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Replace pow(x, 0.75) with sqrtf(x * sqrtf(x)) for a 33% speedup.

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Originally committed as revision 19459 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Alex Converse 2009-07-17 14:21:49 +00:00
parent 4e67aedd6a
commit 3d51be014c
1 changed files with 8 additions and 5 deletions
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13
libavcodec/aaccoder.c
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@ -61,7 +61,8 @@ static const uint8_t *run_value_bits[2] = {
*/
static av_always_inline int quant(float coef, const float Q)
{
return pow(coef * Q, 0.75) + 0.4054;
float a = coef * Q;
return sqrtf(a * sqrtf(a)) + 0.4054;
}
static void quantize_bands(int (*out)[2], const float *in, const float *scaled,
@ -84,8 +85,10 @@ static void abs_pow34_v(float *out, const float *in, const int size)
{
#ifndef USE_REALLY_FULL_SEARCH
int i;
for (i = 0; i < size; i++)
out[i] = pow(fabsf(in[i]), 0.75);
for (i = 0; i < size; i++) {
float a = fabsf(in[i]);
out[i] = sqrtf(a * sqrtf(a));
}
#endif /* USE_REALLY_FULL_SEARCH */
}
@ -110,7 +113,7 @@ static float quantize_band_cost(struct AACEncContext *s, const float *in,
const int dim = cb < FIRST_PAIR_BT ? 4 : 2;
int resbits = 0;
#ifndef USE_REALLY_FULL_SEARCH
const float Q34 = pow(Q, 0.75);
const float Q34 = sqrtf(Q * sqrtf(Q));
const int range = aac_cb_range[cb];
const int maxval = aac_cb_maxval[cb];
int offs[4];
@ -225,7 +228,7 @@ static void quantize_and_encode_band(struct AACEncContext *s, PutBitContext *pb,
const int dim = (cb < FIRST_PAIR_BT) ? 4 : 2;
int i, j, k;
#ifndef USE_REALLY_FULL_SEARCH
const float Q34 = pow(Q, 0.75);
const float Q34 = sqrtf(Q * sqrtf(Q));
const int range = aac_cb_range[cb];
const int maxval = aac_cb_maxval[cb];
int offs[4];