diff --git a/lib_com/options.h b/lib_com/options.h
old mode 100755
new mode 100644
index b3d3c5a736b0144462dae95dbccf7406982bca02..ec3e206c4f96369945787ba892295bc82f8944ec
--- a/lib_com/options.h
+++ b/lib_com/options.h
@@ -154,6 +154,11 @@
 
 #define FIX_I87                                         /*  fix for issue 86: incorrect Ambisonics order set for head rotation in SBA */
 #define SBA_ORDER_BITSTREAM                             /* issue 76: Use input sba order for bitstream coding */
+
+/* NTT switches */
+#define NTT_UPDATE_ITD_SW                               /* contribution 4: Update of ITD switch in stereo downmix for EVS */
+#define NTT_REMOVE_EPS_ROM                              /* contribution 4: Reduction of ROM size in stereo downmix for EVS */
+
 /* ################## End DEVELOPMENT switches ######################### */
 /* clang-format on */
 #endif
diff --git a/lib_enc/ivas_rom_enc.c b/lib_enc/ivas_rom_enc.c
index 783085fb86e1909107cdd3a6719fe8407b813db9..e8048b8f1a9b9f1cce4f04272e36bb9aef8c411a 100644
--- a/lib_enc/ivas_rom_enc.c
+++ b/lib_enc/ivas_rom_enc.c
@@ -534,6 +534,7 @@ const float ari_bit_estimate_s17_LC[RANGE_N_CONTEXT][RANGE_N_SYMBOLS] =
  * Stereo downmix to EVS ROM tables
  *----------------------------------------------------------------------------------*/
 
+#ifndef NTT_REMOVE_EPS_ROM
 const float Stereo_dmx_s_wnd_coef_eps_16k[L_FRAME16k * 3 / 4] = {
     0.00000000f, 0.000385506690f, 0.000770864717f, 0.00115592557f, 0.00154054083f, 0.00192456215f, 0.00230784155f, 0.00269023119f, 0.00307158381f, 0.00345175178f,
     0.00383058959f, 0.00420795102f, 0.00458368938f, 0.00495766103f, 0.00532972161f, 0.00569972629f, 0.00606753491f, 0.00643300405f, 0.00679599261f, 0.00715636183f,
@@ -686,6 +687,7 @@ const float Stereo_dmx_s_wnd_coef_eps_48k[L_FRAME48k * 3 / 4] = {
     -0.00648899190f, -0.00649444433f, -0.00649961829f, -0.00650451379f, -0.00650913082f, -0.00651346892f, -0.00651752809f, -0.00652130833f, -0.00652480870f, -0.00652803015f,
     -0.00653097173f, -0.00653363345f, -0.00653601484f, -0.00653811684f, -0.00653993897f, -0.00654148031f, -0.00654274225f, -0.00654372340f, -0.00654442422f, -0.00654484471f
 };
+#endif
 
 const float Stereo_dmx_s_wnd_coef_16k[L_FRAME16k >> 4] = {
     0.00154133327f, 0.0138150426f, 0.0380602330f, 0.0736799166f, 0.119797014f, 0.175276011f, 0.238750681f, 0.308658302f, 0.383277327f, 0.460770488f,
diff --git a/lib_enc/ivas_rom_enc.h b/lib_enc/ivas_rom_enc.h
index 71942642253d85741b0dc9949c7b640114837aef..2a4f71b8b95603d94147dd42c0c02ede10b27fbb 100644
--- a/lib_enc/ivas_rom_enc.h
+++ b/lib_enc/ivas_rom_enc.h
@@ -120,9 +120,11 @@ extern const uint16_t ECSQ_tab_vals[ECSQ_PARAM_COUNT - 1][1 + ECSQ_TAB_VALS_SIZE
  * Stereo downmix to EVS ROM tables
  *----------------------------------------------------------------------------------*/
 
+#ifndef NTT_REMOVE_EPS_ROM
 extern const float Stereo_dmx_s_wnd_coef_eps_16k[L_FRAME16k * 3 / 4];
 extern const float Stereo_dmx_s_wnd_coef_eps_32k[L_FRAME32k * 3 / 4];
 extern const float Stereo_dmx_s_wnd_coef_eps_48k[L_FRAME48k * 3 / 4];
+#endif
 extern const float Stereo_dmx_s_wnd_coef_16k[L_FRAME16k >> 4];
 extern const float Stereo_dmx_s_wnd_coef_32k[L_FRAME32k >> 4];
 extern const float Stereo_dmx_s_wnd_coef_48k[L_FRAME48k >> 4];
diff --git a/lib_enc/ivas_stereo_dmx_evs.c b/lib_enc/ivas_stereo_dmx_evs.c
index af3430766a0085ccd4fb4117811db5a8658b14a0..3daa28aa96d40312a93ceb7b06f9054ad0127bfb 100644
--- a/lib_enc/ivas_stereo_dmx_evs.c
+++ b/lib_enc/ivas_stereo_dmx_evs.c
@@ -63,6 +63,8 @@
 #define STEREO_DMX_EVS_DMX_EGY_FORGETTING 0.25f
 #define STEREO_DMX_EVS_CORR_FORGETTING    0.78f
 
