SFe 4.0 (pre-release)

After almost five years of development, we are releasing the first version of the SF-enhanced (SFe) specification, the one unofficial extension of the SF2 format to rule them all.

Life before SFe

For a long time, the SF2 (SoundFont*) format served as an way of creating sample libraries that were not only easy to use, but also intuitive to create. However, as the SF2 format was originally designed to be used with sound cards of the 1990s, it lacked many features that musicians wanted to make the libraries that they wanted to.

In response, many SF2 program developers made their own proprietary, incompatible extensions to the format. The most prominent example was compression - at one point there were five different versions of compressed SF2 banks in use! This was a problem until SF3, the de facto standard for open source SF2 players, took over. Some people have even extended the SF2 synthesis model itself, adding features from the less popular DLS (downloadable sounds) format.

However, an even bigger problem was that many players simply didn't implement the entire SF2 specification. For example, they may have omitted the modulators system introduced in SF2.01, or support for 24-bit samples introduced in SF2.04. The result was that sample libraries often worked only with the programs that were used to create them, as well as the programs that they were designed for.

Break past the two gigabyte barrier

With SF2, it was a gamble that the program would work with file sizes larger than 2GB. Some programs used signed integers for file sizes, others didn't. And the SF2 specification didn't mention anything. The SFe specification does. Unsigned integer file sizes are a requirement for SFe compatibility, so the vast majority of players support 4GB. You can stretch out while you make your banks as realistic or as flexible as you want.

Not only that, but we're going beyond 32-bit completely. With the ability to choose different RIFF chunk header types in future SFe 4 versions[2], you will be able to take advantage of 64-bit technology available on almost all of today's computers, with file sizes above 4GB.[1] Imagine turning your large split bank into one large file with everything that you could ever think of.

More banks mean greater compatibility

One of the biggest limitations of SF2 was its limitation to bank select MSB instructions. And with the increasing demand for XG* and GM2-compatible MIDI instrument banks, this just wasn't acceptable. SF2 also was limited to just one bank of percussion kits for general MIDI usage.

SFe is the first SF2 extension to include support for bank select LSB, for a total of 2 million different locations for melodic instruments and 2 million more for percussion kits. While you're never going to be able to use every space, what you do get is increased flexibility, so you can say goodbye to "XG* hacks" and hello to MIDI files that play flawlessly without needing to do anything more.

And with future versions of SFe[1], you will be able to make your banks respond to reset commands to prevent your pianos from becoming guitars that don't work properly, or your muted guitar from becoming a brass sound. The possibilities are almost endless with all the space you get.

Does this player support this feature?

Inside every SFe bank, the feature flags chunk lists every feature that the bank uses. You don't need to load the entire bank just to be disappointed - the program does the checking for you. And the program can warn you if the bank you created won't work properly, so you don't have to test on every player or warn people that you only tested it on one synthesiser.

Developers also benefit from this. You can implement all of the features, or just some of them, and tell users which features you support or don't. You can spend as much or as little time as you want to add the features that you care about.

In the future[2], bank developers can also provide different pathways for different programs that support different feature sets. So, if one SFe player doesn't include specific features that another one does have, you will be able to add a different set of parameters that make your bank continue to work properly, even if the program only supports old SFe versions.

Introducing the ISFe-list chunk

This chunk found inside all SFe banks contains not only the feature flags, but also detailed version information, and the type of bank that is used. This assists you in determining what version of the SFe specification that the bank works with. And future versions[2] add more and more features inside this chunk.

And to legacy players, the metadata interface remains almost identical to legacy SF2, so your banks still work with old players.[3]

SFe Compression

SFe also integrates the Werner SF3 compression format, the standard in SF2 compression technologies selected by leading open source SF2 editors and players. Any existing SF3 players won't have to add any more code to support SFe Compression.

More of a wider range of words

The world is getting smaller, and ASCII isn't getting larger. In fact, pure ASCII is slowly becoming obsolete in favour of Unicode.

With the completely backwards-compatible[3] UTF-8 format, you can use a wider range of characters in your bank's title, comments, sample names, instrument names, preset names etc. Internationalisation benefits are just the tip of the iceberg; you can use accented characters, different alphabets such as Greek or Cyrillic, the wide range of Kanji/CJK characters, and even emoji! (Please don't use emoji, but you could...)

Not only that, but we've removed the size limits for the metadata fields, so you can go on about everything that you want people to know about your banks. Developers of library management systems also benefit from the required use of ISO 8601 for bank creation dates and times.

Long support and constant updates

With SFe 4, we've committed to a long term support plan. After newer versions come out, we'll continue developing the SFe 4 specification with features that are easy to implement on your existing programs!

SFe will also get significant updates over time, further pushing the envelope of what is possible with open-source sample library development. We're always listening to your feature requests and always add these features to the best of our abilities. And even when SFe 4 is superseded by newer versions, we'll keep giving it features for those who want more time to migrate to later versions!

Logo and design of SFe documents

We've put so much care into making a logo that represents the spirit of the SFe format, and SFe 4 introduces a logo based on the motif of an eighth note.

Firstly, the eighth note expands out, symbolising the growth in features that SFe achieves, and will continue to achieve for the foreseeable future. The rotated version number included in the SFe icon makes the design more friendly. A monochrome version of the SFe 4 icon is also available and stands out. All icons are available in PNG and SVG format, so you can scale it as far as necessary.

The design of the SFe technical specification document is heavily inspired by the Frutiger Aero aesthetic, with a large, embossed logo illustrated in glass. The use of Frutiger Aero represents the vision of the future from the time that SF2.04 was published, because SFe 4 brings us one step closer to the utopia that we all hoped for.

The turquoise colour of the SFe 4 logo and documents also stands out from the red, yellow and blue used by the SoundFont* logo, with future versions of SFe likely to use different colours for their design.

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[1] Requires a 64-bit chunk header that is not compatible with legacy SF2. [2] Future versions of SFe may not be compatible with SFe 4. [3] SFe 4 only.

SFe compatible software coming later, read the specification for information to develop/update your software.

The SFe Team is in no way sponsored by or otherwise affiliated with Creative Technology Ltd. or E-mu Systems, Inc.

