summaryrefslogtreecommitdiff
path: root/src/i_oplmusic.c
blob: a1e90506fb99389ca30690df89e205ec0387df0a (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
//
// Copyright(C) 1993-1996 Id Software, Inc.
// Copyright(C) 2005-2014 Simon Howard
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// DESCRIPTION:
//	System interface for music.
//


#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "memio.h"
#include "mus2mid.h"

#include "deh_main.h"
#include "i_sound.h"
#include "i_swap.h"
#include "m_misc.h"
#include "w_wad.h"
#include "z_zone.h"

#include "opl.h"
#include "midifile.h"

// #define OPL_MIDI_DEBUG

#define MAXMIDLENGTH (96 * 1024)
#define GENMIDI_NUM_INSTRS  128
#define GENMIDI_NUM_PERCUSSION 47

#define GENMIDI_HEADER          "#OPL_II#"
#define GENMIDI_FLAG_FIXED      0x0001         /* fixed pitch */
#define GENMIDI_FLAG_2VOICE     0x0004         /* double voice (OPL3) */

#define PERCUSSION_LOG_LEN 16

typedef struct
{
    byte tremolo;
    byte attack;
    byte sustain;
    byte waveform;
    byte scale;
    byte level;
} PACKEDATTR genmidi_op_t;

typedef struct
{
    genmidi_op_t modulator;
    byte feedback;
    genmidi_op_t carrier;
    byte unused;
    short base_note_offset;
} PACKEDATTR genmidi_voice_t;

typedef struct
{
    unsigned short flags;
    byte fine_tuning;
    byte fixed_note;

    genmidi_voice_t voices[2];
} PACKEDATTR genmidi_instr_t;

// Data associated with a channel of a track that is currently playing.

typedef struct
{
    // The instrument currently used for this track.

    genmidi_instr_t *instrument;

    // Volume level

    int volume;

    // Pitch bend value:

    int bend;

} opl_channel_data_t;

// Data associated with a track that is currently playing.

typedef struct
{
    // Data for each channel.

    opl_channel_data_t channels[MIDI_CHANNELS_PER_TRACK];

    // Track iterator used to read new events.

    midi_track_iter_t *iter;
} opl_track_data_t;

typedef struct opl_voice_s opl_voice_t;

struct opl_voice_s
{
    // Index of this voice:
    int index;

    // The operators used by this voice:
    int op1, op2;

    // Currently-loaded instrument data
    genmidi_instr_t *current_instr;

    // The voice number in the instrument to use.
    // This is normally set to zero; if this is a double voice
    // instrument, it may be one.
    unsigned int current_instr_voice;

    // The channel currently using this voice.
    opl_channel_data_t *channel;

    // The midi key that this voice is playing.
    unsigned int key;

    // The note being played.  This is normally the same as
    // the key, but if the instrument is a fixed pitch
    // instrument, it is different.
    unsigned int note;

    // The frequency value being used.
    unsigned int freq;

    // The volume of the note being played on this channel.
    unsigned int note_volume;

    // The current volume (register value) that has been set for this channel.
    unsigned int reg_volume;

    // Next in linked list; a voice is always either in the
    // free list or the allocated list.
    opl_voice_t *next;
};

// Operators used by the different voices.

static const int voice_operators[2][OPL_NUM_VOICES] = {
    { 0x00, 0x01, 0x02, 0x08, 0x09, 0x0a, 0x10, 0x11, 0x12 },
    { 0x03, 0x04, 0x05, 0x0b, 0x0c, 0x0d, 0x13, 0x14, 0x15 }
};

// Frequency values to use for each note.

static const unsigned short frequency_curve[] = {

    0x133, 0x133, 0x134, 0x134, 0x135, 0x136, 0x136, 0x137,   // -1
    0x137, 0x138, 0x138, 0x139, 0x139, 0x13a, 0x13b, 0x13b,
    0x13c, 0x13c, 0x13d, 0x13d, 0x13e, 0x13f, 0x13f, 0x140,
    0x140, 0x141, 0x142, 0x142, 0x143, 0x143, 0x144, 0x144,

    0x145, 0x146, 0x146, 0x147, 0x147, 0x148, 0x149, 0x149,   // -2
    0x14a, 0x14a, 0x14b, 0x14c, 0x14c, 0x14d, 0x14d, 0x14e,
    0x14f, 0x14f, 0x150, 0x150, 0x151, 0x152, 0x152, 0x153,
    0x153, 0x154, 0x155, 0x155, 0x156, 0x157, 0x157, 0x158,

    // These are used for the first seven MIDI note values:

    0x158, 0x159, 0x15a, 0x15a, 0x15b, 0x15b, 0x15c, 0x15d,   // 0
    0x15d, 0x15e, 0x15f, 0x15f, 0x160, 0x161, 0x161, 0x162,
    0x162, 0x163, 0x164, 0x164, 0x165, 0x166, 0x166, 0x167,
    0x168, 0x168, 0x169, 0x16a, 0x16a, 0x16b, 0x16c, 0x16c,

    0x16d, 0x16e, 0x16e, 0x16f, 0x170, 0x170, 0x171, 0x172,   // 1
    0x172, 0x173, 0x174, 0x174, 0x175, 0x176, 0x176, 0x177,
    0x178, 0x178, 0x179, 0x17a, 0x17a, 0x17b, 0x17c, 0x17c,
    0x17d, 0x17e, 0x17e, 0x17f, 0x180, 0x181, 0x181, 0x182,

    0x183, 0x183, 0x184, 0x185, 0x185, 0x186, 0x187, 0x188,   // 2
    0x188, 0x189, 0x18a, 0x18a, 0x18b, 0x18c, 0x18d, 0x18d,
    0x18e, 0x18f, 0x18f, 0x190, 0x191, 0x192, 0x192, 0x193,
    0x194, 0x194, 0x195, 0x196, 0x197, 0x197, 0x198, 0x199,

