Process outline:
- Download podcast episode in mp3 format
- Use ffmpeg to convert podcast to a video
- Upload to youtube
- Wait - let youtube autogenerate the subtitles
- Download the subtitles using youtube-dl
- youtube-dl –write-auto-sub https://www.youtube.com/watch?v=dJtZ8YGyxt
- Convert the resulting vtt file to text using vtt3text.py
If you are a fan of podcast and want to have a way to search for an episode - post it online (on a blog or a wiki).