formulas there is I think mistake that reverses lift/right:

https://github.com/RustAudio/rodio/blame/a352fb53846b47523d828b276b6d625f251aabb2/src/source/spatial.rs#L60-L62

        let left_diff_modifier = (((left_dist - right_dist) / max_diff + 1.0) / 4.0 + 0.5).min(1.0);
        let right_diff_modifier =
            (((right_dist - left_dist) / max_diff + 1.0) / 4.0 + 0.5).min(1.0);

It basically says that if "left_dist" (distance from emitter to "left" listener) is bigger - then modifier to left is bigger (farther - louder, which should be the other way around, i.e closer - louder).
And same for the right.

Essentially at close distances this results in swap in sound - left feels like right and vice versa..

I think it should be

        let left_diff_modifier = (((right_dist - left_dist) / max_diff + 1.0) / 4.0 + 0.5).min(1.0);
        let right_diff_modifier =
            (((left_dist - right_dist) / max_diff + 1.0) / 4.0 + 0.5).min(1.0);

It sort of appears to be obvious mistake in that code, am I missing something here?

[yara-blue]

It sort of appears to be obvious mistake in that code, am I missing something here?

I don't think the spatial audio in Rodio is very good. It "kinda" works but like you've found out it has issues. It's about 6 years old at this point and has not really been touched since. No one working on Rodio now has good context on it. I'm not sure it's worth investing in it.

Instead it could be better to rewrite it. I head a quick search and this paper seemed to give a good intro on the subject: https://arxiv.org/html/2508.10924v2#S5.

I head a look at whats available on crates.io and most of it is AI slop... Firewheel (amazing author) seems to have basic spatial audio, maybe we could borrow from them https://github.com/BillyDM/Firewheel/blob/71fbe0f7bfb0569a725bee9d739d0603f97eef3d/crates/firewheel-nodes/src/spatial_basic.rs#L116. Speaking of Firewheel I do not know your application (and I would love better spatial audio in Rodio) but you may be better off with Firewheel if you are building a game. It's a little harder to set up but for game audio it should be a better match.

Getting back to your suggestion.

Essentially at close distances this results in swap in sound - left feels like right and vice versa..

We can try this! but before we do could you show a table of a few inputs (just use two dimensions) showing some edge cases. Like close, behind, far left etc? Might be even better to have that as tests. Just to make sure we are not replacing one problem with another.