diff --git a/lib_com/cnst.h b/lib_com/cnst.h
index 24af77e23a54efdc584eb71b2661e9994449b0d8..0e1f6dcea1be6550ae9344a514ce5ed92ae73ff6 100644
--- a/lib_com/cnst.h
+++ b/lib_com/cnst.h
@@ -668,6 +668,9 @@ enum
 #define ACELP_TCX_TRANS_NS                  1250000                             /* Duration of the ACELP->TCX overlap - 1.25 ms */
 #define L_FRAME_MAX                         L_FRAME48k                          /* Max 20ms frame size @48kHz              */
 #define L_FRAME_PLUS                        1200                                /* Max frame size (long TCX frame)            */
+#ifdef FIX_1320_STACK_CPE_DECODER
+#define L_FRAME_PLUS_INTERNAL               800                                 /* Max frame size (long TCX frame) at maximum internal sampling rate */
+#endif
 #define L_MDCT_OVLP_MAX                     NS2SA( 48000, ACELP_LOOK_NS )       /* = Max mdct overlap */
 #define N_TCX10_MAX                         480                                 /* Max size of TCX10 MDCT spectrum */
 #define BITS_TEC                            1                                   /* number of bits for TEC */
diff --git a/lib_com/options.h b/lib_com/options.h
index 5700d1f0cc6aace8d7b5c49e36ab6b2ad2fc692f..0201286a2361818130eb746e651f50d5049979b9 100644
--- a/lib_com/options.h
+++ b/lib_com/options.h
@@ -84,6 +84,7 @@
 #define FIX_1129_EXT_REND_OUTPUT_HIGH                   /* Philips: issue 1129: External renderer BINAURAL_ROOM_REVERB format output level too high compared to internal rendering output */
 #define NONBE_1328_FIX_NON_LINEARITY                    /* VA: Fix possible issue when computing bwe_exc_extended and previous frame were almost 0, float issue 1328  */
 #define FIX_1319_STACK_SBA_DECODER                      /* VA: issue 1319: Optimize the definition of buffer lengths in the SBA decoder */
+#define FIX_1320_STACK_CPE_DECODER                      /* VA: issue 1320: Optimize the stack memory consumption in the CPE decoder */
 
 /* #################### End BASOP porting switches ############################ */
 
diff --git a/lib_dec/dec_LPD_fx.c b/lib_dec/dec_LPD_fx.c
index 5549cc809ad29574368e183f5c9d4d96a91604f3..6a06df2678b6e665c8bc76554d4def55120bf8da 100644
--- a/lib_dec/dec_LPD_fx.c
+++ b/lib_dec/dec_LPD_fx.c
@@ -36,7 +36,11 @@ void decoder_LPD_fx(
 )
 {
     Word16 *param_lpc;
+#ifdef FIX_1320_STACK_CPE_DECODER
+    Word16 synth_buf[OLD_SYNTH_INTERNAL_DEC + L_FRAME_PLUS_INTERNAL + M];
+#else
     Word16 synth_buf[OLD_SYNTH_SIZE_DEC + L_FRAME_PLUS + M];
+#endif
     Word16 *synth;
     Word16 synth_bufFB[OLD_SYNTH_SIZE_DEC + L_FRAME_PLUS + M];
     Word16 *synthFB;
@@ -114,7 +118,11 @@ void decoder_LPD_fx(
     synth = synth_buf + hTcxDec->old_synth_len;
     /*st->old_synth: Q_0*/
     Copy( hTcxDec->old_synth, synth_buf, hTcxDec->old_synth_len );
+#ifdef FIX_1320_STACK_CPE_DECODER
+    set16_fx( synth, 0, L_FRAME_PLUS_INTERNAL + M );
+#else
     set16_fx( synth, 0, L_FRAME_PLUS + M );
+#endif
 
     synthFB = synth_bufFB + hTcxDec->old_synth_lenFB;
     Copy( hTcxDec->old_synthFB_fx, synth_bufFB, hTcxDec->old_synth_lenFB );
diff --git a/lib_dec/ivas_core_dec_fx.c b/lib_dec/ivas_core_dec_fx.c
index d9eefa33a52aa408c1e69fc43f4bf2e955b7eab9..92a032ce1c12c47f8f1c7084d710e1580de38837 100644
--- a/lib_dec/ivas_core_dec_fx.c
+++ b/lib_dec/ivas_core_dec_fx.c
@@ -76,7 +76,12 @@ ivas_error ivas_core_dec_fx(
     set16_fx( tmp_buffer_fx, 0, L_FRAME48k );
 
