I implemented a vod streaming system that converts videos to hls with ffmpeg.
And I made a Django program that gives playlists and ts files to the player so that the video can be played.
But I don't know how to record the watching statistics.
I used vediojs and I know that I can send the watching time from the client to the server and record it.
But We are sure that this method is not accurate and the user can change the statistics.
On the other hand, I have seen vod platforms that do not take the statistics from the player (client) at all, as if the statistics are calculated by the server.
One option is to log the statistics for each ts file that is requested, but the video buffering by the player means that these statistics are always wrong, the player may buffer 10 minutes but the user still watches 1 minute.
Any suggestion or experience
I used vediojs and I know that I can send the watching time from the client to the server and record it.
But We are sure that this method is not accurate and the user can change the statistics.
For accurate playback statistics you need to have client side measurement as you have suggested - most of the major streaming analytics solutions provide SDK's that integrate with the most common players and applictaion frameworks.
It is possible for a user to interfere with analytics reported in this way, but it would require quite advanced skills and usually quite some effort to do it, so it would not normally be an issue for regular viewers.
This whole topic is very relevant for advertising, where the person paying for the ad wants to ensure that the ad has actually been viewed (and preferably by a human, which is another significant issue). You may find it useful to look at how the IAB (advertising industry group) discusses this - for example, they describe the use of 'beacons' to report from the client to the advertising accounting server: