webCamTexture playing in high resolution lags

Hi all, I am using webCamTexture to grab the webcam data and show the images on a raw image with a Logitech C920 webcam. I set the resolution as: webcamTexture = new WebCamTexture("HD Pro Webcam C920", 1920, 1080, 30); However it lags and the fps is only around 10. What should I do to avoid lagging when having high-resolution images? I have tried the AVproCamera and choose the mjpg format instead of YUY2. The fps is around 30 which is acceptable. I wonder if there is a way to use mjpg format while using webCamTexture. Anyone can help? Thanks in advance!