     Word16 tmps, incr;
+#ifdef FIX_1320_STACK_CPE_DECODER
+    Word32 *bwe_exc_extended_fx[CPE_CHANNELS] = { NULL, NULL };
+    Word16 flag_bwe_bws;
+#else
     Word32 bwe_exc_extended_fx[CPE_CHANNELS][L_FRAME32k + NL_BUFF_OFFSET];
+#endif
 
     Word16 voice_factors_fx[CPE_CHANNELS][NB_SUBFR16k]; // Q15
     Word16 core_switching_flag[CPE_CHANNELS];
@@ -291,6 +296,9 @@ ivas_error ivas_core_dec_fx(
         set16_fx( voice_factors_fx[n], 0, NB_SUBFR16k );
         set32_fx( hb_synth_32_fx[n], 0, L_FRAME48k );
         set16_fx( hb_synth_16_fx[n], 0, L_FRAME48k );
+#ifdef FIX_1320_STACK_CPE_DECODER
+        bwe_exc_extended_fx[n] = hb_synth_32_fx[n]; /* note: reuse the buffer */
+#endif
 
         /*------------------------------------------------------------------*
          * Decision matrix (selection of technologies)
@@ -1011,9 +1019,18 @@ ivas_error ivas_core_dec_fx(
         }
 
         /* Memories  Re-Scaling */
-        Copy_Scale_sig_16_32_no_sat( hb_synth_16_fx[n], hb_synth_32_fx[n], L_FRAME48k, sub( Q11, Q_hb_synth_fx ) ); // Q11
-        Copy_Scale_sig_16_32_no_sat( output_16_fx[n], output_32_fx[n], L_FRAME48k, sub( Q11, Q_input ) );           // Q11    // Q_input can get value <= -5
-        Copy_Scale_sig_16_32_no_sat( synth_16_fx[n], synth_32_fx[n], output_frame, sub( Q11, Q_synth_fx ) );        // Q11
+#ifdef FIX_1320_STACK_CPE_DECODER
+        test();
+        test();
+        IF( EQ_16( st->extl, WB_TBE ) || ( EQ_16( st->extl, WB_BWE ) && st->bws_cnt == 0 ) )
+        {
+#endif
+            Copy_Scale_sig_16_32_no_sat( hb_synth_16_fx[n], hb_synth_32_fx[n], L_FRAME48k, sub( Q11, Q_hb_synth_fx ) ); // Q11
+#ifdef FIX_1320_STACK_CPE_DECODER
+        }
+#endif
+        Copy_Scale_sig_16_32_no_sat( output_16_fx[n], output_32_fx[n], L_FRAME48k, sub( Q11, Q_input ) );    // Q11    // Q_input can get value <= -5
+        Copy_Scale_sig_16_32_no_sat( synth_16_fx[n], synth_32_fx[n], output_frame, sub( Q11, Q_synth_fx ) ); // Q11
 
         IF( hBWE_FD != NULL )
         {
@@ -1029,9 +1046,18 @@ ivas_error ivas_core_dec_fx(
          * SWB(FB) BWE decoding
          *---------------------------------------------------------------------*/
 
+#ifdef FIX_1320_STACK_CPE_DECODER
+        test();
+        test();
+        test();
+        flag_bwe_bws = ( GE_32( output_Fs, 32000 ) && st->core == ACELP_CORE && st->bwidth > NB && st->bws_cnt > 0 && st->bfi == 0 );
+        move16();
+#endif
+
         Q_white_exc = 0;
         move16();
 
+#ifndef FIX_1320_STACK_CPE_DECODER
         test();
         test();
         test();
@@ -1039,6 +1065,7 @@ ivas_error ivas_core_dec_fx(
         test();
         test();
         test();
+#endif
         test();
         test();
         test();
@@ -1070,7 +1097,11 @@ ivas_error ivas_core_dec_fx(
                 fb_tbe_dec_ivas_fx( st, tmp_buffer_fx /*fb_exc*/, Q_white_exc, hb_synth_32_fx[n], 0, tmp_buffer_fx /*fb_synth_ref*/, Q_white_exc, output_frame );
             }
         }
+#ifdef FIX_1320_STACK_CPE_DECODER
+        ELSE IF( st->extl == SWB_BWE || st->extl == FB_BWE || flag_bwe_bws )
+#else
         ELSE IF( EQ_16( st->extl, SWB_BWE ) || EQ_16( st->extl, FB_BWE ) || ( GE_32( output_Fs, 32000 ) && st->core == ACELP_CORE && st->bwidth > NB && st->bws_cnt > 0 && !st->ppp_mode_dec && !( EQ_16( st->nelp_mode_dec, 1 ) && EQ_16( st->bfi, 1 ) ) ) )
+#endif
         {
             /* SWB BWE decoder */
             Q_syn_hb = swb_bwe_dec_fx32( st, output_32_fx[n], synth_32_fx[n], hb_synth_32_fx[n], use_cldfb_for_dft, output_frame );
@@ -1080,6 +1111,17 @@ ivas_error ivas_core_dec_fx(
             Copy_Scale_sig_32_16( hBWE_FD->L_old_wtda_swb_fx32, hBWE_FD->L_old_wtda_swb_fx, output_frame, sub( hBWE_FD->old_wtda_swb_fx_exp, Q11 ) ); // old_wtda_swb_fx_exp
         }
 