*All trademarks are properties of their respective owners. XG is a registered trademark of Yamaha Corp. SoundFont is a registered trademark of Creative Technology Ltd.

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What's Changed

• SFe 4.0 final version by @sylvia-leaf in #108
• Actual final SFe 4 release! by @sylvia-leaf in #110
• More branching shenanigans by @sylvia-leaf in #112

Full Changelog: 4.0-rc3...4.0

SFe 4.0 Release Candidate 3

SFe 4.0 Release Candidate 3 (4.0-rc3)

This time I know it's for real

This isn't Donna Summer, but it's been decided that Release Candidate 3 will be the final version. There will no longer be changes. We've checked through the specification and everything is all good.

Adding the diagrams

We've added 12 figures (named figures 1 through 12) throughout the specification. These visually describe a wide variety of concepts from versioning to file structure. Like SFSPEC24.PDF, they are also accessible from the table of contents, which has recently been reintroduced (thanks to spessasus!).

Rewriting some parts of the specification to make it easier to read

Now, it is very easy to understand how the bank select logic required by SFe works. It starts with a structure that is split into subsections about how to use bank select MSB, the split of wBank into two, and using multiple percussion banks. Then, we added diagrams showing the structure of SFe banks in the file format. Finally, we added flowcharts to describe the process of selecting banks in SFe compared to that of legacy SF2.04.

Additionally, we consolidated a few more references to UTF-8 fields being used into one section.

The copyright and trademark disclaimers have also been moved to the beginning of the document, to make it more prominent. We want to make sure that users understand more clearly about these topics.

Because of these rewrites, section numbers have changed since RC2, so please ensure that the section numbers match.

SFSpecTest and feature flags

By using the open source SF spec test program by mrbumpy409, an SF author with more than 20 years of experience, and also the author of GeneralUser GS, one of the most legendary banks ever, you can determine whether your program is compliant with not only legacy SF2.04, but also basic elements of SFe.

We've added descriptions of all the tests that SFSpecTest does and the feature flags that correspond to each of the tests. The feature flags have also been modified to correspond more closely to the SFSpecTest tests. We also clarified that feature flag branches F0 to FF are private-use and may be used however you want, but reserved branches/leaves are not to be used as they are planned to be used in a future version.

ISO-8601 and ICRD sub-chunk

As you might know, the ICRD sub-chunk stores the creation date of an SFe or legacy SF2.04 bank. The problem is that it was initially intended for library management systems to allow sorting of banks according to creation date, but with internationalisation being more and more of a concern, program logic to handle ICRD values in different languages becomes more and more complicated.

To solve this issue, SFe now enforces a requirement for all ICRD values to be a valid ISO-8601 date, or a date and time. Library management systems in SFe programs can now check for such a date format, and then sort banks like that, without having to worry about different date and time formats that may have appeared in legacy SF2.04 banks.

64-bit chunk headers and versioning

The wMajor value is also once again equal to 4 when a 64-bit chunk header is detected. This means that programs can no longer rely on the wMajor value being greater than 2 to detect SFe Compression. Instead, programs must look for the compression bit in sfSampleType to detect the presence of SFe Compression.

Introducing SiliconSFe

The RC3 specification also includes SiliconSFe, the implementation of the SiliconSF format described in section 11 of SFSPEC24.PDF. The SiliconSF format was never adopted by other hardware vendors, and the documentation provided by Creative/E-mu was very ambiguous.

By analysing Creative's implementation of SiliconSF, we've written up a more detailed specification that attempts to describe how Creative intended the SiliconSF format to be used. Note that the implementation is different from the pure sample blobs that seem to have been used in the AWE ROMs.

About future plans

In two weeks, we will be doing a lot to prepare SFe for release.

• Firstly, we will create a test bank based on GeneralUser GS, which you can use to test SFe features early while developing software. It will showcase many, but not all of the features that SFe 4.0 has to offer.
• The next thing that we will do is to make a few changes to the specification to remove references to it being a release candidate. This is for obvious reasons.
• After that, we'll make a write-up about the upcoming SiliconSFe 1.0 format, based on SiliconSF and corresponding to SFe 4.0.

We will not release SFe 4.1 until there is at least one program supporting SFe 4.0 (level 1), because we want to make sure that the SFe specification remains still for enough time for software developers to target a specific version. However, development will be starting on not only SFe 4.1, but also SFe 5, the first version not to be 100% compatible with SFe 4 and legacy SF2.04.

We will have the first SFe 4.1 draft milestone (4.1.1) available in February, because work on the major features is already completed and the feature freeze has been done. The feature freeze for SFe 4.2 will be happening shortly after 4.1 starts development, so if you have any ideas for features that we could add in SFe 4.2, please submit them soon!

A recap of future versions:

• 4.1 includes DMOD and PNMM.
• 4.2 includes first new generator enums, SFCF, MIDI lyrics, RMIDI and SFLIST.
• 4.3 includes prsw, extended MIDI resets, filter upgrades, ISMI and IPRI.
• 4.4 includes the first DLS features beyond SFCF, SiliconSFe 1.1 featuring AL2, and IBAG/PBAG override.
• 4.5 includes dynamic RIFF by spessasus and full chunk override.
• 4.6 includes SFZ-based abstraction levels AL3-AL5.
• 4.7 includes conditional start/key switching.

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What's Changed

• Create code-of-conduct.md by @sylvia-leaf in #75
• Update to RC2a by @sylvia-leaf in #76
• Updating to Pre-RC3. by @sylvia-leaf in #85
• Generate TOC by @spessasus in #87
• Update dev branch for probably the final time. by @sylvia-leaf in #93
• Incorrect branch fix by @sylvia-leaf in #95
• The actual RC3 by @sylvia-leaf in #96
• Update contributing.md by @sylvia-leaf in #97
• Move RC3 to main by @sylvia-leaf in #98

Full Changelog: 4.0-rc2...4.0-rc3

SFe 4.0 Release Candidate 2

SFe 4.0 Release Candidate 2 (4.0-rc2)

A few more changes based on things we learnt about legacy SF

We know that a release candidate should mostly be completed in terms of the details of feature implementation, but some changes for consistency and optimisation were required this time.

