shithub: libvpx

Download patch

ref: ffa06b37083d028b50f27e67ae6ed0c6ee9953bb
parent: 1687c47bfdff2a4a6d2a07fb143be3f9b21824ff
author: Yaowu Xu <yaowu@google.com>
date: Tue Nov 18 03:52:21 EST 2014 

Prevent severe rate control errors in CBR mode

In rare cases, the interaction between rate correction factor and Q
choices may cause severe oscillating frame sizes that are way off
target bandwidth. This commit adds tracking of rate control results
for last two frames, and use the information to prevent oscillating
Q choices.

Change-Id: I9a6d125a15652b9bcac0e1fec6d7a1aedc4ed97e


--- a/vp9/encoder/vp9_ratectrl.c
+++ b/vp9/encoder/vp9_ratectrl.c
@@ -430,7 +430,8 @@
       adjustment_limit = 0.75;
       break;
     case 1:
-      adjustment_limit = 0.125 + 0.5 * MIN(1, fabs(log10(0.01 * correction_factor)));
+      adjustment_limit = 0.25 +
+          0.5 * MIN(1, fabs(log10(0.01 * correction_factor)));
       break;
     case 2:
     default:
@@ -438,12 +439,21 @@
       break;
   }
 
+  cpi->rc.q_2_frame = cpi->rc.q_1_frame;
+  cpi->rc.q_1_frame = cm->base_qindex;
+  cpi->rc.rc_2_frame = cpi->rc.rc_1_frame;
+  if (correction_factor > 110)
+    cpi->rc.rc_1_frame = -1;
+  else if (correction_factor < 90)
+    cpi->rc.rc_1_frame = 1;
+  else
+    cpi->rc.rc_1_frame = 0;
+
   if (correction_factor > 102) {
     // We are not already at the worst allowable quality
     correction_factor = (int)(100 + ((correction_factor - 100) *
                                   adjustment_limit));
     rate_correction_factor = (rate_correction_factor * correction_factor) / 100;
-
     // Keep rate_correction_factor within limits
     if (rate_correction_factor > MAX_BPB_FACTOR)
       rate_correction_factor = MAX_BPB_FACTOR;
@@ -494,6 +504,14 @@
     }
   } while (++i <= active_worst_quality);
 
+  // In CBR mode, this makes sure q is between oscillating Qs to prevent
+  // resonance.
+  if (cpi->oxcf.rc_mode == VPX_CBR &&
+      (cpi->rc.rc_1_frame * cpi->rc.rc_2_frame == -1) &&
+      cpi->rc.q_1_frame != cpi->rc.q_2_frame) {
+    q = clamp(q, MIN(cpi->rc.q_1_frame, cpi->rc.q_2_frame),
+              MAX(cpi->rc.q_1_frame, cpi->rc.q_2_frame));
+  }
   return q;
 }
 
--- a/vp9/encoder/vp9_ratectrl.h
+++ b/vp9/encoder/vp9_ratectrl.h
@@ -99,7 +99,14 @@
   int64_t starting_buffer_level;
   int64_t optimal_buffer_level;
   int64_t maximum_buffer_size;
-  // int active_best_quality;
+  // rate control history for last frame(1) and the frame before(2).
+  // -1: undershot
+  //  1: overshoot
+  //  0: not initialized.
+  int rc_1_frame;
+  int rc_2_frame;
+  int q_1_frame;
+  int q_2_frame;
 } RATE_CONTROL;
 
 struct VP9_COMP;