shithub: libvpx

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Safe guard zero median filter outcome case

In case median filter returns 0 value, bypass the Wiener filter
stage. This avoids potential divided by 0 case.

In the same place use a temp variable to take the Wiener filter
output instead of returning to the coeff array.

Change-Id: I45f57c515b4062a0aa1f312eda852462cb655d8e

--- a/vp9/encoder/vp9_encoder.c

+++ b/vp9/encoder/vp9_encoder.c

@@ -4793,9 +4793,12 @@

       // Wiener filter

       for (idx = 1; idx < coeff_count; ++idx) {

         int64_t sqr_coeff = (int64_t)coeff[idx] * coeff[idx];

-        coeff[idx] = (int16_t)((sqr_coeff * coeff[idx]) /

-                               (sqr_coeff + (int64_t)median_val * median_val));

-        wiener_variance += (int64_t)coeff[idx] * coeff[idx];

+        int64_t tmp_coeff = (int64_t)coeff[idx];

+        if (median_val) {

+          tmp_coeff = (sqr_coeff * coeff[idx]) /

+                      (sqr_coeff + (int64_t)median_val * median_val);

+        }

+        wiener_variance += tmp_coeff * tmp_coeff;

       }

       cpi->mb_wiener_variance[mb_row * cm->mb_cols + mb_col] =

           wiener_variance / coeff_count;