libvpx: Pull from upstream

source/libvpx/vp9/encoder/vp9_aq_complexity.c

 /*
  *  Copyright (c) 2014 The WebM project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 29 matching lines @@
     vp9_clearall_segfeatures(seg);
 
     // Select delta coding method.
     seg->abs_delta = SEGMENT_DELTADATA;
 
     // Segment 0 "Q" feature is disabled so it defaults to the baseline Q.
     vp9_disable_segfeature(seg, 0, SEG_LVL_ALT_Q);
 
     // Use some of the segments for in frame Q adjustment.
     for (segment = 1; segment < 2; segment++) {
-      const int qindex_delta =
+      int qindex_delta =
           vp9_compute_qdelta_by_rate(&cpi->rc, cm->frame_type, cm->base_qindex,
                                      in_frame_q_adj_ratio[segment]);
-      vp9_enable_segfeature(seg, segment, SEG_LVL_ALT_Q);
-      vp9_set_segdata(seg, segment, SEG_LVL_ALT_Q, qindex_delta);
+
+      // For AQ mode 2, we dont allow Q0 in a segment if the base Q is not 0.
+      // Q0 (lossless) implies 4x4 only and in AQ mode 2 a segment Q delta
+      // is sometimes applied without going back around the rd loop.
+      // This could lead to an illegal combination of partition size and q.
+      if ((cm->base_qindex != 0) && ((cm->base_qindex + qindex_delta) == 0)) {
+        qindex_delta = -cm->base_qindex + 1;
+      }
+      if ((cm->base_qindex + qindex_delta) > 0) {
+        vp9_enable_segfeature(seg, segment, SEG_LVL_ALT_Q);
+        vp9_set_segdata(seg, segment, SEG_LVL_ALT_Q, qindex_delta);
+      }
     }
   }
 }
 
 // Select a segment for the current SB64
 void vp9_select_in_frame_q_segment(VP9_COMP *cpi,
                                       int mi_row, int mi_col,
                                       int output_enabled, int projected_rate) {
   VP9_COMMON *const cm = &cpi->common;
 
@@ skipping 29 matching lines @@
 
   // Fill in the entires in the segment map corresponding to this SB64.
   for (y = 0; y < ymis; y++) {
     for (x = 0; x < xmis; x++) {
       cpi->segmentation_map[mi_offset + y * cm->mi_cols + x] = segment;
       cpi->complexity_map[mi_offset + y * cm->mi_cols + x] =
         (unsigned char)complexity_metric;
     }
   }
 }