• Trying to watch a lecture without captions in a public space

What it does

Lecture Ninja takes your video files and converts it into an accessible document by:

  1. Transcribing speech in the video
  2. Detecting when someone switches slides on a PowerPoint in the video, and extracting slides to show as figures In addition, Lecture Ninja also has the following features:
  3. Clicking any word within the document brings you to when that word was said in the video
  4. Creates headings for you for organization purposes and ease of reading
  5. Generates a summary for each video

How we built it

Frontend: The frontend was built using Next.js as a framework for React (routing) with JavaScript. For the UI, we also created components (modals, cards, etc.) using Material UI and custom CSS.

Backend: The backend consists of two microservices. One microservice -- written in JavaScript using Node and Express, handles the CRUD operations (e.g adding new videos, handling user login, etc). It depends on our second microservice -- written in Python using FastAPI, OpenCV, ffmpeg, and the Google Cloud API Client. This second microservice is responsible for handling speech-to-text and slide change detection from the video.

Our implementation of slide change detection is based on the algorithm described in this paper:

Jeong, H. J., Kim, T.-E., Kim, H. G., & Kim, M. H. (2015). Automatic detection of slide transitions in lecture videos. Multimedia Tools and Applications, 74(18), 7537–7554.

Challenges we ran into

Only testing the Jeong et al algorithm on one video led to a fragile implementation, which caused problems when we wanted to implemented it on other videos slept too much

Accomplishments that we're proud of

We were able to quickly and effectively implement an algorithm that was described in a research paper.

What we learned

  • We learned how SIFT feature matching can be used to robustly match things across 2 images SIFT stands for “Scale-Invariant Feature Transform”. When applied to an image, the SIFT algorithm extracts keypoints (representing points in the image that are distinctive) and descriptors (vector representations of the detected features).
  • We can compare descriptors between two images in order to see if the same slide is in both images. Using the SIFT algorithm means that we can handle a handheld video recording of a speaker presenting their slides, which is a lot nosier compared to a Zoom presentation where the presenter is screen sharing their slides.
  • We also learned about how to make multiple services coordinate manipulation of large files

Future Updates

  • Use machine learning for more robust slide change detection
  • Allow editing in generated documents in case the user wants to add notes or corrections
  • Allow the video thumbnail in documents to be minimized and/or moved
  • Delete Lecture feature on the dashboard
  • More geese

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