[vlc-devel] [PATCH] vout: wingdi: request filterchain resetting converter for expected display size.

[Steve Lhomme]

On 21/01/2019 07:22, Xie Zhigang wrote:
> When using wingdi as video output module, if picture size is not
> matching the display size, it have to use StretchBlt to perform video
> scaling in poor quality.
>
> If it requests video filter chain resetting the video converter in new
> target picture size which matches display size, wingdi can get better
> scaled picture ready for display in quality.
> ---
>   modules/video_output/win32/wingdi.c | 35 +++++++++++++++++++++++++----------
>   1 file changed, 25 insertions(+), 10 deletions(-)
>
> diff --git a/modules/video_output/win32/wingdi.c b/modules/video_output/win32/wingdi.c
> index 2bead11..e61e2b4 100644
> --- a/modules/video_output/win32/wingdi.c
> +++ b/modules/video_output/win32/wingdi.c
> @@ -75,6 +75,8 @@ struct vout_display_sys_t
>           RGBQUAD    green;
>           RGBQUAD    blue;
>       };
> +
> +    int prev_size_diff;
>   };
>   
>   static picture_pool_t *Pool  (vout_display_t *, unsigned);
> @@ -144,22 +146,35 @@ static void Display(vout_display_t *vd, picture_t *picture)
>   #define rect_src_clipped vd->sys->sys.rect_src_clipped
>   #define rect_dest vd->sys->sys.rect_dest
>   #define rect_dest_clipped vd->sys->sys.rect_dest_clipped
> +
> +    int size_diff = 0;
> +    size_diff = (rect_dest_clipped.right - rect_dest_clipped.left) *
> +                (rect_dest_clipped.bottom - rect_dest_clipped.top)
> +              - (rect_src_clipped.right - rect_src_clipped.left) *
> +                (rect_src_clipped.bottom - rect_src_clipped.top);
> +
>       RECT rect_dst = rect_dest_clipped;
>       HDC hdc = GetDC(sys->sys.hvideownd);
>   
>       OffsetRect(&rect_dst, -rect_dest.left, -rect_dest.top);
>       SelectObject(sys->off_dc, sys->off_bitmap);
>   
> -    if (rect_dest_clipped.right - rect_dest_clipped.left !=
> -        rect_src_clipped.right - rect_src_clipped.left ||
> -        rect_dest_clipped.bottom - rect_dest_clipped.top !=
> -        rect_src_clipped.bottom - rect_src_clipped.top) {
> -        StretchBlt(hdc, rect_dst.left, rect_dst.top,
> -                   rect_dst.right, rect_dst.bottom,
> -                   sys->off_dc,
> -                   rect_src_clipped.left,  rect_src_clipped.top,
> -                   rect_src_clipped.right, rect_src_clipped.bottom,
> -                   SRCCOPY);
> +    if (size_diff != sys->prev_size_diff)
> +    {
> +        sys->prev_size_diff = size_diff;
> +        /* request new vout picture size should be scaled to */
> +        vd->fmt.i_visible_width  = rect_dest_clipped.right  - rect_dest_clipped.left;
> +        vd->fmt.i_visible_height = rect_dest_clipped.bottom - rect_dest_clipped.top;
> +        /* align to 64 is expected to faster access. */
> +        vd->fmt.i_width = (rect_dest_clipped.right  - rect_dest_clipped.left + 63) & (~63);
> +        vd->fmt.i_height = (rect_dest_clipped.bottom - rect_dest_clipped.top + 63) & (~63);

You're not suppsed to change vd->fmt after Open(). I think 
vout_display_SendEventPicturesInvalid() should pass the new format it wants.
> +
> +        video_format_t fmt = vd->fmt;
> +
> +        Clean(vd);
> +        Init(vd, &fmt, fmt.i_width, fmt.i_height);
> +
> +        vout_display_SendEventPicturesInvalid(vd);

If you want to call that you need to set "has_pictures_invalid" to true 
during initialization. In fact it should assert with the current master.
Also you don't handle VOUT_DISPLAY_RESET_PICTURES it should assert as well.

When developing code make sure you use --enable-debug during configure.

>       } else {
>           BitBlt(hdc, rect_dst.left, rect_dst.top,
>                  rect_dst.right, rect_dst.bottom,
> -- 
> 2.7.4
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