diff --git a/app/src/main/java/com/jiangdg/usbcamera/view/USBCameraActivity.java b/app/src/main/java/com/jiangdg/usbcamera/view/USBCameraActivity.java
index eed9bdd..ec85d76 100644
--- a/app/src/main/java/com/jiangdg/usbcamera/view/USBCameraActivity.java
+++ b/app/src/main/java/com/jiangdg/usbcamera/view/USBCameraActivity.java
@@ -44,13 +44,13 @@ public class USBCameraActivity extends AppCompatActivity implements CameraDialog
     public Button mBtnCapture;
     @BindView(R.id.btn_rec_video)
     public Button mBtnRecord;
+    @BindView(R.id.btn_update_resolution)
+    public Button mBtnUpdateResultion;
 
     private USBCameraManager mUSBManager;
     private CameraViewInterface mUVCCameraView;
 
     private boolean isRequest;
-    private static String path = Environment.getExternalStorageDirectory().getAbsolutePath() + "/test1.h264";
-    private BufferedOutputStream outputStream;
 
     /**
      * USB设备事件监听器
@@ -85,8 +85,10 @@ public class USBCameraActivity extends AppCompatActivity implements CameraDialog
 
         // 连接USB设备成功
         @Override
-        public void onConnectDev(UsbDevice device) {
-
+        public void onConnectDev(UsbDevice device,boolean isConnected) {
+            if(! isConnected) {
+                showShortMsg("连接失败，请检查分辨率参数是否正确");
+            }
         }
 
         // 与USB设备断开连接
@@ -115,10 +117,6 @@ public class USBCameraActivity extends AppCompatActivity implements CameraDialog
         if(mUSBManager != null){
             mUSBManager.registerUSB();
         }
-        // 恢复Camera预览
-        if(mUVCCameraView != null){
-            mUVCCameraView.onResume();
-        }
     }
 
     @Override
@@ -128,16 +126,27 @@ public class USBCameraActivity extends AppCompatActivity implements CameraDialog
         if(mUSBManager != null){
             mUSBManager.unregisterUSB();
         }
-        // 暂停Camera预览
-        if(mUVCCameraView != null){
-            mUVCCameraView.onPause();
-        }
     }
 
-    @OnClick({R.id.camera_view, R.id.btn_capture_pic, R.id.btn_rec_video})
+    @OnClick({R.id.camera_view, R.id.btn_capture_pic, R.id.btn_rec_video,R.id.btn_update_resolution})
     public void onViewClick(View view) {
         int vId = view.getId();
         switch (vId) {
+            // 切换分辨率
+            case R.id.btn_update_resolution:
+                if(mUSBManager == null)
+                    return;
+                mUSBManager.updateResolution(this, mUVCCameraView, 320, 240, new USBCameraManager.OnPreviewListener() {
+                    @Override
+                    public void onPreviewResult(boolean isSuccess) {
+                        if(! isSuccess) {
+                            showShortMsg("预览失败，不支持该分辨率");
+                        }else {
+                            showShortMsg("以切换到分辨率为320x240");
+                        }
+                    }
+                });
+                break;
             // 开启或关闭Camera
             case R.id.camera_view:
 //                if(mUSBManager != null){
diff --git a/app/src/main/res/layout/activity_usbcamera.xml b/app/src/main/res/layout/activity_usbcamera.xml
index 1873184..b776f17 100644
--- a/app/src/main/res/layout/activity_usbcamera.xml
+++ b/app/src/main/res/layout/activity_usbcamera.xml
@@ -35,4 +35,14 @@
         android:textSize="16sp"
         android:text="开始录制"/>
 
+    <Button
+        android:layout_above="@id/btn_rec_video"
+        android:id="@+id/btn_update_resolution"
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:layout_marginRight="10dp"
+        android:layout_marginLeft="10dp"
+        android:textSize="16sp"
+        android:text="切换分辨率为320x240"/>
+
 </RelativeLayout>
\ No newline at end of file
diff --git a/libusbcamera/src/main/java/com/jiangdg/usbcamera/USBCameraManager.java b/libusbcamera/src/main/java/com/jiangdg/usbcamera/USBCameraManager.java
index d0e131d..d5c845a 100644
--- a/libusbcamera/src/main/java/com/jiangdg/usbcamera/USBCameraManager.java
+++ b/libusbcamera/src/main/java/com/jiangdg/usbcamera/USBCameraManager.java
@@ -17,8 +17,6 @@ import com.serenegiant.usb.widget.CameraViewInterface;
 import java.io.File;
 import java.util.List;
 
