You can use the Voice typing option in Google Docs to create a quick rough draft transcription of your video. You can type and edit by speaking in Google Docs. This feature is only available in Chrome browsers.
This video explains how you can use a computer speaker and Voice typing to create a rough transcription of your video that you can edit for clarity.
You can access the Voice typing option in Google Docs by going to Tools -> Voice Typing->then clicking on the microphone. You may be prompted to allow access to your microphone before you can use the feature.
More information about accessing and using Voice typing is available from Google at support.google.com/docs/answer/4492226