This specification was released earlier than planned, due to the release of Polyphone 2.5, as well as the fact that @sylvia-leaf will be on holiday. Please expect the next version to release over the next few weeks.

The "nice-looking" version of the specification

Release Candidate 1a was focused on fixing a few issues, but most notably included a formatted specification in .PDF format.

Unfortunately, due to me not having access to the computer where the editable version of this specification is stored, RC2 will only be available in Markdown. RC3 should include a formatted .PDF version however.

Updating the feature flags system

The feature flags system is a system that allows the SFe player to communicate to the bank what features are available. SFe players will need to be able to warn the user whenever banks have a feature flag set that the player is not able to use.

Using feature flags ensures compatibility, and in future versions of SFe, may allow "branching" of parameters depending on whether or not different features are supported. This should improve compatibility for banks that implement such "branching" with SFe players that don't support all the features.

Because we determined that E-mu never released ROM sets other than the basic 1MB General MIDI sound set that you should be familiar with if you used the AWE cards back in the day, we integrated the SiliconSF feature set branch into the extended metadata one.

Slight changes to handling of duplicated presets

Duplicated presets are now handled in the same way, regardless of whether they are within or between files/banks. Previously, we expected users to handle information that would be stored in ISFe-list in the future.

Now, SFe players will allow you to select the preset that you want to use, out of the duplicated presets. If this function isn't implemented, then the prescribed behaviour is simply to select the first preset in the file, or the preset in the first file loaded.

No references to future versions in current specifications

The SFe technical specification is strictly for specifying how programs and banks for the current SFe specification should be written, and not future versions.

We've therefore removed references to the future versions in current specifications. For example, we removed references to dynamic RIFF in RC1a.

It's important to clarify that this is not because we now no longer have any plans to implement these features, but rather that the specification should be focused on the current version rather than any future versions.

Section 3.2 lists a few future improvements that we plan to make, and many of them are listed on GitHub anyway. If it's on either of these places, then we plan to include the feature, just in a future version.

Changes to how we use GitHub

We now use GitHub Projects to visualise the progress of SFe development. GitHub Projects pages are split by SFe major version - for example SFe 5 will have a different project page to SFe 4.

A new issue template for communication has also been added.

About future plans

These haven't changed too much, but here is a recap:

• 4.1 will include DMOD and PNMM subchunk support. Polyphone 2.5 is likely to include at least limited support for the DMOD subchunk.

• 4.2 will include the first new generator ENUMs, preliminary SFCF support, MIDI lyrics, RMIDI and SFLIST support.

• 4.3 will include the prsw subchunk, official support for extended MIDI resets, and changes to the filter part of the SFe synthesis model.

• 4.4 will include the first extra DLS features beyond SFCF, and the first versions of AL1 and AL3.

• 4.5 will include dynamic RIFF by spessasus.

• 4.6 will include the SFZ-based abstraction levels above AL3.

• 4.7 will include conditional start and key switching.

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What's Changed

• RC1a by @sylvia-leaf in #70
• Release Candidate 2 by @sylvia-leaf in #73

Full Changelog: 4.0-rc1...4.0-rc2

SFe 4.0 Release Candidate 1

SFe 4.0 Release Candidate 1 (4.0-rc1)

The first release candidate!

This is our first ever Release Candidate specification for SFe! We're so excited.

In no time, we will be ready to release the first version of the SFe specification. We hope that everyone enjoys it!

Reformatting in progress

Compared to the previous draft milestone that we released yesterday, the structure has been completely changed based on feedback by Spessasus. This structure makes it easier for people to read, because it skips as much of the unnecessary information as possible. While this may sound counter-intuitive, we will provide the detailed description of everything that is added to SFe in future versions. For example, the requested detailed modulator implementation will be added for 4.1, as that is planned to be the modulator update, and things will be completely different from legacy SF2.04.

The only thing that we haven't done yet is the "nice-looking" version of the specification, but that will come in time. It will also come before RC2 is available.

Adding stuff about release candidates

We also added the option of "release candidate" for SFvx, because this was required for this new versioning concept.

Yeah, I know that we said no more versioning updates, but this was necessary because we weren't quite ready to release the final specification!

About future plans

The future plans were already in the 4.0.11 release notes.

Why are the release notes so short?

In short, because we released the previous draft specification, 4.0.11 yesterday!

We just managed to get this re-arranged specification ready in no time.

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What's Changed

• Release Candidate 1 by @sylvia-leaf in #62

Full Changelog: 4.0.11...4.0-rc1

4.0.11

SFe 4.0.11 (Draft Specification) - December 2024

The specification is stable now

This is the eleventh draft milestone of the SFe 4 specification, for December 2024.

After making some style improvements, and defining some new concepts, we are confident that this will be the final draft version of SFe 4 before the final version.

This release candidate quality specification will only differ from the final specification by the presentation. The sections may be changed, the program and compatibility specifications will be included directly into the specification, and the specification won't be in Markdown (.MD) but rather in .PDF. (A machine-readable version in Markdown will also be made available.)

No new illustrations were required for 4.0, but they may be for future versions, especially because 4.1 is planned to be the modulator update, and the majority of the illustrations in SFSPEC21.PDF and SFSPEC24.PDF refer to the modulator system.

Splitting parts of the introduction

In preparation for the final specification, we've split the copyright/trademark and draft disclaimer. The final version of the specification won't include the equivalent of section 0.2b.

While the number of members in the SFe team is the same as it was in 4.0.10, we've split the special thanks part from the SFe Team part in case more people are added to each of these sections. We've also corrected a name in the special thanks section.

More definitions

We've added a lot of definitions which cover many of the new features that will be introduced in SFe. These include:

• "branch", "leaf" and "tree structure"
  • used in the feature flags system
  • section 5.12.3 was clarified using these definitions
• "dynamic RIFF", "RIFD", "RIFF-type format" and "static RIFF"
  • for file chunk headers
  • section 3.1 and 3.1a were rewritten using these definitions
• "Cognitone SF4", "FLAC", "OGG", "Opus", "proprietary compression", "SFe Compression", "Vorbis" and "Werner SF3"
  • for file compression
• "SFe", "SFe 4" and "SFe-compatible"
  • for SFe versioning
• "legacy sound card" and "SB"
  • for compatibility

A few changes were also made.

