shithub: libvpx

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Skip inverse transform when eob is zero

When all the transform coefficients were quantized to zero, skip
the inverse transform operation. For bus_cif at 1000 kbps, the
runtime goes from 154967ms -> 149842ms, i.e., about 3% speed-up,
at speed 0.

Change-Id: Ic0a813fff5e28972d4888ee42d8747846a6c3cc6

--- a/vp9/encoder/vp9_encodemb.c

+++ b/vp9/encoder/vp9_encodemb.c

@@ -533,6 +533,8 @@

   if (x->skip_encode)

     return;

+  if (pd->eobs[block] == 0)

+    return;

   switch (ss_txfrm_size / 2) {

     case TX_32X32:

@@ -657,7 +659,7 @@

       vp9_quantize_b_32x32(coeff, 1024, x->skip_block, p->zbin, p->round,

                            p->quant, p->quant_shift, qcoeff, dqcoeff,

                            pd->dequant, p->zbin_extra, eob, scan, iscan);

-      if (!x->skip_encode)

+      if (!x->skip_encode && *eob)

         vp9_short_idct32x32_add(dqcoeff, dst, pd->dst.stride);

       break;

     case TX_16X16:

@@ -682,7 +684,7 @@

       vp9_quantize_b(coeff, 256, x->skip_block, p->zbin, p->round, p->quant,

                      p->quant_shift, qcoeff, dqcoeff,

                      pd->dequant, p->zbin_extra, eob, scan, iscan);

-      if (!x->skip_encode) {

+      if (!x->skip_encode && *eob) {

         if (tx_type == DCT_DCT)

           vp9_short_idct16x16_add(dqcoeff, dst, pd->dst.stride);

         else

@@ -711,7 +713,7 @@

       vp9_quantize_b(coeff, 64, x->skip_block, p->zbin, p->round, p->quant,

                      p->quant_shift, qcoeff, dqcoeff,

                      pd->dequant, p->zbin_extra, eob, scan, iscan);

-      if (!x->skip_encode) {

+      if (!x->skip_encode && *eob) {

         if (tx_type == DCT_DCT)

           vp9_short_idct8x8_add(dqcoeff, dst, pd->dst.stride);

         else

@@ -743,7 +745,7 @@

       vp9_quantize_b(coeff, 16, x->skip_block, p->zbin, p->round, p->quant,

                      p->quant_shift, qcoeff, dqcoeff,

                      pd->dequant, p->zbin_extra, eob, scan, iscan);

-      if (!x->skip_encode) {

+      if (!x->skip_encode && *eob) {

         if (tx_type == DCT_DCT)

           // this is like vp9_short_idct4x4 but has a special case around eob<=1

           // which is significant (not just an optimization) for the lossless