unity3d 连接外置摄像头

using UnityEngine;
using System.Collections;

public class Test : MonoBehaviour {
    public string deviceName;
    WebCamTexture tex;
    // Use this for initialization
    IEnumerator Start （） {
        //获取授权
        yield return Application.RequestUserAuthorization（UserAuthorization.WebCam）;
        if （Application.HasUserAuthorization（UserAuthorization.We