The top comment on HN says
> So Youtube changed how views are counted and is blaming ad blockers?
When even a cursory look would show that if you block stats-aggregation endpoint .. stats go down. Sometimes it is occam's razor.
The fact that ad revenue didn't change means they do have robust ad tracking, but the view numbers are +/- some unexpected level of fiction.
Ad tracking is usually done client-side too, so ad revenue being stable just means that the missing view counts are probably limited to the users who already weren't viewing ads.
Disclaimer: I work at Google but not at Youtube and have no idea how things work really. This is just based on some info I read online.
Also, with segmented MP4 streams, the files on the backend won't necessarily be easy to match up 1:1 with videos. How do you count the views if someone watches a video, and then skips back to watch the middle section a few times, and then doesn't finish it? Because that would show up as (1, 1, 4, 3, 0) in your database for the different files involved. Now imagine doing that for ~500 people on a shared IP address for their high school. And now your minimum threshold for view counting is tied to the size of your MP4 chunks, or range requests. And now you've put this view counting logic into the hot path of serving terabytes of data.
From a product perspective, you can see why "A video view is counted the first time the user presses the play button and watches for at least 30 seconds" is a much more desirable definition, both technically and for stakeholders (video creators, advertisers, etc) to understand.