    0x19a, 0x19a, 0x19b, 0x19c, 0x19d, 0x19d, 0x19e, 0x19f,   // 3
    0x1a0, 0x1a0, 0x1a1, 0x1a2, 0x1a3, 0x1a3, 0x1a4, 0x1a5,
    0x1a6, 0x1a6, 0x1a7, 0x1a8, 0x1a9, 0x1a9, 0x1aa, 0x1ab,
    0x1ac, 0x1ad, 0x1ad, 0x1ae, 0x1af, 0x1b0, 0x1b0, 0x1b1,

    0x1b2, 0x1b3, 0x1b4, 0x1b4, 0x1b5, 0x1b6, 0x1b7, 0x1b8,   // 4
    0x1b8, 0x1b9, 0x1ba, 0x1bb, 0x1bc, 0x1bc, 0x1bd, 0x1be,
    0x1bf, 0x1c0, 0x1c0, 0x1c1, 0x1c2, 0x1c3, 0x1c4, 0x1c4,
    0x1c5, 0x1c6, 0x1c7, 0x1c8, 0x1c9, 0x1c9, 0x1ca, 0x1cb,

    0x1cc, 0x1cd, 0x1ce, 0x1ce, 0x1cf, 0x1d0, 0x1d1, 0x1d2,   // 5
    0x1d3, 0x1d3, 0x1d4, 0x1d5, 0x1d6, 0x1d7, 0x1d8, 0x1d8,
    0x1d9, 0x1da, 0x1db, 0x1dc, 0x1dd, 0x1de, 0x1de, 0x1df,
    0x1e0, 0x1e1, 0x1e2, 0x1e3, 0x1e4, 0x1e5, 0x1e5, 0x1e6,

    0x1e7, 0x1e8, 0x1e9, 0x1ea, 0x1eb, 0x1ec, 0x1ed, 0x1ed,   // 6
    0x1ee, 0x1ef, 0x1f0, 0x1f1, 0x1f2, 0x1f3, 0x1f4, 0x1f5,
    0x1f6, 0x1f6, 0x1f7, 0x1f8, 0x1f9, 0x1fa, 0x1fb, 0x1fc,
    0x1fd, 0x1fe, 0x1ff, 0x200, 0x201, 0x201, 0x202, 0x203,

    // First note of looped range used for all octaves:

    0x204, 0x205, 0x206, 0x207, 0x208, 0x209, 0x20a, 0x20b,   // 7
    0x20c, 0x20d, 0x20e, 0x20f, 0x210, 0x210, 0x211, 0x212,
    0x213, 0x214, 0x215, 0x216, 0x217, 0x218, 0x219, 0x21a,
    0x21b, 0x21c, 0x21d, 0x21e, 0x21f, 0x220, 0x221, 0x222,

    0x223, 0x224, 0x225, 0x226, 0x227, 0x228, 0x229, 0x22a,   // 8
    0x22b, 0x22c, 0x22d, 0x22e, 0x22f, 0x230, 0x231, 0x232,
    0x233, 0x234, 0x235, 0x236, 0x237, 0x238, 0x239, 0x23a,
    0x23b, 0x23c, 0x23d, 0x23e, 0x23f, 0x240, 0x241, 0x242,

    0x244, 0x245, 0x246, 0x247, 0x248, 0x249, 0x24a, 0x24b,   // 9
    0x24c, 0x24d, 0x24e, 0x24f, 0x250, 0x251, 0x252, 0x253,
    0x254, 0x256, 0x257, 0x258, 0x259, 0x25a, 0x25b, 0x25c,
    0x25d, 0x25e, 0x25f, 0x260, 0x262, 0x263, 0x264, 0x265,

    0x266, 0x267, 0x268, 0x269, 0x26a, 0x26c, 0x26d, 0x26e,   // 10
    0x26f, 0x270, 0x271, 0x272, 0x273, 0x275, 0x276, 0x277,
    0x278, 0x279, 0x27a, 0x27b, 0x27d, 0x27e, 0x27f, 0x280,
    0x281, 0x282, 0x284, 0x285, 0x286, 0x287, 0x288, 0x289,

    0x28b, 0x28c, 0x28d, 0x28e, 0x28f, 0x290, 0x292, 0x293,   // 11
    0x294, 0x295, 0x296, 0x298, 0x299, 0x29a, 0x29b, 0x29c,
    0x29e, 0x29f, 0x2a0, 0x2a1, 0x2a2, 0x2a4, 0x2a5, 0x2a6,
    0x2a7, 0x2a9, 0x2aa, 0x2ab, 0x2ac, 0x2ae, 0x2af, 0x2b0,

    0x2b1, 0x2b2, 0x2b4, 0x2b5, 0x2b6, 0x2b7, 0x2b9, 0x2ba,   // 12
    0x2bb, 0x2bd, 0x2be, 0x2bf, 0x2c0, 0x2c2, 0x2c3, 0x2c4,
    0x2c5, 0x2c7, 0x2c8, 0x2c9, 0x2cb, 0x2cc, 0x2cd, 0x2ce,
    0x2d0, 0x2d1, 0x2d2, 0x2d4, 0x2d5, 0x2d6, 0x2d8, 0x2d9,

    0x2da, 0x2dc, 0x2dd, 0x2de, 0x2e0, 0x2e1, 0x2e2, 0x2e4,   // 13
    0x2e5, 0x2e6, 0x2e8, 0x2e9, 0x2ea, 0x2ec, 0x2ed, 0x2ee,
    0x2f0, 0x2f1, 0x2f2, 0x2f4, 0x2f5, 0x2f6, 0x2f8, 0x2f9,
    0x2fb, 0x2fc, 0x2fd, 0x2ff, 0x300, 0x302, 0x303, 0x304,

