1 files changed, 66 insertions, 2 deletions

diff --git a/media/ffvpx/libavutil/film_grain_params.c b/media/ffvpx/libavutil/film_grain_params.c
index 930d23c7fe..0a6004b6b3 100644
--- a/media/ffvpx/libavutil/film_grain_params.c
+++ b/media/ffvpx/libavutil/film_grain_params.c
@@ -17,6 +17,8 @@
  */
 
 #include "film_grain_params.h"
+#include "mem.h"
+#include "pixdesc.h"
 
 AVFilmGrainParams *av_film_grain_params_alloc(size_t *size)
 {
@@ -30,13 +32,75 @@ AVFilmGrainParams *av_film_grain_params_alloc(size_t *size)
 
 AVFilmGrainParams *av_film_grain_params_create_side_data(AVFrame *frame)
 {
+    AVFilmGrainParams *fgp;
     AVFrameSideData *side_data = av_frame_new_side_data(frame,
                                                         AV_FRAME_DATA_FILM_GRAIN_PARAMS,
                                                         sizeof(AVFilmGrainParams));
     if (!side_data)
         return NULL;
 
-    memset(side_data->data, 0, sizeof(AVFilmGrainParams));
+    fgp = (AVFilmGrainParams *) side_data->data;
+    *fgp = (AVFilmGrainParams) {
+        .color_range     = AVCOL_RANGE_UNSPECIFIED,
+        .color_primaries = AVCOL_PRI_UNSPECIFIED,
+        .color_trc       = AVCOL_TRC_UNSPECIFIED,
+        .color_space     = AVCOL_SPC_UNSPECIFIED,
+    };
 
-    return (AVFilmGrainParams *)side_data->data;
+    return fgp;
+}
+
+const AVFilmGrainParams *av_film_grain_params_select(const AVFrame *frame)
+{
+    const AVFilmGrainParams *fgp, *best = NULL;
+    const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(frame->format);
+    int bit_depth_luma, bit_depth_chroma;
+    if (!desc)
+        return NULL;
+
+    /* There are no YUV formats with different bit depth per component,
+     * so just check both against the first component for simplicity */
+    bit_depth_luma = bit_depth_chroma = desc->comp[0].depth;
+
+    for (int i = 0; i < frame->nb_side_data; i++) {
+        if (frame->side_data[i]->type != AV_FRAME_DATA_FILM_GRAIN_PARAMS)
+            continue;
+        fgp = (const AVFilmGrainParams*)frame->side_data[i]->data;
+        if (fgp->width  && fgp->width  > frame->width ||
+            fgp->height && fgp->height > frame->height)
+            continue;
+
+#define CHECK(a, b, unspec)                                     \
+        if ((a) != (unspec) && (b) != (unspec) && (a) != (b))   \
+            continue
+
+        CHECK(fgp->bit_depth_luma,   bit_depth_luma,         0);
+        CHECK(fgp->bit_depth_chroma, bit_depth_chroma,       0);
+        CHECK(fgp->color_range,      frame->color_range,     AVCOL_RANGE_UNSPECIFIED);
+        CHECK(fgp->color_primaries,  frame->color_primaries, AVCOL_PRI_UNSPECIFIED);
+        CHECK(fgp->color_trc,        frame->color_trc,       AVCOL_TRC_UNSPECIFIED);
+        CHECK(fgp->color_space,      frame->colorspace,      AVCOL_SPC_UNSPECIFIED);
+
+        switch (fgp->type) {
+        case AV_FILM_GRAIN_PARAMS_NONE:
+            continue;
+        case AV_FILM_GRAIN_PARAMS_AV1:
+            /* AOM FGS needs an exact match for the chroma resolution */
+            if (fgp->subsampling_x != desc->log2_chroma_w ||
+                fgp->subsampling_y != desc->log2_chroma_h)
+                continue;
+            break;
+        case AV_FILM_GRAIN_PARAMS_H274:
+            /* H.274 FGS can be adapted to any lower chroma resolution */
+            if (fgp->subsampling_x > desc->log2_chroma_w ||
+                fgp->subsampling_y > desc->log2_chroma_h)
+                continue;
+            break;
+        }
+
+        if (!best || best->width < fgp->width || best->height < fgp->height)
+            best = fgp;
+    }
+
+    return best;
 }