diff --git a/src/classic/btstack_cvsd_plc.c b/src/classic/btstack_cvsd_plc.c
index f6764c232..180b5e2a2 100644
--- a/src/classic/btstack_cvsd_plc.c
+++ b/src/classic/btstack_cvsd_plc.c
@@ -113,14 +113,14 @@ static int PatternMatch(SAMPLE_FORMAT *y){
     return bestmatch;
 }
 
-static float AmplitudeMatch(SAMPLE_FORMAT *y, SAMPLE_FORMAT bestmatch) {
+static float AmplitudeMatch(btstack_cvsd_plc_state_t *plc_state, SAMPLE_FORMAT *y, SAMPLE_FORMAT bestmatch) {
     int   i;
     float sumx = 0;
     float sumy = 0.000001f;
     float sf;
     
-    for (i=0;i<CVSD_FS;i++){
-        sumx += absolute(y[CVSD_LHIST-CVSD_FS+i]);
+    for (i=0;i<plc_state->cvsd_fs;i++){
+        sumx += absolute(y[CVSD_LHIST-plc_state->cvsd_fs+i]);
         sumy += absolute(y[bestmatch+i]);
     }
     sf = sumx/sumy;
@@ -154,39 +154,39 @@ void btstack_cvsd_plc_bad_frame(btstack_cvsd_plc_state_t *plc_state, SAMPLE_FORM
         plc_state->bestlag += CVSD_M; 
         
         // Compute Scale Factor to Match Amplitude of Substitution Packet to that of Preceding Packet
-        sf = AmplitudeMatch(plc_state->hist, plc_state->bestlag);
+        sf = AmplitudeMatch(plc_state, plc_state->hist, plc_state->bestlag);
         for (i=0;i<CVSD_OLAL;i++){
             val = sf*plc_state->hist[plc_state->bestlag+i];
             plc_state->hist[CVSD_LHIST+i] = crop_sample(val);
         }
         
-        for (;i<CVSD_FS;i++){
+        for (;i<plc_state->cvsd_fs;i++){
             val = sf*plc_state->hist[plc_state->bestlag+i]; 
             plc_state->hist[CVSD_LHIST+i] = crop_sample(val);
         }
         
-        for (;i<CVSD_FS+CVSD_OLAL;i++){
+        for (;i<plc_state->cvsd_fs+CVSD_OLAL;i++){
             float left  = sf*plc_state->hist[plc_state->bestlag+i];
             float right = plc_state->hist[plc_state->bestlag+i];
-            val = left*rcos[i-CVSD_FS] + right*rcos[CVSD_OLAL-1-i+CVSD_FS];
+            val = left*rcos[i-plc_state->cvsd_fs] + right*rcos[CVSD_OLAL-1-i+plc_state->cvsd_fs];
             plc_state->hist[CVSD_LHIST+i] = crop_sample(val);
         }
 
-        for (;i<CVSD_FS+CVSD_RT+CVSD_OLAL;i++){
+        for (;i<plc_state->cvsd_fs+CVSD_RT+CVSD_OLAL;i++){
             plc_state->hist[CVSD_LHIST+i] = plc_state->hist[plc_state->bestlag+i];
         }
     } else {
-        for (;i<CVSD_FS+CVSD_RT+CVSD_OLAL;i++){
+        for (;i<plc_state->cvsd_fs+CVSD_RT+CVSD_OLAL;i++){
             plc_state->hist[CVSD_LHIST+i] = plc_state->hist[plc_state->bestlag+i];
         }
     }
-    for (i=0;i<CVSD_FS;i++){
+    for (i=0;i<plc_state->cvsd_fs;i++){
         out[i] = plc_state->hist[CVSD_LHIST+i];
     }
    
    // shift the history buffer 
    for (i=0;i<CVSD_LHIST+CVSD_RT+CVSD_OLAL;i++){
-        plc_state->hist[i] = plc_state->hist[i+CVSD_FS];
+        plc_state->hist[i] = plc_state->hist[i+plc_state->cvsd_fs];
     }
 }
 
@@ -206,16 +206,16 @@ void btstack_cvsd_plc_good_frame(btstack_cvsd_plc_state_t *plc_state, SAMPLE_FOR
         }
     }
 
-    for (;i<CVSD_FS;i++){
+    for (;i<plc_state->cvsd_fs;i++){
         out[i] = in[i];
     }
     // Copy the output to the history buffer
-    for (i=0;i<CVSD_FS;i++){
+    for (i=0;i<plc_state->cvsd_fs;i++){
         plc_state->hist[CVSD_LHIST+i] = out[i];
     }
     // shift the history buffer
     for (i=0;i<CVSD_LHIST;i++){
-        plc_state->hist[i] = plc_state->hist[i+CVSD_FS];
+        plc_state->hist[i] = plc_state->hist[i+plc_state->cvsd_fs];
     }
     plc_state->nbf=0;
 }
@@ -240,30 +240,38 @@ static int count_equal_samples(SAMPLE_FORMAT * packet, uint16_t size){
     return count;
 }
 
-// @assumption frame len 24 samples
-static int bad_frame(SAMPLE_FORMAT * frame, uint16_t size){
-    return count_equal_samples(frame, size) > 20;
+static int bad_frame(btstack_cvsd_plc_state_t *plc_state, SAMPLE_FORMAT * frame, uint16_t size){
+    return count_equal_samples(frame, size) > plc_state->cvsd_fs - 4;
 }
 
