commit c00e95af9381bfac3e1b70314b985dbc12cb94ec
author Bohan Li <bohanli@google.com> Thu Dec 01 14:56:49 2022 -0800
committer Bohan Li <bohanli@google.com> Mon Dec 12 17:22:51 2022 +0000
tree ffd8f75dab4c386a0897b865378a4dd52d1b5e58
parent 5e47dc2cc035f9770de472e246ba1d72941a3a05

Filter noise variance in first pass stats.

This produces neutral results for standard test sets, but helps when
the input stats are not stable.

Change-Id: Id48ef7359c609849eb0b2e45c5565e7f5a741764

av1/encoder/pass2_strategy.c

diff --git a/av1/encoder/pass2_strategy.c b/av1/encoder/pass2_strategy.c
index 1dd9721..0a80915 100644
--- a/av1/encoder/pass2_strategy.c
+++ b/av1/encoder/pass2_strategy.c
@@ -19,6 +19,7 @@
 
 #include <stdint.h>
 
+#include "aom_mem/aom_mem.h"
 #include "config/aom_config.h"
 #include "config/aom_scale_rtcd.h"
 
@@ -3508,6 +3509,39 @@
   }
 }
 
+// Smooth-out the noise variance so it is more stable
+// TODO(bohanli): Use a better low-pass filter than averaging
+static void smooth_filter_noise(FIRSTPASS_STATS *first_stats,
+                                FIRSTPASS_STATS *last_stats) {
+  int len = (int)(last_stats - first_stats);
+  double *smooth_noise = aom_malloc(len * sizeof(*smooth_noise));
+  if (!smooth_noise) return;
+
+  for (int i = 0; i < len; i++) {
+    double total_noise = 0;
+    double total_wt = 0;
+    for (int j = -HALF_FILT_LEN; j <= HALF_FILT_LEN; j++) {
+      int idx = AOMMIN(AOMMAX(i + j, 0), len - 1);
+      if (first_stats[idx].is_flash) continue;
+
+      total_noise += first_stats[idx].noise_var;
+      total_wt += 1.0;
+    }
+    if (total_wt > 0.01) {
+      total_noise /= total_wt;
+    } else {
+      total_noise = first_stats[i].noise_var;
+    }
+    smooth_noise[i] = total_noise;
+  }
+
+  for (int i = 0; i < len; i++) {
+    first_stats[i].noise_var = smooth_noise[i];
+  }
+
+  aom_free(smooth_noise);
+}
+
 // Estimate the noise variance of each frame from the first pass stats
 void av1_estimate_noise(FIRSTPASS_STATS *first_stats,
                         FIRSTPASS_STATS *last_stats) {
@@ -3595,6 +3629,8 @@
        this_stats++) {
     this_stats->noise_var = (first_stats + 2)->noise_var;
   }
+
+  smooth_filter_noise(first_stats, last_stats);
 }
 
 // Estimate correlation coefficient of each frame with its previous frame.

test/ratectrl_qmode_test.cc

diff --git a/test/ratectrl_qmode_test.cc b/test/ratectrl_qmode_test.cc
index fa0c19a..bcbab4b 100644
--- a/test/ratectrl_qmode_test.cc
+++ b/test/ratectrl_qmode_test.cc
@@ -1017,7 +1017,7 @@
                  std::back_inserter(gop_interval_list),
                  [](GopStruct const &x) { return x.show_frame_count; });
   EXPECT_THAT(gop_interval_list,
-              ElementsAre(21, 9, 30, 30, 16, 14, 21, 9, 30, 12, 16, 2, 30, 10));
+              ElementsAre(21, 9, 30, 30, 17, 13, 21, 9, 30, 12, 16, 2, 30, 10));
 }
 
 // TODO(b/242892473): Add a test which passes lookahead GOPs.