    0x306, 0x307, 0x309, 0x30a, 0x30b, 0x30d, 0x30e, 0x310,   // 14
    0x311, 0x312, 0x314, 0x315, 0x317, 0x318, 0x31a, 0x31b,
    0x31c, 0x31e, 0x31f, 0x321, 0x322, 0x324, 0x325, 0x327,
    0x328, 0x329, 0x32b, 0x32c, 0x32e, 0x32f, 0x331, 0x332,

    0x334, 0x335, 0x337, 0x338, 0x33a, 0x33b, 0x33d, 0x33e,   // 15
    0x340, 0x341, 0x343, 0x344, 0x346, 0x347, 0x349, 0x34a,
    0x34c, 0x34d, 0x34f, 0x350, 0x352, 0x353, 0x355, 0x357,
    0x358, 0x35a, 0x35b, 0x35d, 0x35e, 0x360, 0x361, 0x363,

    0x365, 0x366, 0x368, 0x369, 0x36b, 0x36c, 0x36e, 0x370,   // 16
    0x371, 0x373, 0x374, 0x376, 0x378, 0x379, 0x37b, 0x37c,
    0x37e, 0x380, 0x381, 0x383, 0x384, 0x386, 0x388, 0x389,
    0x38b, 0x38d, 0x38e, 0x390, 0x392, 0x393, 0x395, 0x397,

    0x398, 0x39a, 0x39c, 0x39d, 0x39f, 0x3a1, 0x3a2, 0x3a4,   // 17
    0x3a6, 0x3a7, 0x3a9, 0x3ab, 0x3ac, 0x3ae, 0x3b0, 0x3b1,
    0x3b3, 0x3b5, 0x3b7, 0x3b8, 0x3ba, 0x3bc, 0x3bd, 0x3bf,
    0x3c1, 0x3c3, 0x3c4, 0x3c6, 0x3c8, 0x3ca, 0x3cb, 0x3cd,

    // The last note has an incomplete range, and loops round back to
    // the start.  Note that the last value is actually a buffer overrun
    // and does not fit with the other values.

    0x3cf, 0x3d1, 0x3d2, 0x3d4, 0x3d6, 0x3d8, 0x3da, 0x3db,   // 18
    0x3dd, 0x3df, 0x3e1, 0x3e3, 0x3e4, 0x3e6, 0x3e8, 0x3ea,
    0x3ec, 0x3ed, 0x3ef, 0x3f1, 0x3f3, 0x3f5, 0x3f6, 0x3f8,
    0x3fa, 0x3fc, 0x3fe, 0x36c,
};

// Mapping from MIDI volume level to OPL level value.

static const unsigned int volume_mapping_table[] = {
    0, 1, 3, 5, 6, 8, 10, 11,
    13, 14, 16, 17, 19, 20, 22, 23,
    25, 26, 27, 29, 30, 32, 33, 34,
    36, 37, 39, 41, 43, 45, 47, 49,
    50, 52, 54, 55, 57, 59, 60, 61,
    63, 64, 66, 67, 68, 69, 71, 72,
    73, 74, 75, 76, 77, 79, 80, 81,
    82, 83, 84, 84, 85, 86, 87, 88,
    89, 90, 91, 92, 92, 93, 94, 95,
    96, 96, 97, 98, 99, 99, 100, 101,
    101, 102, 103, 103, 104, 105, 105, 106,
    107, 107, 108, 109, 109, 110, 110, 111,
    112, 112, 113, 113, 114, 114, 115, 115,
    116, 117, 117, 118, 118, 119, 119, 120,
    120, 121, 121, 122, 122, 123, 123, 123,
    124, 124, 125, 125, 126, 126, 127, 127
};

static boolean music_initialized = false;

//static boolean musicpaused = false;
static int current_music_volume;

// GENMIDI lump instrument data:

static genmidi_instr_t *main_instrs;
static genmidi_instr_t *percussion_instrs;
static char (*main_instr_names)[32];
static char (*percussion_names)[32];

// Voices:

static opl_voice_t voices[OPL_NUM_VOICES];
static opl_voice_t *voice_free_list;
static opl_voice_t *voice_alloced_list;

// Track data for playing tracks:

static opl_track_data_t *tracks;
static unsigned int num_tracks = 0;
static unsigned int running_tracks = 0;
static boolean song_looping;

// Tempo control variables

static unsigned int ticks_per_beat;
static unsigned int us_per_beat;

// Mini-log of recently played percussion instruments:

static uint8_t last_perc[PERCUSSION_LOG_LEN];
static unsigned int last_perc_count;

// Configuration file variable, containing the port number for the
// adlib chip.

int opl_io_port = 0x388;

// Load instrument table from GENMIDI lump:

static boolean LoadInstrumentTable(void)
{
    byte *lump;

    lump = W_CacheLumpName("GENMIDI", PU_STATIC);

    // Check header

    if (strncmp((char *) lump, GENMIDI_HEADER, strlen(GENMIDI_HEADER)) != 0)
    {
        W_ReleaseLumpName("GENMIDI");

        return false;
    }

    main_instrs = (genmidi_instr_t *) (lump + strlen(GENMIDI_HEADER));
    percussion_instrs = main_instrs + GENMIDI_NUM_INSTRS;
    main_instr_names = (char (*)[32]) (percussion_instrs + GENMIDI_NUM_PERCUSSION);
    percussion_names = main_instr_names + GENMIDI_NUM_INSTRS;

    return true;
}

// Get the next available voice from the freelist.

static opl_voice_t *GetFreeVoice(void)
{
    opl_voice_t *result;

    // None available?

    if (voice_free_list == NULL)
    {
        return NULL;
    }

    // Remove from free list

    result = voice_free_list;
    voice_free_list = voice_free_list->next;

    // Add to allocated list

    result->next = voice_alloced_list;
    voice_alloced_list = result;

    return result;
}

// Remove a voice from the allocated voices list.

static void RemoveVoiceFromAllocedList(opl_voice_t *voice)
{
    opl_voice_t **rover;

    rover = &voice_alloced_list;

    // Search the list until we find the voice, then remove it.

    while (*rover != NULL)
    {
        if (*rover == voice)
        {
            *rover = voice->next;
            voice->next = NULL;
            break;
        }

        rover = &(*rover)->next;
    }
}

// Release a voice back to the freelist.

static void ReleaseVoice(opl_voice_t *voice)
{
    opl_voice_t **rover;

    voice->channel = NULL;
    voice->note = 0;

    // Remove from alloced list.

