Have you checked out Sheeroh Kiarie’s post on Transcription ? If you haven’t please check it out because captioning is a “blood relative” to transcription.
Transcription is a fun and cool way to make money online, but when audio or videos are transcribed, on most occasions the task is halfway done. Transcription has a sister service – Captioning. Captioning is taking already prepared transcripts and creating captions for videos.