JVET-AO0201 Dual layer scalable VVC coding with external HEVC base layer [F. Urban, F. Galpin, E. François, P. de Lagrange (InterDigital)]

Multilayer coding with an external base layer is a functionality that is available in SHVC but not yet in VVC. A multilayer extension for an external base layer was proposed in JVET-AN0178 to add this functionality to VVC.

Using a VVC enhancement layer on top of HEVC instead of using SHVC reportedly shows a compression advantage of over 55%.

It was asked what applications might be? An example was given that HEVC legacy devices might be able to decode the base layer.

Why would a new profile be needed? Because currently VVC is not supporting this functionality in the VPS, and the only way to change it is by defining a profile.

The base layer does not need to be HEVC, can be any external video codec.