Add heuristic quantizer adjustment

AWCY:
https://beta.arewecompressedyet.com/?job=master-c8ca08c77c19514d251b497900d9a24e203caa0b&job=heuristic-sidx-2019-08-19_123457-9a6e4a7

src/rdo.rs

@@ -520,8 +520,24 @@ fn luma_chroma_mode_rdo<T: Pixel>(
 
     // If skip is true, sidx is not coded.
     // If quantizer RDO is disabled, sidx isn't coded either.
-    let sidx_range = if skip || !fi.config.speed_settings.quantizer_rdo {
+    let sidx_range = if skip {
       0..=0
+    } else if !fi.config.speed_settings.quantizer_rdo {
+      let importance =
+        compute_mean_importance(fi, ts.to_frame_block_offset(tile_bo), bsize);
+      // Chosen based on the RDO segment ID statistics for speed 2 on the DOTA2
+      // clip. More precisely:
+      // - Mean importance and the corresponding best sidx chosen by RDO were
+      //   dumped from encoding the DOTA2 clip on --speed 2.
+      // - The values were plotted in a logarithmic 2D histogram.
+      // - Based on that, the value below were chosen.
+      let heuristic_sidx = match importance {
+        x if x >= 0. && x < 2. => 1,
+        x if x >= 2. && x < 4. => 0,
+        x if x >= 4. => 2,
+        _ => unreachable!(),
+      };
+      heuristic_sidx..=heuristic_sidx
     } else {
       0..=2
     };

src/segmentation.rs

@@ -18,28 +18,27 @@ use crate::FrameState;
 pub fn segmentation_optimize<T: Pixel>(
   fi: &FrameInvariants<T>, fs: &mut FrameState<T>,
 ) {
-  // Segmentation is currently used only for the quantizer RDO.
-  if fi.config.speed_settings.quantizer_rdo {
-    fs.segmentation.enabled = true;
-    fs.segmentation.update_map = true;
+  fs.segmentation.enabled = true;
+  fs.segmentation.update_map = true;
 
-    // We don't change the values between frames.
-    fs.segmentation.update_data = fi.primary_ref_frame == PRIMARY_REF_NONE;
+  // We don't change the values between frames.
+  fs.segmentation.update_data = fi.primary_ref_frame == PRIMARY_REF_NONE;
 
-    // A series of AWCY runs with deltas 10, 13, 15, 17, 20 showed this to be
-    // the optimal one.
-    const TEMPORAL_RDO_QI_DELTA: i16 = 15;
+  // A series of AWCY runs with deltas 10, 13, 15, 17, 20 showed this to be
+  // the optimal one.
+  const TEMPORAL_RDO_QI_DELTA: i16 = 15;
 
-    // Fill in 3 slots with 0, delta, -delta.
-    for i in 0..3 {
-      fs.segmentation.features[i][SegLvl::SEG_LVL_ALT_Q as usize] = true;
-      fs.segmentation.data[i][SegLvl::SEG_LVL_ALT_Q as usize] = match i {
-        0 => 0,
-        1 => TEMPORAL_RDO_QI_DELTA,
-        2 => -TEMPORAL_RDO_QI_DELTA,
-        _ => unreachable!(),
-      };
-    }
+  // Fill in 3 slots with 0, delta, -delta. The slot IDs are also used in
+  // luma_chroma_mode_rdo() so if you change things here make sure to check
+  // that place too.
+  for i in 0..3 {
+    fs.segmentation.features[i][SegLvl::SEG_LVL_ALT_Q as usize] = true;
+    fs.segmentation.data[i][SegLvl::SEG_LVL_ALT_Q as usize] = match i {
+      0 => 0,
+      1 => TEMPORAL_RDO_QI_DELTA,
+      2 => -TEMPORAL_RDO_QI_DELTA,
+      _ => unreachable!(),
+    };
   }
 
   /* Figure out parameters */