[Flac-dev] Developing SoundFont FLAC compressor using libFLAC

[Josh Coalson]

--- Josh Green <jgreen at users.sourceforge.net> wrote:
> Its been a while since I was discussing a SoundFont compressor based
> on
> FLAC. I've recently implemented the compressor using an application
> metadata block with the ID 'SFFL' that I registered, which contains
> my
> own header and a block of zlib (gzip) compressed SoundFont info. The
> audio chunk (a block of consecutive 16 bit signed samples separated
> by
> 46 zero samples) is then encoded with FLAC. For the most part using
> libFLAC has been fairly straight forward. But I find the handling of
> metadata lacking in functionality, although I could be overlooking
> something. I admit I'm a bit lazy in not wanting to implement my own
> metadata processing routines, although I will do this if there is no
> other means. 
> 
> ...
>
> Anyways, what do you think of my proposal? Besides the metadata
> stuff,
> libFLAC has been really nice to work with, and theres nothing like
> getting a 128MB SoundFont down to 67MB :) 

Have you seen the API changes in 1.0.3?  Now all metadata is
parsed and at each decoder layer you can specify which blocks
get passed up to the metadata callback.  See the
*_decoder_set_metadata_respond/ignore functions.

Also, on the encoder size, you can now pass a list of arbitrary
metadata blocks to encode, instead of just padding and seektable.

> BTW any plans yet for allowing changing of audio parameters while
> encoding. I think this would give a significant increase in
> compression
> for some SoundFonts because the SoundFont sample chunk is multiple
> consecutive samples and stereo pairs can be determined from the
> SoundFont information. Cheers! 

It's on my TODO list but kind of far down :)  If you want to
have a crack at it and send me a patch that's fine also.  The
decoders should be OK, there's just some extra logic that
would have to be peppered around the stream encoder.

Josh


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