问题
I'm trying to use the web audio API to create an audio stream with the left and right channels generated with different oscillators. The output of the left channel is correct, but the right channel is 0. Based on the spec, I can't see what I'm doing wrong.
Tested in Chrome dev.
Code:
var context = new AudioContext();
var l_osc = context.createOscillator();
l_osc.type = "sine";
l_osc.frequency.value = 100;
var r_osc = context.createOscillator();
r_osc.type = "sawtooth";
r_osc.frequency.value = 100;
// Combine the left and right channels.
var merger = context.createChannelMerger(2);
merger.channelCountMode = "explicit";
merger.channelInterpretation = "discrete";
l_osc.connect(merger, 0, 0);
r_osc.connect(merger, 0, 1);
var dest_stream = context.createMediaStreamDestination();
merger.connect(dest_stream);
// Dump the generated waveform to a MediaStream output.
l_osc.start();
r_osc.start();
var track = dest_stream.stream.getAudioTracks()[0];
var plugin = document.getElementById('plugin');
plugin.postMessage(track);
回答1:
The channelInterpretation means the merger node will mix the stereo oscillator connections to two channels each - but then because you have an explicit channelCountMode, it's stacking the two-channels-per-connection to get four channels and (because it's explicit) just dropping the top two channels. Unfortunately the second two channels are the two channels from the second input - so it loses all channels from the second connection.
In general, you shouldn't need to mess with the channelCount interpretation stuff, and it will do the right thing for stereo.
来源：https://stackoverflow.com/questions/25375751/channelmergernode-in-web-audio-api-not-merging-channels