subdump is a utility program that displays the textual representation of subtitle streams in media files.
Here's an example:
auto-editor subdump resources/subtitle.mp4
file: resources/subtitle.mp4 (0:und:srt)
1
00:00:00,523 --> 00:00:01,016
oop
2
00:00:01,523 --> 00:00:01,916
boop
------
subdump won't work if the subtitle stream is interally represented as a bitmap image instead of formatted text.
You may call subdump with aesubdump.