From 97cdbd047413bd169364c773311795b9ccbf07e7 Mon Sep 17 00:00:00 2001
From: Sandesh Venkatesh <sandesh.venkatesh@ittiam.com>
Date: Thu, 17 Jul 2025 16:36:16 +0530
Subject: [PATCH] Fix for 3GPP issue 1784: High frequency noise on binaural
 room reverb output for main and main-pc branch

Link #1784
---
 lib_rend/ivas_reverb_fft_filter_fx.c |  3 +++
 lib_rend/ivas_reverb_fx.c            | 26 ++++++++++++++++++++++++--
 lib_rend/ivas_stat_rend.h            |  1 +
 3 files changed, 28 insertions(+), 2 deletions(-)

diff --git a/lib_rend/ivas_reverb_fft_filter_fx.c b/lib_rend/ivas_reverb_fft_filter_fx.c
index bbe077f8b..09720d202 100644
--- a/lib_rend/ivas_reverb_fft_filter_fx.c
+++ b/lib_rend/ivas_reverb_fft_filter_fx.c
@@ -232,6 +232,9 @@ void ivas_reverb_t2f_f2t_ClearHistory(
         move32();
     }
 
+    t2f_f2t->prev_shift = 31;
+    move16();
+
     return;
 }
 /*-----------------------------------------------------------------------------------------*
diff --git a/lib_rend/ivas_reverb_fx.c b/lib_rend/ivas_reverb_fx.c
index 9ea501f10..b90cfa91a 100644
--- a/lib_rend/ivas_reverb_fx.c
+++ b/lib_rend/ivas_reverb_fx.c
@@ -1824,6 +1824,7 @@ static void reverb_block_fx(
     Word32 pTemp_fx[INNER_BLK_SIZE];
     Word32 *ppOutput_fx[IVAS_REV_MAX_NR_BRANCHES];
     Word32 Output_fx[IVAS_REV_MAX_NR_BRANCHES][INNER_BLK_SIZE];
+    Word16 shift;
     move16();
     move16();
     move16();
@@ -1894,6 +1895,27 @@ static void reverb_block_fx(
         }
     }
 
+    shift = s_min( L_norm_arr( pOut0_fx, hReverb->fft_filter_ols.block_size ), L_norm_arr( pOut1_fx, hReverb->fft_filter_ols.block_size ) );
+
+    IF( LT_16( shift, hReverb->fft_filter_ols.prev_shift ) )
+    {
+        scale_sig32( pOut0_fx, hReverb->fft_filter_ols.block_size, shift );
+        scale_sig32( pOut1_fx, hReverb->fft_filter_ols.block_size, shift );
+        scale_sig32( hReverb->fft_filter_ols.fft_history_L_fx, hReverb->fft_filter_ols.hist_size, sub( shift, hReverb->fft_filter_ols.prev_shift ) );
+        scale_sig32( hReverb->fft_filter_ols.fft_history_R_fx, hReverb->fft_filter_ols.hist_size, sub( shift, hReverb->fft_filter_ols.prev_shift ) );
+
+        hReverb->fft_filter_ols.prev_shift = shift;
+        move16();
+    }
+    ELSE
+    {
+        scale_sig32( pOut0_fx, hReverb->fft_filter_ols.block_size, hReverb->fft_filter_ols.prev_shift );
+        scale_sig32( pOut1_fx, hReverb->fft_filter_ols.block_size, hReverb->fft_filter_ols.prev_shift );
+
+        shift = hReverb->fft_filter_ols.prev_shift;
+        move16();
+    }
+
     Word16 r_shift;
     r_shift = add( find_guarded_bits_fx( hReverb->fft_filter_ols.fft_size ), 1 );
     // Applying guard bits for the DoRTFT inside the post_fft_filter function
@@ -1913,9 +1935,9 @@ static void reverb_block_fx(
 
     FOR( k = 0; k < hReverb->fft_filter_ols.block_size; k++ )
     {
-        pOut0_fx[k] = (Word32) L_shl( pOut0_fx[k], 1 );
+        pOut0_fx[k] = (Word32) L_shl( pOut0_fx[k], sub( 1, shift ) );
         move32();
-        pOut1_fx[k] = (Word32) L_shl( pOut1_fx[k], 1 );
+        pOut1_fx[k] = (Word32) L_shl( pOut1_fx[k], sub( 1, shift ) );
         move32();
     }
 
diff --git a/lib_rend/ivas_stat_rend.h b/lib_rend/ivas_stat_rend.h
index f8dad9a66..9f853102d 100644
--- a/lib_rend/ivas_stat_rend.h
+++ b/lib_rend/ivas_stat_rend.h
@@ -895,6 +895,7 @@ typedef struct ivas_reverb_t2f_f2t_t
     Word32 fft_history_L_fx[RV_FILTER_MAX_HISTORY];
     // float fft_history_R[RV_FILTER_MAX_HISTORY];
     Word32 fft_history_R_fx[RV_FILTER_MAX_HISTORY];
+    Word16 prev_shift;
 
 } ivas_reverb_t2f_f2t_t;
 /* FFT filter with its frequency response coefficients */
-- 
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