Video subtitles

[Laura Lazzati <laura.lazzati.15@gmail.com>]

Hi!

I have been playing with aegisub today and I would like to share my
experience with that tool, your ideas about how video subtitles should
be included, and your advice too.

I installed aegisub from guix, and when I open it, it has a GUI. There
you load your video, in my case I loaded the final video - the one
everybody loved with Dennis pics, that already had my voice - and
started from there. And ended up with a a final video with subtitles
included. But don't stop reading here.

The first question I need to answer is if subtitles are going to be
present all the time as part of the video, or they should be able to
be disabled. We had that discussion somewhere, but if they are going
to be present as part of the video (hardsubs) only .srt and .ass - the
ones created by default by aegisub - are supported by ffmpeg:
https://trac.ffmpeg.org/wiki/HowToBurnSubtitlesIntoVideo

I remembered how much time each audio file lasted, so I added one
subtitle for each svg file that appears in the video - they were just
three- with the full content of what is said in the audio. The
drawback of this is that each svg file in the video has the full
subtitle text before the speaker mentions those words - I will ask
Björn tomorrow to upload it to their IPFS so that you can see what I
mean.

When choosing the format of the subtitles, Ricardo mentioned that it
was better using usf because it had support for styling. The good news
is that aegisub allows us to do so in their own interface, but  in
their .ass format, one of the two that supports ffmpeg,  which is not
compatible,  I guess, with the formats mentioned in po4a for
translation. However the .ass subtitle can be exported as .ttxt -
which is an XML, and that can be converted back to .ass.

I find a solution for not getting the whole text of the subtitle at
once, that is creating each svg/cli session/whatever
appears-in-the-video-if-needed with their audio and subtitle
separately and glue every piece of video as a last step with ffmpeg.
Apparently, that is possible according to
https://trac.ffmpeg.org/wiki/Concatenate - have not tried it yet.
However, I don't know if, in case of wanting to have the subtitles
separately - not  hardsubs-  in this latter case if it is possible to
concatenate them and use them outside the video.

Sorry if the mail is too long, or if sth is messy, please, let me know.

Regards :)
Laura