+#ifdef FIX_1320_STACK_CPE_DECODER
+        test();
+        test();
+        test();
+        IF( ( st->core == ACELP_CORE && ( st->extl == -1 || st->extl == SWB_CNG ) ) && flag_bwe_bws == 0 )
+        {
+            set32_fx( hb_synth_32_fx[n], 0, L_FRAME48k );
+        }
+
+#endif
+
         /*---------------------------------------------------------------------*
          * FEC - recovery after lost HQ core (smoothing of the BWE component)
          *---------------------------------------------------------------------*/
@@ -1170,6 +1212,7 @@ ivas_error ivas_core_dec_fx(
             }
         }
 
+#ifndef FIX_1320_STACK_CPE_DECODER
         IF( EQ_16( st->element_mode, EVS_MONO ) )
         {
             /*----------------------------------------------------------------*
@@ -1200,7 +1243,7 @@ ivas_error ivas_core_dec_fx(
                 move16();
             }
         }
-
+#endif
         /*----------------------------------------------------------------*
          * Transition and synchronization of BWE components
          *----------------------------------------------------------------*/
@@ -1219,6 +1262,7 @@ ivas_error ivas_core_dec_fx(
             }
             ELSE
             {
+#ifndef FIX_1320_STACK_CPE_DECODER
                 test();
                 IF( EQ_16( st->extl, SWB_BWE_HIGHRATE ) || EQ_16( st->extl, FB_BWE_HIGHRATE ) )
                 {
@@ -1227,9 +1271,12 @@ ivas_error ivas_core_dec_fx(
                 }
                 ELSE
                 {
+#endif
                     /* TBE on top of ACELP@16kHz */
                     tmps = NS2SA_FX2( output_Fs, MAX_DELAY_TBE_NS - DELAY_SWB_TBE_16k_NS );
+#ifndef FIX_1320_STACK_CPE_DECODER
                 }
+#endif
             }
 
             /* Smooth transitions when switching between different technologies */
@@ -1454,8 +1501,12 @@ ivas_error ivas_core_dec_fx(
         test();
         test();
         test();
+#ifdef FIX_1320_STACK_CPE_DECODER
+        IF( st->hTcxDec != NULL && ( ( ( st->core == ACELP_CORE ) && !( EQ_16( st->bfi, 1 ) && EQ_16( st->con_tcx, 1 ) ) ) || EQ_16( st->core, HQ_CORE ) ) )
+#else
         test();
         IF( ( EQ_16( st->codec_mode, MODE1 ) && st->hTcxDec != NULL ) && ( ( ( st->core == ACELP_CORE ) && !( EQ_16( st->bfi, 1 ) && EQ_16( st->con_tcx, 1 ) ) ) || EQ_16( st->core, HQ_CORE ) ) )
+#endif
         {
             Word16 exp_prev_synth_buffer = 0, exp_old_out = 0, exp_delay_buf_out = 0, exp_ouput = 0, exp_synth_history = 0;
             move16();
@@ -1500,24 +1551,20 @@ ivas_error ivas_core_dec_fx(
 
         Scale_sig( st->delay_buf_out_fx, NS2SA_FX2( st->output_Fs, DELAY_CLDFB_NS ), negate( exp_max ) ); // Q0
 
-    } /* n_channels loop */
-
-    FOR( n = 0; n < n_channels; n++ )
-    {
-        st = sts[n];
-        IF( st->cldfbAna )
+        IF( st->cldfbAna != NULL )
         {
             scale_sig32( st->cldfbAna->cldfb_state_fx, st->cldfbAna->cldfb_size, ( Q11 - Q10 ) ); // Q11
             st->cldfbAna->Q_cldfb_state = Q11;
             move16();
         }
-        IF( st->cldfbSynHB )
+        IF( st->cldfbSynHB != NULL )
         {
             scale_sig32( st->cldfbSynHB->cldfb_state_fx, st->cldfbSynHB->cldfb_size, ( Q11 - Q10 ) ); // Q11
             st->cldfbSynHB->Q_cldfb_state = Q11;
             move16();
         }
-    }
+
+    } /* n_channels loop */
 
