  The user experience in adaptive HTTP streaming relies on offering bitrate
ladders with suitable operation points for all users and typically involves
multiple resolutions. While open GOP coding structures are generally known to
provide substantial coding efficiency benefit, their use in HTTP streaming has
been precluded through lacking support of reference picture resampling (RPR) in
AVC and HEVC. The newly emerging Versatile Video Coding (VVC) standard supports
RPR, but only conversational scenarios were primarily investigated during the
design of VVC. This paper aims at enabling usage of RPR in HTTP streaming
scenarios through analysing the drift potential of VVC coding tools and
presenting a constrained encoding method that avoids severe drift artefacts in
resolution switching with open GOP coding in VVC. In typical live streaming
configurations, the presented method achieves -8.57% BD-rate reduction compared
to closed GOP coding while in a typical Video on Demand configuration, -1.89%
BD-rate reduction is reported. The constraints penalty compared to regular open
GOP coding is 0.65% BD-rate in the worst case. The presented method was
integrated into the publicly available open source VVC encoder VVenC v0.3.
