Replacing subtitles in video at run-time with custom text

[Dece Bel]

I want to develop an application with gstreamer to play videos with custom
subtitles that replaces original subtitles with my custom text at run-time
of the video. For example, if a video has english subtitles, I want to
replace the original subtitle with additional comments as the video plays.

I have been playing with the various gstreamer C tutorials to get a basic
understanding of the pipeline and make myself familiar with the necessary
APIs/techniques. One of the examples shows selecting & switching sub-titles
from multiple languages in the sample video stream.

However, I could not find any example or gstreamer element that can be to
added into the pipeline to extract the subtitle text or add back some
custom subtitle in the pipeline.

I was hoping to put together a quick gstreamer pipeline to do the same with
my text replacement module added to the pipeline to do the custom subtitle
replacement.

The design I have in mind is to build a pipeline with an element that
extracts subtitles as the video plays, then pass it through a custom
element that analyses the text and add some comments and put the comments
back to the video stream.

Alternatively, I was wondering if there is a callback available that can be
registered to the gstreamer message-bus that gets called whenever a
subtitle text is about to be displayed, and some capability to edit the
original text.

I do not have experience with gstreamer or other multimedia frameworks but
descent experience with C/C++ development.


Gracias

Dece
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