  Inter prediction is a key technology to reduce the temporal redundancy in
video coding. In natural videos, there are usually multiple moving objects with
variable velocity, resulting in complex motion fields that are difficult to
represent compactly. In Versatile Video Coding (VVC), existing inter prediction
methods usually assume uniform speed motion between consecutive frames and use
the linear models for motion estimation (ME) and motion compensation (MC),
which may not well handle the complex motion fields in the real world. To
address these issues, we introduce a uniformly accelerated motion model (UAMM)
to exploit motion-related elements (velocity, acceleration) of moving objects
between the video frames, and further combine them to assist the inter
prediction methods to handle the variable motion in the temporal domain.
Specifically, first, the theory of UAMM is mentioned. Second, based on that, we
propose the UAMM-based parameter derivation and extrapolation schemes in the
coding process. Third, we integrate the UAMM into existing inter prediction
modes (Merge, MMVD, CIIP) to achieve higher prediction accuracy. The proposed
method is implemented into the VVC reference software, VTM version 12.0.
Experimental results show that the proposed method achieves up to 0.38% and on
average 0.13% BD-rate reduction compared to the VTM anchor, under the Low-delay
P configuration, with a slight increase of time complexity on the
encoding/decoding side.
