This post presents some links and tips on creating a transcript from an online video that doesn't include one. It uses opensource tools that run on Windows, Mac and Linux.
To create a transcript of an online video that doesn't include one you can use the following tools:
1. Record the audio in Audacity [instructions]
2. Add the audio to a movie in OpenShot, you can also add an image (if you want a "sharp" image use a 1280×720 resolution image for 720p, 1920×1080 for 1080p)
3. Export the MP4 from OpenShot
4. Upload the MP4 to YouTube and download the transcript (note below if YouTube doesn't auto transcribe)
YouTube Didn't Auto-Transcribe
If YouTube doesn't auto transcribe you can use tools listed at [link]:
Take a look at this answer for YouTube transcription [link].