YouTube is currently experimenting with server-side ad injection. This means that the ad is being added directly into the video stream.
This breaks sponsorblock since now all timestamps are offset by the ad times.
For now, I set up the server to detect when someone is submitting from a browser with this happening and rejecting the submission to prevent the database from getting filled with incorrect submissions.
Almost certainly not, although fair disclaimer, I don’t actually know. Ads need to be tailored to the user when delivered, so it’s likely the YouTube frontend requesting the next chunk of video to be an ad instead of the next chunk of video from blob storage. yt-dlp likely just requests successive chunks straight from blob storage, passing this.
If YouTube served ads by saying “point to an ad chunk next” in their blob storage, 1. Everyone would see the same ad and 2. Premium users would still see ads.
To patch this, YouTube really needs to stop serving video chunks directly from storage, but I forget the reason they haven’t done that already.
(Technical note; I’m assuming blob storage chunks contain 1-2 seconds of video and metadata pointing to the next one, like a linked list. I’m not sure if this is how YouTube works, but many video platforms do this)
I think the backend could just generate the ad ridden video feed for the specific user. Most probably it would be very resource intensive, but I can only hope so… but then I also don’t know much about HLS and other fragmented streams so it might not be a performance problem at all.
I think the full list of chunks is (currently) known beforehand. That’s how yt-dlp can download on multiple threads, but also how it can show the number of total fragments relatively quickly on the progress bar
yeah that makes sense. i was thinking maybe youtube had servers to decide what chunks clients would get, maybe by looking at whether or not they are premium users first. but anyway youtube still needs a way to differentiate between ad chunks and video chunks, otherwise we would just be able to skip 10 seconds through all the ads. surely that can be exploited somehow.