- ctx->internal->execute(ctx, s->blend_slice, &td, NULL, FFMIN(FFMIN(mainpic->height - s->y, second->height),
+ ctx->internal->execute(ctx, s->blend_slice, &td, NULL, FFMIN(FFMAX(1, FFMIN3(s->y + second->height, FFMIN(second->height, mainpic->height), mainpic->height - s->y)),