Web Audio API将单声道拆分为立体声

Question

Lets say I have a source node that's connected to the destination node. Even if the audio is mono, I want to be able to control each ear's volume independently, like I can do when I have stereo audio with splitter and merger node.

Already tried to use splitter and merger nodes on the mono source node, but right channel comes out empty.

example for stereo:

 var audioCtx = new AudioContext(); var source = audioCtx.createMediaElementSource(myAudio); var gainNodeL = audioCtx.createGain(); var gainNodeR = audioCtx.createGain(); var splitter = audioCtx.createChannelSplitter(2); var merger = audioCtx.createChannelMerger(2); source.connect(splitter); splitter.connect(gainNodeL, 0); splitter.connect(gainNodeR, 1); gainNodeL.connect(merger, 0, 0); gainNodeR.connect(merger, 0, 1); merger.connect(audioCtx.createMediaStreamDestination()); 

When I do this with mono audio, the right channel comes out empty.

Answer 1

If a signal is only mono (or in other words its channelCount is 1) the ChannelSplitterNode is not necessary. I modified the example a bit. It does now split the mono signal of an Oscillator.

var audioCtx = new AudioContext();
var oscillator = audioCtx.createOscillator();
var gainNodeL = audioCtx.createGain();
var gainNodeR = audioCtx.createGain();
var merger = audioCtx.createChannelMerger(2);

oscillator.connect(gainNodeL);
oscillator.connect(gainNodeR);

gainNodeL.connect(merger, 0, 0);
gainNodeR.connect(merger, 0, 1);

merger.connect(audioCtx.destination);

oscillator.start();

function left () {
    gainNodeL.gain.value = 1;
    gainNodeR.gain.value = 0;
}

function right () {
    gainNodeL.gain.value = 0;
    gainNodeR.gain.value = 1;
}

function center () {
    gainNodeL.gain.value = 1;
    gainNodeR.gain.value = 1;
}