avcodec/dovi_rpu: correctly read el_bit_depth_minus8 and ext_mapping_idc

These two fields are coded together into a single 16 bit integer with upper 8
bits for ext_mapping_idc and lower 8 bits for el_bit_depth_minus8.

Furthermore ext_mapping_idc has two components, upper 3 bits and lower 5 bits.
Co-authored-by: Niklas Haas <git@haasn.dev>
Signed-off-by: Niklas Haas <git@haasn.dev>

libavcodec/dovi_rpudec.c

@@ -58,7 +58,7 @@ int ff_dovi_attach_side_data(DOVIContext *s, AVFrame *frame)
 
     /* Copy only the parts of these structs known to us at compiler-time. */
 #define COPY(t, a, b, last) memcpy(a, b, offsetof(t, last) + sizeof((b)->last))
-    COPY(AVDOVIRpuDataHeader, av_dovi_get_header(dovi), &s->header, disable_residual_flag);
+    COPY(AVDOVIRpuDataHeader, av_dovi_get_header(dovi), &s->header, ext_mapping_idc_5_7);
     COPY(AVDOVIDataMapping, av_dovi_get_mapping(dovi), s->mapping, nlq_pivots);
     COPY(AVDOVIColorMetadata, av_dovi_get_color(dovi), s->color, source_diagonal);
     ext_sz = FFMIN(sizeof(AVDOVIDmData), dovi->ext_block_size);
@@ -423,11 +423,17 @@ int ff_dovi_rpu_parse(DOVIContext *s, const uint8_t *rpu, size_t rpu_size,
             int el_bit_depth_minus8 = get_ue_golomb_31(gb);
             int vdr_bit_depth_minus8 = get_ue_golomb_31(gb);
             int reserved_zero_3bits;
+            /* ext_mapping_idc is in the upper 8 bits of el_bit_depth_minus8 */
+            int ext_mapping_idc = el_bit_depth_minus8 >> 8;
+            el_bit_depth_minus8 = el_bit_depth_minus8 & 0xFF;
             VALIDATE(bl_bit_depth_minus8, 0, 8);
             VALIDATE(el_bit_depth_minus8, 0, 8);
+            VALIDATE(ext_mapping_idc, 0, 0xFF);
             VALIDATE(vdr_bit_depth_minus8, 0, 8);
             hdr->bl_bit_depth = bl_bit_depth_minus8 + 8;
             hdr->el_bit_depth = el_bit_depth_minus8 + 8;
+            hdr->ext_mapping_idc_0_4 = ext_mapping_idc & 0x1f; /* 5 bits */
+            hdr->ext_mapping_idc_5_7 = ext_mapping_idc >> 5;
             hdr->vdr_bit_depth = vdr_bit_depth_minus8 + 8;
             hdr->spatial_resampling_filter_flag = get_bits1(gb);
             reserved_zero_3bits = get_bits(gb, 3);

libavcodec/dovi_rpuenc.c

@@ -552,8 +552,9 @@ int ff_dovi_rpu_generate(DOVIContext *s, const AVDOVIMetadata *metadata,
     put_bits(pb, 2, hdr->vdr_rpu_normalized_idc);
     put_bits(pb, 1, hdr->bl_video_full_range_flag);
     if ((hdr->rpu_format & 0x700) == 0) {
+        int ext_mapping_idc = (hdr->ext_mapping_idc_5_7 << 5) | hdr->ext_mapping_idc_0_4;
         set_ue_golomb(pb, hdr->bl_bit_depth - 8);
-        set_ue_golomb(pb, hdr->el_bit_depth - 8);
+        set_ue_golomb(pb, (ext_mapping_idc << 8) | (hdr->el_bit_depth - 8));
         set_ue_golomb(pb, hdr->vdr_bit_depth - 8);
         put_bits(pb, 1, hdr->spatial_resampling_filter_flag);
         put_bits(pb, 3, 0); /* reserved_zero_3bits */