Getting image data from webRTC stream

I am working on a webrtc screen sharing app. I have an extension that does the following:

desktopMediaRequestId = chrome.desktopCapture.chooseDesktopMedia(data_sources, tab, function(streamId) {
if (streamId) {
  msg.type = 'SUCESS';
  msg.streamId = streamId;
} else {
  msg.type = 'FAILURE';
}
port.postMessage(msg);}); 

      

        
        
        
      

    

I can use this thread id for screen sharing. But anyway, I can get image data with this stream id?