-import static android.R.attr.filter;
-
 /**USB摄像头工具类
  *
  * Created by jiangdongguo on 2017/9/30.
@@ -30,8 +28,8 @@ public class USBCameraManager{
     public static final String SUFFIX_PNG = ".png";
     public static final String SUFFIX_MP4 = ".mp4";
     private static final String TAG = "USBCameraManager";
-    private static final int PREVIEW_WIDTH = 640;
-    private static final int PREVIEW_HEIGHT = 480;
+    private int previewWidth = 640;
+    private int previewHeight = 480;
     // 使用MediaVideoBufferEncoder
     private static final int ENCODER_TYPE = 2;
     //0为YUYV，1为MJPEG
@@ -44,6 +42,7 @@ public class USBCameraManager{
     private UVCCameraHandler mCameraHandler;
 
     private Context mContext;
+    private USBMonitor.UsbControlBlock mCtrlBlock;
 
     private USBCameraManager(){}
 
@@ -57,10 +56,14 @@ public class USBCameraManager{
     public interface OnMyDevConnectListener{
         void onAttachDev(UsbDevice device);
         void onDettachDev(UsbDevice device);
-        void onConnectDev(UsbDevice device);
+        void onConnectDev(UsbDevice device,boolean isConnected);
         void onDisConnectDev(UsbDevice device);
     }
 
+    public interface OnPreviewListener{
+        void onPreviewResult(boolean isSuccess);
+    }
+
     /** 初始化
      *
      *  context  上下文
@@ -73,6 +76,7 @@ public class USBCameraManager{
         mContext = activity.getApplicationContext();
 
         mUSBMonitor = new USBMonitor(activity.getApplicationContext(), new USBMonitor.OnDeviceConnectListener() {
+
             // 当检测到USB设备，被回调
             @Override
             public void onAttach(UsbDevice device) {
@@ -91,14 +95,19 @@ public class USBCameraManager{
 
             // 当连接到USB Camera时，被回调
             @Override
-            public void onConnect(UsbDevice device, USBMonitor.UsbControlBlock ctrlBlock, boolean createNew) {
-                if(listener != null){
-                    listener.onConnectDev(device);
-                }
+            public void onConnect(final UsbDevice device, USBMonitor.UsbControlBlock ctrlBlock, boolean createNew) {
+                mCtrlBlock = ctrlBlock;
                 // 打开摄像头
                 openCamera(ctrlBlock);
                 // 开启预览
-                startPreview(cameraView);
+                startPreview(cameraView, new AbstractUVCCameraHandler.OnPreViewResultListener() {
+                    @Override
+                    public void onPreviewResult(boolean isConnected) {
+                        if(listener != null){
+                            listener.onConnectDev(device,isConnected);
+                        }
+                    }
+                });
             }
 
             // 当与USB Camera断开连接时，被回调
@@ -115,11 +124,37 @@ public class USBCameraManager{
             public void onCancel(UsbDevice device) {
             }
         });
+        cameraView.setAspectRatio(previewWidth / (float)previewHeight);
+        mCameraHandler = UVCCameraHandler.createHandler(activity,cameraView,ENCODER_TYPE,
+                previewWidth,previewHeight,PREVIEW_FORMAT);
+    }
 
-        // 设置长宽比
-        cameraView.setAspectRatio(PREVIEW_WIDTH / (float)PREVIEW_HEIGHT);
+    // 切换分辨率
+    public void updateResolution(Activity activity, CameraViewInterface cameraView, int width, int height, final OnPreviewListener mPreviewListener){
+        this.previewWidth = width;
+        this.previewHeight = height;
+
+        // 关闭摄像头
+        closeCamera();
+        // 释放CameraHandler占用的相关资源
+        if(mCameraHandler != null){
+            mCameraHandler.release();
+            mCameraHandler = null;
+        }
+        // 重新初始化mCameraHandler
+        cameraView.setAspectRatio(previewWidth / (float)previewHeight);
         mCameraHandler = UVCCameraHandler.createHandler(activity,cameraView,ENCODER_TYPE,
-                PREVIEW_WIDTH,PREVIEW_HEIGHT,PREVIEW_FORMAT);
+                previewWidth,previewHeight,PREVIEW_FORMAT);
+        openCamera(mCtrlBlock);
+        // 开始预览
+        startPreview(cameraView, new AbstractUVCCameraHandler.OnPreViewResultListener() {
+            @Override
+            public void onPreviewResult(boolean result) {
+                if(mPreviewListener != null){
+                    mPreviewListener.onPreviewResult(result);
+                }
+            }
+        });
     }
 
