The import video procedure is using system video codecs to extract the frames from the video sequence, so sometimes Import Video operation doesn't work straight out of the box. Make sure that the system has proper codecs installed, if you observe any problems with the import video procedure.
Metashape allows to use the video files as a source data for the 3D reconstruction process via File Menu -> Import -> Import Video command.
"Media resource couldn't be resolved" message may be observed on Windows systems. It indicates that some video codecs are missing and in such cases we usually suggest to install K-lite Codec pack or similar in order to guarantee the Import Video operation.
Note that you do not need to install any auxiliary utilities in addition to the codecs themselves.