diff --git a/app/src/main/cpp/audio_player.cpp b/app/src/main/cpp/audio_player.cpp
index 74b67ff..71ec542 100644
--- a/app/src/main/cpp/audio_player.cpp
+++ b/app/src/main/cpp/audio_player.cpp
@@ -287,8 +287,6 @@ AUDIO_PLAYER_FUNC(void, play, jstring input_jstr, jstring filter_jstr) {
 
     auto *fft_filter = static_cast<filter_sys_t *>(malloc(sizeof(filter_sys_t)));
     init_visualizer(fft_filter);
-    uint8_t *data = nullptr;
-    int nb_samples = 0;
     auto *output = static_cast<int16_t *>(malloc(FFT_BUFFER_SIZE * sizeof(int16_t)));
 
     //read audio frame
@@ -313,12 +311,12 @@ AUDIO_PLAYER_FUNC(void, play, jstring input_jstr, jstring filter_jstr) {
         if (got_frame > 0) {
 
             if (frame->nb_samples > 256) {
-                nb_samples = frame->nb_samples;
-                data = static_cast<uint8_t *>(malloc(frame->nb_samples * sizeof(uint8_t)));
+                fft_filter->nb_samples = frame->nb_samples;
+                fft_filter->data = static_cast<uint8_t *>(malloc(frame->nb_samples * sizeof(uint8_t)));
             }
-            if (nb_samples == frame->nb_samples) {
-                memcpy(data, frame->data[0], static_cast<size_t>(frame->nb_samples));
-                fft_once(fft_filter, data, nb_samples, output);
+            if (fft_filter->nb_samples == frame->nb_samples) {
+                memcpy(fft_filter->data, frame->data[0], static_cast<size_t>(frame->nb_samples));
+                fft_once(fft_filter, output);
                 fft_callback(env, thiz, fft_method, output);
             }
 
diff --git a/app/src/main/cpp/visualizer/execute_fft.c b/app/src/main/cpp/visualizer/execute_fft.c
index 4672aae..7e5038b 100644
--- a/app/src/main/cpp/visualizer/execute_fft.c
+++ b/app/src/main/cpp/visualizer/execute_fft.c
@@ -203,14 +203,21 @@ int init_visualizer(filter_sys_t *p_sys)
 void release_visualizer(filter_sys_t *p_filter)
 {
     filter_sys_t *p_sys = p_filter;
-    free(p_sys->p_prev_s16_buff);
+    if (!p_sys) return;
+    if (p_sys->p_prev_s16_buff) {
+        free(p_sys->p_prev_s16_buff);
+    }
     free(&p_sys->wind_param);
+    if (p_sys->data) {
+        free(p_sys->data);
+    }
     free(p_sys);
 }
 
-void fft_once(void *p_data, uint8_t *p_buffer, int nb_samples, int16_t *output)
+void fft_once(void *p_data, int16_t *output)
 {
     filter_sys_t *p_sys = (filter_sys_t*)p_data;
+    int nb_samples = p_sys->nb_samples;
 
     fft_state *p_state = NULL; /* internal FFT data */
     DEFINE_WIND_CONTEXT(wind_ctx); /* internal window data */
@@ -219,7 +226,7 @@ void fft_once(void *p_data, uint8_t *p_buffer, int nb_samples, int16_t *output)
     float p_output[FFT_BUFFER_SIZE];           /* Raw FFT Result  */
     int16_t p_buffer1[FFT_BUFFER_SIZE];        /* Buffer on which we perform
                                                   the FFT (first channel) */
-    float *p_buffl = (float*)p_buffer;  /* Original buffer */
+    float *p_buffl = (float*)p_sys->data;  /* Original buffer */
 
     int16_t  *p_buffs;                         /* int16_t converted buffer */
     int16_t  *p_s16_buff;                      /* int16_t converted buffer */
diff --git a/app/src/main/cpp/visualizer/execute_fft.h b/app/src/main/cpp/visualizer/execute_fft.h
index 3cdf482..d30f670 100644
--- a/app/src/main/cpp/visualizer/execute_fft.h
+++ b/app/src/main/cpp/visualizer/execute_fft.h
@@ -35,6 +35,9 @@ typedef struct
 
     /* FFT window parameters */
     window_param wind_param;
+
+    uint8_t *data;
+    int nb_samples;
 } filter_sys_t;
 
 static void *fft_thread(void *);
@@ -45,7 +48,7 @@ block_t *filter_audio(filter_sys_t *p_sys, void *p_in_buf);
 
 void close_visualizer(filter_sys_t *p_filter);
 
-void fft_once(void *p_data, uint8_t *p_buffer, int nb_samples, int16_t *output);
+void fft_once(void *p_data, int16_t *output);
 
 int init_visualizer(filter_sys_t *p_sys);