-void btstack_cvsd_plc_process_data(btstack_cvsd_plc_state_t * state, SAMPLE_FORMAT * in, uint16_t size, SAMPLE_FORMAT * out){
-    if (size != CVSD_FS){
-        log_error("btstack_cvsd_plc_process_data: audio frame size is incorrect. Expected %d, got %d", CVSD_FS, size);
-        return;
+void btstack_cvsd_plc_process_data(btstack_cvsd_plc_state_t * plc_state, SAMPLE_FORMAT * in, uint16_t size, SAMPLE_FORMAT * out){
+    if (plc_state->cvsd_fs == 0){
+        if (size > CVSD_FS_MAX){
+            log_error("btstack_cvsd_plc_process_data: audio frame size is too large.");
+            return;
+        }
+        plc_state->cvsd_fs = size;
+    } else {
+        if (plc_state->cvsd_fs != size){
+            log_error("btstack_cvsd_plc_process_data: audio frame size differs from initial.");
+            return;    
+        }
     }
-    state->frame_count++;
-    if (bad_frame(in,size)){
+
+    plc_state->frame_count++;
+    if (bad_frame(plc_state, in, size)){
         memcpy(out, in, size * 2);
-        if (state->good_frames_nr > CVSD_LHIST/CVSD_FS){
-            btstack_cvsd_plc_bad_frame(state, out);
-            state->bad_frames_nr++;
+        if (plc_state->good_frames_nr > CVSD_LHIST/plc_state->cvsd_fs){
+            btstack_cvsd_plc_bad_frame(plc_state, out);
+            plc_state->bad_frames_nr++;
         } else {
             memset(out, 0, size * 2);
         }
     } else {
-        btstack_cvsd_plc_good_frame(state, in, out);
-        state->good_frames_nr++;
-        if (state->good_frames_nr == 1){
-            log_info("First good frame at index %d\n", state->frame_count-1);
+        btstack_cvsd_plc_good_frame(plc_state, in, out);
+        plc_state->good_frames_nr++;
+        if (plc_state->good_frames_nr == 1){
+            log_info("First good frame at index %d\n", plc_state->frame_count-1);
         }        
     }
 }
diff --git a/src/classic/btstack_cvsd_plc.h b/src/classic/btstack_cvsd_plc.h
index fa8b8a26a..006aeef94 100644
--- a/src/classic/btstack_cvsd_plc.h
+++ b/src/classic/btstack_cvsd_plc.h
@@ -49,16 +49,16 @@
 extern "C" {
 #endif
 
-#define CVSD_FS 24           /* CVSD Frame Size */
+#define CVSD_FS_MAX 60       /* CVSD Frame Size */
 #define CVSD_N 128           /* 16ms - Window Length for pattern matching */ 
 #define CVSD_M 10            /* Template for matching */
-#define CVSD_LHIST (CVSD_N+CVSD_FS-1)  /* Length of history buffer required */ 
-#define CVSD_RT 5        /*  Reconvergence Time (samples) */
+#define CVSD_LHIST (CVSD_N+CVSD_FS_MAX-1)  /* Length of history buffer required */ 
+#define CVSD_RT 5            /*  Reconvergence Time (samples) */
 #define CVSD_OLAL 16         /* OverLap-Add Length (samples) */
 
 /* PLC State Information */
 typedef struct cvsd_plc_state {
-    int16_t hist[CVSD_LHIST+CVSD_FS+CVSD_RT+CVSD_OLAL];
+    int16_t hist[CVSD_LHIST+CVSD_FS_MAX+CVSD_RT+CVSD_OLAL];
     int16_t bestlag;
     int     nbf;
 
@@ -66,6 +66,7 @@ typedef struct cvsd_plc_state {
     int good_frames_nr;
     int bad_frames_nr;
     int frame_count;
+    uint16_t cvsd_fs;
 } btstack_cvsd_plc_state_t;
 
 // All int16 audio samples are in host endiness
diff --git a/test/hfp/cvsd_plc_test.c b/test/hfp/cvsd_plc_test.c
index d61c47f90..4ce14ba57 100644
--- a/test/hfp/cvsd_plc_test.c
+++ b/test/hfp/cvsd_plc_test.c
@@ -64,14 +64,14 @@ static int bad_frame(int16_t * frame, uint16_t size){
 
 static void btstack_cvsd_plc_mark_bad_frame(btstack_cvsd_plc_state_t * state, int16_t * in, uint16_t size, int16_t * out){
     if (size != 24){
-        printf("btstack_cvsd_plc_mark_bad_frame: audio frame size is incorrect. Expected %d, got %d\n", CVSD_FS, size);
+        printf("btstack_cvsd_plc_mark_bad_frame: audio frame size is incorrect. Expected %d, got %d\n", audio_samples_per_frame, size);
         return;
     }
     state->frame_count++;
     
     if (bad_frame(in,size)){
         memcpy(out, in, size * 2);
-        if (state->good_frames_nr > CVSD_LHIST/CVSD_FS){
+        if (state->good_frames_nr > CVSD_LHIST/audio_samples_per_frame){
             memset(out, 0x33, size * 2);
             state->bad_frames_nr++;
         }