1) Speed : the site is often showing heroku errors. Seems like you are running the entire processing in the request-response cycle. If not already done, please try to use a queueing system to perform async processing - and then let the user know when their video is ready to view as steps (probably via email or browser notifications). This will stop your site from crashing frequently and you'll be able to scale to many users very quickly.

2) Please add link-backs to the specific time in the video from where the step is shown.

Cheers!