Graphics Reference
In-Depth Information
B
3
B
4
B
7
B
8
B
2
B
6
I
0
P
1
P
5
Fig. 2.15
Example referencing structure
Tabl e 2. 4
RPS for each picture of Fig.
2.15
Picture
POC
RefPicSetStCurr
RefPicSetStFoll
RefPicSetLtCurr
RefPicSetLtFoll
I
0
0
-
-
-
-
P
1
4
I
0
-
-
-
B
2
2
I
0
,P
1
-
-
-
B
3
1
I
0
,B
2
P
1
-
-
B
4
3
P
1
,B
2
,B
3
-
-
I
0
P
5
8
P
1
-
I
0
-
B
6
6
P
1
,P
5
-
-
I
0
B
7
5
P
1
,B
6
P
5
-
I
0
B
8
7
P
5
,B
7
-
-
I
0
An IDR picture resets the codec which includes turning all pictures in the DPB
into non-reference pictures. Since the RPSs of IDR pictures are empty, there is no
RPS syntax signaled for IDR pictures. All lists in Table
2.4
are therefore empty for
the IDR picture I
0
. At picture B
3
, picture P
1
is put in RefPicSetStFoll since P
1
is not
referenced by B
3
.P
1
is however kept in the DPB since it is used for future pictures.
At picture B
4
,I
0
is made into a long-term picture in this example, it is therefore put
in RefPicSetLtFoll since it is not referenced by B
4
. At picture P
5
, the encoder makes
pictures B
2
and B
3
non-reference pictures by not including them in the RPS at all.
At the same time, picture I
0
is moved to RefPicSetLtCurr since it is referenced by
P
5
.I
0
is thereafter kept in RefPicSetLtFoll for later use.
The encoder is required to ensure that every picture that is indicated in RefPic-
SetStCurr and RefPicSetStFoll are present in the DPB. If this is not the case, the
decoder should infer that as a bitstream error and take appropriate action. However,
if there is no corresponding picture in the DPB for an entry in the RPS that is
indicated not to be used for reference for the current picture, the decoder takes no
action since this situation may occur due to the removal of individual sub-layer non-
reference pictures or entire higher temporal sub-layers.
Although no RPS is sent for IDR pictures, both CRA and BLA pictures may
have pictures in their RPS so that the associated RASL pictures can use those
