How to extract video embedded subtitle from a video URL and show in a text widget in flutter?

Question

I'm using flutter VLC player to play videos in my flutter app. I want to change the subtitle size dynamically in my video. But Flutter VLC player did not provide the function to change subtitle size dynamically. So I would like to extract the subtitle from the video and show it in a text widget instead of VLC player's subtitle. Can someone help me to extract the subtitle from the video URL? Or any other method to solve this issue?

I have tried to extract subtitles using ffmpegkit .

 await FFmpegKit.executeAsync('-i $url -map 0:s:0 -codec:s srt $outputPath');

This code returns a blank srt file.