On 1/11/2021 5:45 PM, Mark Thompson wrote:
+static int FUNC(vui_parameters)(CodedBitstreamContext *ctx, RWContext
*rw,
+ H266RawVUI *current)
+{
+ int err;
+
+ flag(vui_progressive_source_flag);
+ flag(vui_interlaced_source_flag);
+ flag(vui_non_packed_constraint_flag);
+ flag(vui_non_projected_constraint_flag);
+ flag(vui_aspect_ratio_info_present_flag);
+ if (current->vui_aspect_ratio_info_present_flag) {
+ flag(vui_aspect_ratio_constant_flag);
+ ub(8, vui_aspect_ratio_idc);
+ if (current->vui_aspect_ratio_idc == 255) {
+ ub(16, vui_sar_width);
+ ub(16, vui_sar_height);
+ }
+ } else {
+ infer(vui_aspect_ratio_constant_flag, 0);
+ infer(vui_aspect_ratio_idc, 0);
+ }
+ flag(vui_overscan_info_present_flag);
+ if (current->vui_overscan_info_present_flag)
+ flag(vui_overscan_appropriate_flag);
+ flag(vui_colour_description_present_flag);
+ if (current->vui_colour_description_present_flag) {
+ ub(8, vui_colour_primaries);
+ ub(8, vui_transfer_characteristics);
+ ub(8, vui_matrix_coeffs);
+ flag(vui_full_range_flag);
+ } else {
+ infer(vui_colour_primaries, 2);
+ infer(vui_transfer_characteristics, 2);
+ infer(vui_matrix_coeffs, 2);
+ infer(vui_full_range_flag, 0);
+ }
+ flag(vui_chroma_loc_info_present_flag);
+ if (current->vui_chroma_loc_info_present_flag) {
+ if (current->vui_progressive_source_flag &&
+ !current->vui_interlaced_source_flag) {
+ ue(vui_chroma_sample_loc_type_frame, 0, 6);
+ } else {
+ ue(vui_chroma_sample_loc_type_top_field, 0, 6);
+ ue(vui_chroma_sample_loc_type_bottom_field, 0, 6);
+ }
+ }
These are inferred as 6 when not present?
6 only happened when ChromaFormatIdc = 1, others are not defined.
and 6 is the unspecific value in the spec...
Do we really need to infer it :)
To match the colour description cases probably yes?
"When vui_chroma_loc_info_present_flag is equal to 0,
vui_chroma_sample_loc_type_frame is not present and is inferred to be
equal to 6, which indicates that the location of the chroma samples is
unknown or unspecified or specified by other means not specified in this
Specification. When vui_chroma_sample_loc_type_top_field and
vui_chroma_sample_loc_type_bottom_field are not present, the values of
vui_chroma_sample_loc_type_top_field and
vui_chroma_sample_loc_type_bottom_field are inferred to be equal to
vui_chroma_sample_loc_type_frame."
So the correct implementation i think would be
flag(vui_chroma_loc_info_present_flag);
if (current->vui_chroma_loc_info_present_flag) {
if (current->vui_progressive_source_flag &&
!current->vui_interlaced_source_flag) {
ue(vui_chroma_sample_loc_type_frame, 0, 6);
infer(vui_chroma_sample_loc_type_top_field,
current->vui_chroma_sample_loc_type_frame);
infer(vui_chroma_sample_loc_type_bottom_field,
current->vui_chroma_sample_loc_type_frame);
} else {
infer(vui_chroma_sample_loc_type_frame, 6);
ue(vui_chroma_sample_loc_type_top_field, 0, 6);
ue(vui_chroma_sample_loc_type_bottom_field, 0, 6);
}
} else {
infer(vui_chroma_sample_loc_type_frame, 6);
infer(vui_chroma_sample_loc_type_top_field,
current->vui_chroma_sample_loc_type_frame);
infer(vui_chroma_sample_loc_type_bottom_field,
current->vui_chroma_sample_loc_type_frame);
}
Also, you also need to infer the default value of almost everything when
sps_vui_parameters_present_flag is 0. See section D.8 and how h265 does
it with the vui_parameters_default() custom function.
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