diff --git a/src/platform/android/app/src/main/java/org/xproger/openlara/MainActivity.java b/src/platform/android/app/src/main/java/org/xproger/openlara/MainActivity.java
index 17d958a..7e9dba4 100644
--- a/src/platform/android/app/src/main/java/org/xproger/openlara/MainActivity.java
+++ b/src/platform/android/app/src/main/java/org/xproger/openlara/MainActivity.java
@@ -226,12 +226,14 @@ class Sound {
     void start(final Wrapper wrapper) {
         int rate = 44100;
         int size = AudioTrack.getMinBufferSize(rate, AudioFormat.CHANNEL_OUT_STEREO, AudioFormat.ENCODING_PCM_16BIT);
-        //System.out.println(String.format("sound buffer size: %d", bufSize));
-        buffer = new short[size / 2];
+        size /= 2; // bytes -> words
+        while (size % 4704 != 0) size++;
+        //System.out.println(String.format("sound buffer size: %d", size));
+        buffer = new short[size];
 
         try {
             audioTrack = new AudioTrack(AudioManager.STREAM_MUSIC, 44100, AudioFormat.CHANNEL_OUT_STEREO,
-                    AudioFormat.ENCODING_PCM_16BIT, size, AudioTrack.MODE_STREAM);
+                    AudioFormat.ENCODING_PCM_16BIT, size * 2, AudioTrack.MODE_STREAM);
         }catch (IllegalArgumentException e){
             System.out.println("Error: buffer size is zero");
             return;
diff --git a/src/utils.h b/src/utils.h
index 46c4958..3fe3de1 100644
--- a/src/utils.h
+++ b/src/utils.h
@@ -1391,8 +1391,12 @@ void osLoadGame(Stream *stream) {
 #ifdef OS_PTHREAD_MT
 // multi-threading
 void* osMutexInit() {
+    pthread_mutexattr_t attr;
+    pthread_mutexattr_init(&attr);
+    pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_RECURSIVE_NP);
+
     pthread_mutex_t *mutex = new pthread_mutex_t();
-    pthread_mutex_init(mutex, NULL);
+    pthread_mutex_init(mutex, &attr);
     return mutex;
 }
 
diff --git a/src/video.h b/src/video.h
index 9c4a925..c32a023 100644
--- a/src/video.h
+++ b/src/video.h
@@ -431,6 +431,8 @@ struct Video {
         }
 
         virtual bool decodeVideo(Color32 *pixels) {
+            OS_LOCK(Sound::lock);
+
             if (curVideoChunk >= chunksCount)
                 return false;
 
@@ -892,6 +894,8 @@ struct Video {
         }
 
         bool nextFrame() {
+            OS_LOCK(Sound::lock);
+
             uint8 data[SECTOR_SIZE];
 
             VideoFrame *vFrame = vFrames + vFrameIndex;
@@ -1154,7 +1158,8 @@ struct Video {
         isPlaying = true;
     }
 
-    ~Video() {
+    virtual ~Video() {
+        OS_LOCK(Sound::lock);
         sample->decoder = NULL;
         sample->stop();
         delete decoder;