From: Niklas Haas <git@haasn.dev> Alpha planes must always be full range, so complain loudly if fed limited range grayscale input. --- libavfilter/vf_alphamerge.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/libavfilter/vf_alphamerge.c b/libavfilter/vf_alphamerge.c index 4bbc06da36..a5f5baf77e 100644 --- a/libavfilter/vf_alphamerge.c +++ b/libavfilter/vf_alphamerge.c @@ -60,6 +60,12 @@ static int do_alphamerge(FFFrameSync *fs) if (!alpha_buf) return ff_filter_frame(ctx->outputs[0], main_buf); + if (alpha_buf->color_range == AVCOL_RANGE_MPEG) { + av_log(ctx, AV_LOG_WARNING, "alpha plane color range tagged as %s, " + "output will be wrong!\n", + av_color_range_name(alpha_buf->color_range)); + } + if (s->is_packed_rgb) { int x, y; uint8_t *pin, *pout; -- 2.42.0