Hey guys,
You might want to take a look at the tutorial I updated for 4.9.1 recently in regards to the Media Player asset and controlling playback. You will also want to look into our Documentation which warns users about the compatibility issues with certain media files, particularly H.264 and .mp4 enconded files.
Media Player Tutorial
Media Player Documentation
Let me know if you have further questions or need additional assistance. We are aware of certain compatibility issues and are working to have these resolved. We try to urge users not to use this feature as a major focus of their projects as it is still considered experimental at this time.
Thank you,