Prediction Coding - Advanced Video Coding Systems - page 75

Fig. 4.18 Hierarchical P and hierarchical P/B coding structure. a Hierarchical P coding structure
and b Hierarchical P/B coding structure

By marking and transmitting the COI information, the decoder side could figure out
the actual coding order of current picture even there are some pictures lost during
transmission. Meanwhile, the delta _ poi is defined to derive the POI in decoder side.
And delta _ poi is defined as the equation

delta _ poi = COI − POI . (4.46)

The syntax element delta _ poi is used to denote the only display order of current
picture. And the decoder side derives the POI of current coding picture by subtract
delta _ poi which can be decoded from picture header from COI.
In the reference picture list and removed picture list, the delta COI of reference
pictures is recorded. And by deriving the COI and POI of reference pictures the
reference pictures for current coding picture can be set. At the encoder side, it is
necessary to write the reference manage information with additional bit. However, it
is redundant to transmit RCS for each picture since the RCS is of great similarity for
the same position in the different GOP. The bits for reference informationwill account
for a high percentage especially when for low resolution. In our proposed scheme,
several reference configuration sets (RCS) are used and written to the sequence
header to save bitrate instead of writing reference configuration set of each coding
picture in picture header. And in picture header only the index of RCS is transmitted,
signalling the reference scheme that the current coding or decoding picture takes.
At the same time, a special RCS set can be also written into picture header if none
of the RCS scheme from the sequence header is taken for the decoding picture. In