How to set maximum fragment size when using MediaRecoder() API?

I am trying to use MediaRecoder API to record video in format 'webm/h264'. It works well, until I wanna set the maximum group of picture(GOP) size cause I don't want many video formatted in a whole fragment. After reading some material I found there might be two solutions:

1. Making each blob produced by mediaRecorder.ondataavailable() a single fragment.

2. set maximum gop size. But I still don't know what to write in my code to realize these ways. Here is part of the code:

   var options = {mimeType: 'video/webm;codecs=h264'}
   recordedBlobs = [];
   mediaRecorder = new MediaRecorder(window.stream, options);
   mediaRecorder.onstop = handleStop;
   mediaRecorder.ondataavailable = handleDataAvailable;
   mediaRecorder.start(100);
   
   function handleDataAvailable(event) {
       if (event.data && event.data.size > 0) {
       recordedBlobs.push(event.data);
       }
   }
   
   

   Anyone help? Thanks!!