The default volume is too small.

[atsushieno]

Maybe the driver could initialize the audio output with louder value.

[atsushieno]

I tried the code below in new_fluid_opensles_audio_driver2(), and the result was the same. So it's already at the maximum level at OpenSLES...

// ok, things are slightly renamed here...
const SLInterfaceID ids[] = {SL_IID_ANDROIDSIMPLEBUFFERQUEUE, SL_IID_VOLUME};
const SLboolean req[] = {SL_BOOLEAN_TRUE, SL_BOOLEAN_TRUE};

<snip>

SLmillibel maxvol = SL_MILLIBEL_MIN;
SLVolumeItf volctl;
(_dev->audio_player)->GetInterface(dev->audio_player,
SL_IID_VOLUME, &volctl);
(_volctl)->GetMaxVolumeLevel(volctl, &maxvol);
(*volctl)->SetVolumeLevel(volctl, maxvol);

[wutaodev]

I have also encountered this problem, how can I solve it? How to turn up the volume？

[atsushieno]

As I described above, it is ALREADY at the maximum value. The only way to raise the volume is to manually change input raw wave data.

[wutaodev]

I tried playing AudioTrack and the volume was higher than Open SL ES

[atsushieno]

Comparing what to what? There is nothing that indicates OpenSLES itself being lower volume than AudioTrack itself.

[wutaodev]

I also find it strange, but the fact is the case.

[atsushieno]

Let me write simpler question: what kind of sound did you play on both? Are you saying that AudioTrack played the wave data from fluidsynth in louder volume? Is the comparison between equivalent audio data?