If the video has sound but no picture (or vice versa), it may be encoded with a specific codec. Tools like Handbrake can convert it into a more standard MP4 format.
If you are looking for a guide on how to handle or understand this file, here is a general breakdown based on its and common naming conventions: 1. Understanding the MP4 Format inu_un_8.mp4
If you downloaded this from an unknown source, run it through a scanner like VirusTotal before opening it. If the video has sound but no picture
Often translates to "dog" in Japanese. This could indicate the video features a dog or is related to a Japanese project. inu_un_8.mp4