+#define Q_BAND 0.25f
+
 /*-----------------------------------------------------------------------*
  * Local function prototypes
  *-----------------------------------------------------------------------*/
@@ -150,26 +152,34 @@ static void calc_poc(
 {
     int16_t i, n1, n2;
     int16_t n0, *itdLR;
-    const float *c, *s;
+#ifndef NTT_REMOVE_EPS_ROM
+	const float *c;
+#endif
+	const float *s;
     float *P;
     float tmp1, tmp2, Lr, Li, Rr, Ri, gamma, igamma, iN;
     float specPOr[L_FRAME48k], specPOi[L_FRAME48k];
     float tmpPOC1[L_FRAME48k], tmpPOC2[L_FRAME48k];
     float rfft_buf[L_FRAME48k];
     int16_t step, bias;
+#ifdef NTT_REMOVE_EPS_ROM
+    int16_t i_for;
+    int16_t cos_step, cos_max;
+    float eps_cos, eps_sin, EPS;
+#endif
 
     /* Initialization */
     iN = 1.0f / (float) input_frame;
 
+#ifndef NTT_REMOVE_EPS_ROM
     c = hPOC->sin + ( input_frame >> 2 );
+#endif
     s = hPOC->sin;
     P = hPOC->P;
     n0 = input_frame / 2;
     itdLR = hPOC->itdLR;
     igamma = STEREO_DMX_EVS_POC_GAMMA * iN;
     gamma = 1.0f - igamma;
-    set_zero( tmpPOC1, L_FRAME48k );
-    set_zero( tmpPOC2, L_FRAME48k );
 
     if ( input_frame == L_FRAME16k )
     {
@@ -185,6 +195,65 @@ static void calc_poc(
     specPOr[0] = sign( specLr[0] ) * sign( specRr[0] ) * wnd[bias];
     specPOi[0] = 0.0f;
 
+#ifdef NTT_REMOVE_EPS_ROM
+    EPS = hPOC->eps;
+
+    if ( input_frame == L_FRAME16k )
+    {
+        cos_step = 4;
+        cos_max = input_frame;
+    }
+    else /* for 32 kHz & 48 kHz */
+    {
+        cos_step = 2;
+        cos_max = n0;
+    }
+
+    for ( i = 1; i < n0 / 2; i++ )
+    {
+        Lr = specLr[i];
+        Li = specLi[i];
+        Rr = specRr[i];
+        Ri = specRi[i];
+        i_for = i * cos_step;
+        eps_cos = s[cos_max - i_for] * EPS;
+        eps_sin = s[i_for] * EPS;
+        Lr += ( specRr[i] * eps_cos + specRi[i] * eps_sin );
+        Li += ( -specRr[i] * eps_sin + specRi[i] * eps_cos );
+        Rr += ( specLr[i] * eps_cos + specLi[i] * eps_sin );
+        Ri += ( -specLr[i] * eps_sin + specLi[i] * eps_cos );
+        tmp1 = wnd[i * step + bias] * gamma / ( sqrtf( ( ( Lr * Lr + Li * Li ) ) * ( ( Rr * Rr + Ri * Ri ) ) ) + EPS );
+
+        specPOr[i] = ( Lr * Rr + Li * Ri ) * tmp1;
+        specPOi[i] = ( Lr * Ri - Li * Rr ) * tmp1;
+
+        gamma -= igamma;
+    }
+
+    for ( i = n0 >> 1; i < n0; i++ )
+    {
+        Lr = specLr[i];
+        Li = specLi[i];
+        Rr = specRr[i];
+        Ri = specRi[i];
+
+        i_for = ( n0 - i ) * cos_step;
+        eps_cos = s[cos_max - i_for] * EPS;
+        eps_sin = s[i_for] * EPS;
+
+        Lr += ( -specRr[i] * eps_cos + specRi[i] * eps_sin );
+        Li += ( -specRr[i] * eps_sin - specRi[i] * eps_cos );
+        Rr += ( -specLr[i] * eps_cos + specLi[i] * eps_sin );
+        Ri += ( -specLr[i] * eps_sin - specLi[i] * eps_cos );
+
+        tmp1 = wnd[i * step + bias] * gamma / ( sqrtf( ( ( Lr * Lr + Li * Li ) ) * ( ( Rr * Rr + Ri * Ri ) ) ) + EPS );
+
+        specPOr[i] = ( Lr * Rr + Li * Ri ) * tmp1;
+        specPOi[i] = ( Lr * Ri - Li * Rr ) * tmp1;
+        gamma -= igamma;
+    }
+    //end NTT_REMOVE_EPS_ROM
+#else
     for ( i = 1; i < n0; i++ )
     {
         Lr = specLr[i];
@@ -204,6 +273,8 @@ static void calc_poc(
 