     /**
@@ -247,10 +282,10 @@ public class USBCameraManager{
         }
     }
 
-    public void startPreview(CameraViewInterface cameraView) {
+    public void startPreview(CameraViewInterface cameraView,AbstractUVCCameraHandler.OnPreViewResultListener mPreviewListener) {
         SurfaceTexture st = cameraView.getSurfaceTexture();
         if(mCameraHandler != null){
-            mCameraHandler.startPreview(st);
+            mCameraHandler.startPreview(st,mPreviewListener);
         }
     }
 }
diff --git a/libusbcamera/src/main/java/com/serenegiant/usb/common/AbstractUVCCameraHandler.java b/libusbcamera/src/main/java/com/serenegiant/usb/common/AbstractUVCCameraHandler.java
index 3edfe46..d9bacab 100644
--- a/libusbcamera/src/main/java/com/serenegiant/usb/common/AbstractUVCCameraHandler.java
+++ b/libusbcamera/src/main/java/com/serenegiant/usb/common/AbstractUVCCameraHandler.java
@@ -66,11 +66,16 @@ public  abstract class AbstractUVCCameraHandler extends Handler {
 	}
 
 	public static OnEncodeResultListener mListener;
+	public static OnPreViewResultListener mPreviewListener;
 
 	public interface OnEncodeResultListener{
 		void onEncodeResult(byte[] data, int offset, int length, long timestamp, int type);
 	}
 
+	public interface OnPreViewResultListener{
+		void onPreviewResult(boolean result);
+	}
+
 	private static final int MSG_OPEN = 0;
 	private static final int MSG_CLOSE = 1;
 	private static final int MSG_PREVIEW_START = 2;
@@ -163,11 +168,13 @@ public  abstract class AbstractUVCCameraHandler extends Handler {
 	}
 
 	// 开启Camera预览
-	protected void startPreview(final Object surface) {
+	protected void startPreview(final Object surface,OnPreViewResultListener listener) {
 		checkReleased();
 		if (!((surface instanceof SurfaceHolder) || (surface instanceof Surface) || (surface instanceof SurfaceTexture))) {
 			throw new IllegalArgumentException("surface should be one of SurfaceHolder, Surface or SurfaceTexture");
 		}
+
+		this.mPreviewListener = listener;
 		sendMessage(obtainMessage(MSG_PREVIEW_START, surface));
 	}
 
@@ -210,7 +217,6 @@ public  abstract class AbstractUVCCameraHandler extends Handler {
 	public void startRecording(final RecordParams params, OnEncodeResultListener listener) {
 		AbstractUVCCameraHandler.mListener = listener;
 		checkReleased();
-//		sendEmptyMessage(MSG_CAPTURE_START);
 		sendMessage(obtainMessage(MSG_CAPTURE_START, params));
 	}
 
@@ -503,14 +509,21 @@ public  abstract class AbstractUVCCameraHandler extends Handler {
 			if ((mUVCCamera == null) || mIsPreviewing) return;
 			try {
 				mUVCCamera.setPreviewSize(mWidth, mHeight, 1, 31, mPreviewMode, mBandwidthFactor);
+				if(mPreviewListener != null){
+					mPreviewListener.onPreviewResult(true);
+				}
 			} catch (final IllegalArgumentException e) {
-				try {
-					// fallback to YUV mode
-					mUVCCamera.setPreviewSize(mWidth, mHeight, 1, 31, UVCCamera.DEFAULT_PREVIEW_MODE, mBandwidthFactor);
-				} catch (final IllegalArgumentException e1) {
-					callOnError(e1);
-					return;
+				// 添加分辨率参数合法性检测
+				if(mPreviewListener != null){
+					mPreviewListener.onPreviewResult(false);
 				}
+//				try {
+//					// fallback to YUV mode
+//					mUVCCamera.setPreviewSize(mWidth, mHeight, 1, 31, UVCCamera.DEFAULT_PREVIEW_MODE, mBandwidthFactor);
+//				} catch (final IllegalArgumentException e1) {
+//					callOnError(e1);
+//					return;
+//				}
 			}
 			if (surface instanceof SurfaceHolder) {
 				mUVCCamera.setPreviewDisplay((SurfaceHolder)surface);
@@ -659,7 +672,7 @@ public  abstract class AbstractUVCCameraHandler extends Handler {
 		}
 
 		private void startVideoRecord() {
-			mH264Consumer = new H264EncodeConsumer();
+			mH264Consumer = new H264EncodeConsumer(getWidth(),getHeight());
 			mH264Consumer.setOnH264EncodeResultListener(new H264EncodeConsumer.OnH264EncodeResultListener() {
 				@Override
 				public void onEncodeResult(byte[] data, int offset, int length, long timestamp) {
diff --git a/libusbcamera/src/main/java/com/serenegiant/usb/common/UVCCameraHandler.java b/libusbcamera/src/main/java/com/serenegiant/usb/common/UVCCameraHandler.java
index d605880..7617b60 100644
--- a/libusbcamera/src/main/java/com/serenegiant/usb/common/UVCCameraHandler.java
+++ b/libusbcamera/src/main/java/com/serenegiant/usb/common/UVCCameraHandler.java
@@ -119,8 +119,8 @@ public class UVCCameraHandler extends AbstractUVCCameraHandler {
 	}
 