    RemoveVoiceFromAllocedList(voice);

    // Search to the end of the freelist (This is how Doom behaves!)

    rover = &voice_free_list;

    while (*rover != NULL)
    {
        rover = &(*rover)->next;
    }

    *rover = voice;
    voice->next = NULL;
}

// Load data to the specified operator

static void LoadOperatorData(int operator, genmidi_op_t *data,
                             boolean max_level)
{
    int level;

    // The scale and level fields must be combined for the level register.
    // For the carrier wave we always set the maximum level.

    level = (data->scale & 0xc0) | (data->level & 0x3f);

    if (max_level)
    {
        level |= 0x3f;
    }

    OPL_WriteRegister(OPL_REGS_LEVEL + operator, level);
    OPL_WriteRegister(OPL_REGS_TREMOLO + operator, data->tremolo);
    OPL_WriteRegister(OPL_REGS_ATTACK + operator, data->attack);
    OPL_WriteRegister(OPL_REGS_SUSTAIN + operator, data->sustain);
    OPL_WriteRegister(OPL_REGS_WAVEFORM + operator, data->waveform);
}

// Set the instrument for a particular voice.

static void SetVoiceInstrument(opl_voice_t *voice,
                               genmidi_instr_t *instr,
                               unsigned int instr_voice)
{
    genmidi_voice_t *data;
    unsigned int modulating;

    // Instrument already set for this channel?

    if (voice->current_instr == instr
     && voice->current_instr_voice == instr_voice)
    {
        return;
    }

    voice->current_instr = instr;
    voice->current_instr_voice = instr_voice;

    data = &instr->voices[instr_voice];

    // Are we usind modulated feedback mode?

    modulating = (data->feedback & 0x01) == 0;

    // Doom loads the second operator first, then the first.
    // The carrier is set to minimum volume until the voice volume
    // is set in SetVoiceVolume (below).  If we are not using
    // modulating mode, we must set both to minimum volume.

    LoadOperatorData(voice->op2, &data->carrier, true);
    LoadOperatorData(voice->op1, &data->modulator, !modulating);

    // Set feedback register that control the connection between the
    // two operators.  Turn on bits in the upper nybble; I think this
    // is for OPL3, where it turns on channel A/B.

    OPL_WriteRegister(OPL_REGS_FEEDBACK + voice->index,
                      data->feedback | 0x30);

    // Hack to force a volume update.

    voice->reg_volume = 999;
}

static void SetVoiceVolume(opl_voice_t *voice, unsigned int volume)
{
    genmidi_voice_t *opl_voice;
    unsigned int full_volume;
    unsigned int op_volume;
    unsigned int reg_volume;

    voice->note_volume = volume;

    opl_voice = &voice->current_instr->voices[voice->current_instr_voice];

    // Multiply note volume and channel volume to get the actual volume.

    full_volume = (volume_mapping_table[voice->note_volume]
                   * volume_mapping_table[voice->channel->volume]
                   * volume_mapping_table[current_music_volume]) / (127 * 127);

    // The volume of each instrument can be controlled via GENMIDI:

    op_volume = 0x3f - opl_voice->carrier.level;

    // The volume value to use in the register:

    reg_volume = (op_volume * full_volume) / 128;
    reg_volume = (0x3f - reg_volume) | opl_voice->carrier.scale;

    // Update the volume register(s) if necessary.

    if (reg_volume != voice->reg_volume)
    {
        voice->reg_volume = reg_volume;

        OPL_WriteRegister(OPL_REGS_LEVEL + voice->op2, reg_volume);

        // If we are using non-modulated feedback mode, we must set the
        // volume for both voices.
        // Note that the same register volume value is written for
        // both voices, always calculated from the carrier's level
        // value.

        if ((opl_voice->feedback & 0x01) != 0)
        {
            OPL_WriteRegister(OPL_REGS_LEVEL + voice->op1, reg_volume);
        }
    }
}

// Initialize the voice table and freelist

static void InitVoices(void)
{
    int i;

    // Start with an empty free list.

    voice_free_list = NULL;

    // Initialize each voice.

    for (i=0; i<OPL_NUM_VOICES; ++i)
    {
        voices[i].index = i;
        voices[i].op1 = voice_operators[0][i];
        voices[i].op2 = voice_operators[1][i];
        voices[i].current_instr = NULL;

        // Add this voice to the freelist.

