MPEG Reconfigurable Video Coding - Signal Processing Systems - page 286

Fig. 7 FSM structure in a C AL actor

Fig. 8 Priority structure
in a C AL actor

The Route actor, in the Fig. 8 , forwards the token on the input port A to one of
the three output ports. Upon instantiation it takes two parameters, the functions P
and Q , which are used as predicates in the guard conditions. The selection of which
action to fire is in this example not only determined by the availability of tokens and
the guards conditions, by also depends on the priority statement.

4.2.3 C AL Subset Language for RVC

For an in-depth description of the language, the reader is referred to the language
report [ 15 ] , for the specific subset specified and standardized by ISO in the Annex
Cof[ 26 ] . This subset only deals with fully typed actors and some restrictions on
the C AL language constructs from [ 15 ] to have efficient hardware and software
code generations without changing the expressivity of the algorithm. For instance,
Figs. 6 , 7 and 8 are not RVC-C AL compliant and must be changed as the Figs. 9 , 10
and 11 where T1, T2, T are the types and only typed parameters can be passed to
the actors not functions as P, Q .
A large selection of example actors is available at the OpenDF repository [ 46 ] ,
among them can also be found the MPEG-4 decoder discussed below. Many
other actors written in RVC-C AL are available as reference SW of the standard