Is this possible to record the audio tracks only if video is also enabled with MediaRecorder?

I am working on a scenario where I will ask for the camera and mic permissions before joining the session. so I applied the following constraints in navigator.mediaDevices.getUserMedia

const constraints = {
    audio: true,
    video: {
        width: 1280, height: 720
    }
};

Everything works fine till here. But now I want to record the audio tracks only by using MediaRecorder. Other users can see the other peer’s video but in the current session, I just want to record the audio content only for all users.

I tried setting up the MimeType but it still records the video content as well. I think MimeType is just for setting up the mime type for each track.

Do I need to do something on the server side where the blob data is uploaded?