sub: support straight alpha additionally to premultiplied alpha

This is for VAAPI support. VAAPI does not support premultiplied alpha
for OSD. (Normally, we prefer premultiplied, because it has better
behavior on scaling.)

I'm not sure whether blending in the ASS->RGBA part is correct and I
didn't test it extensively.

1 files changed, 11 insertions, 1 deletions

diff --git a/sub/sub.c b/sub/sub.c
index a5ff9e2593..0e297e3bf8 100644
--- a/sub/sub.c
+++ b/sub/sub.c
@@ -202,13 +202,23 @@ static void render_object(struct osd_state *osd, struct osd_object *obj,
     if (formats[SUBBITMAP_RGBA] && out_imgs->format == SUBBITMAP_INDEXED)
         cached |= osd_conv_idx_to_rgba(obj->cache[1], out_imgs);
 
-    if (out_imgs->format == SUBBITMAP_RGBA && opts->sub_gauss != 0.0f)
+    if (formats[SUBBITMAP_RGBA_STR] && out_imgs->format == SUBBITMAP_INDEXED)
+        cached |= osd_conv_idx_to_rgba_str(obj->cache[1], out_imgs);
+
+    if ((out_imgs->format == SUBBITMAP_RGBA ||
+         out_imgs->format == SUBBITMAP_RGBA_STR)
+        && opts->sub_gauss != 0.0f)
+    {
         cached |= osd_conv_blur_rgba(obj->cache[2], out_imgs, opts->sub_gauss);
+    }
 
     // Do this conversion last to not trigger gauss blurring for ASS
     if (formats[SUBBITMAP_RGBA] && out_imgs->format == SUBBITMAP_LIBASS)
         cached |= osd_conv_ass_to_rgba(obj->cache[3], out_imgs);
 
+    if (formats[SUBBITMAP_RGBA_STR] && out_imgs->format == SUBBITMAP_LIBASS)
+        cached |= osd_conv_ass_to_rgba_str(obj->cache[3], out_imgs);
+
     if (cached)
         obj->cached = *out_imgs;
 }