Hi,
the attached patch changes blending behaviour for the vdpau-driver to classical
alpha blending.
So far it expects premultiplied alpha. This is not in line with, at least, what
intel-driver expects.
Why would one need this change? In lack of an implementation of vaSetSubpictureGlobalAlpha() in the
libva-backend/vdpau-driver, the only way to implement fading in/out of subpictures/OSD-elements is
to change alpha values per-pixel. That is already expensive and becomes even more expensive if you
need to premultiply RGB values. And makes it almost impossible to implement such a feature if
blending is handled differently by different libva-backends.
Please redirect me, if I should open a ticket for that.
Thanks for reviewing and considering this patch,
Holger
diff --git a/src/vdpau_video_x11.c b/src/vdpau_video_x11.c
index 4ddfd1b..4ac558b 100644
--- a/src/vdpau_video_x11.c
+++ b/src/vdpau_video_x11.c
@@ -612,10 +612,10 @@ render_subpicture(
VdpOutputSurfaceRenderBlendState blend_state;
blend_state.struct_version = VDP_OUTPUT_SURFACE_RENDER_BLEND_STATE_VERSION;
- blend_state.blend_factor_source_color = VDP_OUTPUT_SURFACE_RENDER_BLEND_FACTOR_ONE;
+ blend_state.blend_factor_source_color = VDP_OUTPUT_SURFACE_RENDER_BLEND_FACTOR_SRC_ALPHA;
blend_state.blend_factor_source_alpha = VDP_OUTPUT_SURFACE_RENDER_BLEND_FACTOR_ONE;
blend_state.blend_factor_destination_color = VDP_OUTPUT_SURFACE_RENDER_BLEND_FACTOR_ONE_MINUS_SRC_ALPHA;
- blend_state.blend_factor_destination_alpha = VDP_OUTPUT_SURFACE_RENDER_BLEND_FACTOR_ONE_MINUS_SRC_ALPHA;
+ blend_state.blend_factor_destination_alpha = VDP_OUTPUT_SURFACE_RENDER_BLEND_FACTOR_ZERO;
blend_state.blend_equation_color = VDP_OUTPUT_SURFACE_RENDER_BLEND_EQUATION_ADD;
blend_state.blend_equation_alpha = VDP_OUTPUT_SURFACE_RENDER_BLEND_EQUATION_ADD;
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