        ReleaseVoice(&voices[i]);
    }
}

// Set music volume (0 - 127)

static void I_OPL_SetMusicVolume(int volume)
{
    unsigned int i;

    // Internal state variable.

    current_music_volume = volume;

    // Update the volume of all voices.

    for (i=0; i<OPL_NUM_VOICES; ++i)
    {
        if (voices[i].channel != NULL)
        {
            SetVoiceVolume(&voices[i], voices[i].note_volume);
        }
    }
}

static void VoiceKeyOff(opl_voice_t *voice)
{
    OPL_WriteRegister(OPL_REGS_FREQ_2 + voice->index, voice->freq >> 8);
}

// Get the frequency that we should be using for a voice.

static void KeyOffEvent(opl_track_data_t *track, midi_event_t *event)
{
    opl_channel_data_t *channel;
    unsigned int key;
    unsigned int i;

/*
    printf("note off: channel %i, %i, %i\n",
           event->data.channel.channel,
           event->data.channel.param1,
           event->data.channel.param2);
*/

    channel = &track->channels[event->data.channel.channel];
    key = event->data.channel.param1;

    // Turn off voices being used to play this key.
    // If it is a double voice instrument there will be two.

    for (i=0; i<OPL_NUM_VOICES; ++i)
    {
        if (voices[i].channel == channel && voices[i].key == key)
        {
            VoiceKeyOff(&voices[i]);

            // Finished with this voice now.

            ReleaseVoice(&voices[i]);
        }
    }
}

// Compare the priorities of channels, returning either -1, 0 or 1.

static int CompareChannelPriorities(opl_channel_data_t *chan1,
                                    opl_channel_data_t *chan2)
{
    // TODO ...

    return 1;
}

// When all voices are in use, we must discard an existing voice to
// play a new note.  Find and free an existing voice.  The channel
// passed to the function is the channel for the new note to be
// played.

static opl_voice_t *ReplaceExistingVoice(opl_channel_data_t *channel)
{
    opl_voice_t *rover;
    opl_voice_t *result;

    // Check the allocated voices, if we find an instrument that is
    // of a lower priority to the new instrument, discard it.
    // If a voice is being used to play the second voice of an instrument,
    // use that, as second voices are non-essential.
    // Lower numbered MIDI channels implicitly have a higher priority
    // than higher-numbered channels, eg. MIDI channel 1 is never
    // discarded for MIDI channel 2.

    result = NULL;

    for (rover = voice_alloced_list; rover != NULL; rover = rover->next)
    {
        if (rover->current_instr_voice != 0
         || (rover->channel > channel
             && CompareChannelPriorities(channel, rover->channel) > 0))
        {
            result = rover;
            break;
        }
    }

    // If we didn't find a voice, find an existing voice being used to
    // play a note on the same channel, and use that.

    if (result == NULL)
    {
        for (rover = voice_alloced_list; rover != NULL; rover = rover->next)
        {
            if (rover->channel == channel)
            {
                result = rover;
                break;
            }
        }
    }

    // Still nothing found?  Give up and just use the first voice in
    // the list.

    if (result == NULL)
    {
        result = voice_alloced_list;
    }

    // Stop playing this voice playing and release it back to the free
    // list.

    VoiceKeyOff(result);
    ReleaseVoice(result);

    // Re-allocate the voice again and return it.

    return GetFreeVoice();
}


static unsigned int FrequencyForVoice(opl_voice_t *voice)
{
    genmidi_voice_t *gm_voice;
    unsigned int freq_index;
    unsigned int octave;
    unsigned int sub_index;
    unsigned int note;

    note = voice->note;

    // Apply note offset.
    // Don't apply offset if the instrument is a fixed note instrument.

    gm_voice = &voice->current_instr->voices[voice->current_instr_voice];

    if ((SHORT(voice->current_instr->flags) & GENMIDI_FLAG_FIXED) == 0)
    {
        note += (signed short) SHORT(gm_voice->base_note_offset);
    }

    // Avoid possible overflow due to base note offset:

    if (note > 0x7f)
    {
        note = voice->note;
    }

    freq_index = 64 + 32 * note + voice->channel->bend;

    // If this is the second voice of a double voice instrument, the
    // frequency index can be adjusted by the fine tuning field.

    if (voice->current_instr_voice != 0)
    {
        freq_index += (voice->current_instr->fine_tuning / 2) - 64;
    }

    // The first 7 notes use the start of the table, while
    // consecutive notes loop around the latter part.

    if (freq_index < 284)
    {
        return frequency_curve[freq_index];
    }

    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);
}

// Update the frequency that a voice is programmed to use.

static void UpdateVoiceFrequency(opl_voice_t *voice)
{
    unsigned int freq;

    // Calculate the frequency to use for this voice and update it
    // if neccessary.

    freq = FrequencyForVoice(voice);

    if (voice->freq != freq)
    {
        OPL_WriteRegister(OPL_REGS_FREQ_1 + voice->index, freq & 0xff);
        OPL_WriteRegister(OPL_REGS_FREQ_2 + voice->index, (freq >> 8) | 0x20);

        voice->freq = freq;
    }
}

// Program a single voice for an instrument.  For a double voice 
// instrument (GENMIDI_FLAG_2VOICE), this is called twice for each
// key on event.

static void VoiceKeyOn(opl_channel_data_t *channel,
                       genmidi_instr_t *instrument,
                       unsigned int instrument_voice,
                       unsigned int key,
                       unsigned int volume)
{
    opl_voice_t *voice;

    // Find a voice to use for this new note.

    voice = GetFreeVoice();

    // If there are no more voices left, we must decide what to do.
    // If this is the first voice of the instrument, free an existing
    // voice and use that.  Otherwise, if this is the second voice,
    // it isn't as important; just discard it.

    if (voice == NULL)
    {
        if (instrument_voice == 0)
        {
            voice = ReplaceExistingVoice(channel);
        }
        else
        {
            return;
        }
    }

    voice->channel = channel;
    voice->key = key;

    // Work out the note to use.  This is normally the same as
    // the key, unless it is a fixed pitch instrument.

    if ((SHORT(instrument->flags) & GENMIDI_FLAG_FIXED) != 0)
    {
        voice->note = instrument->fixed_note;
    }
    else
    {
        voice->note = key;
    }

    // Program the voice with the instrument data:

    SetVoiceInstrument(voice, instrument, instrument_voice);

    // Set the volume level.

