@@ -77,12 +77,20 @@ static void FN(inter_pred)(AVCodecContext *ctx)

                               ref1->data[2], ref1->linesize[2], tref1,

                               row << 3, col << (3 - s->ss_h),

                               &b->mv[0][0], 8 >> s->ss_h, 4, w1, h1, 0);

+                // BUG for 4:2:2 bs=8x4, libvpx uses the wrong block index

+                // to get the motion vector for the bottom 4x4 block

+                // https://code.google.com/p/webm/issues/detail?id=993

+                if (s->ss_h == 0) {

+                    uvmv = b->mv[2][0];

+                } else {

+                    uvmv = ROUNDED_DIV_MVx2(b->mv[0][0], b->mv[2][0]);

+                }

                 mc_chroma_dir(s, mc[3 + s->ss_h][b->filter][0],

                               s->dst[1] + 4 * ls_uv, s->dst[2] + 4 * ls_uv, ls_uv,

                               ref1->data[1], ref1->linesize[1],

                               ref1->data[2], ref1->linesize[2], tref1,

                               (row << 3) + 4, col << (3 - s->ss_h),

-                              &b->mv[2][0], 8 >> s->ss_h, 4, w1, h1, 0);

+                              &uvmv, 8 >> s->ss_h, 4, w1, h1, 0);

             }

             if (b->comp) {

@@ -110,12 +118,20 @@ static void FN(inter_pred)(AVCodecContext *ctx)

                                   ref2->data[2], ref2->linesize[2], tref2,

                                   row << 3, col << (3 - s->ss_h),

                                   &b->mv[0][1], 8 >> s->ss_h, 4, w2, h2, 1);

+                    // BUG for 4:2:2 bs=8x4, libvpx uses the wrong block index

+                    // to get the motion vector for the bottom 4x4 block

+                    // https://code.google.com/p/webm/issues/detail?id=993

+                    if (s->ss_h == 0) {

+                        uvmv = b->mv[2][1];

+                    } else {

+                        uvmv = ROUNDED_DIV_MVx2(b->mv[0][1], b->mv[2][1]);

+                    }

                     mc_chroma_dir(s, mc[3 + s->ss_h][b->filter][1],

                                   s->dst[1] + 4 * ls_uv, s->dst[2] + 4 * ls_uv, ls_uv,

                                   ref2->data[1], ref2->linesize[1],

                                   ref2->data[2], ref2->linesize[2], tref2,

                                   (row << 3) + 4, col << (3 - s->ss_h),

-                                  &b->mv[2][1], 8 >> s->ss_h, 4, w2, h2, 1);

+                                  &uvmv, 8 >> s->ss_h, 4, w2, h2, 1);

                 }

             }

         } else if (b->bs == BS_4x8) {

@@ -239,7 +255,10 @@ static void FN(inter_pred)(AVCodecContext *ctx)

                                   ref1->data[2], ref1->linesize[2], tref1,

                                   row << 3, col << 2,

                                   &uvmv, 4, 4, w1, h1, 0);

-                    uvmv = ROUNDED_DIV_MVx2(b->mv[2][0], b->mv[3][0]);

+                    // BUG libvpx uses wrong block index for 4:2:2 bs=4x4

+                    // bottom block

+                    // https://code.google.com/p/webm/issues/detail?id=993

+                    uvmv = ROUNDED_DIV_MVx2(b->mv[1][0], b->mv[2][0]);

                     mc_chroma_dir(s, mc[4][b->filter][0],

                                   s->dst[1] + 4 * ls_uv, s->dst[2] + 4 * ls_uv, ls_uv,

                                   ref1->data[1], ref1->linesize[1],

@@ -327,7 +346,10 @@ static void FN(inter_pred)(AVCodecContext *ctx)

                                       ref2->data[2], ref2->linesize[2], tref2,

                                       row << 3, col << 2,

                                       &uvmv, 4, 4, w2, h2, 1);

-                        uvmv = ROUNDED_DIV_MVx2(b->mv[2][1], b->mv[3][1]);

+                        // BUG libvpx uses wrong block index for 4:2:2 bs=4x4

+                        // bottom block

+                        // https://code.google.com/p/webm/issues/detail?id=993

+                        uvmv = ROUNDED_DIV_MVx2(b->mv[1][1], b->mv[2][1]);

                         mc_chroma_dir(s, mc[4][b->filter][1],

                                       s->dst[1] + 4 * ls_uv, s->dst[2] + 4 * ls_uv, ls_uv,

                                       ref2->data[1], ref2->linesize[1],