If you have separate video ( .mp4 ) and audio ( .m4a ) files, you can merge them using FFmpeg in the command line:

Here is a deep guide on what this file usually is, how to handle it, and how to fix potential issues. 1. Understanding videoplayback.mp4

Open the partially downloaded file with a robust media player like VLC Media Player , which can often play partially downloaded or corrupted video files. 3. Using videoplayback.mp4 in Programming (Python)

If you are having trouble with a specific videoplayback.mp4 file, let me know: What size is the file? Are you trying to open it or edit it? I can provide the specific commands or steps to fix it.