What is soft subtitles?
Soft subtitles are subtitles that are not embedded in the video or image. It can be turn on ond off by the software.
In VLC player, enable from main menu - Video - Subtitle track. In Quicktime player, enable from main menu - View - Subtitles.
In iPhone/iPod video player, there is an extra icon if the mp4 video has soft subtitles.
If the mp4 video does not have soft subtitles, the icon will not appear.
The subtitles can be added into the mp4 video when you create or convert the video. Or it can be added after the mp4 video was created.
I have tried to use muxo and iHex editor to add in the subtitles. Using Subler is much easier.
Subler quick tutorial
Add soft subtitles
To add a soft subtitles, click on the (+) button, choose the external subtitles (current support srt format). If you are using double byte subtitles file, prefer to save it as UTF-8 encoding.
Movie info and artwork
You can add your video (or movie) description into the mp4 file, by clicking the (+) button at the bottom. The information will be displayed at iOS players or iTunes software.
To make your job easier, you can get movie information online, from menu - File - Import Search metadata online. Search the movie information by name, if the movie is found, the information and artwork can be downloaded from the internet.
Create chapter info
The last function I want to show here is to create chapter information using Subler.
Chapter information supported by VLC, Quicktime and iOS player. The chapter information can be added in when you create the mp4 file.
create chapter info with handbrake software
Sometimes chapter information is not available, you can add in using Subler, from menu - Edit - Insert a Chapter Every (nn minutes).
If the chapter information created by the software (eg. handbrake) is not supported by Quicktime or iOS players, save the mp4 file with Subler again will solve the problem.
Subler is powerful and easy to use open-source software. I just show a few feature of the software. There are more features and functions came with Subler, you need to explore it yourself.