shithub: libvpx

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optimize fast_quantizer c version

As the zbin and rounding constants are normalized, rounding effectively
does the zbinning, therefore the zbin operation can be removed. In
addition, the memset on the two arrays are no longer necessary.

Change-Id: If39c353c42d7e052296cb65322e5218810b5cc4c

--- a/vp8/encoder/quantize.c

+++ b/vp8/encoder/quantize.c

@@ -125,7 +125,6 @@

     int zbin;

     int x, y, z, sz;

     short *coeff_ptr  = &b->coeff[0];

-    short *zbin_ptr   = &b->zbin[0][0];

     short *round_ptr  = &b->round[0][0];

     short *quant_ptr  = &b->quant[0][0];

     short *qcoeff_ptr = d->qcoeff;

@@ -132,31 +131,23 @@

     short *dqcoeff_ptr = d->dqcoeff;

     short *dequant_ptr = &d->dequant[0][0];

-    vpx_memset(qcoeff_ptr, 0, 32);

-    vpx_memset(dqcoeff_ptr, 0, 32);

-

     eob = -1;

-

     for (i = 0; i < 16; i++)

     {

         rc   = vp8_default_zig_zag1d[i];

         z    = coeff_ptr[rc];

-        zbin = zbin_ptr[rc] ;

         sz = (z >> 31);                                 // sign of z

         x  = (z ^ sz) - sz;                             // x = abs(z)

-        if (x >= zbin)

-        {

-            y  = ((x + round_ptr[rc]) * quant_ptr[rc]) >> 16; // quantize (x)

-            x  = (y ^ sz) - sz;                         // get the sign back

-            qcoeff_ptr[rc] = x;                          // write to destination

-            dqcoeff_ptr[rc] = x * dequant_ptr[rc];        // dequantized value

+        y  = ((x + round_ptr[rc]) * quant_ptr[rc]) >> 16; // quantize (x)

+        x  = (y ^ sz) - sz;                         // get the sign back

+        qcoeff_ptr[rc] = x;                          // write to destination

+        dqcoeff_ptr[rc] = x * dequant_ptr[rc];        // dequantized value

-            if (y)

-            {

-                eob = i;                                // last nonzero coeffs

-            }

+        if (y)

+        {

+            eob = i;                                // last nonzero coeffs

         }

     }

     d->eob = eob + 1;