CDN: Animated and still images

Table of Contents

Heavyweight -> Separated service

When the user sends an image

frontend sends image to backend
backend publishes image (Valkey pubsub)
CDN subscribed, recieves image
CDN generates an UUID for this image
CDN saves the association (UUID, hash, completed) with completed set to false
- postgres? sqlite? simple key-value db?
  - key-value is simple, probably faster for associations this simple
  - postgres keeps the same stack and allows for adding more data later (keywords, date, description, ...)
CDN sends an access URL to the backend
backend sends the URL to the frontends (so the message appears immediately, without the image)
CDN converts to AVIF (supports animated and still images, good compression, but slow)
- ffmpeg -i INPUT -an -c:v libsvtav1 -crf 35 -preset 6 -svtav1-params 'fast-decode=2' -g 1 -loop 0 -f avif OUTPUT
- other option: WebP -> gain conversion speed, looses compression
- look up: limit at max 20 fps?
- look up: use AV1 for animated images? gain inter-frames compression, but lose ability to display as images.
  - something like ffmpeg -i INPUT -an -c:v libsvtav1 -crf 35 -preset 6 -svtav1-params 'fast-decode=2' -g 60 -f webm OUTPUT
CDN wipes the metadata (mat2? or manual wipe with ffmpeg?)
CDN stores the resulting image with a hash as the name
- perceptual hash? only works for still images
- sha256? works for everything but allow duplicate images (if they are slightly different quality, size or encoding, different codec... the sha256 will be different)
frontends load the image

frontend sends a GET request with the URL
CDN looks up the DB
[OPTION] the image is completed
- CDN gets the image identified by hash and returns it to the frontend
[OPTION] the image is not completed
- CDN sends an HTTP response code 425 (Too Early)
[OPTION] the image is not in the DB
- CDN sends an HTTP response code 404 (Not Found)

Note: add an admin-customizable file size limit