ref: 14bcdd1008db070bc4a12be73e3f692c1990966e
parent: a8e79308562fbcea7a39ed1846329959cbf343b3
author: Simon Howard <[email protected]>
date: Sun Oct 25 13:07:55 EDT 2009
Emulate odd octave 7 behavior of Vanilla Doom. Subversion-branch: /branches/opl-branch Subversion-revision: 1725
--- a/src/i_oplmusic.c
+++ b/src/i_oplmusic.c
@@ -739,6 +739,26 @@
sub_index = (freq_index - 284) % (12 * 32);
octave = (freq_index - 284) / (12 * 32);
+ // Once the seventh octave is reached, things break down.
+ // We can only go up to octave 7 as a maximum anyway (the OPL
+ // register only has three bits for octave number), but for the
+ // notes in octave 7, the first five bits have octave=7, the
+ // following notes have octave=6. This 7/6 pattern repeats in
+ // following octaves (which are technically impossible to
+ // represent anyway).
+
+ if (octave >= 7)
+ {+ if (sub_index < 5)
+ {+ octave = 7;
+ }
+ else
+ {+ octave = 6;
+ }
+ }
+
// Calculate the resulting register value to use for the frequency.
return frequency_curve[sub_index + 284] | (octave << 10);