         gamma -= igamma;
     }
+#endif //end !NTT_REMOVE_EPS_ROM
+
     specPOr[n0] = sign( specLr[i] ) * sign( specRr[i] ) * wnd[i * step + bias] * gamma;
 
     rfft_buf[0] = specPOr[0];
@@ -305,7 +376,7 @@ static float find_poc_peak(
     itd_cand[0] = itd_cand[1] = 0;
     P = hPOC->P;
 
-    for ( i = 1; i < hPOC->shift_limit; i++ )
+    for ( i = 1; i < hPOC->shift_limit; i++ ) /*find peaks of POC P[] with positive and negative ITD */
     {
         if ( P[Lh - i] > Q[0] )
         {
@@ -327,7 +398,7 @@ static float find_poc_peak(
         cnt[n] = 0;
         cQ[n] = P[Lh - itd_cand[n]];
 
-        peak_range = (int16_t) ( abs( itd_cand[n] ) + hPOC->shift_limit / STEREO_DMX_EVS_FIND_POC_PEAK_TAU ) / STEREO_DMX_EVS_FIND_POC_PEAK_TAU2;
+        peak_range = ( int16_t )( abs( itd_cand[n] ) + hPOC->shift_limit / STEREO_DMX_EVS_FIND_POC_PEAK_TAU ) / STEREO_DMX_EVS_FIND_POC_PEAK_TAU2;
 
         for ( i = 1; i <= peak_range; i++ )
         {
@@ -340,7 +411,7 @@ static float find_poc_peak(
         Q[n] = ( 1.0f - ( cQ[n] / ( peak_range * 2 + 1 ) + eps2 ) / ( Q[n] + eps2 ) );
         Q[n] = max( Q[n], 0.0f );
 
-        if ( on[n] )
+        if ( on[n] ) /*if channel n was active (likely to be preceding) in the previous frame*/
         {
             tmpf = ( 0.3f - 0.2f * (float) abs( itd_cand[n] ) / (float) hPOC->shift_limit ) * peakQ[n];
             if ( Q[n] < tmpf )
@@ -357,7 +428,7 @@ static float find_poc_peak(
 
             peakQ[n] = max( peakQ[n], Q[n] );
         }
-        else
+        else /*if channel n was not active (not likely to be preceding) in the previous frame*/
         {
             tmpf = ( 0.75f - 0.2f * (float) abs( itd_cand[n] ) / (float) hPOC->shift_limit );
 
@@ -374,6 +445,7 @@ static float find_poc_peak(
         }
     }
 
+#ifndef NTT_UPDATE_ITD_SW
     if ( on[0] && prev_off[0] )
     {
         *itd = (float) itdLR[0];
@@ -386,8 +458,38 @@ static float find_poc_peak(
     {
         *itd = ( *itd > 0 ) ? (float) itdLR[0] : (float) itdLR[1];
     }
+#else
+    if ( ( on[0] && prev_off[0] ) && ( on[1] && prev_off[1] ) ) /*if both channels have newly detected as active (possibility of preceding), select channel by peakness Q[] of POC */
+    {
+        *itd = ( Q[0] > Q[1] ) ? (float) itdLR[0] : (float) itdLR[1];
+    }
+    else if ( ( on[0] && prev_off[0] ) && ( Q[0] > ( Q[1] - 0.1 ) ) ) /* if channel 0 becomes active, select channel 0*/
+    {
+        *itd = (float) itdLR[0];
+    }
+    else if ( ( on[1] && prev_off[1] ) && ( Q[1] > ( Q[0] - 0.1 ) ) ) /*if channel 1 becomes active, selsect channel 1*/
+    {
+        *itd = (float) itdLR[1];
+    }
+    else if ( Q[0] > ( Q[1] + Q_BAND ) ) /* if no status change, use Q[]*/
+    {
+        *itd = (float) itdLR[0];
+    }
+    else if ( Q[1] > ( Q[0] + Q_BAND ) ) /* if no status change, use Q[]*/
+    {
+        *itd = (float) itdLR[1];
+    }
+    else if ( *itd == 0.0 ) /*if no channels are likely to be preceding, follow the status of the previous frame*/
+    {
+        *itd = 0;
+    }
+    else /*follow the status of the previous frame*/
+    {
+        *itd = ( *itd > 0 ) ? (float) itdLR[0] : (float) itdLR[1];
+    }
+#endif
 
