I am attempting to use an AVAudioEnvironmentNode to produce 3D spatialized sound for a game I'm working on. The AVAudioEnvironmentNode documentation states, "It is important to note that only inputs with a mono channel connection format to the environment node are spatialized. If the input is stereo, the audio is passed through without being spatialized. Currently inputs with connection formats of more than 2 channels are not supported." I have indeed found this to be the case. When I load audio buffers with two channels into an AudioPlayerNode and connect the node to an AVAudioEnvironmentNode, the output sound is not spatialize. My question is, how can I send mono data to the AVAudioEnvironmentNode?
I've tried creating a mono .wav file using Audacity as well as loading an AVAudioPCMBuffer with sine wave data programmatically. I find that either way, when I create a single channel audio buffer and attempt to load the buffer into an AudioPlayerNode, my program crashes with the following error:
2016-02-17 06:36:07.695 Test Scene[1577:751557] 06:36:07.694 ERROR:
[0x1a1691000] AVAudioPlayerNode.mm:423: ScheduleBuffer: required condition is false: _outputFormat.channelCount == buffer.format.channelCount 2016-02-17 06:36:07.698 Test Scene[1577:751557] *** Terminating app due to uncaught exception 'com.apple.coreaudio.avfaudio', reason: 'required condition is false: _outputFormat.channelCount == buffer.format.channelCount'
Checking the AVAudioPlayerNode output bus does indeed reveal that it expects 2 channels. It's unclear to me how this can be changed, or even if it should be.
I stipulate that I have very little experience working with AVFoundation or audio data in general. Any help you can provide would be greatly appreciated.
I hope you have solved this already, but for anyone else:
When connecting your AVAudioPlayerNode to an AVAudioMixerNode or any other node that it can connect to, you need to specify the number of channels there:
audioEngine.connect(playerNode, to: audioEngine.mainMixerNode, format: AVAudioFormat.init(standardFormatWithSampleRate: 96000, channels: 1))
You can check if the sample rate is 96000 for your file in Audacity, or 'Get Info' in Finder.