    SetVoiceVolume(voice, volume);

    // Write the frequency value to turn the note on.

    voice->freq = 0;
    UpdateVoiceFrequency(voice);
}

static void KeyOnEvent(opl_track_data_t *track, midi_event_t *event)
{
    genmidi_instr_t *instrument;
    opl_channel_data_t *channel;
    unsigned int key;
    unsigned int volume;

/*
    printf("note on: channel %i, %i, %i\n",
           event->data.channel.channel,
           event->data.channel.param1,
           event->data.channel.param2);
*/

    key = event->data.channel.param1;
    volume = event->data.channel.param2;

    // A volume of zero means key off. Some MIDI tracks, eg. the ones
    // in AV.wad, use a second key on with a volume of zero to mean
    // key off.
    if (volume <= 0)
    {
        KeyOffEvent(track, event);
        return;
    }

    // The channel.
    channel = &track->channels[event->data.channel.channel];

    // Percussion channel (10) is treated differently.

    if (event->data.channel.channel == 9)
    {
        if (key < 35 || key > 81)
        {
            return;
        }

        instrument = &percussion_instrs[key - 35];

        last_perc[last_perc_count] = key;
        last_perc_count = (last_perc_count + 1) % PERCUSSION_LOG_LEN;
    }
    else
    {
        instrument = channel->instrument;
    }

    // Find and program a voice for this instrument.  If this
    // is a double voice instrument, we must do this twice.

    VoiceKeyOn(channel, instrument, 0, key, volume);

    if ((SHORT(instrument->flags) & GENMIDI_FLAG_2VOICE) != 0)
    {
        VoiceKeyOn(channel, instrument, 1, key, volume);
    }
}

static void ProgramChangeEvent(opl_track_data_t *track, midi_event_t *event)
{
    int channel;
    int instrument;

    // Set the instrument used on this channel.

    channel = event->data.channel.channel;
    instrument = event->data.channel.param1;
    track->channels[channel].instrument = &main_instrs[instrument];

    // TODO: Look through existing voices that are turned on on this
    // channel, and change the instrument.
}

static void SetChannelVolume(opl_channel_data_t *channel, unsigned int volume)
{
    unsigned int i;

    channel->volume = volume;

    // Update all voices that this channel is using.

    for (i=0; i<OPL_NUM_VOICES; ++i)
    {
        if (voices[i].channel == channel)
        {
            SetVoiceVolume(&voices[i], voices[i].note_volume);
        }
    }
}

// Handler for the MIDI_CONTROLLER_ALL_NOTES_OFF channel event.
static void AllNotesOff(opl_channel_data_t *channel, unsigned int param)
{
    unsigned int i;

    for (i = 0; i < OPL_NUM_VOICES; ++i)
    {
        if (voices[i].channel == channel)
        {
            VoiceKeyOff(&voices[i]);
            ReleaseVoice(&voices[i]);
        }
    }
}

static void ControllerEvent(opl_track_data_t *track, midi_event_t *event)
{
    unsigned int controller;
    unsigned int param;
    opl_channel_data_t *channel;

/*
    printf("change controller: channel %i, %i, %i\n",
           event->data.channel.channel,
           event->data.channel.param1,
           event->data.channel.param2);
*/

    channel = &track->channels[event->data.channel.channel];
    controller = event->data.channel.param1;
    param = event->data.channel.param2;

    switch (controller)
    {
        case MIDI_CONTROLLER_MAIN_VOLUME:
            SetChannelVolume(channel, param);
            break;

        case MIDI_CONTROLLER_ALL_NOTES_OFF:
            AllNotesOff(channel, param);
            break;

        default:
#ifdef OPL_MIDI_DEBUG
            fprintf(stderr, "Unknown MIDI controller type: %i\n", controller);
#endif
            break;
    }
}

// Process a pitch bend event.

static void PitchBendEvent(opl_track_data_t *track, midi_event_t *event)
{
    opl_channel_data_t *channel;
    unsigned int i;

    // Update the channel bend value.  Only the MSB of the pitch bend
    // value is considered: this is what Doom does.

    channel = &track->channels[event->data.channel.channel];
    channel->bend = event->data.channel.param2 - 64;

    // Update all voices for this channel.

    for (i=0; i<OPL_NUM_VOICES; ++i)
    {
        if (voices[i].channel == channel)
        {
            UpdateVoiceFrequency(&voices[i]);
        }
    }
}

static void MetaSetTempo(unsigned int tempo)
{
    OPL_AdjustCallbacks((float) us_per_beat / tempo);
    us_per_beat = tempo;
}

// Process a meta event.

static void MetaEvent(opl_track_data_t *track, midi_event_t *event)
{
    byte *data = event->data.meta.data;
    unsigned int data_len = event->data.meta.length;

    switch (event->data.meta.type)
    {
        // Things we can just ignore.

        case MIDI_META_SEQUENCE_NUMBER:
        case MIDI_META_TEXT:
        case MIDI_META_COPYRIGHT:
        case MIDI_META_TRACK_NAME:
        case MIDI_META_INSTR_NAME:
        case MIDI_META_LYRICS:
        case MIDI_META_MARKER:
        case MIDI_META_CUE_POINT:
        case MIDI_META_SEQUENCER_SPECIFIC:
            break;

        case MIDI_META_SET_TEMPO:
            if (data_len == 3)
            {
                MetaSetTempo((data[0] << 16) | (data[1] << 8) | data[2]);
            }
            break;

        // End of track - actually handled when we run out of events
        // in the track, see below.

        case MIDI_META_END_OF_TRACK:
            break;

        default:
#ifdef OPL_MIDI_DEBUG
            fprintf(stderr, "Unknown MIDI meta event type: %i\n",
                            event->data.meta.type);
#endif
            break;
    }
}

