From a1ff5a75ba4997f1a54fe1820624b600312eb50c Mon Sep 17 00:00:00 2001
From: Hans Keksnascher <21247718+HansKeksnascher@users.noreply.github.com>
Date: Thu, 24 Sep 2026 00:08:57 +0200
Subject: [PATCH] fix: saturate eSBR QMF synthesis output on all backends

ixheaacd_esbr_qmfsyn64_winadd() and ixheaacd_esbr_qmfsyn32_winadd() in the
generic C and ARMv7 paths cast (syn_out >> 31) straight to WORD32. The
WORD64 accumulator can exceed WORD32 range on a full-scale sample, so the
cast wraps it to a negative spike instead of clipping - audible as
crackling / overdrive on loud material.

The ARMv8 64-band implementation already does the saturating narrowing
with ixheaac_sat64_32(). Apply the same to the generic C, ARMv7 C and
ARMv8 32-band variants, and use VQSHRN.S64 instead of VSHRN.S64 in the
ARMv7 assembly.
---
 decoder/armv7/ixheaacd_esbr_qmfsyn64_winadd.s | 16 ++++++++--------
 decoder/armv7/ixheaacd_qmf_dec_armv7.c        |  2 +-
 decoder/armv8/ixheaacd_qmf_dec_armv8.c        |  2 +-
 decoder/generic/ixheaacd_qmf_dec_generic.c    |  4 ++--
 4 files changed, 12 insertions(+), 12 deletions(-)

diff --git a/decoder/armv7/ixheaacd_esbr_qmfsyn64_winadd.s b/decoder/armv7/ixheaacd_esbr_qmfsyn64_winadd.s
index ebfca727..0483ca7e 100644
--- a/decoder/armv7/ixheaacd_esbr_qmfsyn64_winadd.s
+++ b/decoder/armv7/ixheaacd_esbr_qmfsyn64_winadd.s
@@ -114,12 +114,12 @@ ixheaacd_esbr_qmfsyn64_winadd:          @ PROC
     VMLAL.S32       Q13, D16, D18
     VMLAL.S32       Q14, D17, D19
 
-    VSHRN.S64       D26 , Q13, #31
+    VQSHRN.S64       D26 , Q13, #31
 
     VST1.32         D26[0], [R3], R5
     VST1.32         D26[1], [R3], R5
 
-    VSHRN.S64       D27 , Q14, #31
+    VQSHRN.S64       D27 , Q14, #31
 
     VST1.32         D27[0], [R3], R5
     VST1.32         D27[1], [R3], R5
@@ -207,12 +207,12 @@ LOOP_1:
     VMLAL.S32       Q13, D16, D18
     VMLAL.S32       Q14, D17, D19
 
-    VSHRN.S64       D26 , Q13, #31
+    VQSHRN.S64       D26 , Q13, #31
 
     VST1.32         D26[0], [R3], R5
     VST1.32         D26[1], [R3], R5
 
-    VSHRN.S64       D27 , Q14, #31
+    VQSHRN.S64       D27 , Q14, #31
 
     VST1.32         D27[0], [R3], R5
     VST1.32         D27[1], [R3], R5
@@ -299,12 +299,12 @@ LOOP_1:
     VMLAL.S32       Q13, D16, D18
     VMLAL.S32       Q14, D17, D19
 
-    VSHRN.S64       D26 , Q13, #31
+    VQSHRN.S64       D26 , Q13, #31
 
     VST1.32         D26[0], [R3], R5
     VST1.32         D26[1], [R3], R5
 
-    VSHRN.S64       D27 , Q14, #31
+    VQSHRN.S64       D27 , Q14, #31
 
     VST1.32         D27[0], [R3], R5
     VST1.32         D27[1], [R3], R5
@@ -395,12 +395,12 @@ LOOP_1:
     VMLAL.S32       Q13, D16, D18
     VMLAL.S32       Q14, D17, D19
 
-    VSHRN.S64       D26 , Q13, #31
+    VQSHRN.S64       D26 , Q13, #31
 
     VST1.32         D26[0], [R3], R5
     VST1.32         D26[1], [R3], R5
 
-    VSHRN.S64       D27, Q14, #31
+    VQSHRN.S64       D27, Q14, #31
 
     VST1.32         D27[0], [R3], R5
     VST1.32         D27[1], [R3], R5
diff --git a/decoder/armv7/ixheaacd_qmf_dec_armv7.c b/decoder/armv7/ixheaacd_qmf_dec_armv7.c
index 3a18da41..3b4ae1a6 100644
--- a/decoder/armv7/ixheaacd_qmf_dec_armv7.c
+++ b/decoder/armv7/ixheaacd_qmf_dec_armv7.c
@@ -485,6 +485,6 @@ VOID ixheaacd_esbr_qmfsyn32_winadd(WORD32 *tmp1, WORD32 *tmp2, WORD32 *inp1,
     syn_out =
         ixheaac_add64(syn_out, ixheaac_mult64(tmp2[576 + k], inp1[2 * (k + 288)]));
 
-    sample_buffer[ch_fac * k] = (WORD32)(syn_out >> 31);
+    sample_buffer[ch_fac * k] = ixheaac_sat64_32(syn_out >> 31);
   }
 }
diff --git a/decoder/armv8/ixheaacd_qmf_dec_armv8.c b/decoder/armv8/ixheaacd_qmf_dec_armv8.c
index ebd34d52..035649ed 100644
--- a/decoder/armv8/ixheaacd_qmf_dec_armv8.c
+++ b/decoder/armv8/ixheaacd_qmf_dec_armv8.c
@@ -1323,7 +1323,7 @@ VOID ixheaacd_esbr_qmfsyn32_winadd(WORD32 *tmp1, WORD32 *tmp2, WORD32 *inp1,
     syn_out =
         ixheaac_add64(syn_out, ixheaac_mult64(tmp2[576 + k], inp1[2 * (k + 288)]));
 
-    sample_buffer[ch_fac * k] = (WORD32)(syn_out >> 31);
+    sample_buffer[ch_fac * k] = ixheaac_sat64_32(syn_out >> 31);
   }
 }
 
diff --git a/decoder/generic/ixheaacd_qmf_dec_generic.c b/decoder/generic/ixheaacd_qmf_dec_generic.c
index e3e8e4ac..0b381e72 100644
--- a/decoder/generic/ixheaacd_qmf_dec_generic.c
+++ b/decoder/generic/ixheaacd_qmf_dec_generic.c
@@ -1570,7 +1570,7 @@ VOID ixheaacd_esbr_qmfsyn64_winadd(WORD32 *tmp1, WORD32 *tmp2, WORD32 *inp1,
     syn_out =
         ixheaac_add64(syn_out, ixheaac_mult64(tmp2[1152 + k], inp1[k + 576]));
 
-    sample_buffer[ch_fac * k] = (WORD32)(syn_out >> 31);
+    sample_buffer[ch_fac * k] = ixheaac_sat64_32(syn_out >> 31);
   }
 }
 
@@ -1603,7 +1603,7 @@ VOID ixheaacd_esbr_qmfsyn32_winadd(WORD32 *tmp1, WORD32 *tmp2, WORD32 *inp1,
     syn_out =
         ixheaac_add64(syn_out, ixheaac_mult64(tmp2[576 + k], inp1[2 * (k + 288)]));
 
-    sample_buffer[ch_fac * k] = (WORD32)(syn_out >> 31);
+    sample_buffer[ch_fac * k] = ixheaac_sat64_32(syn_out >> 31);
   }
 }