-    cconfidence = sqrtf( fabsf( Q[0] - Q[1] ) );
+    cconfidence = sqrtf( fabsf( Q[0] - Q[1] ) ); /*higher value indicates higher confidence for one preceding channel*/
 
     return hPOC->confidence = hPOC->confidence * STEREO_DMX_EVS_CORR_FORGETTING + cconfidence * ( 1.0f - STEREO_DMX_EVS_CORR_FORGETTING );
 }
@@ -649,7 +751,7 @@ void stereo_dmx_evs_enc(
     float dmx_data[L_FRAME48k];
     int16_t input_frame;
 
-    input_frame = (int16_t) ( input_Fs / FRAMES_PER_SEC );
+    input_frame = ( int16_t )( input_Fs / FRAMES_PER_SEC );
 
     for ( n = 0; n < input_frame; n++ )
     {
@@ -696,7 +798,7 @@ ivas_error stereo_dmx_evs_init_encoder(
     STEREO_DMX_EVS_ENC_HANDLE hStereoDmxEVS;
     int16_t n, input_frame;
 
-    input_frame = (int16_t) ( input_Fs / FRAMES_PER_SEC );
+    input_frame = ( int16_t )( input_Fs / FRAMES_PER_SEC );
 
     hStereoDmxEVS = NULL;
     if ( ( hStereoDmxEVS = (STEREO_DMX_EVS_ENC_HANDLE) count_malloc( sizeof( STEREO_DMX_EVS_ENC_DATA ) ) ) == NULL )
@@ -738,7 +840,7 @@ ivas_error stereo_dmx_evs_init_encoder(
         return ( IVAS_ERROR( IVAS_ERR_FAILED_ALLOC, "Can not allocate memory for STEREO_DMX_EVS_POC_DATA\n" ) );
     }
 
-    hStereoDmxEVS->hPOC->shift_limit = (int16_t) ( STEREO_DMX_EVS_SHIFT_LIMIT * input_Fs / 1000 );
+    hStereoDmxEVS->hPOC->shift_limit = ( int16_t )( STEREO_DMX_EVS_SHIFT_LIMIT * input_Fs / 1000 );
     for ( n = 0; n < CPE_CHANNELS; n++ )
     {
         hStereoDmxEVS->hPOC->peakQ[n] = 0.0f;
@@ -766,6 +868,24 @@ ivas_error stereo_dmx_evs_init_encoder(
     }
     hStereoDmxEVS->hPOC->eps = 2.0f * EVS_PI / ( (float) input_frame );
 
+#ifdef NTT_REMOVE_EPS_ROM
+    if ( input_frame == L_FRAME16k )
+    {
+        hStereoDmxEVS->hPOC->sin = dft_trigo_32k;
+    }
+    else if ( input_frame == L_FRAME32k )
+    {
+        hStereoDmxEVS->hPOC->sin = dft_trigo_32k;
+    }
+    else if ( input_frame == L_FRAME48k )
+    {
+        hStereoDmxEVS->hPOC->sin = dft_trigo_48k;
+    }
+    else
+    {
+        return IVAS_ERROR( IVAS_ERR_INTERNAL_FATAL, "invalid frame length\n" );
+    }
+#else
     if ( input_frame == L_FRAME16k )
     {
         hStereoDmxEVS->hPOC->sin = Stereo_dmx_s_wnd_coef_eps_16k;
@@ -782,6 +902,8 @@ ivas_error stereo_dmx_evs_init_encoder(
     {
         return IVAS_ERROR( IVAS_ERR_INTERNAL_FATAL, "invalid frame length\n" );
     }
+#endif
+
     hStereoDmxEVS->hPOC->confidence = 0.0f;
 
     *hStereoDmxEVS_out = hStereoDmxEVS;