An MP4 is just a "container." If the video inside is encoded with an outdated or overly modern codec (like H.265 on an old player), the file may show a black screen or play only audio.
If you own the Dead Poets Society DVD or Blu-ray, you can use free, open-source software like to "rip" the disc into a high-quality MP4. dead poets society mp4 work
23.976 fps (the standard film rate) to avoid "jittery" movement. Conclusion: Seize the Stream An MP4 is just a "container