ref: 2794b63083124b236ef8159485d65a3173269c8e
parent: ccd51fe9478abba60bc97fa1a85a16781d680673
author: Jean-Marc Valin <[email protected]>
date: Wed Oct 13 13:32:57 EDT 2010
Adding a high-pass filter in front of the transient analysis code
--- a/libcelt/celt.c
+++ b/libcelt/celt.c
@@ -189,18 +189,44 @@
celt_word32 ratio;
celt_word32 threshold;
VARDECL(celt_word32, begin);
+ VARDECL(celt_word16, tmp);
+ celt_word32 mem0=0,mem1=0;
SAVE_STACK;
+ ALLOC(tmp, len, celt_word16);
ALLOC(begin, len+1, celt_word32);
- begin[0] = 0;
+
if (C==1)
{for (i=0;i<len;i++)
- begin[i+1] = MAX32(begin[i], ABS32(in[i]));
+ tmp[i] = SHR32(in[i],SIG_SHIFT);
} else {for (i=0;i<len;i++)
- begin[i+1] = MAX32(begin[i], MAX32(ABS32(in[C*i]),
- ABS32(in[C*i+1])));
+ tmp[i] = SHR32(ADD32(in[C*i],in[C*i+1]), SIG_SHIFT+1);
}
+
+ /* High-pass filter: (1 - 2*z^-1 + z^-2) / (1 - z^-1 + .5*z^-2) */
+ for (i=0;i<len;i++)
+ {+ celt_word32 x,y;
+ x = tmp[i];
+ y = ADD32(mem0, x);
+#ifdef FIXED_POINT
+ mem0 = mem1 + y - SHL32(x,1);
+ mem1 = x - SHR32(y,1);
+#else
+ mem0 = mem1 + y - 2*x;
+ mem1 = x - .5*y;
+#endif
+ tmp[i] = EXTRACT16(SHR(y,2));
+ }
+ /* First few samples are bad because we don't propagate the memory */
+ for (i=0;i<24;i++)
+ tmp[i] = 0;
+
+ begin[0] = 0;
+ for (i=0;i<len;i++)
+ begin[i+1] = MAX32(begin[i], ABS32(tmp[i]));
+
n = -1;
threshold = MULT16_32_Q15(QCONST16(.4f,15),begin[len]);