Graphics Reference
In-Depth Information
Tabl e 8. 3
Coding of delta QP in HEVC and H.264/AVC
Underlined symbols are bypass coded
assigned to a category, which determines the offset that is added to the sample.
The value of the offset for a given category is set by the encoder. Band offset (BO)
involves dividing the intensity range into four bands and then adding a different
offset to the sample depending which band its sample intensity belongs to. For more
details on SAO, please refer to Chap.
7
.
The type, direction and offsets used to define the SAO filter can change for each
CTB; however, all samples belonging to a CTB are processed with the same SAO
filter (but luma and chroma CTBs may use different SAO filters). The SAO type is
signaled using
sao_type_idx_luma
and
sao_type_idx_chroma
with TrU
binarization. The first bin indicates whether the SAO filter is enabled and is regular
coded, while the second bin indicates if edge or band offset is used and is bypass
coded.
If edge offset is used, the direction of the edge is signaled using
sao_eo
_class_luma
and
sao_eo_class_chroma
with FL binarization of two bins,
all of which are bypass coded. If band offset is used, four
sao_band_position
syntax elements are signaled to indicate the start position of each band with a FL
binarization of five bins, all of which are bypass coded.
For both types of SAO filtering, four
sao_offset_abs
are signaled (one for
each category or band) using TrU with cMax computed by Eq. (
8.4
)andallbinsare
bypass coded.
cMax
D
.1 << .min.bitDepth; 10/
5//
1
(8.4)
