AV1 RT: Limit RT RDO TX types to DCT only

5-6% speed up on Speed6 on lowres with 0.5% BDRate loss
1.4% Max BDRate loss
No impact on other speeds

Change-Id: I0aa260b563d19dbcbe58dc088c1578efccefdc7d

av1/encoder/speed_features.c

diff --git a/av1/encoder/speed_features.c b/av1/encoder/speed_features.c
index 0024c66..6035876 100644
--- a/av1/encoder/speed_features.c
+++ b/av1/encoder/speed_features.c
@@ -813,6 +813,7 @@
 
     sf->tx_sf.tx_type_search.prune_mode = PRUNE_2D_MORE;
     sf->tx_sf.use_inter_txb_hash = 0;
+    sf->tx_sf.refine_fast_tx_search_results = 0;
 
     sf->rd_sf.optimize_coefficients = NO_TRELLIS_OPT;
     sf->rd_sf.simple_model_rd_from_var = 1;
@@ -1042,6 +1043,7 @@
   tx_sf->adaptive_txb_search_level = 0;
   tx_sf->use_intra_txb_hash = 0;
   tx_sf->use_inter_txb_hash = 1;
+  tx_sf->refine_fast_tx_search_results = 1;
 }
 
 static AOM_INLINE void init_rd_sf(RD_CALC_SPEED_FEATURES *rd_sf,

av1/encoder/speed_features.h

diff --git a/av1/encoder/speed_features.h b/av1/encoder/speed_features.h
index e45c18c..acb1e35 100644
--- a/av1/encoder/speed_features.h
+++ b/av1/encoder/speed_features.h
@@ -766,6 +766,9 @@
   // Use hash table to store inter txb transform search results
   // to avoid repeated search on the same residue signal.
   int use_inter_txb_hash;
+
+  // Refine TX type after fast TX search.
+  int refine_fast_tx_search_results;
 } TX_SPEED_FEATURES;
 
 typedef struct RD_CALC_SPEED_FEATURES {

av1/encoder/tx_search.c

diff --git a/av1/encoder/tx_search.c b/av1/encoder/tx_search.c
index ee85454..d6a0fdc 100644
--- a/av1/encoder/tx_search.c
+++ b/av1/encoder/tx_search.c
@@ -3154,7 +3154,7 @@
   // If fast_tx_search is true, only DCT and 1D DCT were tested in
   // select_inter_block_yrd() above. Do a better search for tx type with
   // tx sizes already decided.
-  if (fast_tx_search) {
+  if (fast_tx_search && cpi->sf.tx_sf.refine_fast_tx_search_results) {
     if (!inter_block_yrd(cpi, x, rd_stats, bsize, ref_best_rd, FTXS_NONE))
       return INT64_MAX;
   }

test/rt_end_to_end_test.cc

diff --git a/test/rt_end_to_end_test.cc b/test/rt_end_to_end_test.cc
index 1de22f0..124a719 100644
--- a/test/rt_end_to_end_test.cc
+++ b/test/rt_end_to_end_test.cc
@@ -32,11 +32,11 @@
 std::unordered_map<std::string,
                    std::unordered_map<int, std::unordered_map<int, double>>>
     kPsnrThreshold = { { "park_joy_90p_8_420.y4m",
-                         { { 6, { { 0, 35.4 }, { 3, 36.2 } } },
+                         { { 6, { { 0, 35.3 }, { 3, 36.2 } } },
                            { 7, { { 0, 34.9 }, { 3, 35.8 } } },
                            { 8, { { 0, 35.0 }, { 3, 35.8 } } } } },
                        { "paris_352_288_30.y4m",
-                         { { 6, { { 0, 36.2 }, { 3, 36.7 } } },
+                         { { 6, { { 0, 36.1 }, { 3, 36.6 } } },
                            { 7, { { 0, 35.5 }, { 3, 36.0 } } },
                            { 8, { { 0, 36.0 }, { 3, 36.5 } } } } },
                        { "niklas_1280_720_30.y4m",