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lavc/wmadec: replace pow by faster functions 

Further speedups possible by getting rid of exp2f...

Reviewed-by: Paul B Mahol <onemda@gmail.com>
Signed-off-by: Ganesh Ajjanagadde <gajjanagadde@gmail.com>
This commit is contained in:
Ganesh Ajjanagadde 2016-01-15 13:51:03 -05:00
parent cea529dd7f
commit 1fb5ae44c4
1 changed files with 3 additions and 2 deletions
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5
libavcodec/wmadec.c
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@ -35,6 +35,7 @@
#include "libavutil/attributes.h"
#include "libavutil/internal.h"
#include "libavutil/libm.h"
#include "avcodec.h"
#include "internal.h"
@ -164,7 +165,7 @@ static av_cold void wma_lsp_to_curve_init(WMACodecContext *s, int frame_len)
/* tables for x^-0.25 computation */
for (i = 0; i < 256; i++) {
e = i - 126;
s->lsp_pow_e_table[i] = pow(2.0, e * -0.25);
s->lsp_pow_e_table[i] = exp2f(e * -0.25);
}
/* NOTE: these two tables are needed to avoid two operations in
@ -173,7 +174,7 @@ static av_cold void wma_lsp_to_curve_init(WMACodecContext *s, int frame_len)
for (i = (1 << LSP_POW_BITS) - 1; i >= 0; i--) {
m = (1 << LSP_POW_BITS) + i;
a = (float) m * (0.5 / (1 << LSP_POW_BITS));
a = pow(a, -0.25);
a = 1/sqrt(sqrt(a));
s->lsp_pow_m_table1[i] = 2 * a - b;
s->lsp_pow_m_table2[i] = b - a;
b = a;