8-bit sample changes

From suggestions I saw on GitHub relating to the 8-bit sample playback mode, we've made changes to the format to ensure that SFe players don't attempt to play a corrupted legacy SF2.04 bank with a missing smpl sub-chunk but with a present sm24 sub-chunk from attempting to load the bank as an bank that uses 8-bit samples.

This is implemented by using a new SFty sub-chunk value. If this value matches SFe-static (8-bit) or SFe-static (8-bit) with TSC, then it will ignore the smpl sub-chunk and just play the sm24 sub-chunk instead. However, if the value doesn't match, the player should think that it is just a corrupted bank that was intended to have an smpl sub-chunk but doesn't.

Section 6.2c was also added, which also defines sm24 and sm32 sub-chunks without a matching smpl sub-chunk as "orphaned", and describes how orphaned sm24 and sm32 sub-chunks shall be handled.

Introducing SFe Compression

After communication with FluidSynth, we decided to standardise on the August 2021 draft specification of Werner SF3, and we've included the contents of the specification into SFe. This standardised version of Werner SF3 is called SFe Compression 1.0, and SFe compliant programs will be required to implement it.

Because programs that implement Werner SF3 may add their own features to the format (MuseScore's sftools programs are seen as the reference implementation), we aim to include as many of these extensions to SF3 inside SFe Compression. If you are developing a program that uses SFe with extensions to SFe Compression, we would rather you share a specification to your changes so everyone can benefit.

SFe Compression requires OGG support, because OGG is the most common compression format used by Werner SF3 players, but more compression formats (most notably FLAC) will need to be supported in later versions of SFe Compression.

Versioning changes for the final time

When E-mu released the legacy SF standard to the public for the first time with version 2.00, the first public version was referred to as 2.00a. Shortly after, an update called 2.00b was released. However, E-mu never used a letter after the version number after that.

Because this was how E-mu versioned their standard, we attempted to adopt this naming ourselves. However, this resulted in the downside that first versions of a draft specification would retroactively have an "a" added to their version number, causing all sorts of confusion. Versions that never got a revision before being replaced by another version would never get the letter "a".

This was way too confusing, so we simplified the versioning system to start without any letters, and then when a version gets a revision, letters are included, starting with "a" instead of "b".

Making the specification consistent

The specification often used different names for the legacy SoundFont 2.04 specification, but this was confusing. So, we decided to standardise on the term "legacy SF2.04" when used to describe it, with "SF2.04" being replaced by "SF2.01" or "SF2.0x" as needed. Similar modifications were made to references to different SFe versions. We've standardised on "SFe [VersionNumber]" - for example, "SFe 4" or "SFe 4.0".

Additionally, we've decided to make all chunk names, variables and similar things use in-line code.

Version 4.0.11a also makes sure that all mentions of the word "sub-chunk" are hyphenated.

Introducing SiliconSFe

In SFSPEC24.PDF there is a section about what E-mu termed "Silicon SoundFonts". These were basically ROM chips that contained samples that would be used by legacy SF2.04; there is a header with information about the ROM, and the header includes the start address of the SoundFont bank.

Because the SFe feature set is a strict subset of the legacy SF2.04 feature set, it follows that there is a version of SiliconSF that supports SFe. The starter specification included in 4.0.11 simply states that the SiliconSF specification as in legacy SF2.04 is usable in SFe.

Eventually, we will adapt the SiliconSFe system for SFe-AL3, the system that allows "blobs" of samples to be present away from the instruments and presets. After SFe-AL3 is implemented, we will then include subtractive synthesis, one of the long term goals that we had for SFe. That being said, it is very unlikely that we will implement it in SFe 4.

About future plans

Now with development of SFe 4.0 nearing the end, we can start thinking about future versions. The text for 4.0.11a is generally "frozen", which means that we won't make major changes to the contents of the specification. SFe 4.0 is now for the most part a non-moving specification that Polyphone 3 can target. If the specification keeps changing, then it can be very difficult for it to be implemented.

Generally, when a version is finalised, we aim to have drafts of the components of version n+1, and then to start thinking of the components included in version n+2. The feature freeze only happens after the previous version has been completely finalised (a final specification has been released).

The status of 4.1 is that it remains the modulator update, with its two main features being the DMOD (default modulators) and PNMM (parameter-number-modulator-map) chunks, both of which have a significantly advanced draft specification by Spessasus, the person who came up with these ideas. We've got space for a large number of features in 4.1, but all other features are planned for a later version.

After 4.1 comes 4.2. Generally, 4.2 is a player update that also implements the first of the new generator enums. The player features planned for 4.2 include a standardised feature set for MIDI lyrics, as well as the integration of Spessasus/Falcosoft RMIDI into SFe, and the generator enum features currently planned are round-robin sample playback, more sample modes, exclusive class release and initial attenuation modes. It will also integrate SFCF (SynthFont Custom Features).

After that, each version from 4.3 to 4.7 has at least one feature planned:

• 4.3 - independent envelopes/filters and filter controls, prsw sub-chunk with XG/GS/GM2 reset support
• 4.4 - preset library management system with the plms sub-chunk and dwLibrary/dwGenre/dwMorphology plus the first of the remaining DLS features
• 4.5 - dynamic RIFF file format scaling from 32-bit to 64-bit and beyond
• 4.6 - SFe-AL3 using SiliconSFe, and SFe-AL4, SFe-AL5 and SFe-AL6 using SFZ, with compilation between SFe and SFZ
• 4.7 - Conditional start and key switching

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What's Changed

• 4.0.11 pull request by @sylvia-leaf in #59

Full Changelog: 4.0.10...4.0.11

4.0.10 - Nov 2024 Refresh

SFe Version 4.0.10 (Draft Specification) - November 2024 Refresh

SFe is now static (for now)

This is the tenth draft milestone of the SFe specification version 4.

We're focusing on changes that help compatibility between different SFe players, by adding features such as extended version sub-chunks, feature flags and more. We're also streamlining the format by reducing the number of variants; this has recently been a point of contention.

