From 415c110b284bdd519e6dedcfea97e45edcb8977a Mon Sep 17 00:00:00 2001
From: Michael Forney <mforney@mforney.org>
Date: Mon, 8 Feb 2021 04:58:49 +0100
Subject: games/gb: fix reversed audio channels The high bits correspond to the
 left channel, and the low bits to the right channel.

Reference: https://gbdev.io/pandocs/#sound-control-registers

Tested with pokemon crystal.
---
 sys/src/games/gb/apu.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/sys/src/games/gb/apu.c b/sys/src/games/gb/apu.c
index 900f7e793..e0862ebdf 100644
--- a/sys/src/games/gb/apu.c
+++ b/sys/src/games/gb/apu.c
@@ -115,13 +115,13 @@ filter(int t)
 		if(i == 2 ? ((reg[NR30] & 0x80) == 0) : ((*sndch[i].env & 0xf8) == 0))
 			continue;
 		v = sndch[i].samp * 2 - 15;
-		if((cnth & 1<<i) != 0)
-			ov0 += v;
 		if((cnth & 1<<4<<i) != 0)
+			ov0 += v;
+		if((cnth & 1<<i) != 0)
 			ov1 += v;
 	}
-	ov0 *= 1 + (cntl & 7);
-	ov1 *= 1 + (cntl >> 4 & 7);
+	ov0 *= 1 + (cntl >> 4 & 7);
+	ov1 *= 1 + (cntl & 7);
 }
 
 static void
-- 
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