ref: 51231750178c8a4bf87157d82fb3cd2fb93b50b2
parent: 58107d896811f0e975bc1f8f75a5c1c2f6e746b0
author: Jean-Marc Valin <[email protected]>
date: Wed Jan 29 05:16:53 EST 2014
Speeding up ec_tell_frac()
--- a/celt/entcode.c
+++ b/celt/entcode.c
@@ -62,10 +62,31 @@
}
#endif
+#if 1
+/* This is a faster version of ec_tell_frac() that takes advantage
+ of the low (1/8 bit) resolution to use just a linear function
+ followed by a lookup to determine the exact transition thresholds. */
opus_uint32 ec_tell_frac(ec_ctx *_this){+ static const unsigned correction[8] =
+ {35733, 38967, 42495, 46340,+ 50535, 55109, 60097, 65535};
opus_uint32 nbits;
opus_uint32 r;
int l;
+ unsigned b;
+ nbits=_this->nbits_total<<BITRES;
+ l=EC_ILOG(_this->rng);
+ r=_this->rng>>(l-16);
+ b = (r>>12)-8;
+ b += r>correction[b];
+ l = (l<<3)+b;
+ return nbits-l;
+}
+#else
+opus_uint32 ec_tell_frac(ec_ctx *_this){+ opus_uint32 nbits;
+ opus_uint32 r;
+ int l;
int i;
/*To handle the non-integral number of bits still left in the encoder/decoder
state, we compute the worst-case number of bits of val that must be
@@ -91,6 +112,7 @@
}
return nbits-l;
}
+#endif
#ifdef USE_SMALL_DIV_TABLE
/* Result of 2^32/(2*i+1), except for i=0. */