Making SFe variants easier to understand

We've listened to feedback, and now we're going to reduce the number of variants of SFe.

Previously, there was SFe32, SFe64L and SFe64. Now, we've postponed the divergence of features between 32-bit and 64-bit formats to version 5.0. Now, there is one SFe specification for both 32-bit and 64-bit versions of the format, and the only current difference is the chunk header format. We also plan on adding a new "dynamic" chunk header designed by SFe Team member spessasus that can scale from 32-bit to 64-bit and beyond in a future version (likely 4.5).

It is called "dynamic" because the length of the chunk size in the header is dynamic and depends on another value. This allows the format to be much more scalable, and wastes less space when compared to standard RIFF64. We will also replace the sfbk fourcc with sfen so legacy SF programs don't accidentally attempt to run an SFe bank.

We've also added a section detailing LTS versions of SFe, which will continue getting feature updates even after structurally incompatible changes (with a higher major version) have been made. For example, when the structurally incompatible SFe 5 releases, it is expected that we maintain feature additions to SFe 4 for some time after. This should strike the perfect balance between supporting legacy players and getting features included quickly!

It may be possible to also abandon the SFty sub-chunk, making the proposition of selecting a variant of SFe even simpler. Even if the SFty sub-chunk is not abandoned, it will still be much simpler for everyone.

Introducing the SFvx sub-chunk

The SFvx sub-chunk includes extended version information about the SFe bank, including:

• specification version
  • differs from ifil version
• specification type
  • drafts, milestones and final versions are supported
• draft milestone (when applicable)
• full version tag (when applicable)

By including such a sub-chunk in the ISFe-info subchunk, we can solve the problem with providing more version information without breaking compatibility with legacy SF players. The ifil value is strictly defined as two WORD values in legacy SF.

Feature flags and the flag sub-chunk

After the SFvx sub-chunk is the flag sub-chunk. This implements feature flags, and is split into branches, leaves and flags. Generally, branches correspond to types of features, leaves correspond to specific features and flags represent the features themselves.

The idea is that a bank has feature flags that are determined by the features in use by samples/instruments/presets. The SFe editor will add the feature flags automatically. The list of feature flags is included in the compatibility specification for 4.0.10, but should be moved to the same document in the final specification.

When an SFe player reads the bank, it will recognise the feature flags that it supports, but if it detects an unrecognised flag, then the user is warned. The user is also warned when flags that are not available in the specification corresponding to the SFvx sub-chunk are found, as the presence of such flags may indicate proprietary extensions.

We also include a "private-use" area (branch 240 to 255), but as the SFe license is copyleft and strongly discourages unpublished proprietary extensions, features may be moved to the main area of flags.

Other versioning changes

Previous drafts have described the first version of SFe as version 4.00. Two zeros are used due to legacy SF using this in its naming conventions (for example, the versions written in SFSPEC21.PDF and SFSPEC24.PDF are 2.01 and 2.04 respectively).

However, some programs have used the terms 2.1 and 2.4 to describe legacy SF. Therefore, we've made the decision to remove the leading zeros. This means that version 4.00 becomes 4.0 and 4.01 becomes 4.1. This is easier to understand for those who are not familiar with the legacy versioning system.

This is also a good time to mention that there will not be illogical version jumping in SFe, unlike in legacy SF. For example, E-mu updated version 1.0 to 1.5 and then to 2.00. As expected, 2.00 was replaced by 2.01, but 2.02 and 2.03 were skipped and 2.04 was the final version ever released by E-mu. Meanwhile in SFe, version 4.0 will be replaced by 4.1 or 5.0, not 4.2, 4.3 or 4.4.

In the future, we'll refer to major versions as "episodes". This naming is used to make it a bit easier for us to describe the development process of SFe versions.

Removing the info-list subchunk length limits

These limits inherited from legacy SF don't make sense for modern computers. Therefore, we're removing them, allowing bank developers to have an unlimited length for information.

Fixing a few other issues

We've also fixed some issues, including an incorrect reference to a chunk that was intended for version 4.4 being listed in section 4 as being intended for version 4.5 and some references in sections 7.4 and 7.5 to features that are to be implemented in version 4.1. We are also rewriting the definitions of more fields that convey multiple values using different bits in a similar vein to the byBankMSB and byBankLSB changes.

License changes

To make the SFe license compliant with the Open Source Definition, we've removed the requirements to share all modifications implemented in programs under the SFe license (or a compatible license) or not removing the link to the latest version of the specification (for final versions). Instead, these are simply considered "good practice".

This new version of the license supersedes the previous version. All SFe data that has been released in the past is now available without the need to share all modifications or to retain the link to the latest version.

It is likely that the SFe program specification containing all "good practice" tips will instead include these requirements in the future.

We will write the full version of the license in time, but there are other things that we need to focus on.

More features for SFe in the future!

According to feedback from team member davy7125 we're adding a few features to the plan to versions beyond 4.0!

We've got a list of baseline features that SFe should include in first implementations:

• default modulators
  • already planned for 4.1
  • using the DMOD chunk
• initial value of MIDI control changes
  • listed as "not sure it is useful though"
  • may be included in 4.1
• sample storage
  • listed as solved by Werner SF3
• round-robin
  • will be added in 4.2
  • 4.2 will consist mostly of generator enum definitions
• independent envelopes/LFOs for pitch/attenuation/filter
  • will likely be added in 4.3 but may be moved forward to 4.2
• sample modes
  • likely to be added in 4.5
• MSB/LSB banks
  • will be added in 4.0
• 64-bit mode
  • static 64-bit SFe is included in the 4.0 specification
  • dynamic SFe is 64-bit by default and will be released in 5.0
• conversion between sfz/sf2
  • this is achieved using the abstraction level system
  • AL6, AL5 and AL4 are SFZ, AL2 is SFe and AL1 is SiliconSFe
  • basic specification for AL6, AL5 and AL4 will be ready for 4.6
  • full AL3 specification will be 4.7 or 5.0
  • during episode 4, we add DLS features, and during episode 5, SFZ features

The comment also includes other features that are less-critical and will be delayed for future versions. Here is a similar list:

• multiple loops at sample level - sometime in episode 6
• different kinds of filters - very likely to be 4.3
• modulator inputs - might be as early as 4.1 but it's unknown what this means
• conditional starts/key switches - 4.7, but if significant structural changes are required, during episode 5
• exclusive class normal release - likely 4.2
• field length limitations - 4.0 for SFe64 only
• negative attenuation - 4.0, its feature flag is already there
• real attenuation - 4.0, its feature flag is already there
• sm32 chunk - 4.0

About other future plans

So, at this point, we are almost ready to release the final version of SFe version 4.0. However, we need to communicate with program developers such as FluidSynth, so we can get an agreement of features to be implemented, as well as a final specification of Werner SF3 that can be included in SFe.

