From af69ed20c4be1d8fda493334105a51ecb45cd6d4 Mon Sep 17 00:00:00 2001
From: Jerome Jiang <jianj@google.com>
Date: Mon, 1 May 2017 10:49:54 -0700
Subject: [PATCH] vp9: Enable noise estimation on low res.

Set noise level to kLowLow for high motion low res clips.
Change the normalization in noise metric for low res.
Reduce the initial time-window for all resolutions.

Change-Id: Iaed39dbb50b205cd9c735dc5b84822304fb01987
---
 vp9/encoder/vp9_noise_estimate.c | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/vp9/encoder/vp9_noise_estimate.c b/vp9/encoder/vp9_noise_estimate.c
index fc2e32448..5652ded95 100644
--- a/vp9/encoder/vp9_noise_estimate.c
+++ b/vp9/encoder/vp9_noise_estimate.c
@@ -26,25 +26,27 @@ void vp9_noise_estimate_init(NOISE_ESTIMATE *const ne, int width, int height) {
   ne->level = kLowLow;
   ne->value = 0;
   ne->count = 0;
-  ne->thresh = 100;
+  ne->thresh = 90;
   ne->last_w = 0;
   ne->last_h = 0;
   if (width * height >= 1920 * 1080) {
     ne->thresh = 200;
   } else if (width * height >= 1280 * 720) {
     ne->thresh = 140;
+  } else if (width * height >= 640 * 360) {
+    ne->thresh = 100;
   }
-  ne->num_frames_estimate = 20;
+  ne->num_frames_estimate = 15;
 }
 
 static int enable_noise_estimation(VP9_COMP *const cpi) {
 #if CONFIG_VP9_HIGHBITDEPTH
   if (cpi->common.use_highbitdepth) return 0;
 #endif
-// Enable noise estimation if denoising is on, but not for low resolutions.
+// Enable noise estimation if denoising is on.
 #if CONFIG_VP9_TEMPORAL_DENOISING
   if (cpi->oxcf.noise_sensitivity > 0 && denoise_svc(cpi) &&
-      cpi->common.width >= 640 && cpi->common.height >= 360)
+      cpi->common.width >= 320 && cpi->common.height >= 180)
     return 1;
 #endif
   // Only allow noise estimate under certain encoding mode.
@@ -97,6 +99,7 @@ NOISE_LEVEL vp9_noise_estimate_extract_level(NOISE_ESTIMATE *const ne) {
 void vp9_update_noise_estimate(VP9_COMP *const cpi) {
   const VP9_COMMON *const cm = &cpi->common;
   NOISE_ESTIMATE *const ne = &cpi->noise_estimate;
+  const int low_res = (cm->width <= 352 && cm->height <= 288);
   // Estimate of noise level every frame_period frames.
   int frame_period = 8;
   int thresh_consec_zeromv = 6;
@@ -127,7 +130,7 @@ void vp9_update_noise_estimate(VP9_COMP *const cpi) {
       ne->last_h = cm->height;
     }
     return;
-  } else if (cpi->rc.avg_frame_low_motion < 50) {
+  } else if (cpi->rc.avg_frame_low_motion < (low_res ? 70 : 50)) {
     // Force noise estimation to 0 and denoiser off if content has high motion.
     ne->level = kLowLow;
 #if CONFIG_VP9_TEMPORAL_DENOISING
@@ -210,7 +213,8 @@ void vp9_update_noise_estimate(VP9_COMP *const cpi) {
               // Avoid blocks with high brightness and high spatial variance.
               if ((sse2 - spatial_variance) < thresh_sum_spatial &&
                   spatial_variance < thresh_spatial_var) {
-                avg_est += variance / ((spatial_variance >> 9) + 1);
+                avg_est += low_res ? variance >> 4
+                                   : variance / ((spatial_variance >> 9) + 1);
                 num_samples++;
               }
             }
-- 
2.40.0