[WebCamTexture] Require high resolution (1280*720) yields Green Screen

I want to use WebCamTexture to show the preview window of camera in Android Device (which has only one camera). If I use the default resolution (640*480), everything work fine.

However, If I change the resolution to 1280*720, I get the weird green-screen image (as shown in the attached file). It seems that the image from camera had been transferred to grayscale, assigned only to green value, and divided into 4-parts...

Here is my code:

     public class UnityWebCamAPI : MonoBehaviour
     {
         [SerializeField] private GUITexture displayedGUITexture;
     
         private WebCamTexture photoCamera;
     
         private void Awake()
         {
             // Initialize Camera Devices.
             this.photoCamera = new WebCamTexture(1280, 720);
             this.photoCamera.Play();
         }
         private void Start()
         {
             this.displayedGUITexture.texture = this.photoCamera;
         }

I'm using Unity 4.6.1f1. I'm sure the camera can support the 1280*720 (which has been proven by another APP written by Android API). Any ideas?

Thanks,

Joshua P. R. Pan

[1]: /storage/temp/53170-screenshot-2000-07-27-21-34-47.png