Ideally, this should be done before the release of Polyphone 3 (the first planned version of Polyphone with SFe used by default). We should also communicate with other SF editing and playback programs (for example the Swami editor and the Bassmidi player) to ensure that SFe does not simply become a "Polyphone and FluidSynth Custom Features" that suffers from the same problems as SFCF. Remember that one of the fundamental goals of SFe is to tackle the inevitable problem of "format wars".

Once we've created the near-finalised text of specification version 4.0 (this will appear as a draft milestone), then we can work on creating the logos and niceties so we can release a finalised specification. The finalised specification is likely to have a somewhat different structure to the draft specifications, which closely followed the structure of legacy SF2.04. Parts that are identical ...

4.00.9 (Draft) - November 2024

SFe Version 4.00.9 (Draft Specification)

Getting closer to release

This is the November 2024 draft milestone of the SFe specification, version 4.00.

Unlike last milestone, we've included a few new features, as well as an improvement to make the specification more readable.

ASCII is now obsolete

The original legacy SF specification stated that all fields that stored a string were to use ASCII encoding.

However, since the 1990s, ASCII (or more precisely, US-ASCII) has been almost completely replaced with UTF-8 in modern computer systems. Because all ASCII text is also valid UTF-8, text that uses only ascii characters is completely compatible.

Some programs (including Polyphone) had unofficial support for UTF-8 in the ICMT subchunk, but it didn't extend to other string fields (that were still limited to ascii). Starting with 4.00.9, you can use UTF-8 in all string fields, including those found in the INFO-list and pdta-list chunks. You can now use kana, CJK characters and other non-ascii characters anywhere in SFe banks.

For the sake of completion, we've also redefined "case-sensitive" and "case-insensitive" to explicitly define the character encoding as UTF-8, rather than ascii.

wPreset changes

In the last announcement, we said that we would rework the wPreset system in 7.2 to allow the bank creator to define the use of the second bit of the wPreset word in version 4.04. Therefore, the second bit of wPreset is currently undefined for SFe versions between 4.00 and 4.03.

This is subject to change, so please review the specification every time there is an update.

Preset library management system plans

In previous drafts of SFe, we defined dwLibrary and dwGenre. However, we then realised that they were not strings, but rather DWORDs (integers), so we cannot encode strings.

Therefore, we've updated the specification to expect a DWORD that's linked to a value in an enum, which will be defined in the ISFe-list chunk. This subchunk will be defined in version 4.05.

Introducing the SFe license

A license is included for the first time to clarify what developers are allowed to do with the specification text. It's included in the specification, as well as LICENSE.MD.

It is a copyleft license that allows developers to extend the SFe specification provided that they document any changes and extra features that are implemented in their SFe compliant programs. This is to ensure that proprietary extensions to the SFe format aren't made that may misbehave when used with a player that supports a newer version of SFe.

We do not permit the removal of copyright notices, the removal of the link to the latest version of the specification, or any claim that we're affiliated with E-mu or Creative. This reduces the risk of a misunderstanding.

For draft versions, we also add the condition that the specification be clearly marked as such, because implementation of features can differ wildly between draft specifications and the corresponding final version. The license for final versions of the specification can be found in LICENSE-FINAL.MD.

Like most open-source licenses, we provide the specification "as-is" and disclaim any implied warranty.

On implementation accuracy

Section 9.7 of SFSPEC24.PDF gave information on implementation accuracy, and said that implementations are almost always going to be less accurate than the specification due to computational performance of hardware that implementations would run on.

Due to computers being much faster than in the 1990s when the specification was designed, implementation accuracy requirements are now significantly higher, with implementation of the feature flags system (coming in the next draft) becoming strongly recommended.

WernerSF3 compression

The WernerSF3 compression implementation has effectively been completed for a long time. We are just awaiting a final version of the specification of WernerSF3 from FluidSynth.

However, in this milestone, we've declared CognitoneSF4 to be a proprietary compression format due to its incompatibility with WernerSF3. We've also cited it as the reason that the .sf4 file extension is not used.

File format versioning for SFe32

We've decided to modify the file format versioning for SFe32 to make it easier to read. Please read the SFe32 specification for more information.

Defining a subset of SFe32, SFe32L

Some features found in SFe do not affect the sound output when a bank containing these features is used on a legacy SF player. This subset is called SFe32L.

Please implement the SFe32L features before implementing other features.

File extensions and ISFe-list subchunk

For this version, we've finalised the required file extension to be used. It is .sft, as suggested by spessasus.

We decided that having to use different file extensions for each variant of SFe was unnecessary. Instead, the SFty (SFe type) subchunk, found inside the ISFe-list subchunk, is used to determine the SFe variant to use, but if missing or unknown, there will be other features in the format to allow the program to determine the variant itself.

The ISFe-list subchunk, found inside the INFO-list chunk contains SFe-specific information. The first subchunk, as mentioned before, is the SFty subchunk. The next version, 4.00.10, will add the flag subchunk for feature flags. Other subchunks that are coming soon include prsw (preset switch, 4.04 and later), and plms (preset library management system, 4.05 and later).

Readability changes (4.00.9b)

Very shortly after the initial release of 4.00.9, we made a readability change that does not affect the file format itself at all, and will be a precedent for other similar readability changes. This readability change consists of removing wBank and replacing it with byBankMSB and byBankLSB.

This is completely compatible with wBank, as the actual data doesn't change at all. One WORD value (2 bytes) is replaced with two individual BYTE values, with the first byte corresponding to the bank select MSB (CC00) as used in legacy SF, and the second byte corresponding to the unused byte of the previously-used wBank value.

