Some (stereo?) audio files don't spatialize

if you are wearing headphones, sounds will spatialize, i.e. a sound to your right will sound louder in your right ear than your left. but this only works for some sounds.

this one spatializes: http://silverfish-freestuff.s3.amazonaws.com/TestStuff/SoundEntities/dtmf2.mp3

but these two don't: https://files.freemusicarchive.org/storage-freemusicarchive-org/music/no_curator/Scott_Holmes/Inspiring__Upbeat_Music/Scott_Holmes_-_04_-_Upbeat_Party.mp3 https://brainstormer.s3.us-west-2.amazonaws.com/Sounds/Balloon+Popping-SoundBible.com-1247261379.wav

this affects both sound entities and the old audio injectors:

{
  let sound = SoundCache.getSound(<sound URL>);
  let injector = Audio.playSound(sound, {
    position: MyAvatar.position,
    volume: 1.0,
    loop: true,
    pitch: 1.0
  });
}

this is probably related to this block of code in AudioClient.cpp:

                if (options.ambisonic) {
...
                    // spatialize into mixBuffer
                    injector->getLocalFOA().render(_localScratchBuffer, mixBuffer, HRTF_DATASET_INDEX,
                                                   qw, qx, qy, qz, gain, AudioConstants::NETWORK_FRAME_SAMPLES_PER_CHANNEL);
                } else if (options.stereo) {
...
                    // direct mix into mixBuffer
                    injector->getLocalHRTF().mixStereo(_localScratchBuffer, mixBuffer, gain,
                                                       AudioConstants::NETWORK_FRAME_SAMPLES_PER_CHANNEL);
                } else {  // injector is mono
...
                        // spatialize into mixBuffer
                        injector->getLocalHRTF().render(_localScratchBuffer, mixBuffer, HRTF_DATASET_INDEX,
                                                        azimuth, distance, gain, AudioConstants::NETWORK_FRAME_SAMPLES_PER_CHANNEL);
                    } else {
                        // direct mix into mixBuffer
                        injector->getLocalHRTF().mixMono(_localScratchBuffer, mixBuffer, gain,
                                                         AudioConstants::NETWORK_FRAME_SAMPLES_PER_CHANNEL);
                    }
                }

if the comments are to be believed, ambisonic and positional mono sounds spatialize, but stereo sounds only ever mix directly.

overte-org / overte

Some (stereo?) audio files don't spatialize #929