diff --git a/lib_com/options.h b/lib_com/options.h
index 339ca8a072e6bfbbc0539befe0c85289645c5e8f..a5263a49211ffedee314a98108f9e2301f19e86d 100644
--- a/lib_com/options.h
+++ b/lib_com/options.h
@@ -88,6 +88,7 @@
 #define NONBE_1122_KEEP_EVS_MODE_UNCHANGED              /* FhG: Disables fix for issue 1122 in EVS mode to keep BE tests green. This switch should be removed once the 1122 fix is added to EVS via a CR.  */
 #define HARMONIZE_2502_GENERATE_COMFORT_NOISE_DEC       /* FhG: harmonize generate_comfort_noise_dec_fx() and generate_comfort_noise_dec_ivas_fx() */
 #define FIX_BASOP_2650_DEC_PRM_TCX                      /* FhG: Simplify calculation of st->bits_frame_core in dec_prm_tcx(), align function name to float */
+#define FIX_2648_IVAS_ISM_DEC_DIGEST_TC                 /* FhG: improvements on ivas_ism_dec_digest_tc_fx() */
 
 /* #################### End BE switches ################################## */
 
diff --git a/lib_dec/ivas_ism_param_dec_fx.c b/lib_dec/ivas_ism_param_dec_fx.c
index 4a00c193c703a89fbfffcba56ee390a324ee8a8a..74ce0273dd8d6cbc2618b5a17f6c4516c9ada97e 100644
--- a/lib_dec/ivas_ism_param_dec_fx.c
+++ b/lib_dec/ivas_ism_param_dec_fx.c
@@ -947,13 +947,26 @@ void ivas_ism_dec_digest_tc_fx(
         ( EQ_32( st_ivas->renderer_type, RENDERER_BINAURAL_MIXER_CONV_ROOM ) && st_ivas->hDecoderConfig->Opt_Headrotation == 0 ) )
     {
         Word16 i;
+#ifdef FIX_2648_IVAS_ISM_DEC_DIGEST_TC
+        Word16 output_frame;
+#endif
 
         /* we have a full frame interpolator, adapt it */
         /* for BE testing */
+#ifdef FIX_2648_IVAS_ISM_DEC_DIGEST_TC
+        output_frame = extract_l( Mpy_32_32_r( st_ivas->hDecoderConfig->output_Fs, ONE_BY_FRAMES_PER_SEC_Q31 ) );
+        IF( EQ_16( output_frame, st_ivas->hTcBuffer->n_samples_available ) )
+#else
         i = extract_l( Mpy_32_32_r( st_ivas->hDecoderConfig->output_Fs, ONE_BY_FRAMES_PER_SEC_Q31 ) );
         IF( EQ_16( i, st_ivas->hTcBuffer->n_samples_available ) )
+#endif
         {
+#ifdef FIX_2648_IVAS_ISM_DEC_DIGEST_TC
+            Word16 interpolator_length = output_frame;
+            move16();
+#else
             Word16 interpolator_length = i;
+#endif
 
             test();
             test();
@@ -985,7 +998,11 @@ void ivas_ism_dec_digest_tc_fx(
         }
         ELSE
         {
+#ifdef FIX_2648_IVAS_ISM_DEC_DIGEST_TC
+            ivas_dec_get_adapted_linear_interpolator_fx( output_frame, st_ivas->hTcBuffer->n_samples_available, st_ivas->hIsmRendererData->interpolator_fx );
+#else
             ivas_dec_get_adapted_linear_interpolator_fx( extract_l( Mpy_32_32( st_ivas->hDecoderConfig->output_Fs, ONE_BY_FRAMES_PER_SEC_Q31 ) ), st_ivas->hTcBuffer->n_samples_available, st_ivas->hIsmRendererData->interpolator_fx );
+#endif
             move16();
         }
 
@@ -1001,13 +1018,17 @@ void ivas_ism_dec_digest_tc_fx(
             {
                 Word16 gains_fx[CPE_CHANNELS];
 
+#ifdef FIX_2648_IVAS_ISM_DEC_DIGEST_TC
+                ivas_ism_get_stereo_gains_fx( extract_l( L_shr( st_ivas->hIsmMetaData[i]->azimuth_fx, 22 ) ), extract_l( L_shr( st_ivas->hIsmMetaData[i]->elevation_fx, 22 ) ), &gains_fx[0], &gains_fx[1] ); // gains_fx[]: Q15
+#else
                 ivas_ism_get_stereo_gains_fx( (Word16) L_shr( st_ivas->hIsmMetaData[i]->azimuth_fx, 22 ), (Word16) L_shr( st_ivas->hIsmMetaData[i]->elevation_fx, 22 ), &gains_fx[0], &gains_fx[1] );
+#endif
 
                 st_ivas->hIsmRendererData->gains_fx[i][0] = L_shr( L_deposit_h( gains_fx[0] ), 1 ); // Q31 -> Q30
                 move32();
                 st_ivas->hIsmRendererData->gains_fx[i][1] = L_shr( L_deposit_h( gains_fx[1] ), 1 ); // Q31 -> Q30
                 move32();
-                // TODO: Align Q values
+
                 IF( NE_32( st_ivas->hIsmMetaData[i]->edited_gain_fx, ONE_IN_Q29 ) )
                 {
                     v_multc_fx( st_ivas->hIsmRendererData->gains_fx[i], st_ivas->hIsmMetaData[i]->edited_gain_fx, st_ivas->hIsmRendererData->gains_fx[i], CPE_CHANNELS ); // Q30, Q29 --> Q28