Add assert for zero_motion_factor range

Change clamp to an assert so we are warned if changes to input
ranges or defaults in the future lead to an invalid value.

Change-Id: Idb4e0729f477a519bfff3083cdce3891e2fc6faa

diff --git a/vp9/encoder/vp9_firstpass.c b/vp9/encoder/vp9_firstpass.c
index ce7590fe4cbcc95cc72a0e1a18e2eadac21e82e8..b63d47a05e01b20214132dd1abb268ae7b5b9add 100644 (file)
--- a/vp9/encoder/vp9_firstpass.c
+++ b/vp9/encoder/vp9_firstpass.c
@@ -1882,13 +1882,8 @@ static double get_prediction_decay_rate(const TWO_PASS *const twopass,
   double zero_motion_factor =
       twopass->zm_factor * (frame_stats->pcnt_inter - frame_stats->pcnt_motion);
 
-  // Clamp value to range 0.0 to 1.0
-  // This should happen anyway if input values are sensibly clamped but checked
-  // here just in case.
-  if (zero_motion_factor > 1.0)
-    zero_motion_factor = 1.0;
-  else if (zero_motion_factor < 0.0)
-    zero_motion_factor = 0.0;
+  // Check that the zero motion factor is valid
+  assert(zero_motion_factor >= 0.0 && zero_motion_factor <= 1.0);
 
   return VPXMAX(zero_motion_factor,
                 (sr_decay_rate + ((1.0 - sr_decay_rate) * zero_motion_factor)));