Thanks for the explanation.
After reading the code, I realized all the media files are created as DataPart in PresentationBuilder and the Non-Public memember TargetFileExtension is “.bin”. For images, OpenXml SDK adds .bin to media files. For audio and video files, it doesn’t add any extension. I know audios created by OpenXml SDK are playable, but not video. I’m not sure if it is caused by file extension. I thought using OpenXm SDK I can create exactly folder layouts as pptx generated by PowerPoint. It seems like not exactly.
I’m wondering how [Content_Type].xml is created by sdk. Which sdk api or part is related to its generation? Can I load in this xml and modify it and save it back to some part. When package is saved, my modified content is in [Content_Type].xml?