SNESFM is an extremely configurable sound driver. Options can increase the amount of space it takes, and increase or decrease the amount of space the instrument or song data takes. This is a guide to configuring SNESFM.
Configuration names are marked in code, !SNESFM_CFG is omitted from all of them. Every option features a brief description of its action, possible influence on/by other options, and its code usage.
Here's a few phrases and symbols often used here:
- "Enabled" = defined as 1 or more
- "Disabled" = defined as 0
- "By default" = if not defined
- Logical operations:
- ¬ - the NOT operation
- ∧ - the AND operation
- ∨ - the OR operation
Dictates whether to include the code that can generate samples - the main gimmick of the SNESFM sound driver. It can reduce space that samples would've taken up in your game, however it is unfortunately pretty costly space-wise by itself.
If not enabled, automatically enables INSGEN_USE_CUSTOM_SAMPLES if latter not defined.
Enables several other options and blocks of options.
Disabled by default.
- 0: +0 bytes;
- 1: +520 bytes.
Whether to be able to generate samples using BRR filter mode 1. These samples have finer details, but take longer to produce, and due to the rough nature of the algorithm, may have some details wrong.
Only works if SAMPLE_GENERATE is enabled.
Disabled by default.
- 0: +0 bytes;
- 1: +193 bytes.
Enables the resampling routine, which resamples samples from 128 sample points (so-called long samples) to 32 sample points (short samples).
Only works if SAMPLE_GENERATE is enabled.
Disabled by default.
- 0: The basis, +0 bytes;
- 1: +48 bytes while also enabling other chunks of code.
These options enable the phase modulation routine.
Internal name: PHASEMOD_ANY (cannot be overridden).
+44 bytes + additional space usage on top of that depending on the option.
Enables phase modulation with long samples.
Disabled by default.
- 0: The basis, +0 bytes;
- 1: +111 bytes.
Enables phase modulation with short samples.
Disabled by default.
- 0: The basis, +0 bytes;
- 1: +140 bytes.
If enabled, enables both PHASEMOD_LONG and PHASEMOD_SHORT.
If not defined, set to PHASEMOD_LONG∧PHASEMOD_SHORT.
+9 bytes on top of PHASEMOD_LONG and PHASEMOD_SHORT.
These options enable the pulse generation routine.
Internal name: PULSEGEN_ANY (cannot be overridden).
+5 bytes + additional space usage on top of that depending on the option.
Enables the long-sample version of the pulse generation routine.
Disabled by default.
- 0: The basis, +0 bytes;
- 1: +154 bytes.
Enables the short-sample version of the pulse generation routine.
Disabled by default.
- 0: The basis, +0 bytes;
- 1: +189 bytes.
If enabled, enables both PULSEGEN_LONG and PULSEGEN_SHORT.
If not defined, set to PULSEGEN_LONG∧PULSEGEN_SHORT.
+4 bytes on top of PULSEGEN_LONG and PULSEGEN_SHORT.
Should this be moved? probably yes
Allocates slots for repeating arguments for opcode. Each slot has a bitmask, and it conserves options according to that bitmask (saving bytes in instrument data), and a counter decrementing with every opcode, counting until it no longer applies.
Disabled by default.
- 0: The basis, +0 bytes;
- 1: +20 bytes;
- 2: +33 bytes;
- 3: +39 bytes;
- 4: +45 bytes.
+11 additional bytes are used if PHASEMOD is also set.
- 0: The basis,+0 bytes inside code, but you have to supply 192 bytes of the pitchtable itself somewhere along the way;
- 1: +137 bytes (will increase due to not yet parsing song data header to generate pitch tables at will) inside code.
With how confusing some of the configuration space usage options can be, i have compiled a table containing the space impacts. It's probably the only good part of this document lmao
PHASEMOD_ ommitted from option names.
LONG >SHORT v |
0 |
1 |
|---|---|---|
| 0 | +0 | +155 |
| 1 | +184 | +309 |
PULSEGEN_ ommitted from option names.
LONG >SHORT v |
0 |
1 |
|---|---|---|
| 0 | +0 | +159 |
| 1 | +194 | +352 |
PHASEMOD_ANY shortended to PHASEMOD.
INSGEN_REPEAT_AMOUNT shortened to REPEAT.
PHASEMOD >REPEAT v |
0 |
1 |
|---|---|---|
| 0 | +0 | +0 |
| 1 | +20 | +31 |
| 2 | +33 | +44 |
| 3 | +39 | +50 |
| 4 | +45 | +56 |