Fix partially hidden macroblocks for 10-bit DNxHD.

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/dnxhdenc.c

@@ -71,13 +71,21 @@ static void dnxhd_8bit_get_pixels_8x4_sym(DCTELEM *restrict block, const uint8_t
 static av_always_inline void dnxhd_10bit_get_pixels_8x4_sym(DCTELEM *restrict block, const uint8_t *pixels, int line_size)
 {
     int i;
-
-    block += 32;
+    const uint16_t* pixels16 = pixels;
+    line_size >>= 1;
 
     for (i = 0; i < 4; i++) {
-        memcpy(block + i     * 8, pixels + i * line_size, 8 * sizeof(*block));
-        memcpy(block - (i+1) * 8, pixels + i * line_size, 8 * sizeof(*block));
+        block[0] = pixels16[0]; block[1] = pixels16[1];
+        block[2] = pixels16[2]; block[3] = pixels16[3];
+        block[4] = pixels16[4]; block[5] = pixels16[5];
+        block[6] = pixels16[6]; block[7] = pixels16[7];
+        pixels16 += line_size;
+        block += 8;
     }
+    memcpy(block,      block -  8, sizeof(*block) * 8);
+    memcpy(block +  8, block - 16, sizeof(*block) * 8);
+    memcpy(block + 16, block - 24, sizeof(*block) * 8);
+    memcpy(block + 24, block - 32, sizeof(*block) * 8);
 }
 
 static int dnxhd_10bit_dct_quantize(MpegEncContext *ctx, DCTELEM *block,