Make Unity delay frame until VideoPlayer seek completed

Is it possible to make Unity wait for the seekCompleted-Event of the VideoPlayer before it begins the next frame? I am trying to record a video out of unity by making a screenshot of every frame. Because of that, the framerate drops to about 4-5fps. When all screenshots are made, I put them together to a 30fps video using an external software. To make the Video Players in the scene match the correct speed, I have to sync them to the current Time.time. Otherwise the videos would be running way faster in the final video. But one video in my scene is too big (4k video) to complete the syncing during one frameupdate. Is there a way to make Unity wait for all VideoPlayers to finish their seeking before starting a new frame?