     pop_wmops();
     return error;
diff --git a/lib_dec/ivas_cpe_dec_fx.c b/lib_dec/ivas_cpe_dec_fx.c
index 02068c9cfd20c56e5d1a3997ea7359175dea0ea8..a5e71297268f93c900cd7da5eb06ae59d4ec813f 100644
--- a/lib_dec/ivas_cpe_dec_fx.c
+++ b/lib_dec/ivas_cpe_dec_fx.c
@@ -51,6 +51,10 @@ static void read_stereo_mode_and_bwidth_fx( CPE_DEC_HANDLE hCPE, const Decoder_S
 
 static void stereo_mode_combined_format_dec_fx( const Decoder_Struct *st_ivas, CPE_DEC_HANDLE hCPE );
 
+#ifdef FIX_1320_STACK_CPE_DECODER
+static ivas_error stereo_dft_dec_main( CPE_DEC_HANDLE hCPE, const Word32 ivas_total_brate, const Word16 n_channels, Word32 *p_res_buf_fx, Word32 *output[], Word32 outputHB[][L_FRAME48k], const Word16 output_frame, const Word32 output_Fs );
+#endif
+
 
 /*--------------------------------------------------------------------------*
  * ivas_cpe_dec_fx()
@@ -71,8 +75,12 @@ ivas_error ivas_cpe_dec_fx(
     Word16 last_bwidth;
     Word16 tdm_ratio_idx;
     Word32 outputHB_fx[CPE_CHANNELS][L_FRAME48k]; /* buffer for output HB synthesis, both channels */ /* Q11 */
+#ifdef FIX_1320_STACK_CPE_DECODER
+    Word32 *res_buf_fx = NULL; /* Q8 */
+#else
     Word16 q_res_buf;
-    Word32 res_buf_fx[STEREO_DFT_N_8k]; /* Q(q_res_buf) */
+    Word32 res_buf_fx[STEREO_DFT_N_8k];                  /* Q(q_res_buf) */
+#endif
     CPE_DEC_HANDLE hCPE;
     STEREO_DFT_CONFIG_DATA_HANDLE hConfigDft;
     Decoder_State **sts;
@@ -84,8 +92,10 @@ ivas_error ivas_cpe_dec_fx(
 
     error = IVAS_ERR_OK;
     move32();
+#ifndef FIX_1320_STACK_CPE_DECODER
     q_res_buf = Q8;
     move16();
+#endif
 
     push_wmops( "ivas_cpe_dec" );
 
@@ -345,6 +355,10 @@ ivas_error ivas_cpe_dec_fx(
             }
             ELSE
             {
+#ifdef FIX_1320_STACK_CPE_DECODER
+                res_buf_fx = outputHB_fx[0]; /* note: temporarily reused buffer */
+
+#endif
                 test();
                 IF( EQ_32( st_ivas->ivas_format, MASA_FORMAT ) || EQ_32( st_ivas->ivas_format, MASA_ISM_FORMAT ) )
                 {
@@ -613,6 +627,12 @@ ivas_error ivas_cpe_dec_fx(
     test();
     IF( EQ_16( hCPE->element_mode, IVAS_CPE_DFT ) && !( EQ_16( hCPE->nchan_out, 1 ) && EQ_16( hConfigDft->res_cod_mode, STEREO_DFT_RES_COD_OFF ) ) )
     {
+#ifdef FIX_1320_STACK_CPE_DECODER
+        IF( NE_32( ( error = stereo_dft_dec_main( hCPE, ivas_total_brate, n_channels, res_buf_fx, output, outputHB_fx, output_frame, st_ivas->hDecoderConfig->output_Fs ) ), IVAS_ERR_OK ) )
+        {
+            return error;
+        }
+#else
         Word32 DFT_fx[CPE_CHANNELS][STEREO_DFT_BUF_MAX]; // q_dft
         set32_fx( DFT_fx[0], 0, STEREO_DFT_BUF_MAX );
         set32_fx( DFT_fx[1], 0, STEREO_DFT_BUF_MAX );
@@ -777,6 +797,7 @@ ivas_error ivas_cpe_dec_fx(
             hCPE->q_output_mem_fx[n] = Q11;
             move16();
         }
+#endif
     }
     ELSE IF( EQ_16( hCPE->element_mode, IVAS_CPE_TD ) )
     {
@@ -816,7 +837,6 @@ ivas_error ivas_cpe_dec_fx(
      * Update parameters for stereo CNA
      *----------------------------------------------------------------*/
 
-    // stereo_cna_update_params( hCPE, output_flt, output_frame, tdm_ratio_idx );
     stereo_cna_update_params_fx( hCPE, output, output_frame, tdm_ratio_idx );
 
