diff options
-rw-r--r-- | libavcodec/cook.c | 11 |
1 files changed, 9 insertions, 2 deletions
diff --git a/libavcodec/cook.c b/libavcodec/cook.c index d8fb736828..1b38019a69 100644 --- a/libavcodec/cook.c +++ b/libavcodec/cook.c @@ -166,10 +166,17 @@ static float rootpow2tab[127]; /* table generator */ static av_cold void init_pow2table(void) { + /* fast way of computing 2^i and 2^(0.5*i) for -63 <= i < 64 */ int i; + static const float exp2_tab[2] = {1, M_SQRT2}; + float exp2_val = powf(2, -63); + float root_val = powf(2, -32); for (i = -63; i < 64; i++) { - pow2tab[63 + i] = pow(2, i); - rootpow2tab[63 + i] = sqrt(pow(2, i)); + if (!(i & 1)) + root_val *= 2; + pow2tab[63 + i] = exp2_val; + rootpow2tab[63 + i] = root_val * exp2_tab[i & 1]; + exp2_val *= 2; } } |