SOUND BANK FORMAT
  *****************

6:22 AM 12/13/2009

ADDRESS TABLE (must not cross banks)
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 BYTE		number of modules in bank (MAX 85)
 BYTE*N*3	pointers to MODULES (Laddr,Haddr,Bank) (Cxxx region)

MODULE (must not cross banks)
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 000h	byte		initial tempo "sbm_itempo"
 001h	byte		initial speed "sbm_ispeed"
 002h	byte		initial volume "sbm_ivolume"
 003h	byte		number of patterns in module "sbm_pattcount"
 004h	byte		number of instruments in module "sbm_inscount"
 005h	byte		length of order list "sbm_length"
 006h	byte		number of channels in module
 007h	byte		expansion chips used (copy of NSF entry)
 [reserved data]
 010h	byte*64		N106 wavetable (used with N106 expansion only)
 050h	byte*16		channel map
 060h	byte*len	sequence "sbm_tables"
 +len	byte*npatt	pattern addresses LBYTE
 +npatt	byte*npatt	pattern addresses HBYTE (must point to Cxxx region)
 +npatt	byte*npatt	pattern addresses BANK
 +npatt byte*ninst	instrument addresses LBYTE
 +npatt byte*ninst	instrument addresses HBYTE (must point to Dxxx region)
 +npatt byte*ninst	instrument addresses BANK
 
INSTRUMENT (must not cross banks)
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byte:TYPE "sbi_type"
  0: 2A03 PULSE		1: 2A03 TRIANGLE
  2: 2A03 NOISE		3: 2A03 DPCM
  4: VRC6 SQUARE	5: VRC6 SAWTOOTH
  6: N106 SOUND		7: VRC7 STOCK
  8: VRC7 CUSTOM	9: MMC5 PULSE
  A: FME-07 PULSE	B: FDS SOUND

  TYPE must match CHANNEL TYPE

byte:DEFAULT VOLUME "sbi_dvolume"
	0-64

byte:PITCH BASE L "sbi_pbase"
byte:PITCH BASE H "sbi_pbase2"
  pitch base should be adjusted to match the actual hardware pitch

byte:MODULATION DELAY "sbi_mdelay"
	1..256 (60hz ticks)

byte:MODULATION SWEEP PERIOD "sbi_msweep"
	1..256 (60hz ticks)

byte:MODULATION DEPTH "sbi_mdepth" *
	0..15 (0=off, 15 = +-~1 semitones)

byte:MODULATION RATE "sbi_mspeed"
	0..63

byte: envelope mask "sbi_envelopemask"
  &1 = has volume envelope
  &2 = has pitch envelope
  &4 = has duty/special envelope

byte*16: type specific data (see below)

[**DPCM**]
 byte:dpcm source bank "sbi_dpcmbank"
 byte:dpcm offset "sbi_dpcmoffset"
 byte:dpcm length "sbi_dpcmlength"
 byte:dpcm loop flag "sbi_dpcmloop"

[**VRC7 CUSTOM**]
 byte*8: instrument configuration "sbi_vrc7custom"

[**NOISE**]
 byte:looped noise "sbi_noiseloop" 128=looped, 0=normal

(see table below for which instruments have which envelopes)
[VOLUME ENVELOPE]
[PITCH ENVELOPE] (PITCH BEND ......)
[DUTY/SPECIAL ENVELOPE]

[FDS SAMPLE] *

envelope format
---------------
byte:size (offset to next envelope)
envelope data (sequence of BYTES)
  0..253	envelope data
  254		SUSTAIN (sustain loop point follows)
  255		LOOP (loop point follows)

 loop points are a byte offset from the beginning
 of the envelope data *PLUS 1*

instrument envelopes/ranges:
------------------------------------------------------
2A03 PULSE	vpD	0..16	-128..+125 *	0..3
2A03 TRIANGLE	vp-	0..16?	-128..+125	-
2A03 NOISE	v-d	0..16 	-		0..15 &16 *
2A03 DPCM	--d	-	-		0..15 &0x40
VRC6 SQUARE	vpD	0..16	-128..+125	0..7
VRC6 SAWTOOTH	vp-	0..16	-128..+125	-
N106 STOCK	vpD	0..16	-128..+125	0..63
VRC7 STOCK	vpD	0..16	-128..+125	1..15 *16
VRC7 CUSTOM	vpD	0..16	-128..+125	0
MMC5 PULSE	vpD	0..16	-128..+125	0..3
FME-07 PULSE	vp-	0..16	-128..+125	-
FDS SOUND	vp-	0..16	-128..+125	-
------------------------------------------------------
 v = optional volume envelope
 p = optional panning envelope
 d = optional duty/special envelope
 D = required duty/special envelope
 - = envelope type not supported

 * MODULATION is ingored for noise and dpcm.

 * FDS SAMPLE is 64 bytes of sample data for the FDS expansion sound.

 * pitch bend range is +- ~8 semitones.
   (E/4 semitones) (x*16 is added to the pitch)

 * DUTY/SPECIAL controls duty for pulse, "PERIOD INDEX" and LOOP for 
    noise and dpcm (&16=LOOP), and WAVEFORM INDEX for N106. 
    enveloped "PERIOD INDEX" cancels pitch input for noise and dpcm
    ...and instrument for vrc7

important formatting notes:
  2a03 pulse:
    value 0..3 is stored as "(V<<6) OR 00110000b"
    (used to set length counter halt and envelope disable)
  vrc6 pulse:
    value 0..7 is stored as "(V<<4)"
  vrc7:
    value 1..15 is stored as "(V<<4)"

  VOLUME ENVELOPE:
    stored as '128' (if max) or with 'reversed' and 'inversed' 4bit value (if < max)
    examples input:00001101, output:00000100
             input:00010000, output:10000000
             input:00000001, output:00000111

PATTERN (may flow into next bank)
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byte	number of rows (1..256) (0=256)
byte*?	pattern data (IT compression, with slight modification)