From 651bfd0dad07b9eb6de6bc810f665f32c4d01865 Mon Sep 17 00:00:00 2001 From: Niklas Haas Date: Wed, 19 Feb 2025 22:08:30 +0100 Subject: [PATCH] avfilter/vf_libplacebo: set correct alpha mode before blending &pl_alpha_overlay expects straight alpha, but the alpha output may be premultiplied as a result of the target alpha mode (or in the absence of an alpha channel). Fix it by requesting independent alpha explicitly when blending. --- libavfilter/vf_libplacebo.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/libavfilter/vf_libplacebo.c b/libavfilter/vf_libplacebo.c index 1c494fdc09..0c245cda7f 100644 --- a/libavfilter/vf_libplacebo.c +++ b/libavfilter/vf_libplacebo.c @@ -908,6 +908,9 @@ static int output_frame(AVFilterContext *ctx, int64_t pts) opts->params.skip_caching_single_frame = high_fps; update_crops(ctx, in, &target, out->pts * av_q2d(outlink->time_base)); pl_render_image_mix(in->renderer, &in->mix, &target, &opts->params); + + /* Force straight output and set correct blend mode */ + target.repr.alpha = PL_ALPHA_INDEPENDENT; opts->params.blend_params = &pl_alpha_overlay; #if PL_API_VER >= 346 opts->params.background = opts->params.border = PL_CLEAR_SKIP;