More experienced SF developers may continue to think of the 2-byte bank select space as a single wBank value equalling (cc00 + 1024 * cc32), but the formatting of the space as two values is easier to understand for less experienced SF developers.

Future data values that encode more than one value that correspond to different bytes may be split to make it easier to understand. It is our responsibility to make the specification as easy to understand for those who want to create SFe-compatible programs.

About future plans

The next version, 4.00.10, will include the first version of the feature flags system. SFe programs that implement the system would read the flags that the bank requests, and warn end-users if an unrecognised or unsupported flag is requested. It is planned for release in December 2024.

Since the release of 4.00.8, we've received communication from Polyphone that Polyphone 3 is planned to include support for SFe 4.0x, and it will be the default export format, with legacy SF being an option. However, Davy has said that more features should be added for SFe as soon as possible. Therefore, there is a good chance that the number of features to add in 4.02 will increase significantly. 4.01 (the DMOD and PNMM update) remains unchanged, except for the potential move of the chunks to the ISFe-list chunk (from the root of the INFO-list chunk).

Work on reverse engineering SFCF features has begun by spessasus. Ideally, we should be getting an official specification from the SynthFont author, but further reverse engineering may be required if this isn't possible. We've found out that unused generator type values are being used by SFCF, and we'll avoid using such values when adding features that require new generator type values. This is for interoperability reasons and should be okay. The plan is that we add SFCF support in version 4.03, but should there be any objection, we can simply leave out SFCF feature support and move all features forward by one version.

Versions 4.04 and 4.05 include support for manipulation of the unused byte in wPreset, and definitions of enums for dwLibrary, dwGenre and dwMorphology respectively, with more DLS features incoming after this. The last version of SFe 4 to release should have feature parity with DLS, with feature parity with SFZ and the abstraction level system fully implemented in the last version of SFe 5.

Feedback

Your feedback is appreciated! Please use the discussion page of the GitHub repository to give feedback. You can also fork and create a pull request if you have any changes that you want to make.

---

What's Changed

• Update to version 4.00.9a by @sylvia-leaf in #26

Full Changelog: 4.00.8...4.00.9

4.00.8

SFe Version 4.00.8 (Draft Specification)

Fixing Some Things

This is the eighth draft milestone of the SFe specification.

This release of the specification doesn't include new features in the format spec. In fact we'll stop mentioning it as there won't be any new features until 4.01.

Introducing the file repair specification

For 4.00.8, we've written a file repair specification for programs that fix SFe banks that are Structurally Unsound. Programs that meet this specification should help bank developers by reducing the amount of time spent fixing problems with files that don't load.

We've included both automatic and manual repair, as well as detailed explanations of each type of error that can happen.

We're looking for feedback for it, so please tell us what should and shouldn't be included in the file repair specification.

An implementation of the file repair specification will happen in the far future. It will likely not be available for version 4.00's final release.

Fixing the format outline

For a long time, the format outline found in section 4 was based on a very old draft of SFe, and was no longer representative of the current state of the specification.

There has already been confusion by some with regard to this format outline, so we've spent some time to update it to be accurate to the current version of the specification.

We've also included the ISFe sub-chunk, but there is currently no information that is defined in this sub-chunk.

Compression issues fixed

Previous versions of the SFe draft specification assumed that the data was uncompressed, which meant that Werner SF3 data was technically not compliant with the SFe spec.

We've now fixed the specification to take into account Werner SF3 compressed data. Now there should not be conflicts between SFe and the August 2021 revision of Werner SF3.

About future plans

We are planning the next few draft milestones of SFe:

• 4.00.9: SFe player reference implementation
• 4.00.10: Feature flags system
• 4.00: Final release, similar to 4.00.10 with problems fixed

Planned rework of section 7.2

We plan on removing the wPreset changes in section 7.2, and instead we would allow users to define what each bit in the wPreset value does.

If removed, then the wPreset changes would be reimplemented in 4.04 with the configuration as a part of the ISFe sub-chunk.

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Full Changelog: 4.00.7...4.00.8

4.00.7

SFe Version 4.00.7 (Draft Specification) - October 2024

Getting Some Help

This is the 7th draft milestone of the SFe specification. Sorry that we forgot to make a pre-packaged release of the 6th milestone; we will try not to forget again.

This release of the specification does not include new features in the format spec itself, as there has been a feature freeze for SFe version 4.00, but focuses on fixing the small issues. We thank @spessasus for taking the time to fix some issues that were in 4.00.6.

In this announcement, we will also include changes that were included in 4.00.6 for the sake of completeness.

Significant structural changes

We've split the SFe specification into three different smaller specifications:

• SFe32 for full 32-bit compatibility
• SFe64L for a 64-bit format that is mostly similar to SFe32 to help users move to 64 bits more easily
• SFe64 for the more divergent 64-bit specification

Currently, there are two specifications released, SFe32 and SFe64. However, SFe64 will have structural changes that break backwards compatibility starting with version 5.00, so the first version of SFe64L, 5.00, will be based on the structure of SFe64 4.x.

Additionally, a pull request by @spessasus was merged by team member @stgiga, merging the admittedly hard-to-read separated sections of the format specification into just one document. This pull request also adds for the first time, a table of contents.

Section 7.1a was removed, because it will only be relevant when SFe64 version 5.00 is released.

Versioning system changes

Yes, we've changed the versioning system again. However, this time it is just the naming. Now, because SFe development is done on a rolling basis, and any update to the specification can be considered a draft, we've renamed the SFe drafts to draft milestones to make the purpose of these releases more clear.

Initially, we planned the file repair specification for 4.00.6. However, 4.00.6 was the version which we split SFe32 from SFe64. It was then moved to 4.00.7. However, when we decided to merge the aforementioned pull request, the structural change meant that we could no longer refer to the specification as 4.00.6a-1, so we renamed this update to 4.00.7. Now, the file repair specification is planned for version 4.00.8.

Modulators

The modulator system that we originally planned for SFe was scrapped. Instead, we will implement spessasus's DMOD sub-chunk for 4.01, and add back some of the features that were planned in this update.

