[XviD-devel] MotionVector implementation in the case of decoding field predicted MB of interlaced mode

mayfig mayfig99 at yahoo.com.cn
Thu Dec 2 09:12:26 CET 2004


  in the case of interlaced mode , it seems Xvid do not  implement well when
the decoded MacroBlock is a field predicted MB. I am trying to correct it, but
it seems something wrong with my understanding . For when I add the part of
MotionVector for the bottom field and then perform  the relevant interpolation
of half-pel in the source code,   the resulted picture has more problem than
before.  

1. I am not sure  when the current MB is a field predicted MB. if the function
below pmv = get_pmv2(dec->mbs, dec->mb_width, bound, x, y, k) 
still valid(Consider the three cases in Section 7.7.2..1 of MPEG4 Standard)?

2. To implement the interpolation of MotionVectors of Top field and bottom
field
interpolate8x8_field_switch(dec->cur.y, dec->refn[ref].y, 16*x_pos, 16*y_pos,
                           mv[0].x, mv[0].y, stride, rounding);

interpolate8x8_field_switch(dec->cur.y, dec->refn[ref].y, 16*x_pos + 8,
16*y_pos,
                           mv[0].x, mv[0].y, stride, rounding);

interpolate8x8_field_switch(dec->cur.y, dec->refn[ref].y, 16*x_pos, 16*y_pos+8,
                           mv[1].x, mv[1].y, stride, rounding);

interpolate8x8_field_switch(dec->cur.y, dec->refn[ref].y, 16*x_pos+ 8,   
16*y_pos+8,mv[1].x, mv[1].y, stride, rounding);
     It seems something wrong.

     Is there anyone would like to give me some suggestion?


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