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To: 9front@9front.org
From: Michael Forney <mforney@mforney.org>
Date: Mon, 08 Feb 2021 00:12:28 +0000
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X-Bullshit: lossless object-oriented singleton NoSQL framework software-scale backend 
Subject: [9front] games/gb: fix reversed audio channels
Reply-To: 9front@9front.org
Precedence: bulk

The high bits correspond to the left channel, and the low bits to the
right channel.

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

diff 3fc115a6ff6eef65210fb78a51128958d2b55910 9d0249f7a978b4e84f3cd9083f787b4f3f533b41
--- a/sys/src/games/gb/apu.c	Sun Feb  7 15:22:39 2021
+++ b/sys/src/games/gb/apu.c	Sun Feb  7 16:12:28 2021
@@ -115,13 +115,13 @@
 		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