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Directly saturate the comb filter output

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Otherwise, the output can grow as large as SIG_SAT/(1-0.75), which can cause
an overflow when adding two values (before multiplying by the filter tap).
This commit is contained in:
Jean-Marc Valin 2016-07-24 15:30:40 -04:00
parent b1d38ed32e
commit cbceaa8579
1 changed files with 8 additions and 9 deletions
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17
celt/celt.c
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@ -111,26 +111,31 @@ void comb_filter_const_c(opus_val32 *y, opus_val32 *x, int T, int N,
t = MAC16_32_Q16(x[i], g10, x2);
t = MAC16_32_Q16(t, g11, ADD32(x1,x3));
t = MAC16_32_Q16(t, g12, ADD32(x0,x4));
t = SATURATE(t, SIG_SAT);
y[i] = t;
x4=SHL32(x[i-T+3],1);
t = MAC16_32_Q16(x[i+1], g10, x1);
t = MAC16_32_Q16(t, g11, ADD32(x0,x2));
t = MAC16_32_Q16(t, g12, ADD32(x4,x3));
t = SATURATE(t, SIG_SAT);
y[i+1] = t;
x3=SHL32(x[i-T+4],1);
t = MAC16_32_Q16(x[i+2], g10, x0);
t = MAC16_32_Q16(t, g11, ADD32(x4,x1));
t = MAC16_32_Q16(t, g12, ADD32(x3,x2));
t = SATURATE(t, SIG_SAT);
y[i+2] = t;
x2=SHL32(x[i-T+5],1);
t = MAC16_32_Q16(x[i+3], g10, x4);
t = MAC16_32_Q16(t, g11, ADD32(x3,x0));
t = MAC16_32_Q16(t, g12, ADD32(x2,x1));
t = SATURATE(t, SIG_SAT);
y[i+3] = t;
x1=SHL32(x[i-T+6],1);
t = MAC16_32_Q16(x[i+4], g10, x3);
t = MAC16_32_Q16(t, g11, ADD32(x2,x4));
t = MAC16_32_Q16(t, g12, ADD32(x1,x0));
t = SATURATE(t, SIG_SAT);
y[i+4] = t;
}
#ifdef CUSTOM_MODES
@ -141,6 +146,7 @@ void comb_filter_const_c(opus_val32 *y, opus_val32 *x, int T, int N,
t = MAC16_32_Q16(x[i], g10, x2);
t = MAC16_32_Q16(t, g11, ADD32(x1,x3));
t = MAC16_32_Q16(t, g12, ADD32(x0,x4));
t = SATURATE(t, SIG_SAT);
y[i] = t;
x4=x3;
x3=x2;
@ -169,6 +175,7 @@ void comb_filter_const_c(opus_val32 *y, opus_val32 *x, int T, int N,
+ MULT16_32_Q15(g10,x2)
+ MULT16_32_Q15(g11,ADD32(x1,x3))
+ MULT16_32_Q15(g12,ADD32(x0,x4));
y[i] = SATURATE(y[i], SIG_SAT);
x4=x3;
x3=x2;
x2=x1;
@ -225,6 +232,7 @@ void comb_filter(opus_val32 *y, opus_val32 *x, int T0, int T1, int N,
+ MULT16_32_Q15(MULT16_16_Q15(f,g10),x2)
+ MULT16_32_Q15(MULT16_16_Q15(f,g11),ADD32(x1,x3))
+ MULT16_32_Q15(MULT16_16_Q15(f,g12),ADD32(x0,x4));
y[i] = SATURATE(y[i], SIG_SAT);
x4=x3;
x3=x2;
x2=x1;
@ -236,20 +244,11 @@ void comb_filter(opus_val32 *y, opus_val32 *x, int T0, int T1, int N,
/* OPT: Happens to work without the OPUS_MOVE(), but only because the current encoder already copies x to y */
if (x!=y)
OPUS_MOVE(y+overlap, x+overlap, N-overlap);
#ifdef FIXED_POINT
for (i=0; i < overlap; i++)
y[i] = SATURATE(y[i], SIG_SAT);
#endif
return;
}
/* Compute the part with the constant filter. */
comb_filter_const(y+i, x+i, T1, N-i, g10, g11, g12, arch);
#ifdef FIXED_POINT
for (i=0; i < N; i++)
y[i] = SATURATE(y[i], SIG_SAT);
#endif
}
#endif /* OVERRIDE_comb_filter */