Message 1: sf3 - lack of documentation

• Sep 9, 2015 - 22:17


As the developer of the software Polyphone, one user asked me to work on the sf3 support. We exchanged a couple of emails and I'm now convinced of its benefits. By dividing by 10 the size of a soundfont and keeping most of its quality, it makes it easy to embed in a lot of applications (video games, mobile applications, ...). The idea is not new in that the format sf2pack (please note the "2") already exists for example, but it is now an open-source format which is promoted by a well-driven software with a pretty big community. Thus, I added the sf3 import / export.

The background being stated, I have several remarks and interrogations (most of them being technical). This message is part of a series comprising other messages.

Message 1: sf3 - lack of documentation

(GitHub issue created here )

A developer could expect to find a technical documentation regarding the Sf3 format, with more details than just "sf3 is like sf2 but using OGG samples". I indeed found that:

  • the flag 0x10 has been added to the attribute sfSampleType, characterizing a sample,
  • loop start and end are stored based on the beginning of the corresponding sample and not on the beginning of the smpl chunk anymore,
  • moreover, we could expect that the 24-bit mode introduced in the 2.04 version of the sf2 format is not allowed.

Moreover a readme making it easy to build and use the sfTool library is missing. It could contain:

  • the list of dependencies (ogg, vorbis, Qt, ...),
  • the explanation of the variable "smallSf"?

A clear view of the format and what it proposes is essential for its spreading. Maybe a wiki dedicated to the sf3 should be created, with a page speaking of its specifications.


I suspect that you would be best to communicate with Werner directly on this, and the other aspects of SF3 you have commented on, as it is his code.

You can then find out directly what his plans are, if any, for further development.

My proposal would be to fork the code on github and push it forward yourself. If Werner is not answering, it's because he has no interest to further working on this.

In reply to by Thomas

When I have time I'll try to document and promote - as much as I can - this format. It can however change a bit to meet with other requirements (the sf3 format is not the first attempt to provide compressed soundfonts) and I hope Warner will be more open to a discussion if ever a part of a code must be slightly modified accordingly. I took time to write these reports and I expected at least a short answer coming from him.

If you do take a look at this, it would be great if it could be made to use the Opus format instead of Ogg Vorbis, since Opus is superior and it looks like it will become standard. I think rights issues prevented Werner from using Vorbis in the first place, but these have been ironed out now.

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