I was inspired by this tool, http://www.randomhacks.net/substudy/ It required to cut the video, with a lot of processing, cli knowledge and to storage the cut videos taking a lot of space, my idea was to make the process as lightweight as possible, the outcome of the extension it's a CSV with the marks for when the video starts and stops for each sentence, it has a negligible output size in comparison and can be used in low-end computers.

You described the functionality perfectly, I made it as a tool to have custom cards for practising languages without having to be locked in any platform, in my opinion language platforms are very bland with their spoken lessons and only have perfectly pronounced sentences, with the tool you can practice more real and engaging topics for yourself.

Another usage that some users commented was to use it as a learning tool for lectures and presentations, that's why I included a merge subtitles functionality recently, so the cards can hold more information as opposed a single sentence.