To concatenate two MP4 files using FFmpeg, you can follow these steps:
1. Open a terminal or command prompt on your computer.
2. Navigate to the directory where your MP4 files are located using the "cd" command.
3. Type the following command to concatenate the files:

```go
ffmpeg -i input1.mp4 -c copy -bsf:v h264_mp4toannexb -f mpegts intermediate1.ts
ffmpeg -i input2.mp4 -c copy -bsf:v h264_mp4toannexb -f mpegts intermediate2.ts
ffmpeg -i "concat:intermediate1.ts|intermediate2.ts" -c copy output.mp4
```

In this command, replace "input1.mp4" and "input2.mp4" with the names of your input MP4 files, and replace "output.mp4" with the desired name for your output file. The "concat" command tells FFmpeg to concatenate the two intermediate files into a single output file.
1. Press Enter to run the command.

After the command has finished running, you should have a new MP4 file containing the concatenated video from the two input files.
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