Modifying frames of existing WebM video

[darind]

I have a WebM file (single video track encoded with VP9) and was wondering if I can use ts-ebml to perform the following:

1. Parse the file and extract each frame
2. Decode parsed frames (using W3C VideoDecoder)
3. Apply some transformation on the frame (for example draw a rectangle in the middle)
4. Encode the new frame back using VP9
5. Assemble the new frames back to a WebM container file