vp7: skip DC transform for empty block

diff --git a/nihav-duck/src/codecs/vp7.rs b/nihav-duck/src/codecs/vp7.rs
index ea423ad26145b2070bd88df7c038eea9620b9a23..50fe5db8f983cae96cf3f4d8e5a1393c1bd8e581 100644 (file)
--- a/nihav-duck/src/codecs/vp7.rs
+++ b/nihav-duck/src/codecs/vp7.rs
@@ -552,7 +552,7 @@ impl VP7Decoder {
             }
             if has_ac[24] {
                 idct4x4(y2block);
-            } else {
+            } else if y2block[0] != 0 {
                 idct4x4_dc(y2block);
             }
             for i in 0..16 {
@@ -562,7 +562,7 @@ impl VP7Decoder {
         for i in 0..24 {
             if has_ac[i] {
                 idct4x4(&mut self.coeffs[i]);
-            } else {
+            } else if self.coeffs[i][0] != 0 {
                 idct4x4_dc(&mut self.coeffs[i]);
             }
         }