     /*----------------------------------------------------------------*
@@ -850,7 +870,6 @@ ivas_error ivas_cpe_dec_fx(
 
     stereo_tca_dec_fx( hCPE, output, output_frame );
 
-
     /*----------------------------------------------------------------*
      * Common Stereo updates
      *----------------------------------------------------------------*/
@@ -882,6 +901,205 @@ ivas_error ivas_cpe_dec_fx(
     return error;
 }
 
+#ifdef FIX_1320_STACK_CPE_DECODER
+
+/*-------------------------------------------------------------------------
+ * stereo_dft_dec_main()
+ *
+ * DFT decoder main function
+ *-------------------------------------------------------------------------*/
+
+static ivas_error stereo_dft_dec_main(
+    CPE_DEC_HANDLE hCPE,              /* i/o: CPE decoder structure               */
+    const Word32 ivas_total_brate,    /* i  : IVAS total bitrate                  */
+    const Word16 n_channels,          /* i  : number of channels to be decoded    */
+    Word32 *p_res_buf_fx,             /* i  : DFT stereo residual S signal        */
+    Word32 *output[],                 /* o  : output synthesis signal             */
+    Word32 outputHB_fx[][L_FRAME48k], /* o  : output HB synthesis signal          */
+    const Word16 output_frame,        /* i  : output frame length per channel     */
+    const Word32 output_Fs            /* i  : output sampling rate                */
+)
+{
+    Word32 DFT_fx[CPE_CHANNELS][STEREO_DFT_BUF_MAX];
+    Word32 res_buf_fx[STEREO_DFT_N_8k]; /* Q(q_res_buf) */
+    Word16 n;
+    Word16 q_res_buf, q_dft;
+    Decoder_State *st0;
+    ivas_error error;
+    Word16 shift;
+    Word32 tmp1, tmp2;
+    Word16 shift1, shift2;
+
+    st0 = hCPE->hCoreCoder[0];
+
+    q_res_buf = Q8;
+    move16();
+
+    set32_fx( DFT_fx[0], 0, STEREO_DFT_BUF_MAX );
+    set32_fx( DFT_fx[1], 0, STEREO_DFT_BUF_MAX );
+
+    /* copy from temporary buffer */
+    test();
+    IF( hCPE->hStereoDft->res_cod_band_max > 0 && !st0->bfi )
+    {
+        Copy32( p_res_buf_fx, res_buf_fx, STEREO_DFT_N_8k );
+    }
+
+    /* core decoder */
+    IF( NE_32( ( error = ivas_core_dec_fx( NULL, NULL, hCPE, NULL, n_channels, output, outputHB_fx, DFT_fx, 0 ) ), IVAS_ERR_OK ) )
+    {
+        return error;
+    }
+
+    /* Scaling of DFT's */
+    maximum_abs_32_fx( DFT_fx[0], STEREO_DFT_BUF_MAX, &tmp1 );
+    maximum_abs_32_fx( DFT_fx[1], STEREO_DFT_BUF_MAX, &tmp2 );
+
+    IF( tmp1 == 0 )
+    {
+        shift1 = Q31;
+        move16();
+    }
+    ELSE
+    {
+        shift1 = norm_l( tmp1 );
+    }
+    IF( tmp2 == 0 )
+    {
+        shift2 = Q31;
+        move16();
+    }
+    ELSE
+    {
+        shift2 = norm_l( tmp2 );
+    }
+    shift = s_min( shift1, shift2 );
+
+    IF( NE_16( shift, 31 ) )
+    {
+        shift = sub( add( hCPE->hStereoDft->q_dft, shift ), Q16 ); /* Q16 for guard bits */
+
+        IF( GT_16( shift, hCPE->hStereoDft->q_dft ) )
+        {
+            Scale_sig32( DFT_fx[0], STEREO_DFT_BUF_MAX, sub( shift, hCPE->hStereoDft->q_dft ) ); // shift
+            Scale_sig32( DFT_fx[1], STEREO_DFT_BUF_MAX, sub( shift, hCPE->hStereoDft->q_dft ) ); // shift
+            hCPE->hStereoDft->q_dft = shift;
+            move16();
+        }
+    }
+    ELSE
+    {
+        hCPE->hStereoDft->q_dft = Q8;
+        move16();
+    }
+
+    /* DFT Stereo residual decoding */
+    test();
+    IF( hCPE->hStereoDft->res_cod_band_max > 0 && !st0->bfi )
+    {
+        Word16 q;
+        Word16 q_out_DFT[2];
+
+        q = Q11;
+        move16();
+
+        Copy_Scale_sig_32_16( hCPE->hCoreCoder[0]->old_pitch_buf_fx, hCPE->hCoreCoder[0]->old_pitch_buf_16_fx, ( ( 2 * NB_SUBFR16k ) + 2 ), -( Q10 ) ); // Q16->Q6
+
+        stereo_dft_dec_res_fx( hCPE, res_buf_fx, q_res_buf, output[1] );
+
+        Copy_Scale_sig_16_32_DEPREC( hCPE->hCoreCoder[0]->old_pitch_buf_16_fx, hCPE->hCoreCoder[0]->old_pitch_buf_fx, ( ( 2 * NB_SUBFR16k ) + 2 ), 10 ); // Q6->Q16
+