 	@Override
-	public void startPreview(final Object surface) {
-		super.startPreview(surface);
+	public void startPreview(final Object surface,final AbstractUVCCameraHandler.OnPreViewResultListener listener) {
+		super.startPreview(surface, listener);
 	}
 
 	@Override
diff --git a/libusbcamera/src/main/java/com/serenegiant/usb/common/UVCCameraHandlerMultiSurface.java b/libusbcamera/src/main/java/com/serenegiant/usb/common/UVCCameraHandlerMultiSurface.java
index b0e214a..53f7b63 100644
--- a/libusbcamera/src/main/java/com/serenegiant/usb/common/UVCCameraHandlerMultiSurface.java
+++ b/libusbcamera/src/main/java/com/serenegiant/usb/common/UVCCameraHandlerMultiSurface.java
@@ -136,10 +136,10 @@ public class UVCCameraHandlerMultiSurface extends AbstractUVCCameraHandler {
 		}
 	}
 
-	public synchronized void startPreview() {
+	public synchronized void startPreview(OnPreViewResultListener listener) {
 		checkReleased();
 		if (mRendererHolder != null) {
-			super.startPreview(mRendererHolder.getSurface());
+			super.startPreview(mRendererHolder.getSurface(),listener);
 		} else {
 			throw new IllegalStateException();
 		}
diff --git a/libusbcamera/src/main/java/com/serenegiant/usb/encoder/biz/H264EncodeConsumer.java b/libusbcamera/src/main/java/com/serenegiant/usb/encoder/biz/H264EncodeConsumer.java
index c649642..df089a1 100644
--- a/libusbcamera/src/main/java/com/serenegiant/usb/encoder/biz/H264EncodeConsumer.java
+++ b/libusbcamera/src/main/java/com/serenegiant/usb/encoder/biz/H264EncodeConsumer.java
@@ -60,6 +60,15 @@ public class H264EncodeConsumer extends Thread {
         this.listener = listener;
     }
 
+    public H264EncodeConsumer(){
+
+    }
+
+    public H264EncodeConsumer(int width,int height){
+        this.mWidth = width;
+        this.mHeight = height;
+    }
+
     public synchronized void setTmpuMuxer(Mp4MediaMuxer mMuxer){
         this.mMuxerRef =  new WeakReference<>(mMuxer);
         Mp4MediaMuxer muxer = mMuxerRef.get();
@@ -77,8 +86,11 @@ public class H264EncodeConsumer extends Thread {
         // 根据编码器支持转换颜色空间格式
         // 即 nv21 ---> YUV420sp(21)
         //    nv21 ---> YUV420p (19)
-        mWidth = width;
-        mHeight = height;
+        if(mWidth != width || mHeight != height){
+            mWidth = width;
+            mHeight = height;
+            return;
+        }
         try {
             if (lastPush == 0) {
                 lastPush = System.currentTimeMillis();
@@ -240,7 +252,7 @@ public class H264EncodeConsumer extends Thread {
             return;
         }
 
-        final MediaFormat format = MediaFormat.createVideoFormat(MIME_TYPE, 640, 480);
+        final MediaFormat format = MediaFormat.createVideoFormat(MIME_TYPE, mWidth, mHeight);
         format.setInteger(MediaFormat.KEY_COLOR_FORMAT, mColorFormat);
         format.setInteger(MediaFormat.KEY_BIT_RATE, calcBitRate());
         format.setInteger(MediaFormat.KEY_FRAME_RATE, 15);
@@ -283,7 +295,7 @@ public class H264EncodeConsumer extends Thread {
     private static final int FRAME_RATE = 15;
     private static final float BPP = 0.50f;
     private int calcBitRate() {
-        final int bitrate = (int)(BPP * FRAME_RATE * 640 * 480);
+        final int bitrate = (int)(BPP * FRAME_RATE * mWidth * mHeight);
         Log.i(TAG, String.format("bitrate=%5.2f[Mbps]", bitrate / 1024f / 1024f));
         return bitrate;
     }