From 37131e3ab391adfe7da68d9c457da677789ecb68 Mon Sep 17 00:00:00 2001
From: Jean-Marc Valin <jean-marc.valin@usherbrooke.ca>
Date: Fri, 29 Feb 2008 20:03:41 +1100
Subject: [PATCH] Just realised half the twiddles in the real FFT weren't even
used. Removing them saves another 1kB for fixed-point (2kB for float or full
precision)
---
libcelt/kiss_fftr.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)
diff --git a/libcelt/kiss_fftr.c b/libcelt/kiss_fftr.c
index 833699f4b..979aac95a 100644
--- a/libcelt/kiss_fftr.c
+++ b/libcelt/kiss_fftr.c
@@ -35,6 +35,7 @@ struct kiss_fftr_state{
kiss_fftr_cfg kiss_fftr_alloc(int nfft,void * mem,size_t * lenmem)
{
int i;
+ int twiddle_size;
kiss_fftr_cfg st = NULL;
size_t subsize, memneeded;
@@ -43,9 +44,9 @@ kiss_fftr_cfg kiss_fftr_alloc(int nfft,void * mem,size_t * lenmem)
return NULL;
}
nfft >>= 1;
-
+ twiddle_size = nfft/2+1;
kiss_fft_alloc (nfft, NULL, &subsize);
- memneeded = sizeof(struct kiss_fftr_state) + subsize + sizeof(kiss_twiddle_cpx)*nfft;
+ memneeded = sizeof(struct kiss_fftr_state) + subsize + sizeof(kiss_twiddle_cpx)*twiddle_size;
if (lenmem == NULL) {
st = (kiss_fftr_cfg) KISS_FFT_MALLOC (memneeded);
@@ -65,12 +66,12 @@ kiss_fftr_cfg kiss_fftr_alloc(int nfft,void * mem,size_t * lenmem)
#endif
#if defined (FIXED_POINT) && !defined(DOUBLE_PRECISION)
- for (i=0;i<nfft;++i) {
+ for (i=0;i<twiddle_size;++i) {
celt_word32_t phase = i+(nfft>>1);
kf_cexp2(st->super_twiddles+i, DIV32(SHL32(phase,16),nfft));
}
#else
- for (i=0;i<nfft;++i) {
+ for (i=0;i<twiddle_size;++i) {
const double pi=3.14159265358979323846264338327;
double phase = pi*(((double)i) /nfft + .5);
kf_cexp(st->super_twiddles+i, phase );
--
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