[FFmpeg-devel] [PATCH 1/2] lavfi/libplacebo: apply dovi metadata correctly

[Niklas Haas <ffmpeg@haasn.xyz>]

From: Niklas Haas <git@haasn.dev>

libplacebo supports dolby vision application, but it requires some help
from us to set a sensible default output color space, and also strip the
dolby vision metadata from the output frame. Failing to do the latter
results in an error inside libplacebo. (It can't encode back into a
dolby vision color space)

Make this functionality toggleable by the user. Note that we also strip
dovi metadata from the output in the apply_dolbyvision=0 case, which is
partly out of laziness but also partly justified by the fact that dolby
vision metadata will generally no longer make sense after passing
through a color space conversion or tone mapping filter. (And in the
general case, we don't know what libplacebo is doing internally)

Signed-off-by: Niklas Haas <git@haasn.dev>
---
 libavfilter/vf_libplacebo.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/libavfilter/vf_libplacebo.c b/libavfilter/vf_libplacebo.c
index 5b1e7b5285..e479d6c935 100644
--- a/libavfilter/vf_libplacebo.c
+++ b/libavfilter/vf_libplacebo.c
@@ -47,6 +47,7 @@ typedef struct LibplaceboContext {
     int force_divisible_by;
     int normalize_sar;
     int apply_filmgrain;
+    int apply_dovi;
     int colorspace;
     int color_range;
     int color_primaries;
@@ -400,6 +401,22 @@ static int filter_frame(AVFilterLink *link, AVFrame *in)
     out->width = outlink->w;
     out->height = outlink->h;
 
+#if PL_API_VER >= 191
+    /* libplacebo cannot (currently) encode back to Dolby Vision */
+    av_frame_remove_side_data(out, AV_FRAME_DATA_DOVI_RPU_BUFFER);
+    av_frame_remove_side_data(out, AV_FRAME_DATA_DOVI_METADATA);
+    if (s->apply_dovi && av_frame_get_side_data(in, AV_FRAME_DATA_DOVI_METADATA)) {
+        /* Output of dovi reshaping is always BT.2020+PQ, so infer the correct
+         * output colorspace defaults */
+        out->colorspace = AVCOL_SPC_BT2020_NCL;
+        out->color_primaries = AVCOL_PRI_BT2020;
+        out->color_trc = AVCOL_TRC_SMPTE2084;
+    } else {
+        /* Prevent Dolby Vision metadata from getting applied by libplacebo */
+        av_frame_remove_side_data(in, AV_FRAME_DATA_DOVI_METADATA);
+    }
+#endif
+
     if (s->colorspace >= 0)
         out->colorspace = s->colorspace;
     if (s->color_range >= 0)
@@ -559,6 +576,7 @@ static const AVOption libplacebo_options[] = {
     { "antiringing", "Antiringing strength (for non-EWA filters)", OFFSET(antiringing), AV_OPT_TYPE_FLOAT, {.dbl = 0.0}, 0.0, 1.0, DYNAMIC },
     { "sigmoid", "Enable sigmoid upscaling", OFFSET(sigmoid), AV_OPT_TYPE_BOOL, {.i64 = 1}, 0, 1, DYNAMIC },
     { "apply_filmgrain", "Apply film grain metadata", OFFSET(apply_filmgrain), AV_OPT_TYPE_BOOL, {.i64 = 1}, 0, 1, DYNAMIC },
+    { "apply_dolbyvision", "Apply Dolby Vision metadata", OFFSET(apply_dovi), AV_OPT_TYPE_BOOL, {.i64 = 1}, 0, 1, DYNAMIC },
 
     { "deband", "Enable debanding", OFFSET(deband), AV_OPT_TYPE_BOOL, {.i64 = 0}, 0, 1, DYNAMIC },
     { "deband_iterations", "Deband iterations", OFFSET(deband_iterations), AV_OPT_TYPE_INT, {.i64 = 1}, 0, 16, DYNAMIC },
-- 
2.34.1

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