Recording audio doesn't work

[miladmeidanshahi]

Hi, when i mix two audio streams and recording with MediaRecorder after stop recording no blob file generated.
but in video every thing is nice.

const audioMixer = new MultiStreamsMixer([microphone1, microphone2]);

// record using MediaRecorder API
const recorder = new MediaRecorder(audioMixer.getMixedStream());

Here is my question i have mixing just audio why CanvasCaptureMediaStreamTrack is video ?