You must provide attribution in an appropriate way for the medium. If your video shows credits, you should also put the attribution there. Otherwise, I'd add a small but legible attribution note at the bottom of the frame during the start or end of the video.
As a rule of thumb, ask yourself: how do you want to credit/advertise yourself or your organization as the creator of this video? The attribution for the CC-licensed content should be similar, but can of course be less prominent.
It might be ok to place the attribution outside of the video, e.g. in the video description when you upload the video to some sharing platform. However, this attribution is not visible when the video is embedded or downloaded, or re-uploaded elsewhere. Therefore, I do not think that external attribution would generally satisfy the CC-BY license.