// Process a MIDI event from a track.

static void ProcessEvent(opl_track_data_t *track, midi_event_t *event)
{
    switch (event->event_type)
    {
        case MIDI_EVENT_NOTE_OFF:
            KeyOffEvent(track, event);
            break;

        case MIDI_EVENT_NOTE_ON:
            KeyOnEvent(track, event);
            break;

        case MIDI_EVENT_CONTROLLER:
            ControllerEvent(track, event);
            break;

        case MIDI_EVENT_PROGRAM_CHANGE:
            ProgramChangeEvent(track, event);
            break;

        case MIDI_EVENT_PITCH_BEND:
            PitchBendEvent(track, event);
            break;

        case MIDI_EVENT_META:
            MetaEvent(track, event);
            break;

        // SysEx events can be ignored.

        case MIDI_EVENT_SYSEX:
        case MIDI_EVENT_SYSEX_SPLIT:
            break;

        default:
#ifdef OPL_MIDI_DEBUG
            fprintf(stderr, "Unknown MIDI event type %i\n", event->event_type);
#endif
            break;
    }
}

static void ScheduleTrack(opl_track_data_t *track);

// Restart a song from the beginning.

static void RestartSong(void *unused)
{
    unsigned int i;

    running_tracks = num_tracks;

    for (i=0; i<num_tracks; ++i)
    {
        MIDI_RestartIterator(tracks[i].iter);
        ScheduleTrack(&tracks[i]);
    }
}

// Callback function invoked when another event needs to be read from
// a track.

static void TrackTimerCallback(void *arg)
{
    opl_track_data_t *track = arg;
    midi_event_t *event;

    // Get the next event and process it.

    if (!MIDI_GetNextEvent(track->iter, &event))
    {
        return;
    }

    ProcessEvent(track, event);

    // End of track?

    if (event->event_type == MIDI_EVENT_META
     && event->data.meta.type == MIDI_META_END_OF_TRACK)
    {
        --running_tracks;

        // When all tracks have finished, restart the song.
        // Don't restart the song immediately, but wait for 5ms
        // before triggering a restart.  Otherwise it is possible
        // to construct an empty MIDI file that causes the game
        // to lock up in an infinite loop. (5ms should be short
        // enough not to be noticeable by the listener).

        if (running_tracks <= 0 && song_looping)
        {
            OPL_SetCallback(5000, RestartSong, NULL);
        }

        return;
    }

    // Reschedule the callback for the next event in the track.

    ScheduleTrack(track);
}

static void ScheduleTrack(opl_track_data_t *track)
{
    unsigned int nticks;
    uint64_t us;

    // Get the number of microseconds until the next event.

    nticks = MIDI_GetDeltaTime(track->iter);
    us = ((uint64_t) nticks * us_per_beat) / ticks_per_beat;

    // Set a timer to be invoked when the next event is
    // ready to play.

    OPL_SetCallback(us, TrackTimerCallback, track);
}

// Initialize a channel.

static void InitChannel(opl_track_data_t *track, opl_channel_data_t *channel)
{
    // TODO: Work out sensible defaults?

    channel->instrument = &main_instrs[0];
    channel->volume = 127;
    channel->bend = 0;
}

// Start a MIDI track playing:

static void StartTrack(midi_file_t *file, unsigned int track_num)
{
    opl_track_data_t *track;
    unsigned int i;

    track = &tracks[track_num];
    track->iter = MIDI_IterateTrack(file, track_num);

    for (i=0; i<MIDI_CHANNELS_PER_TRACK; ++i)
    {
        InitChannel(track, &track->channels[i]);
    }

    // Schedule the first event.

    ScheduleTrack(track);
}

// Start playing a mid

static void I_OPL_PlaySong(void *handle, boolean looping)
{
    midi_file_t *file;
    unsigned int i;

    if (!music_initialized || handle == NULL)
    {
        return;
    }

    file = handle;

    // Allocate track data.

    tracks = malloc(MIDI_NumTracks(file) * sizeof(opl_track_data_t));

    num_tracks = MIDI_NumTracks(file);
    running_tracks = num_tracks;
    song_looping = looping;

    ticks_per_beat = MIDI_GetFileTimeDivision(file);

    // Default is 120 bpm.
    // TODO: this is wrong

    us_per_beat = 500 * 1000;

    for (i=0; i<num_tracks; ++i)
    {
        StartTrack(file, i);
    }
}

static void I_OPL_PauseSong(void)
{
    unsigned int i;

    if (!music_initialized)
    {
        return;
    }

    // Pause OPL callbacks.

    OPL_SetPaused(1);

    // Turn off all main instrument voices (not percussion).
    // This is what Vanilla does.

    for (i=0; i<OPL_NUM_VOICES; ++i)
    {
        if (voices[i].channel != NULL
         && voices[i].current_instr < percussion_instrs)
        {
            VoiceKeyOff(&voices[i]);
        }
    }
}

static void I_OPL_ResumeSong(void)
{
    if (!music_initialized)
    {
        return;
    }

    OPL_SetPaused(0);
}

static void I_OPL_StopSong(void)
{
    unsigned int i;

    if (!music_initialized)
    {
        return;
    }

    OPL_Lock();

    // Stop all playback.