Right now, discussions have been made about designing the new modulator system around the CC94 (InsertionEFX) format as used by Roland in the SC-88Pro and SC-8850.

About the ISFe sub-chunk

The ISFe sub-chunk will be used by the SFe format for SFe-specific metadata. Currently, no data is defined, and there will likely be no definitions in 4.00, however we've started to formulate plans for how we can use this sub-chunk.

As every soundfont developer knows, each soundfont player supports a different amount of the 2.04 spec, and few soundfont players support everything. Therefore, a few soundfonts (most notably GeneralUserGS by S. Christian Collins) include a built-in player test (in the case of GUGS, it is the GUTest preset).

Therefore, the plan is to use part of the ISFe sub-chunk as a sort of "feature flags" system. The SFe editor program will add the feature flags that are used by the bank to ISFe. Once the bank is played by software that doesn't support all of the features, the software can then read the ISFe sub-chunk, figure out what features are being used, and then give a warning if the bank is trying to use an SFe feature that isn't supported by the software.

Currently, we plan on developing one or two features at once, and then release a new version of the format. However, if we use ISFe to implement feature flags, then we can add many different features with each format update, and then allow the SFe program developers to implement features at their own pace. Just using the ifil version to communicate available features has the disadvantage of being unable to clearly mention which of the features are supported.

The feature flags that we plan on adding would also include features included in the base SF 2.04 format, because there are still problems with certain soundfont players not supporting soundfonts that were written to legacy SF standards.

Arguably, we could make programs reject any structures that they don't recognise. However, this would severely affect compatibility, as newer SFe files would simply not run on older players.

The ISFe sub-chunk will eventually do way more than just be a feature flags system, but this is the first idea that we are going to try to implement.

About future plans

We are planning the next few draft milestones of the SFe specification:

• 4.00.8: Redo the RIFF structure and program repair specification
• 4.00.9: SFe SDK release, start to solve the TSC implementation problem
• 4.00.10: Update the SDK with a few more things

Program specification

The program specification is mostly the same as previous versions, but has changes that correspond to the changes in 4.00.7. Namely, TSC mode support is no longer required, as it is now a separate specification to SFe itself.

Compatibility specification

In the compatibility spec, we've added information on how to handle proprietary compression formats, and we fixed a mistake in the INFO chunk information.

Where is TSC mode?

We've had some discussion about TSC mode, where the sdta chunk is placed last to extend the maximum SFe32 file size to 8 GiB. However, it's been determined that TSC mode was obviously not compatible with legacy sound card hardware, so it has been removed. Instead, TSC is now available as a separate specification: https://github.com/SFe-Team-was-taken/TSC

We will bring it back once we have the original documentation about TSC mode, we can test it on legacy sound card hardware and we can create test SFe files implementing TSC. After that, it is likely to be moved into SFe64(L) or included as a separate specification. If TSC mode is a separate specification, then we'll just implement it into SFe as a feature flag. Then, if developers don't feel like rewriting their code, then they can just detect the feature flag in TSC banks and then reject the bank.

What's coming up?

For 4.00.8, we plan on providing an SFe file repair specification for development of programs. This is to be released in late 2024 or early 2025. After that, 4.00.9 will be the first version with an implementation of SFe, based on SpessaSynth, and 4.00.10 will introduce the feature flags system implementation. If you have any suggestions for other features that we could add, or additional information that we could include in future specs, then please open an issue and describe what you would like to see.

New Contributors

• @spessasus made their first contribution in #14

Full Changelog: 4.00.5...4.00.7

4.00.5 (Draft)

SFe Version 4.00.5 (Draft Specification) - August 2024

Welcome Autumn, Welcome GitHub

This is the fifth draft of the SFe specification, and we have started to use GitHub for SFe specification development.

This release of the specification does not include new features in the format spec itself, as there has been a feature freeze for SFe version 4.00, but focuses on the release of the reference implementation of samples used for the ROM emulator that SFe implementations will need to implement.

For this reason, the changes made in this draft are mostly limited to a few formatting changes and new references to the reference implementation of the ROM samples.

SFe and GitHub

We've made the decision to host the spec on GitHub, and allow users to start issues and pull requests to improve the format.

ROM sample specification

We hope that SFe players will allow more users to enjoy soundfonts that use legacy sound card ROM samples, so SFe implementations should include an AWE ROM emulator. The problem is that the original samples are copyrighted, so we have provided a specification for samples that if met, should provide the same results as the original ROM samples. You can find this as part of the compatibility spec.

Initially, we have started with ROM samples for the 1MB wavetable that was implemented in the AWE32, but if necessary we will extend the ROM sample specification for larger wavetables.

New versioning system

In 4.00.4, we introduced a new versioning system. This system, borrowing many features from semantic versioning, makes it easy to identify:

• whether two spec versions are compatible with each other
• whether two spec versions have the same feature set
• whether or not a spec version has new features
• whether or not a spec version is a draft version

We've added an explanation of the new versioning system in section 0.1a of the format spec, and a clarification about the version of the compatibility spec.

About future plans

We've added section 1.5a, "Future Plans" to the format spec, to formalise the planned future of the format. Most importantly, the feature freeze for version 4.00 has been reached, and any more features will be considered for future versions starting from 4.01.

Program specification

Since 4.00.4, programs have been prohibited from using proprietary compression formats (such as sfArk, SFPack, SF2Pack and sfq). We made this decision based on the restrictive licensing of many (but not all) of the programs used to compress/decompress these formats, and incompatibility of these formats with major open source soundfont programs.

In SFe version 4.00, the only permitted compression format will be Werner SF3, which was created by Werner Schweer for MuseScore, and adopted widely. This format is also the reason why SFe specification versions start from 4:

• legacy SF is version 2
• Werner SF3 builds from legacy SF, and is version 3
• SFe builds from Werner SF3, and is version 4.

Compatibility specification

In the compatibility spec, we've added information on how to handle proprietary compression formats, and we fixed a mistake in the INFO chunk information.

What's coming up?

For 4.00.6, we plan on providing an SFe file repair specification for development of programs. This is to be released in late 2024 or early 2025. If you have any suggestions for other features that we could add, or additional information that we could include in future specs, then please open an issue and describe what you would like to see.