How to add own, subtitles (resp. pure text) into existing MP4 video?

[pxstein]

Assume I have an existing well-encoded MP4 video WITHOUT subtitles.

Now I want to add the text "foobar testtext" with fontsize=18 and fontfamily Verdana into video beginning at 1min23sec and ending at 3min44sec centralized 30 pixels above lower border.

How can I most easily achieve this?

If possible/necessary the text could be put fix encoded into video and not only as traditional subtitle.

Peter

[manono]

If you want to play the video with external subs, then create a subtitle file for it with the same name as the video. Aegisub can set up the styles (font, text size ) for you and create the subs.

Encoding the subs into the video degrades the video and should be avoided. You can embed the subs without reencoding. I don't know if MP4 allows for that but repacking it as an MKV does allow for it,

[Sharc]

..... You can embed the subs without reencoding. I don't know if MP4 allows for that ….

.ass seems not to be supportet for embedding into the .mp4 container, only .srt, .sub, .idx, .xml and .ttxt

[Fragha]

You can create a mkv container with .ass subtitles and then rip to mp4 with Handbrake.

[amaipaipai]

Open you video with Aegisub:
1. Mark the start and end position of your subtitle
2. Export it to *.srt
3. Get the latest MP4Box, install MeGUI to get the last one, my version is "MP4Box - GPAC version 0.7.2-DEV-rev357-g7115eeb8-master"
4. Convert the .srt to .ttxt with the command below:

mp4box -ttxt your_subtitle.srt -out converted_subtitle.ttxt
Timed Text (SRT) import - text track 400 x 60, font Serif (size 18)
Conversion done

5. Open your "converted_subtitle.ttxt" in a text editor (Notepad++, Geany) and edit the "fontName" with the font you want, same for "fontSize" and save it.
6. To mux it in to your mp4 use the command below:

mp4box -add converted_subtitle.ttxt:lang=eng":name=English":layout=0x60x0x-1:group=2 your_video.mp4 -out subtitled_video.mp4
Timed Text (GPAC TTXT) Import
Saving to subtitled.mp4: 0.500 secs Interleaving

Like .ASS subtitles, only compatible players will display the desired font type and size.

This extra information will be listed inside your MP4:

Text
ID                                       : 3
Format                                   : Timed Text
Codec ID                                 : tx3g
Duration                                 : 4 min 55 s
Bit rate mode                            : Variable
Bit rate                                 : 65 b/s
Stream size                              : 2.36 KiB (0%)
Title                                    : English
Language                                 : English
Default                                  : Yes
Forced                                   : No
Alternate group                          : 2
Encoded date                             : UTC 2018-12-22 21:01:44
Tagged date                              : UTC 2018-12-22 21:01:44