Turn on row-based multi-threading in the encoder

Turned on row-based multi-threading in the encoder by default.

Change-Id: I92b560d2b51c1ff098e449a3ed396569625690cf
diff --git a/apps/aomenc.c b/apps/aomenc.c
index 87534c5..82448c8 100644
--- a/apps/aomenc.c
+++ b/apps/aomenc.c
@@ -415,7 +415,7 @@
     ARG_DEF(NULL, "cpu-used", 1, "CPU Used (0..8)");
 static const arg_def_t rowmtarg =
     ARG_DEF(NULL, "row-mt", 1,
-            "Enable row based multi-threading (0: off (default), 1: on)");
+            "Enable row based multi-threading (0: off, 1: on (default))");
 static const arg_def_t tile_cols =
     ARG_DEF(NULL, "tile-columns", 1, "Number of tile columns to use, log2");
 static const arg_def_t tile_rows =
diff --git a/av1/av1_cx_iface.c b/av1/av1_cx_iface.c
index 03b061e..26d4319 100644
--- a/av1/av1_cx_iface.c
+++ b/av1/av1_cx_iface.c
@@ -136,7 +136,7 @@
   0,                       // noise_sensitivity
   CONFIG_SHARP_SETTINGS,   // sharpness
   0,                       // static_thresh
-  0,                       // row_mt
+  1,                       // row_mt
   0,                       // tile_columns
   0,                       // tile_rows
   0,                       // enable_tpl_model