Of itu-t sg16 wp3 and iso/iec jtc1/SC29/WG11

JCTVC-M0182 AHG17: complexity analysis of SHM1.0 [J. Dong, Y. Ye, Y. He (Interdigital)]

SHM1.0 complexity assessment was done as part of the AHG17 activities, and the anchor results were released in the JCTVC-L0440 package. Using the SHM1.0 anchor results in the JCTVC-L0440 package ("r2" version), this contribution summarizes the complexity of the PU-based RefIdx, the Picture-based RefIdx, and the IntraBL implementations. It is reported that the PU-based RefIdx and IntraBL solutions have similar complexity characteristics, whereas the complexity characteristics of the Picture-based RefIdx solution are very different. It is also reported that the RefIdx solution offers the design flexibility and allows different applications to choose from block-based or picture based implementation based on its specific complexity considerations.

Decoder complexity: Compared to simulcast, both refidx and textureBL approaches have memory bandwidth of approx. 92-93% on average (refidx in PU-based operation). With picture-based refidx, approx. 102%. Number of computations around 94-95% for PU-based (both), 144% for picture-based refidx

No separate analysis is given in this contribution for the different cases (AI, RA, LD-P/B)

Worst-case complexity is identical to full simulcast decoding (base and enhancement) in PU-based processing (since spatial upsampling is less complex than MC bi-pred), and full simulcast plus upsampling filter for picture-based processing.

In worst case, with block-based upsampling, bipred with the RefIdx approach requires performing both upsampling and MC and then averaging the results together, whereas in the IntraBL approach this combination is not allowed. When this bipred case occurs, the MC part is higher or equal complexity than the upsampling part, and the total complexity is less than or equal to that of ordinary enhancement-layer temporal bipred.

The IntraBL as previously designed has a CU-based switch (whereas the similar switch point in RefIdx is the PU level). As previously designed, the coding efficiency difference is about 1% for LB, in favor of IntraBL. It was remarked that a modification of the switching point as proposed in JCTVC-M0220 can increase this to 2%.