rtc: Relax conditions for setting high_motion_flag

Relax the conditions for setting the
rc->high_motion_content_screen_rtc flag, and
fix the usage of rc->last_frame_low_source_sad to be
based on rc->frame_number_encoded (to account for layers
and dropped frames).

This is to bring back some speedup for some high motion
content in nautural video sequences. It should heve
little/no effect on text scrolling content sequences.

Bug: b:456115209, b:444116924
Change-Id: I12f3a82f527c9f6f3edc5a96c61f3729e852467d

av1/encoder/ratectrl.c

diff --git a/av1/encoder/ratectrl.c b/av1/encoder/ratectrl.c
index 161527d..69ade17 100644
--- a/av1/encoder/ratectrl.c
+++ b/av1/encoder/ratectrl.c
@@ -2481,13 +2481,15 @@
   }
   if (cpi->refresh_frame.golden_frame)
     rc->frame_num_last_gf_refresh = current_frame->frame_number;
+
+  if (rc->frame_source_sad < 10000)
+    rc->last_frame_low_source_sad = rc->frame_number_encoded;
+
   rc->prev_coded_width = cm->width;
   rc->prev_coded_height = cm->height;
   rc->frame_number_encoded++;
   rc->prev_frame_is_dropped = 0;
   rc->drop_count_consec = 0;
-  if (rc->frame_source_sad < 10000)
-    rc->last_frame_low_source_sad = current_frame->frame_number;
 }
 
 void av1_rc_postencode_update_drop_frame(AV1_COMP *cpi) {
@@ -3362,12 +3364,12 @@
     cpi->rc.high_motion_content_screen_rtc = 0;
     if (cpi->oxcf.speed >= 11 &&
         cpi->oxcf.tune_cfg.content == AOM_CONTENT_SCREEN &&
-        rc->num_col_blscroll_last_tl0 == 0 &&
-        rc->num_row_blscroll_last_tl0 == 0 &&
+        rc->num_col_blscroll_last_tl0 < 5 &&
+        rc->num_row_blscroll_last_tl0 < 5 &&
         rc->percent_blocks_with_motion > 40 &&
         rc->prev_avg_source_sad > thresh_high_motion &&
         rc->avg_source_sad > thresh_high_motion &&
-        cm->current_frame.frame_number - rc->last_frame_low_source_sad > 10 &&
+        rc->frame_number_encoded - rc->last_frame_low_source_sad > 12 &&
         rc->avg_frame_low_motion < 60 && unscaled_src->y_width >= 1280 &&
         unscaled_src->y_height >= 720) {
       cpi->rc.high_motion_content_screen_rtc = 1;