From 4a7027b27e2d962dedc63360a45db5ff74dc1131 Mon Sep 17 00:00:00 2001
From: Jean-Marc Valin <jmvalin@jmvalin.ca>
Date: Thu, 27 Oct 2011 13:51:21 -0400
Subject: [PATCH] Allow wrap-around in silk_LPC_analysis_filter()
---
silk/LPC_analysis_filter.c | 18 ++++++++++--------
silk/SigProc_FIX.h | 3 +++
2 files changed, 13 insertions(+), 8 deletions(-)
diff --git a/silk/LPC_analysis_filter.c b/silk/LPC_analysis_filter.c
index a8d1c3339..5fc4349bd 100644
--- a/silk/LPC_analysis_filter.c
+++ b/silk/LPC_analysis_filter.c
@@ -58,18 +58,20 @@ void silk_LPC_analysis_filter(
in_ptr = &in[ ix - 1 ];
out32_Q12 = silk_SMULBB( in_ptr[ 0 ], B[ 0 ] );
- out32_Q12 = silk_SMLABB( out32_Q12, in_ptr[ -1 ], B[ 1 ] );
- out32_Q12 = silk_SMLABB( out32_Q12, in_ptr[ -2 ], B[ 2 ] );
- out32_Q12 = silk_SMLABB( out32_Q12, in_ptr[ -3 ], B[ 3 ] );
- out32_Q12 = silk_SMLABB( out32_Q12, in_ptr[ -4 ], B[ 4 ] );
- out32_Q12 = silk_SMLABB( out32_Q12, in_ptr[ -5 ], B[ 5 ] );
+ /* Allowing wrap around so that two wraps can cancel each other. The rare
+ cases where the result wraps around can only be triggered by invalid streams*/
+ out32_Q12 = silk_SMLABB_ovflw( out32_Q12, in_ptr[ -1 ], B[ 1 ] );
+ out32_Q12 = silk_SMLABB_ovflw( out32_Q12, in_ptr[ -2 ], B[ 2 ] );
+ out32_Q12 = silk_SMLABB_ovflw( out32_Q12, in_ptr[ -3 ], B[ 3 ] );
+ out32_Q12 = silk_SMLABB_ovflw( out32_Q12, in_ptr[ -4 ], B[ 4 ] );
+ out32_Q12 = silk_SMLABB_ovflw( out32_Q12, in_ptr[ -5 ], B[ 5 ] );
for( j = 6; j < d; j += 2 ) {
- out32_Q12 = silk_SMLABB( out32_Q12, in_ptr[ -j ], B[ j ] );
- out32_Q12 = silk_SMLABB( out32_Q12, in_ptr[ -j - 1 ], B[ j + 1 ] );
+ out32_Q12 = silk_SMLABB_ovflw( out32_Q12, in_ptr[ -j ], B[ j ] );
+ out32_Q12 = silk_SMLABB_ovflw( out32_Q12, in_ptr[ -j - 1 ], B[ j + 1 ] );
}
/* Subtract prediction */
- out32_Q12 = silk_SUB32( silk_LSHIFT( (opus_int32)in_ptr[ 1 ], 12 ), out32_Q12 );
+ out32_Q12 = silk_SUB32_ovflw( silk_LSHIFT( (opus_int32)in_ptr[ 1 ], 12 ), out32_Q12 );
/* Scale to Q0 */
out32 = silk_RSHIFT_ROUND( out32_Q12, 12 );
diff --git a/silk/SigProc_FIX.h b/silk/SigProc_FIX.h
index 24052ff9c..d24eac6f2 100644
--- a/silk/SigProc_FIX.h
+++ b/silk/SigProc_FIX.h
@@ -421,6 +421,9 @@ static inline opus_int32 silk_ROR32( opus_int32 a32, opus_int rot )
(just standard two's complement implementation-specific behaviour) */
#define silk_SUB32_ovflw(a, b) ((opus_int32)((opus_uint32)(a) - (opus_uint32)(b)))
+/* a32 + (opus_int32)((opus_int16)(b32)) * (opus_int32)((opus_int16)(c32)) output have to be 32bit int */
+#define silk_SMLABB_ovflw(a32, b32, c32) (silk_ADD32_ovflw((a32) , ((opus_int32)((opus_int16)(b32))) * (opus_int32)((opus_int16)(c32))))
+
/* Multiply-accumulate macros that allow overflow in the addition (ie, no asserts in debug mode)*/
#define silk_MLA_ovflw(a32, b32, c32) silk_ADD32_ovflw((a32), (opus_uint32)(b32) * (opus_uint32)(c32))
#ifndef silk_SMLABB_ovflw
--
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