From 4726ca2c24097a4545b92c8e95556166def945c5 Mon Sep 17 00:00:00 2001
From: Kostya Shishkov <kostya.shishkov@gmail.com>
Date: Thu, 6 Feb 2020 18:44:32 +0100
Subject: [PATCH] vp7: skip DC transform for empty block

---
 nihav-duck/src/codecs/vp7.rs | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/nihav-duck/src/codecs/vp7.rs b/nihav-duck/src/codecs/vp7.rs
index ea423ad..50fe5db 100644
--- 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]);
             }
         }
-- 
2.30.2