Fix direct and skip MB motion compensation in RV4:

two conditions were incomplete and zeroing motion
vectors was performed only on half of them.

Originally committed as revision 17947 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/rv34.c

@@ -787,15 +787,16 @@ static int rv34_decode_mv(RV34DecContext *r, int block_type)
     case RV34_MB_B_DIRECT:
         //surprisingly, it uses motion scheme from next reference frame
         next_bt = s->next_picture_ptr->mb_type[s->mb_x + s->mb_y * s->mb_stride];
-        if(IS_INTRA(next_bt))
+        if(IS_INTRA(next_bt) || IS_SKIP(next_bt)){
             fill_rectangle(s->current_picture_ptr->motion_val[0][s->mb_x * 2 + s->mb_y * 2 * s->b8_stride], 2, 2, s->b8_stride, 0, 4);
-        else
+            fill_rectangle(s->current_picture_ptr->motion_val[1][s->mb_x * 2 + s->mb_y * 2 * s->b8_stride], 2, 2, s->b8_stride, 0, 4);
+        }else
             for(j = 0; j < 2; j++)
                 for(i = 0; i < 2; i++)
                     for(k = 0; k < 2; k++)
                         for(l = 0; l < 2; l++)
                             s->current_picture_ptr->motion_val[l][mv_pos + i + j*s->b8_stride][k] = calc_add_mv(r, l, s->next_picture_ptr->motion_val[0][mv_pos + i + j*s->b8_stride][k]);
-        if(IS_16X16(next_bt)) //we can use whole macroblock MC
+        if(!(IS_16X8(next_bt) || IS_8X16(next_bt) || IS_8X8(next_bt))) //we can use whole macroblock MC
             rv34_mc_2mv(r, block_type);
         else
             rv34_mc_2mv_skip(r);