[Communication] Defining the SFe Bank selection algorithm

[spessasus]

I'm pretty certain that I have now finalized the bank LSB system in spessasynth.

This issue is here to explain and potentially transfer the bank selection algorithm to SFe.

The code is here:

https://github.com/spessasus/spessasynth_core/blob/master/src/soundbank/basic_soundbank/preset_selector.ts

Now for the description

MIDI Patch

Each preset is a MIDI Patch. This means that it has 4 properties:

• program - the MIDI program number.
• bankMSB - the CC#0 value.
• bankLSB - the CC#32 value.
• isGMGSDrum - a flag indicating if this is a drum patch.

This allows to select presets accurately with extensive fallback options for all 4 bank selection systems.

Below is how each of the three formats loads the patch:

SF2 presets

• program - copied directly from wPreset.
• bankMSB - copied directly from wBank.
• bankLSB - set to zero/copied from the top wBank byte (if it's not zero). But it will mostly be zero.
• isGMGSDrums - copied directly from wBank drum bit (bit 8).

DLS instrument

• program - copied directly from ulInstrument.
• bankMSB - copied directly from ulBank.
• bankLSB - copied directly from ulBank.
• isGMGSDrums - copied directly from ulBank drum bit

SFe preset

• program - copied directly from wPreset.
• bankMSB - copied directly from wBank.
• bankLSB - copied directly from wBank.
• isGMGSDrums - copied directly from wBank drum bit (bit 8).

System behaviors

default

By default, the synthesizer is initialized in GS mode.

Note that all modes use the same bank selection system.

gs

Triggered by: GS/SC-88 reset, boot up of the synthesizer.

All banks and all programs are set to 0. Channel 10's isGMGSDrum is set to true, everywhere else set to false.
A GS Use for Drums Part SysEx can be used to toggle the isGMGSDrum on any channel

gm

Triggered by: GM1 mode on.

All banks and all programs are set to 0. Channel 10's isGMGSDrum is set to true, everywhere else set to false.
Bank select messages are ignored.

gm2

Triggered by: GM2 mode on, GS mode off.

All programs are set to 0. All channels' bank MSB is set to 121, with the exception of channe 10 where it is set to 120. (per GM2 spec) isGMGSDrum is set to false on all channels.

xg

Triggered by: XG reset.

All programs are set to 0. All channels' bank MSB is set to 0, with the exception of channe 10 where it is set to 127. isGMGSDrum` is set to false on all channels.

Definitions

Below are the few definitions when selecting a preset.

Valid XG bank

Each sound bank in the list has to be validated for XG compatibility. This is done because some sound bank set the bank MSB of 127 for Roland MT presets.
Each bank's presets are tied to that bank, i.e. even with an SFList consisting of multiple sound banks, each of the presets must know if it's a part of a valid XG bank or not.

Checking algorithm

• Assume that bank is not a valid XG bank.
• Iterate through all the presets.
• If bank MSB = 120, 126 or 127, check the program:
• If the program is one of these values: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 16, 17, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 40, 41, 48, 56, 57, 58, 64, 65, 66, 126, 127
  • Set the bank to a valid XG bank and continue iteration.
• If not:
  • Set bank as not XG valid and end the iteration immediately.

Is XG drums

A preset is considered xg drums if the following conditions are met:

• bankMSB of this preset is 120 or 126.
• AND
• the parent sound bank of this preset is a valid XG bank.

Is any drums

A preset is considered any drums if the following conditions are met:

• isGMGSDrum flag is set.
• OR
• the preset is xg drums.

Bank selection algorithm

The bank selection takes two arguments:

• MIDI Patch: the 4 properties described.
• System: the bank selection system currently active.

BEGIN:

Look for an exactly matching preset:

• Program matches.
• Bank MSB matches.
• Bank LSB matches.
• isGMGSDrum flag matches.

If a match is found, select it.

if isGMGSDrums is true:

• Look for a preset with a matching program number and isGMGSDrums flag set. If a match is found, select it.
• Look for any drums preset with a matching program. If a match is found, select it.
• Look for any preset with the isGMGSDrums flag. If a match is found, select it.
• Look for any drums preset. If a match is found, select it.
• Select the first available preset.

if bank MSB is 120, 126 or 127 AND the bank selection system is xg or gm2

• Look for a preset with a matching program number that is xg drums. If a match is found, select it.
• Look for any drums preset with a matching program. If a match is found, select it.
• Look for any preset that is xg drums. If a match is found, select it.
• Look for any drums preset. If a match is found, select it.
• Select the first available preset.

If the conditions above don't apply, this is a melodic preset.

• Find all presets with a matching program number that are not any drums.
• Store them in matchingPrograms

if matchingPrograms is empty

Select the first available preset.

if the bank selection system is xg or gm2

• Look for a preset in matchingPrograms that has a bank LSB match. If a match is found, select it.

else

• Look for a preset in matchingPrograms that has a bank MSB match. If a match is found, select it.

• Find the larger bank number of the two and call it bank.

• Look for a preset in matchingPrograms that has a bank LSB OR bank MSB match with bank. If a match is found, select it.

• Select the first matchingPrograms.

@sylvia-leaf
@stgiga
@nehochupechatat

What do you think about this preset selection system? I've tested it extensively and it works with both GM2 files (nokia DLS sound banks), XG files (DLSByXG.dls as well as the SF2 conversion) and regular GS sound banks.

[nehochupechatat]

Would this work with GS MIDIs that have multiple drum channels besides ch10? That's a rather important feature. Example MIDI: COLDWAVE from WinGroove.

If so then yes. I'm still excited for the LFO and better/line based envelope support (rather than the simple AHDSR of SF2/DLS)

[spessasus]

If they have the GS drum sysEx properly implemented then yes. If no, they violate GM specification unless a sound canvas plays the drum channel.

[nehochupechatat]

Well, sounds good then to me!

[stgiga]

https://sinclairdesign.com/download_file/view/481/1558

GM2 list but different with funny mapping

[spessasus]

https://sinclairdesign.com/download_file/view/481/1558

GM2 list but different with funny mapping

That's strange. The GM2 spec says:

[stgiga]

What's also interesting is that there's a Mobile SF2 type akin to Mobile DLS, I think Awave Studio and potentially Audio Compositor support it, and I do recall it getting used.

[stgiga]

Mobile SF2 can be finicky on some apps.

[stgiga]

Also MU2000EX GM2 may have funny mappings, especially with PLG cards. MU2000EX in MAME is an ongoing effort and it's done using the latest version/revision of the BIOSes for the MU2000 core, which is heavily WIP.

[stgiga]

Also Korg XG may be worth investigating. XGlite isn't equivalent to XG Level 1. SD-90's manual mentions an XGlite mode.

[stgiga]

Basically when we talk about GS and XG, there's investigations into mappings that need to be made beyond the most popular devices, even by our standards.

[nehochupechatat]

What is Mobile SF2? I know a lot about phone synths and have never even heard of such a thing.