using (var presentationDocument =DocumentFormat.OpenXml.Packaging.PresentationDocument.Open(@"小视频.pptx", false)){var presentationPart = presentationDocument.PresentationPart;var slidePart = presentationPart.SlideParts.FirstOrDefault();// 忽略代码}

<p:pic><p:nvpicpr><p:cnvpr id="4" name="视频"><a:hlinkclick action="ppaction://media" r:id=""></a:hlinkclick></p:cnvpr><p:cnvpicpr><a:piclocks nochangeaspect="1"></a:piclocks></p:cnvpicpr><p:nvpr><a:videofile r:link="rId2"></a:videofile><p:extlst><p:ext uri="{DAA4B4D4-6D71-4841-9C94-3DE7FCFB9230}"><p14:media r:embed="rId1" xmlns:p14="http://schemas.microsoft.com/office/powerpoint/2010/main"></p14:media></p:ext></p:extlst></p:nvpr></p:nvpicpr>
</p:pic>

                var picture = slidePart.Slide.CommonSlideData.ShapeTree.OfType<Picture>().FirstOrDefault();var videoFromFile = picture.NonVisualPictureProperties.ApplicationNonVisualDrawingProperties.GetFirstChild<VideoFromFile>();

           var openXmlPart = (DataPartReferenceRelationship) slidePart.GetReferenceRelationship(videoFromFile.Link.Value);

                var stream = openXmlPart.DataPart.GetStream();var file = System.IO.Path.Combine(System.IO.Path.GetTempPath(), "林德熙是逗比.mp4");File.WriteAllBytes(file, ReadAllBytes(stream));