It's all about how the quality of the video, the relevance of the video to what the user expects / wants to have happen as part of their experience in that moment of the app.

Most of all, the video has to be as short as possible to convey it's meaning & message.

Finally, it has to create the right feeling for the user. Are they happier or better educated/informed or feeling a sense of accomplishment or feeling whatever feeling they're supposed (by your promises to the user) to be feeling?