  This paper enhances the intra prediction by using multiple neural network
modes (NM). Each NM serves as an end-to-end mapping from the neighboring
reference blocks to the current coding block. For the provided NMs, we present
two schemes (appending and substitution) to integrate the NMs with the
traditional modes (TM) defined in high efficiency video coding (HEVC). For the
appending scheme, each NM is corresponding to a certain range of TMs. The
categorization of TMs is based on the expected prediction errors. After
determining the relevant TMs for each NM, we present a probability-aware mode
signaling scheme. The NMs with higher probabilities to be the best mode are
signaled with fewer bits. For the substitution scheme, we propose to replace
the highest and lowest probable TMs. New most probable mode (MPM) generation
method is also employed when substituting the lowest probable TMs. Experimental
results demonstrate that using multiple NMs will improve the coding efficiency
apparently compared with the single NM. Specifically, proposed appending scheme
with seven NMs can save 2.6%, 3.8%, 3.1% BD-rate for Y, U, V components
compared with using single NM in the state-of-the-art works.
