vp7: fix intra prediction corner cases

[nihav.git] / nihav-duck / src / codecs / vp7.rs

diff --git a/nihav-duck/src/codecs/vp7.rs b/nihav-duck/src/codecs/vp7.rs
index ea423ad26145b2070bd88df7c038eea9620b9a23..59b1c22ea44e0e2d64390a90f5eebc0e88545cb3 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]);
             }
         }
@@ -871,13 +871,14 @@ impl VP7Decoder {
                     }
                 }
             }
+            let tr_edge = if has_top { ydst[yoff - ystride + 15] } else { 0x80 };
             for y in 0..4 {
                 for x in 0..4 {
                     ipred_ctx_y.has_left = has_left || x > 0;
                     let bmode = self.ymodes[iidx + x];
                     let cur_yoff = yoff + x * 4;
-                    let has_tr = has_top && ((x < 3) || ((y == 0) && (mb_y < self.mb_w - 1)));
-                    let has_dl = ipred_ctx_y.has_left && (y < 3);
+                    let has_tr = ipred_ctx_y.has_top && ((x < 3) || ((y == 0) && (mb_y < self.mb_w - 1)));
+                    let has_dl = ipred_ctx_y.has_left && (x == 0) && (y < 3);
                     ipred_ctx_y.fill(ydst, cur_yoff, ystride,
                                      if has_tr { 8 } else { 4 },
                                      if has_dl { 8 } else { 4 });
@@ -890,6 +891,11 @@ impl VP7Decoder {
                             tr_save[x * 4 + i] = ipred_ctx_y.top[i + 4];
                         }
                     }
+                    if (mb_x == self.mb_w - 1) && has_top && (x == 3) {
+                        for i in 0..4 {
+                            ipred_ctx_y.top[i + 4] = tr_edge;
+                        }
+                    }
                     match bmode {
                         PredMode::DCPred => IPred4x4::ipred_dc(ydst, cur_yoff, ystride, ipred_ctx_y),
                         PredMode::TMPred => IPred4x4::ipred_tm(ydst, cur_yoff, ystride, ipred_ctx_y),