Table of Gain Modes

The S-DSP has five gain modes, to which Nintendo gave official names [1], but they are numbered differently by different emulator authors.

nocash numbers the gain modes with bits 5 & 6 of VxGAIN. [2] Note that direct gain mode uses these bits for the fixed volume instead and thus has no number in this scheme.

Near numbers the gain modes with the top 3 bits of ADSR(1). Note that when bit 7 is clear, bits 5 & 6 are "don't care" and thus Modes 0-3 are actually all the same - direct gain.

| Official Ninteno Name		| nocash numbering/naming	| Near numbering/naming
|-------------------------------+-------------------------------|----------------------------------
| Direct Designation		|	   Direct Gain		| Modes 0-3 (direct)
| Increase Mode (Linear)	| Mode 2 = Linear Increase	| Mode 6    (linear increase)
| Increase Mode (Bent Line)	| Mode 3 = Bent Increase	| Mode 7    (two-slope linear increase)
| Decrease Mode (Linear)	| Mode 0 = Linear Decrease	| Mode 4    (linear decrease)
| Decrease Mode (Exponential)	| Mode 1 = Exp Decrease		| Mode 5    (exponential decrease)

References

• [1] page 3-7-4, "GAIN" of the official Super Nintendo development manual: https://archive.org/details/SNESDevManual/book1/page/n170
• https://problemkaputt.de/fullsnes.htm#snesapudspadsrgainenvelope
• https://github.com/ares-emulator/ares/blob/master/ares/sfc/dsp/envelope.cpp