diff --git a/app/src/main/java/net/ossrs/yasea/demo/MainActivity.java b/app/src/main/java/net/ossrs/yasea/demo/MainActivity.java
index f71e8c9..7cae54e 100644
--- a/app/src/main/java/net/ossrs/yasea/demo/MainActivity.java
+++ b/app/src/main/java/net/ossrs/yasea/demo/MainActivity.java
@@ -106,9 +106,7 @@ public class MainActivity extends AppCompatActivity implements RtmpHandler.RtmpL
         btnSwitchCamera.setOnClickListener(new View.OnClickListener() {
             @Override
             public void onClick(View v) {
-                if (Camera.getNumberOfCameras() > 0) {
-                    mPublisher.switchCameraFace((mPublisher.getCamraId() + 1) % Camera.getNumberOfCameras());
-                }
+                mPublisher.switchCameraFace((mPublisher.getCamraId() + 1) % Camera.getNumberOfCameras());
             }
         });
 
diff --git a/library/src/main/java/net/ossrs/yasea/SrsEncoder.java b/library/src/main/java/net/ossrs/yasea/SrsEncoder.java
index 51797e7..93a1cb0 100644
--- a/library/src/main/java/net/ossrs/yasea/SrsEncoder.java
+++ b/library/src/main/java/net/ossrs/yasea/SrsEncoder.java
@@ -52,6 +52,7 @@ public class SrsEncoder {
     private boolean networkWeakTriggered = false;
     private boolean mCameraFaceFront = true;
     private boolean useSoftEncoder = false;
+    private boolean canSoftEncoder = false;
 
     private long mPresentTimeUs;
 
@@ -113,8 +114,11 @@ public class SrsEncoder {
         setEncoderBitrate(vBitrate);
         setEncoderPreset(x264Preset);
 
-        if (useSoftEncoder && !openSoftEncoder()) {
-            return false;
+        if (useSoftEncoder) {
+            canSoftEncode = openSoftEncoder();
+            if (!canSoftEncode) {
+                return false;
+            }
         }
 
         // aencoder pcm to aac raw stream.
@@ -170,6 +174,7 @@ public class SrsEncoder {
     public void stop() {
         if (useSoftEncoder) {
             closeSoftEncoder();
+            canSoftEncode = false;
         }
 
         if (aencoder != null) {
@@ -195,11 +200,11 @@ public class SrsEncoder {
         mCameraFaceFront = false;
     }
 
-    public void swithToSoftEncoder() {
+    public void switchToSoftEncoder() {
         useSoftEncoder = true;
     }
 
-    public void swithToHardEncoder() {
+    public void switchToHardEncoder() {
         useSoftEncoder = false;
     }
 
@@ -207,6 +212,18 @@ public class SrsEncoder {
         return useSoftEncoder;
     }
 
+    public boolean canHardEncode() {
+        return vencoder != null;
+    }
+
+    public boolean canSoftEncode() {
+        return canSoftEncode;
+    }
+
+    public boolean isEnabled() {
+        return canHardEncode() || canSoftEncode();
+    }
+
     public void setPreviewResolution(int width, int height) {
         vPrevWidth = width;
         vPrevHeight = height;
diff --git a/library/src/main/java/net/ossrs/yasea/SrsPublisher.java b/library/src/main/java/net/ossrs/yasea/SrsPublisher.java
index eef5bdc..32bbb59 100644
--- a/library/src/main/java/net/ossrs/yasea/SrsPublisher.java
+++ b/library/src/main/java/net/ossrs/yasea/SrsPublisher.java
@@ -144,12 +144,12 @@ public class SrsPublisher {
         }
     }
 
-    public void swithToSoftEncoder() {
-        mEncoder.swithToSoftEncoder();
+    public void switchToSoftEncoder() {
+        mEncoder.switchToSoftEncoder();
     }
 
-    public void swithToHardEncoder() {
-        mEncoder.swithToHardEncoder();
+    public void switchToHardEncoder() {
+        mEncoder.switchToHardEncoder();
     }
 
     public boolean isSoftEncoder() {
@@ -207,14 +207,16 @@ public class SrsPublisher {
     }
 
     public void switchCameraFace(int id) {
-        mCameraView.setCameraId(id);
-        mCameraView.stopCamera();
-        if (id == 0) {
-            mEncoder.setCameraBackFace();
-        } else {
-            mEncoder.setCameraFrontFace();
+        if (mEncoder.isEnabled()) {
+            mCameraView.stopCamera();
+            mCameraView.setCameraId(id);
+            if (id == 0) {
+                mEncoder.setCameraBackFace();
+            } else {
+                mEncoder.setCameraFrontFace();
+            }
+            mCameraView.startCamera();
         }
-        mCameraView.startCamera();
     }
 
     private void startAudio() {