+        Scale_sig32( output[1], L_FRAME8k, ( Q11 - Q15 ) ); // Q15 -> Q11
+
+        q_out_DFT[0] = q_out_DFT[1] = hCPE->hStereoDft->q_dft;
+        move16();
+        move16();
+
+        stereo_dft_dec_analyze_fx( hCPE, output[1], DFT_fx, 1, L_FRAME8k, output_frame, DFT_STEREO_DEC_ANA_LB, 0, 0, &q, q_out_DFT );
+
+        Scale_sig32( DFT_fx[1], STEREO_DFT_BUF_MAX, sub( hCPE->hStereoDft->q_dft, q_out_DFT[1] ) ); // q_dft
+    }
+
+    /* DFT stereo CNG */
+    q_dft = hCPE->hStereoDft->q_dft;
+    move16();
+    stereo_dtf_cng_fx( hCPE, ivas_total_brate, DFT_fx, output_frame, q_dft );
+
+    /* decoding */
+    IF( EQ_16( hCPE->nchan_out, 1 ) )
+    {
+        IF( EQ_16( hCPE->hStereoDft->first_frame, 1 ) )
+        {
+            hCPE->hStereoDft->q_smoothed_nrg = hCPE->hStereoDft->q_dft;
+            move16();
+            FOR( Word16 ii = 0; ii < (Word16) ( sizeof( hCPE->hStereoDft->q_DFT_past_DMX_fx ) / sizeof( hCPE->hStereoDft->q_DFT_past_DMX_fx[0] ) ); ii++ )
+            {
+                hCPE->hStereoDft->q_DFT_past_DMX_fx[ii] = hCPE->hStereoDft->q_dft;
+                move16();
+            }
+            hCPE->hStereoDft->first_frame = 0;
+            move16();
+        }
+
+        scale_sig32( hCPE->hStereoDft->res_cod_mem_fx, STEREO_DFT_OVL_8k, sub( hCPE->hStereoDft->q_dft, hCPE->hStereoDft->q_res_cod_mem_fx ) ); // q_dft
+        hCPE->hStereoDft->q_res_cod_mem_fx = hCPE->hStereoDft->q_dft;
+        move16();
+        stereo_dft_unify_dmx_fx( hCPE->hStereoDft, st0, DFT_fx, hCPE->input_mem_fx[1], hCPE->hStereoCng->prev_sid_nodata );
+        scale_sig32( hCPE->hStereoDft->res_cod_mem_fx, STEREO_DFT_OVL_8k, sub( Q15, hCPE->hStereoDft->q_res_cod_mem_fx ) ); // Q15
+        hCPE->hStereoDft->q_res_cod_mem_fx = Q15;
+        move16();
+    }
+    ELSE
+    {
+        IF( EQ_16( hCPE->hStereoDft->first_frame, 1 ) )
+        {
+            hCPE->hStereoDft->q_smoothed_nrg = hCPE->hStereoDft->q_dft;
+            move16();
+            FOR( Word16 ii = 0; ii < (Word16) ( sizeof( hCPE->hStereoDft->q_DFT_past_DMX_fx ) / sizeof( hCPE->hStereoDft->q_DFT_past_DMX_fx[0] ) ); ii++ )
+            {
+                hCPE->hStereoDft->q_DFT_past_DMX_fx[ii] = hCPE->hStereoDft->q_dft;
+                move16();
+            }
+            hCPE->hStereoDft->first_frame = 0;
+            move16();
+        }
+
+        scale_sig32( hCPE->hStereoDft->res_cod_mem_fx, STEREO_DFT_OVL_8k, sub( hCPE->hStereoDft->q_dft, hCPE->hStereoDft->q_res_cod_mem_fx ) ); // q_dft
+        hCPE->hStereoDft->q_res_cod_mem_fx = hCPE->hStereoDft->q_dft;
+        move16();
+
+        stereo_dft_dec_fx( hCPE->hStereoDft, st0, DFT_fx, hCPE->input_mem_fx[1], hCPE->hStereoCng, 0, 0, 0, 0, 0, 0, MAX_PARAM_SPATIAL_SUBFRAMES );
+        scale_sig32( hCPE->hStereoDft->res_cod_mem_fx, STEREO_DFT_OVL_8k, sub( Q15, hCPE->hStereoDft->q_res_cod_mem_fx ) ); // Q15
+        hCPE->hStereoDft->q_res_cod_mem_fx = Q15;
+        move16();
+    }
+
+    FOR( n = 0; n < hCPE->nchan_out; n++ )
+    {
+        Scale_sig32( output[n], L_FRAME48k, sub( hCPE->hStereoDft->q_dft, Q11 ) );                                                 // q_dft
+        scale_sig32( hCPE->output_mem_fx[n], NS2SA_FX2( output_Fs, STEREO_DFT32MS_OVL_NS ), sub( hCPE->hStereoDft->q_dft, Q11 ) ); // q_dft
+        hCPE->q_output_mem_fx[n] = hCPE->hStereoDft->q_dft;
+        move16();
+    }
+
+    /* synthesis iFFT */
+    FOR( n = 0; n < hCPE->nchan_out; n++ )
+    {
+        stereo_dft_dec_synthesize_fx( hCPE, DFT_fx, n, output[n], output_frame );
+    }
+
+    FOR( n = 0; n < hCPE->nchan_out; n++ )
+    {
+        Scale_sig32( output[n], L_FRAME48k, sub( Q11, hCPE->hStereoDft->q_dft ) );                                                 // Q11
+        scale_sig32( hCPE->output_mem_fx[n], NS2SA_FX2( output_Fs, STEREO_DFT32MS_OVL_NS ), sub( Q11, hCPE->hStereoDft->q_dft ) ); // Q11
+        hCPE->q_output_mem_fx[n] = Q11;
+        move16();
+    }
+
+    return IVAS_ERR_OK;
+}
+
+#endif
 