    OPL_ClearCallbacks();

    // Free all voices.

    for (i=0; i<OPL_NUM_VOICES; ++i)
    {
        if (voices[i].channel != NULL)
        {
            VoiceKeyOff(&voices[i]);
            ReleaseVoice(&voices[i]);
        }
    }

    // Free all track data.

    for (i=0; i<num_tracks; ++i)
    {
        MIDI_FreeIterator(tracks[i].iter);
    }

    free(tracks);

    tracks = NULL;
    num_tracks = 0;

    OPL_Unlock();
}

static void I_OPL_UnRegisterSong(void *handle)
{
    if (!music_initialized)
    {
        return;
    }

    if (handle != NULL)
    {
        MIDI_FreeFile(handle);
    }
}

// Determine whether memory block is a .mid file 

static boolean IsMid(byte *mem, int len)
{
    return len > 4 && !memcmp(mem, "MThd", 4);
}

static boolean ConvertMus(byte *musdata, int len, char *filename)
{
    MEMFILE *instream;
    MEMFILE *outstream;
    void *outbuf;
    size_t outbuf_len;
    int result;

    instream = mem_fopen_read(musdata, len);
    outstream = mem_fopen_write();

    result = mus2mid(instream, outstream);

    if (result == 0)
    {
        mem_get_buf(outstream, &outbuf, &outbuf_len);

        M_WriteFile(filename, outbuf, outbuf_len);
    }

    mem_fclose(instream);
    mem_fclose(outstream);

    return result;
}

static void *I_OPL_RegisterSong(void *data, int len)
{
    midi_file_t *result;
    char *filename;

    if (!music_initialized)
    {
        return NULL;
    }

    // MUS files begin with "MUS"
    // Reject anything which doesnt have this signature

    filename = M_TempFile("doom.mid");

    if (IsMid(data, len) && len < MAXMIDLENGTH)
    {
        M_WriteFile(filename, data, len);
    }
    else
    {
	// Assume a MUS file and try to convert

        ConvertMus(data, len, filename);
    }

    result = MIDI_LoadFile(filename);

    if (result == NULL)
    {
        fprintf(stderr, "I_OPL_RegisterSong: Failed to load MID.\n");
    }

    // remove file now

    remove(filename);
    free(filename);

    return result;
}

// Is the song playing?

static boolean I_OPL_MusicIsPlaying(void)
{
    if (!music_initialized)
    {
        return false;
    }

    return num_tracks > 0;
}

// Shutdown music

static void I_OPL_ShutdownMusic(void)
{
    if (music_initialized)
    {
        // Stop currently-playing track, if there is one:

        I_OPL_StopSong();

        OPL_Shutdown();

        // Release GENMIDI lump

        W_ReleaseLumpName("GENMIDI");

        music_initialized = false;
    }
}

// Initialize music subsystem

static boolean I_OPL_InitMusic(void)
{
    OPL_SetSampleRate(snd_samplerate);

    if (!OPL_Init(opl_io_port))
    {
        printf("Dude.  The Adlib isn't responding.\n");
        return false;
    }

    // Load instruments from GENMIDI lump:

    if (!LoadInstrumentTable())
    {
        OPL_Shutdown();
        return false;
    }

    InitVoices();

    tracks = NULL;
    num_tracks = 0;
    music_initialized = true;

    return true;
}

static snddevice_t music_opl_devices[] =
{
    SNDDEVICE_ADLIB,
    SNDDEVICE_SB,
};

music_module_t music_opl_module =
{
    music_opl_devices,
    arrlen(music_opl_devices),
    I_OPL_InitMusic,
    I_OPL_ShutdownMusic,
    I_OPL_SetMusicVolume,
    I_OPL_PauseSong,
    I_OPL_ResumeSong,
    I_OPL_RegisterSong,
    I_OPL_UnRegisterSong,
    I_OPL_PlaySong,
    I_OPL_StopSong,
    I_OPL_MusicIsPlaying,
    NULL,  // Poll
};

//----------------------------------------------------------------------
//
// Development / debug message generation, to help developing GENMIDI
// lumps.
//
//----------------------------------------------------------------------

static int NumActiveChannels(void)
{
    int i;

    for (i = MIDI_CHANNELS_PER_TRACK - 1; i >= 0; --i)
    {
        if (tracks[0].channels[i].instrument != &main_instrs[0])
        {
            return i + 1;
        }
    }

    return 0;
}

static int ChannelInUse(opl_channel_data_t *channel)
{
    opl_voice_t *voice;

    for (voice = voice_alloced_list; voice != NULL; voice = voice->next)
    {
        if (voice->channel == channel)
        {
            return 1;
        }
    }

    return 0;
}

void I_OPL_DevMessages(char *result, size_t result_len)
{
    char tmp[80];
    int instr_num;
    int lines;
    int i;

    if (num_tracks == 0)
    {
        M_snprintf(result, result_len, "No OPL track!");
        return;
    }

    M_snprintf(result, result_len, "Tracks:\n");
    lines = 1;

    for (i = 0; i < NumActiveChannels(); ++i)
    {
        if (tracks[0].channels[i].instrument == NULL)
        {
            continue;
        }

        instr_num = tracks[0].channels[i].instrument - main_instrs;

        M_snprintf(tmp, sizeof(tmp),
                   "chan %i: %c i#%i (%s)\n",
                   i,
                   ChannelInUse(&tracks[0].channels[i]) ? '\'' : ' ',
                   instr_num + 1,
                   main_instr_names[instr_num]);
        M_StringConcat(result, tmp, result_len);

        ++lines;
    }

    M_snprintf(tmp, sizeof(tmp), "\nLast percussion:\n");
    M_StringConcat(result, tmp, result_len);
    lines += 2;

    i = (last_perc_count + PERCUSSION_LOG_LEN - 1) % PERCUSSION_LOG_LEN;

    do {
        if (last_perc[i] == 0)
        {
            break;
        }

        M_snprintf(tmp, sizeof(tmp),
                   "%cp#%i (%s)\n",
                   i == 0 ? '\'' : ' ',
                   last_perc[i],
                   percussion_names[last_perc[i] - 35]);
        M_StringConcat(result, tmp, result_len);
        ++lines;

        i = (i + PERCUSSION_LOG_LEN - 1) % PERCUSSION_LOG_LEN;
    } while (lines < 25 && i != last_perc_count);
}