AX: make volume field signed

[Tilka]

This fixes overly loud sounds in Freestyle Metal X (issue 13120).

[Pokechu22]

This seems like a plausible fix; I haven't attempted to confirm it though (I don't own Freestyle Metal X and don't want to dig through AX right now). I am curious as to what value of cur_volume was the game setting here, though.

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Looking at how it's implemented:

dolphin/Source/Core/Core/HW/DSPHLE/UCodes/AXVoice.h

Lines 424 to 430 in ec69ed2

	// Apply a global volume ramp using the volume envelope parameters.
	for (u32 i = 0; i < count; ++i)
	{
	const s32 sample = ((s32)samples[i] * pb.vol_env.cur_volume) >> 15;
	samples[i] = std::clamp(sample, -32767, 32767); // -32768 ?
	pb.vol_env.cur_volume += pb.vol_env.cur_volume_delta;
	}

the maximum value of 32767 or 0x7fff would be multiplied by the sample and then shifted by 15. Since 0x7fff >> 15 == 0 but 0x8000u >> 15 == 1, I'm pretty sure this means that the volume is always reduced slightly (e.g. (0x7fff * 0x7fff) >> 15 == 0x7ffe, (-0x8000 * 0x7fff) >> 15 == -0x7fff).

The clamping would only apply if the volume and sample were both -0x8000, as (-0x8000 * -0x8000) >> 15 == +0x8000 which would be clamped to +0x7fff. I don't think there's any cases where -0x8000 could be generated (and clamped to -0x7fff) anymore. Even still, if they are using the normal saturation functionality in the DSP, it would be clamped to -0x8000 through +0x7fff. In practice, this probably doesn't matter.

[Tilka]

I am curious as to what value of cur_volume was the game setting here, though.

The volume is 0xFF64 aka -156 (delta is 0).

[Pokechu22]

I am curious as to what value of cur_volume was the game setting here, though.

The volume is 0xFF64 aka -156 (delta is 0).

OK, so effectively -0.00476, which would behave basically the same as 0.00476, but was instead being treated as 1.99524 (or 419 times larger, though I don't know how much louder that would actually be perceived as).

[Tilka]

Here is a comparison without the background music (careful, it's quite loud):

broken.mp4

fixed.mp4

[Pokechu22]

That's a pretty significant difference and definitely seems better (though I can't really hear the chickens at all in the fixed version). For the chickens specifically, does the game try to change the volume based on distance, or are they at a constant volume? I'm curious if there's some kind of overflow or something there. (Though this would also depend on the chickens actually existing in the world, which I'm not 100% sure is the case.)

[Tilka]

They do get louder when you get closer to a barn.

[Pokechu22]

Seems plausible enough. I haven't done any testing though.