[mythtv] bob deint issue with latest cvs

[Andy McMullan]

System is bt878/PAL/nvidia/tvout.

With latest cvs, I see image 'vibration' when using bob deint. This is
similar to a problem I had a long time ago, which was fixed by
offsetting the second field vertically by one pixel. This code (in
videoout_xv.cpp) seems to have been reworked recently, causing my
problem:

                int halfLineSrc = (int)round(((float)disphoff) / imgh - 0.001f);
                src_h -= (halfLineSrc) ? 1 : 0;
                XvShmPutImage(data->XJ_disp, xv_port, data->XJ_curwin,
                              data->XJ_gc, image, src_x, src_y, src_w, src_h,
                              dispxoff, dest_y   + halfLineSrc,
                              dispwoff, disphoff - halfLineSrc, False);


I can fix my problem by either commenting out the src_h modification
in line 2 above, or by changing the penultimate argument to
XvShmPutImage from 'disphoff - halfLineSrc' to 'disphoff -
(2*halfLineSrc)'.

I think the latter fix fits better with the recent modifications, but
I'm not sure it's really the correct solution.

Andy Mc