Re: [fluid-dev] File output with FluidSynth API

[Felix Krause]

On 11.02.2010, at 18:56, David Henningsson wrote:

> Felix Krause wrote:
>> Hi all,
>> 
>> I'm trying to save FluidSynth's audio output into a file using the API. My 
>> code basically does this:
>> 
>> - get settings object with new_fluid_settings
>> - set audio.driver to "file"
>> - set audio.file.* settings (tried different output types - raw, aiff, wav)
>> - create synth with new_fluid_synth
>> - create audio driver with new_fluid_audio_driver
>> - load a SoundFont
>> 
>> And for testing:
>> - do some sound output with fluid_synth_noteon / noteoff
>> - create a midi player with new_fluid_player, load and play a midi file with 
>> it
>> 
>> The file specified by audio.file.name is created, but FluidSynth does not 
>> write anything to it. Did I miss to do something in order to start writing 
>> the output to the file?
> 
> First, if you want output as fast as possible, and then I suggest you
> use the new filerenderer API (see fluidsynth.c's fast_render_loop
> function for inspiration).
> 
> Otherwise I think your version should work, assuming you wait a while
> between doing new_fluid_audio_driver and delete_fluid_audio_driver. At
> least you should have a file larger than 0 bytes.
> 
> // David
> 

I can't use fast file rendering as the output depends on user interaction. The 
file FluidSynth creates is always 4KB on disk (256 bytes) which I believe is 
just the header. I also checked fluid_synth_error for errors, there is none.

I tested using FluidSynth 1.0.9 with raw output and that works with my code - 
however, 1.1.1 does not. I also tested the FS command line utility:

fluidsynth -F output.wav -i -n -T wav soundfont.sf2 midifile.mid

This works as it should and renders the midi file to output.wav.

fluidsynth -a file -i -n -T wav -o audio.file.name=output.wav soundfont.sf2 
midifile.mid

This just creates a 4KB file. Is it possible that this is a FS bug?