From 3013c508e7785252d2ecee37cfcba918c8fa7277 Mon Sep 17 00:00:00 2001
From: Sandesh Venkatesh <sandesh.venkatesh@ittiam.com>
Date: Thu, 3 Jul 2025 16:14:17 +0530
Subject: [PATCH] Fix for 3GPP issue 1797: Decoder crash for MC 7.1+4 at
 128kbps decoding to mono/stereo in
 ivas_ls_setup_conversion_process_mdct_param_mc_fx()

Link #1797
---
 lib_dec/ivas_out_setup_conversion_fx.c | 38 ++++++++++++++++++++------
 1 file changed, 29 insertions(+), 9 deletions(-)

diff --git a/lib_dec/ivas_out_setup_conversion_fx.c b/lib_dec/ivas_out_setup_conversion_fx.c
index 93a7c204e..2135cd6d6 100644
--- a/lib_dec/ivas_out_setup_conversion_fx.c
+++ b/lib_dec/ivas_out_setup_conversion_fx.c
@@ -1028,6 +1028,7 @@ void ivas_ls_setup_conversion_process_mdct_param_mc_fx(
 
     Word16 start, stop, start_tcx5, stop_tcx5;
     Word16 mct_chan_mode[MAX_CICP_CHANNELS];
+    Word16 all_ch_ignored; // Flag for checking if all channels are ignored
 
     /* Declare all handles */
     LSSETUP_CONVERSION_HANDLE hLsSetUpConversion;
@@ -1130,13 +1131,22 @@ void ivas_ls_setup_conversion_process_mdct_param_mc_fx(
     set_zero_fx( target_ch_ener_fx, MAX_OUTPUT_CHANNELS );
     Word16 max_e = 0;
     move16();
+    all_ch_ignored = 1;
+    move16();
     FOR( idx = 0; idx < nchan_transport; idx++ )
     {
         IF( NE_16( mct_chan_mode[idx], MCT_CHAN_MODE_IGNORE ) )
         {
             max_e = s_max( max_e, x_e[idx][0] );
+            all_ch_ignored = 0;
+            move16();
         }
     }
+    if ( all_ch_ignored )
+    {
+        max_e = 31;
+        move16();
+    }
     FOR( bandIdx = 0; bandIdx < hLsSetUpConversion->sfbCnt; bandIdx++ )
     {
         set_zero_fx( real_in_buffer_fx, PARAM_MC_MAX_BANDS_IN_PARAMETER_BAND * PARAM_MC_BAND_TO_MDCT_BAND_RATIO * MAX_TRANSPORT_CHANNELS );
@@ -1164,22 +1174,32 @@ void ivas_ls_setup_conversion_process_mdct_param_mc_fx(
                 }
             }
         }
-        Word16 shift = 1;
+        input_exp = max_e;
         move16();
-        FOR( i = 0; i < num_bands * nchan_transport; ++i )
+        IF( all_ch_ignored == 0 )
         {
-            real_in_buffer_fx[i] = L_shr( real_in_buffer_fx[i], shift );
-            move32();
-            imag_in_buffer_fx[i] = L_shr( imag_in_buffer_fx[i], shift );
-            move32();
+            Word16 shift = 1;
+            move16();
+            FOR( i = 0; i < num_bands * nchan_transport; ++i )
+            {
+                real_in_buffer_fx[i] = L_shr( real_in_buffer_fx[i], shift );
+                move32();
+                imag_in_buffer_fx[i] = L_shr( imag_in_buffer_fx[i], shift );
+                move32();
+            }
+            input_exp = add( input_exp, shift );
         }
-        input_exp = max_e;
-        move16();
-        input_exp = add( input_exp, shift );
+
         cmplx_matrix_square_fx( real_in_buffer_fx, imag_in_buffer_fx, num_bands, nchan_transport, real_buffer_fx, imag_buffer_fx, input_exp, &output_exp );
         v_add_32( cx_fx[bandIdx], real_buffer_fx, cx_fx[bandIdx], i_mult( nchan_transport, nchan_transport ) );           /*Q=Q_real_buffer=Q_imag_buffer=output_exp*/
         v_add_32( cx_imag_fx[bandIdx], imag_buffer_fx, cx_imag_fx[bandIdx], i_mult( nchan_transport, nchan_transport ) ); /*Q=Q_real_buffer=Q_imag_buffer=output_exp*/
     }
+    if ( all_ch_ignored )
+    {
+        output_exp = 29;
+        move16();
+    }
+
     Word16 exp_in = 10, exp_out = 0;
     move16();
     move16();
-- 
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