Graphics Reference
In-Depth Information
rqt_root_cbf=1
cbf_cb=1,
cbf_cr=1
RQT
depth = 0
split_transform_flag=0
split_transform_flag=0
split_transform_flag=1
split_transform_flag=0
cbf_cb=1,
cbf_cr=0
cbf_cb,
cbf_cr,
cbf_luma
cbf_cb,
cbf_cr,
cbf_luma
cbf_cb,
cbf_cr,
cbf_luma
RQT
depth = 1
split_transform_flag=1 split_transform_flag=0
split_transform_flag=0
cbf_cb
cbf_luma
cbf_cb
cbf_luma
cbf_cb
cbf_luma
RQT
depth = 2
cbf_cb=1
split_transform_flag=1
split_transform_flag=0
for each
TB
split_transform_flag=0
cbf_cb
RQT
depth = 3
cbf_cb
cbf_luma
cbf_cb
cbf_luma
cbf_cb
cbf_luma
RQT
depth = 4
cbf_luma
cbf_luma
cbf_luma
cbf_luma
Fig. 8.11
Illustration of signaling of
split_transform_flag
,
cbf_luma
,
cbf_cb
,and
cbf_cr
for an RQT with depth 4. Note that at RQT depth = 0, no
split_transform_flag
is signaled since an implicit transform split occurs for CU of 64 as n
max
32.
cbf_luma
is only
signaled for leaf transform blocks (highlighted in
red
).
cbf_cb
and
cbf_cr
are signaled for the
root node and all nodes where the corresponding CBF at the parent node is non-zero, except for
the nodes related to TrafoSize
D
D
4
cbf_cb
and
cbf_cr
, four contexts are used such that the corresponding context
increment depends on the RQT depth (with admissible values between 0 and 3, since
for the case of TrafoSize
D
4 no chroma CBFs are transmitted), whereas for
cbf
_luma
only two contexts are provided with its discriminating context increment
depending on the condition RQT depth
D
0. For more background on the use of
RQT and related syntax elements, please refer to Chap.
3
.
8.6.4
Significance Map
In H.264/AVC, the significance map for each transform block is signaled by
transmitting a
significant_coeff_flag
(SIG) for each position to indicate
whether the coefficient is non-zero. The positions are processed in an order based
on a zig-zag scan. After each non-zero SIG, an additional flag called
last
_significant_coeff_flag
(LAST) is immediately sent to indicate whether