JVET-AM0156 AHG9: On Digitally Signing a SEI message [Y. Gao, P. Wu, Y. Bai, S. Xie, C. Huang (ZTE)]

This contribution proposes the following changes related to optimize the functionality of digitally signing a SEI message.

Adding a flag(sei_digital_signature_initialization_present_flag) to specify whether the digital signing initialization related syntax elements are present in the SEI message that requires digital signature verification.

It was noted that JVET-AM0118 was decided to be included in VSEI v4.

Signing of SEI messages has been resolved and there is no interest of the group to further study signing of SEI messages.