3Play Media offers transcripts and closed captions for content being published to the edX platform.
In order to do this, an API key and API Secret key will first need to be obtained by setting up an API collection for the 3Play Media project that content will be uploaded to.
Once the API keys are created, click here to view edX's documentation regarding how to obtain transcripts and closed captions for edX content.
Please note that edX requires transcripts and/or closed captions for all video content.