shithub: libvpx

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vp9: Updates to noise estimation.

Add threshold/condition on spatial_variance and brightness level.
Modification to normalization of block variance.
Change resolution limit below which we disable noise estimation.

Change-Id: If5be08a26ceda351242d8a58d2f0bc88c0a918f0

--- a/vp9/encoder/vp9_noise_estimate.c

+++ b/vp9/encoder/vp9_noise_estimate.c

@@ -28,11 +28,11 @@

   ne->level = kLow;

   ne->value = 0;

   ne->count = 0;

-  ne->thresh = 20;

+  ne->thresh = 90;

   if (width * height >= 1920 * 1080) {

-    ne->thresh = 70;

+    ne->thresh = 200;

   } else if (width * height >= 1280 * 720) {

-    ne->thresh = 40;

+    ne->thresh = 130;

   }

 }

@@ -55,8 +55,8 @@

       cpi->resize_state == ORIG &&

       !cpi->use_svc &&

       cpi->oxcf.content != VP9E_CONTENT_SCREEN &&

-      cpi->common.width > 352 &&

-      cpi->common.height > 288)

+      cpi->common.width >= 640 &&

+      cpi->common.height >= 480)

     return 1;

   else

     return 0;

@@ -86,6 +86,8 @@

   int frame_period = 10;

   int thresh_consec_zeromv = 8;

   unsigned int thresh_sum_diff = 128;

+  unsigned int thresh_sum_spatial = (200 * 200) << 8;

+  unsigned int thresh_spatial_var = (32 * 32) << 8;

   int num_frames_estimate = 20;

   int min_blocks_estimate = cm->mi_rows * cm->mi_cols >> 7;

   // Estimate is between current source and last source.

@@ -108,8 +110,7 @@

     uint64_t avg_est = 0;

     int bsize = BLOCK_16X16;

     static const unsigned char const_source[16] = {

-         128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128,

-         128, 128};

+        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0};

     // Loop over sub-sample of 16x16 blocks of frame, and for blocks that have

     // been encoded as zero/small mv at least x consecutive frames, compute

     // the variance to update estimate of noise in the source.

@@ -164,8 +165,12 @@

               const unsigned int spatial_variance =

                   cpi->fn_ptr[bsize].vf(src_y, src_ystride, const_source,

                                         0, &sse2);

-              avg_est += variance / (10 + spatial_variance);

-              num_samples++;

+              // 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);

+                num_samples++;

+              }

             }

           }

         }

@@ -184,7 +189,7 @@

     // duplicate frames).

     if (num_samples > min_blocks_estimate && avg_est > 0) {

       // Normalize.

-      avg_est = (avg_est << 8) / num_samples;

+      avg_est = avg_est / num_samples;

       // Update noise estimate.

       ne->value = (int)((3 * ne->value + avg_est) >> 2);

       ne->count++;