 /*-------------------------------------------------------------------------
  * create_cpe_dec_fx()
diff --git a/lib_dec/ivas_mdct_core_dec_fx.c b/lib_dec/ivas_mdct_core_dec_fx.c
index 4e080bb2fe4e9fb3615a1ca5a7e7d81a6c6f68ed..40dac596b25fb10ffc9fe1153d9e108cebb04019 100644
--- a/lib_dec/ivas_mdct_core_dec_fx.c
+++ b/lib_dec/ivas_mdct_core_dec_fx.c
@@ -1085,23 +1085,27 @@ void ivas_mdct_core_invQ_fx(
  *-----------------------------------------------------------------*/
 
 void ivas_mdct_core_reconstruct_fx(
-    CPE_DEC_HANDLE hCPE, /* i/o: CPE decoder structure               */
-    Word32 *x_fx[][NB_DIV],
-    /* i/o: synthesis @internal_FS              */ // Q(q_x)
-    Word16 signal_outFB_fx[CPE_CHANNELS][L_FRAME_PLUS],
-    /* o  : synthesis @output_FS                */ // e_sig
-    Word16 fUseTns[CPE_CHANNELS][NB_DIV],          /* i  : flage TNS enabled                   */
-    const Word16 MCT_flag,                         /* i  : hMCT handle allocated (1) or not (0)*/
+    CPE_DEC_HANDLE hCPE,                                /* i/o: CPE decoder structure               */
+    Word32 *x_fx[][NB_DIV],                             /* i/o: synthesis @internal_FS       Q(q_x) */
+    Word16 signal_outFB_fx[CPE_CHANNELS][L_FRAME_PLUS], /* o  : synthesis @output_FS          e_sig */
+    Word16 fUseTns[CPE_CHANNELS][NB_DIV],               /* i  : flage TNS enabled                   */
+    const Word16 MCT_flag,                              /* i  : hMCT handle allocated (1) or not (0)*/
     Word16 q_x,
     Word16 e_sig[CPE_CHANNELS] )
 {
     Word16 ch, k, bfi;
     Decoder_State **sts, *st;
+
     /* Framing */
     Word16 L_frame[CPE_CHANNELS], L_frameTCX[CPE_CHANNELS], nSubframes[CPE_CHANNELS];
     Word16 L_frame_global[CPE_CHANNELS], L_frame_globalTCX[CPE_CHANNELS];
+
     /* Synth */
+#ifdef FIX_1320_STACK_CPE_DECODER
+    Word16 synth_buf_fx[OLD_SYNTH_INTERNAL_DEC + L_FRAME_PLUS_INTERNAL + M];
+#else
     Word16 synth_buf_fx[OLD_SYNTH_SIZE_DEC + L_FRAME_PLUS + M];
+#endif
     Word16 *synth_fx;
     Word16 synth_bufFB_fx[OLD_SYNTH_SIZE_DEC + L_FRAME_PLUS + M];
     Word16 *synthFB_fx;
@@ -1109,6 +1113,7 @@ void ivas_mdct_core_reconstruct_fx(
     move16();
     Word16 q_win = 0;
     Word16 q_winFB = 0;
+
     /* TCX */
     Word16 xn_buf_fx[L_MDCT_OVLP_MAX + L_FRAME_PLUS + L_MDCT_OVLP_MAX]; // Q(-2)
     Word16 tcx_offset[CPE_CHANNELS];
@@ -1171,7 +1176,11 @@ void ivas_mdct_core_reconstruct_fx(
         }
         q_syn = st->hTcxDec->q_old_synth;
         move16();
+#ifdef FIX_1320_STACK_CPE_DECODER
+        set16_fx( synth_fx, 0, L_FRAME_PLUS_INTERNAL + M );
+#else
         set16_fx( synth_fx, 0, L_FRAME_PLUS + M );
+#endif
         set16_fx( synthFB_fx, 0, L_FRAME_PLUS + M );
         IF( st->core != ACELP_CORE )
         {
diff --git a/lib_dec/ivas_stereo_mdct_core_dec_fx.c b/lib_dec/ivas_stereo_mdct_core_dec_fx.c
index 8a1d339d427537c73ec2be05c7d8ff4b856aacf6..b2a894a34286b4c3a56972f9b2849ebc849c4d48 100644
--- a/lib_dec/ivas_stereo_mdct_core_dec_fx.c
+++ b/lib_dec/ivas_stereo_mdct_core_dec_fx.c
@@ -176,7 +176,7 @@ void stereo_mdct_core_dec_fx(
     Word16 x_len[CPE_CHANNELS][NB_DIV];
 
