Add compound_round experiment

This experiment extracts the post compound rounding feature
from convolve_round experiment

                      lowres
convolve_round       -1.493%
compound_round only  -0.874%

Change-Id: I084cf10b5155edd408848e44681f8af66b803724

av1/common/convolve.c

@@ -230,8 +230,13 @@ void av1_convolve_2d(const uint8_t *src, int src_stride, CONV_BUF_TYPE *dst,
       for (k = 0; k < filter_params_x->taps; ++k) {
         sum += x_filter[k] * src_horiz[y * src_stride + x - fo_horiz + k];
       }
+#if CONFIG_COMPOUND_ROUND
+      im_block[y * im_stride + x] =
+          clip_pixel(ROUND_POWER_OF_TWO_SIGNED(sum, conv_params->round_0));
+#else
       im_block[y * im_stride + x] =
           ROUND_POWER_OF_TWO_SIGNED(sum, conv_params->round_0);
+#endif
     }
   }
 

av1/common/convolve.h

@@ -64,7 +64,11 @@ static INLINE ConvolveParams get_conv_params_no_round(int ref, int plane,
   ConvolveParams conv_params;
   conv_params.ref = ref;
   conv_params.round = CONVOLVE_OPT_NO_ROUND;
+#if CONFIG_COMPOUND_ROUND
+  conv_params.round_0 = FILTER_BITS;
+#else
   conv_params.round_0 = 5;
+#endif
   conv_params.round_1 = 0;
   conv_params.dst = dst;
   conv_params.dst_stride = dst_stride;

configure

@@ -252,6 +252,7 @@ EXPERIMENT_LIST="
     tpl_mv
     dual_filter
     convolve_round
+    compound_round
     ext_tx
     tx64x64
     sub8x8_mc
@@ -510,6 +511,7 @@ post_process_cmdline() {
     enabled ec_multisymbol && ! enabled daala_ec && soft_enable ans
     enabled palette_throughput && soft_enable palette
     enabled txk_sel && soft_enable lv_map
+    enabled compound_round && soft_enable convolve_round
     if enabled rawbits && ! enabled daala_ec; then
       log_echo "rawbits requires daala_ec, so disabling rawbits"
       disable_feature rawbits