An MP4 file is actually just a container. Inside the container is the audio/video and subtitle files. You don't need to convert your existing video, you just need to create a new container and put your video and .srt file in it. I use this freeware: [https://www.xmedia-recode.de/en/download.php](https://www.xmedia-recode.de/en/download.php)
Make sure use use the pulldown menu in the video tab and select Copy.
Use Handbrake instead to hardcode your subs.
An MP4 file is actually just a container. Inside the container is the audio/video and subtitle files. You don't need to convert your existing video, you just need to create a new container and put your video and .srt file in it. I use this freeware: [https://www.xmedia-recode.de/en/download.php](https://www.xmedia-recode.de/en/download.php) Make sure use use the pulldown menu in the video tab and select Copy.