     /*needed to allocate N_MAX to prevent stereo switching crash */
-    Word32 x_0_buf_fx[CPE_CHANNELS][N_MAX];
+    Word32 x_0_buf_fx[CPE_CHANNELS][N_MAX]; /* note: in FLP, this buffer is shared with signal_outFB_tmp_fx[][] */
     Word32 *x_0_fx[CPE_CHANNELS][NB_DIV];
 
     /* Concealment */
@@ -229,6 +229,7 @@ void stereo_mdct_core_dec_fx(
         set32_fx( x_0_buf_fx[ch], 0, N_MAX );
         x_0_fx[ch][0] = &x_0_buf_fx[ch][0];
         x_0_fx[ch][1] = &x_0_buf_fx[ch][0] + L_FRAME48k / 2;
+
         nTnsBitsTCX10[ch][0] = 0;
         move16();
         nTnsBitsTCX10[ch][1] = 0;
diff --git a/lib_dec/ivas_tcx_core_dec_fx.c b/lib_dec/ivas_tcx_core_dec_fx.c
index 0be01f7b88612b359fb0b5b88b1fda3028fdeceb..81b67ec10b994dec97c8656a0c502079912cba02 100644
--- a/lib_dec/ivas_tcx_core_dec_fx.c
+++ b/lib_dec/ivas_tcx_core_dec_fx.c
@@ -228,7 +228,11 @@ void stereo_tcx_core_dec_fx(
     Word16 pit_gain_fx[NB_SUBFR16k];
 
     /*Synth*/
+#ifdef FIX_1320_STACK_CPE_DECODER
+    Word16 synth_buf_fx[OLD_SYNTH_INTERNAL_DEC + L_FRAME_PLUS_INTERNAL + M];
+#else
     Word16 synth_buf_fx[OLD_SYNTH_SIZE_DEC + L_FRAME_PLUS + M];
+#endif
     Word16 *synth_fx;
     Word16 synth_bufFB_fx[OLD_SYNTH_SIZE_DEC + L_FRAME_PLUS + M];
     Word16 *synthFB_fx;
@@ -302,7 +306,11 @@ void stereo_tcx_core_dec_fx(
     synthFB_fx = synth_bufFB_fx + hTcxDec->old_synth_lenFB;
     Copy_Scale_sig( hTcxDec->old_synth, synth_buf_fx, hTcxDec->old_synth_len, negate( st->Q_syn ) ); /* q_old_synth - st->Q_syn */
     Copy( hTcxDec->old_synthFB_fx, synth_bufFB_fx, hTcxDec->old_synth_lenFB );                       /* q_old_synthFB */
+#ifdef FIX_1320_STACK_CPE_DECODER
+    set16_fx( synth_fx, 0, L_FRAME_PLUS_INTERNAL + M );
+#else
     set16_fx( synth_fx, 0, L_FRAME_PLUS + M );
+#endif
     set16_fx( synthFB_fx, 0, L_FRAME_PLUS + M );
 
     /*--------------------------------------------------------------------------------*