[libav-devel] [PATCH 1/1] opus: simplify fft15 by repeating the first 4 expat values at the end

[Janne Grunau]

---
typo fixed, rebased onto the v2 patch and using FFMAX(N, 19)

 libavcodec/opus_imdct.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/libavcodec/opus_imdct.c b/libavcodec/opus_imdct.c
index 671f8d5..d4ffd95 100644
--- a/libavcodec/opus_imdct.c
+++ b/libavcodec/opus_imdct.c
@@ -27,6 +27,7 @@
 #include <math.h>
 
 #include "libavutil/attributes.h"
+#include "libavutil/common.h"
 
 #include "fft.h"
 #include "opus.h"
@@ -121,7 +122,7 @@ av_cold int ff_celt_imdct_init(CeltIMDCTContext **ps, int N)
 
     for (i = 0; i < FF_ARRAY_ELEMS(s->exptab); i++) {
         int N = 15 * (1 << i);
-        s->exptab[i] = av_malloc(sizeof(*s->exptab[i]) * N);
+        s->exptab[i] = av_malloc(sizeof(*s->exptab[i]) * FFMAX(N, 19));
         if (!s->exptab[i])
             goto fail;
 
@@ -131,6 +132,10 @@ av_cold int ff_celt_imdct_init(CeltIMDCTContext **ps, int 
N)
         }
     }
 
+    // wrap around to simplify fft15
+    for (j = 15; j < 19; j++)
+        s->exptab[0][j] = s->exptab[0][j - 15];
+
     *ps = s;
 
     return 0;
@@ -192,9 +197,8 @@ static void fft15(CeltIMDCTContext *s, FFTComplex *out, 
const FFTComplex *in, in
         out[k].re = tmp[k].re + t1.re + t2.re;
         out[k].im = tmp[k].im + t1.im + t2.im;
 
-        // FIXME
         CMUL(t1, tmp1[k], exptab[k + 5]);
-        CMUL(t2, tmp2[k], k < 3 ? exptab[2 * (k + 5)] : exptab[2 * (k + 5) - 
15]);
+        CMUL(t2, tmp2[k], exptab[2 * (k + 5)]);
         out[k + 5].re = tmp[k].re + t1.re + t2.re;
         out[k + 5].im = tmp[k].im + t1.im + t2.im;
 
-- 
1.9.2

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