I can't forward & view the length of the file recorded in RecordRTC

Question

I can only backward/forward and view the length of the mp3 file recorded from RecordRTC when it's done playing, and also I can't even play the file in vlc. I only played it in chrome browser.

Here is my code:

        $.each($('#remoteVideos video'), function(index, val) {
             el[index] = val.srcObject;
        });
        el.push(stream);

        mediaRecorder = RecordRTC(el, {
            type: 'audio',
            mimeType: 'audio/webm',
            sampleRate: 96000,
            bufferSize: 4096
        });

        mediaRecorder.startRecording();