[mythtv-users] New deinterlacer for perfect image quality when using an interlaced display, mode that matches the source

[Tom Dexter]

On Sun, Mar 29, 2009 at 2:58 PM, Paul Gardiner <lists at glidos.net> wrote:

> I think I've just sussed what is causing this. The deinterlacer gets
> given each frame twice. Each time it overwrites the bottom field,
> but leaves the top field unchanged. After each call the OSD will
> be rendered over the frame. The fact that I don't update the
> top field in the second call to the deinterlacer means the OSD gets
> rendered over the top of a previous rendering. That doesn't matter
> for a solid OSD, but if translucent the top field will be
> darker than the bottom.
>
> Should be easy to fix:
>
> Change
>
>   if (y & tff)
>   {
>       if(parity)
>       {
>           /* Second call: put back the second field to its previous state */
>           memcpy(dst + dst_offsets[i] + y*dst_stride[i],
> &p->ref[nr_c][i][y*refs], w);
>       }
>       else
>       {
>           /* First call: replace second field by that of the previous frame
> */
>           memcpy(dst + dst_offsets[i] + y*dst_stride[i],
> &p->ref[nr_p][i][y*refs], w);
>       }
>   }
>
> to
>   if(parity)
>   {
>       /* Second call: put back the whole frame to its previous state.
>        * Although we have not altered first field, we need to overwrite
>        * it because the OSD will have been rendered to the copy passed
>        * in. */
>       memcpy(dst + dst_offsets[i] + y*dst_stride[i],
> &p->ref[nr_c][i][y*refs], w);
>   }
>   else
>   {
>       /* First call: replace second field by that of the previous frame */
>       if (y & tff)
>       {
>           memcpy(dst + dst_offsets[i] + y*dst_stride[i],
> &p->ref[nr_p][i][y*refs], w);
>       }
>   }
>

Paul...a quick question about this OSD flicker fix.  Can you think of
any reason that this fix could affect overall clarity of 1080i in any
way?  I'm probably just getting cross-eyed from all this testing :D,
but I almost thought the version without this fix may have been
slightly clearer.  It's too bad I have no way to test one right after
the other...I can only switch after a one hour re-compile.

Just curious.  If there is in fact any difference it's extremely
subtle, and may be only with those NBC shows.

Tom