From 2da3721b16291b5a15928bb88691d8ee65e411e8 Mon Sep 17 00:00:00 2001
From: Jean-Marc Valin <jmvalin@jmvalin.ca>
Date: Sun, 8 Oct 2017 03:21:38 -0400
Subject: [PATCH] Simplifying celt_fir5() since x==y and mem[]={0}

Addresses issue https://github.com/xiph/opus/issues/58
---
 celt/pitch.c | 27 ++++++++++-----------------
 1 file changed, 10 insertions(+), 17 deletions(-)

diff --git a/celt/pitch.c b/celt/pitch.c
index 5b061d86..38a9e68d 100644
--- a/celt/pitch.c
+++ b/celt/pitch.c
@@ -102,11 +102,9 @@ static void find_best_pitch(opus_val32 *xcorr, opus_val16 *y, int len,
    }
 }
 
-static void celt_fir5(const opus_val16 *x,
+static void celt_fir5(opus_val16 *x,
          const opus_val16 *num,
-         opus_val16 *y,
-         int N,
-         opus_val16 *mem)
+         int N)
 {
    int i;
    opus_val16 num0, num1, num2, num3, num4;
@@ -116,11 +114,11 @@ static void celt_fir5(const opus_val16 *x,
    num2=num[2];
    num3=num[3];
    num4=num[4];
-   mem0=mem[0];
-   mem1=mem[1];
-   mem2=mem[2];
-   mem3=mem[3];
-   mem4=mem[4];
+   mem0=0;
+   mem1=0;
+   mem2=0;
+   mem3=0;
+   mem4=0;
    for (i=0;i<N;i++)
    {
       opus_val32 sum = SHL32(EXTEND32(x[i]), SIG_SHIFT);
@@ -134,13 +132,8 @@ static void celt_fir5(const opus_val16 *x,
       mem2 = mem1;
       mem1 = mem0;
       mem0 = x[i];
-      y[i] = ROUND16(sum, SIG_SHIFT);
+      x[i] = ROUND16(sum, SIG_SHIFT);
    }
-   mem[0]=mem0;
-   mem[1]=mem1;
-   mem[2]=mem2;
-   mem[3]=mem3;
-   mem[4]=mem4;
 }
 
 
@@ -150,7 +143,7 @@ void pitch_downsample(celt_sig * OPUS_RESTRICT x[], opus_val16 * OPUS_RESTRICT x
    int i;
    opus_val32 ac[5];
    opus_val16 tmp=Q15ONE;
-   opus_val16 lpc[4], mem[5]={0,0,0,0,0};
+   opus_val16 lpc[4];
    opus_val16 lpc2[5];
    opus_val16 c1 = QCONST16(.8f,15);
 #ifdef FIXED_POINT
@@ -211,7 +204,7 @@ void pitch_downsample(celt_sig * OPUS_RESTRICT x[], opus_val16 * OPUS_RESTRICT x
    lpc2[2] = lpc[2] + MULT16_16_Q15(c1,lpc[1]);
    lpc2[3] = lpc[3] + MULT16_16_Q15(c1,lpc[2]);
    lpc2[4] = MULT16_16_Q15(c1,lpc[3]);
-   celt_fir5(x_lp, lpc2, x_lp, len>>1, mem);
+   celt_fir5(x_lp, lpc2, len>>1);
 }
 
 /* Pure C implementation. */