diff --git a/app/src/main/AndroidManifest.xml b/app/src/main/AndroidManifest.xml
index 53a615a..13284ed 100644
--- a/app/src/main/AndroidManifest.xml
+++ b/app/src/main/AndroidManifest.xml
@@ -6,7 +6,6 @@
     <uses-permission android:name="android.permission.RECORD_AUDIO" />
     <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
 
-    <uses-feature android:name="android.hardware.camera.autofocus" />
     <uses-feature android:glEsVersion="0x00020000" android:required="true" />
 
     <application
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 490c1b8..f71e8c9 100644
--- a/app/src/main/java/net/ossrs/yasea/demo/MainActivity.java
+++ b/app/src/main/java/net/ossrs/yasea/demo/MainActivity.java
@@ -116,8 +116,9 @@ public class MainActivity extends AppCompatActivity implements RtmpHandler.RtmpL
             @Override
             public void onClick(View v) {
                 if (btnRecord.getText().toString().contentEquals("record")) {
-                    mPublisher.startRecord(recPath);
-                    btnRecord.setText("pause");
+                    if (mPublisher.startRecord(recPath)) {
+                        btnRecord.setText("pause");
+                    }
                 } else if (btnRecord.getText().toString().contentEquals("pause")) {
                     mPublisher.pauseRecord();
                     btnRecord.setText("resume");
diff --git a/library/src/main/java/net/ossrs/yasea/SrsMp4Muxer.java b/library/src/main/java/net/ossrs/yasea/SrsMp4Muxer.java
index d559aae..ca4675d 100644
--- a/library/src/main/java/net/ossrs/yasea/SrsMp4Muxer.java
+++ b/library/src/main/java/net/ossrs/yasea/SrsMp4Muxer.java
@@ -112,7 +112,11 @@ public class SrsMp4Muxer {
     /**
      * start recording.
      */
-    public void record(File outputFile) {
+    public boolean record(File outputFile) {
+        if (videoFormat == null && audioFormat == null) {
+            return false;
+        }
+
         mRecFile = outputFile;
         createMovie(mRecFile);
         mHandler.notifyRecordStarted(mRecFile.getPath());
@@ -145,6 +149,8 @@ public class SrsMp4Muxer {
             }
         });
         worker.start();
+
+        return true;
     }
 
     /**
@@ -680,10 +686,12 @@ public class SrsMp4Muxer {
         }
 
         public void addTrack(MediaFormat format, boolean isAudio) {
-            if (isAudio) {
-                tracks.put(AUDIO_TRACK, new Track(tracks.size(), format, true));
-            } else {
-                tracks.put(VIDEO_TRACK, new Track(tracks.size(), format, false));
+            if (format != null) {
+                if (isAudio) {
+                    tracks.put(AUDIO_TRACK, new Track(tracks.size(), format, true));
+                } else {
+                    tracks.put(VIDEO_TRACK, new Track(tracks.size(), format, false));
+                }
             }
         }
 
diff --git a/library/src/main/java/net/ossrs/yasea/SrsPublisher.java b/library/src/main/java/net/ossrs/yasea/SrsPublisher.java
index 6b68e94..9a14ceb 100644
--- a/library/src/main/java/net/ossrs/yasea/SrsPublisher.java
+++ b/library/src/main/java/net/ossrs/yasea/SrsPublisher.java
@@ -121,10 +121,8 @@ public class SrsPublisher {
         }
     }
 
-    public void startRecord(String recPath) {
-        if (mMp4Muxer != null) {
-            mMp4Muxer.record(new File(recPath));
-        }
+    public boolean startRecord(String recPath) {
+        return mMp4Muxer != null && mMp4Muxer.record(new File(recPath));
     }
 
     public void stopRecord() {
@@ -265,15 +263,6 @@ public class SrsPublisher {
         }
     }
 
-    public void switchMute() {
-        AudioManager audioManager = (AudioManager) mCameraView.getContext().getSystemService(Context.AUDIO_SERVICE);
-        int oldMode = audioManager.getMode();
-        audioManager.setMode(AudioManager.MODE_IN_COMMUNICATION);
-        boolean isMute = !audioManager.isMicrophoneMute();
-        audioManager.setMicrophoneMute(isMute);
-        audioManager.setMode(oldMode);
-    }
-
     public void setRtmpHandler(RtmpHandler handler) {
         mFlvMuxer = new SrsFlvMuxer(handler);
         if (mEncoder != null) {