Video performance reporting

We were asked if there was some way to provide a way to measure how users were experiencing video playback. That is, how long to people spend buffering and how often does the player run out of video and have to rebuffer. We're using Omniture SiteCatalyst for this, and already do the standard video reporting.
It's important to get this kind of information from the client side. We can do server-side reporting, but all we'll know from that is how many times the files were requested. The approach we took gives us information direct from our customers, so we can quantify what they actually experience.
I started out by creating an eVar (conversion variable) for the video identifier and another for the video player. Handily this is also what we'll need to do to start using the SiteCatalyst 15 video solution, which saves us one task there. Another eVar captures the buffer time. I also created four new custom events to captur
e the different steps in video playback. These events are recorded alongside the eVars and so we can report by video identifier (and its classifications) or player.
When the user first requests the video, we send the "Video request" event. When the video has finished buffering, we send the "Video first frame" event, alongside the number of milliseconds spent buffering, rounded to the nearest 100 milliseconds.
If, during playback, the player runs out of video and has to start buffering, we send the "Buffer underrun" event. Again when the video starts playing again, the "Buffer underrun first frame" event is sent, alongside the rounded buffering time.

So now we've got our eVars for video ID, video play
er and buffer time, alongside these video events. We can report on any of these events happening with those eVars.
A simple report looks something like this using a simple "buffer underruns / first frame" calculated metric to show us the videos that people are finding most problematic.

The problem is that the "worst" videos according to this report are viewed by a miniscule number of people. Some poor sucker has been desperately trying to watch VOD:37367 on his dialup connection, with 521 buffer underruns. That doesn't sound like much fun, but it doesn't really help us optimise our service for the majority of people.
So I came up with some simple calculated metrics that insert a modifier to show us poorly performing videos, but weighted towards ones where the poor performance is widespread.

So now we can see there's a few videos that are problematic, and for a reasonably number of people. We can start optimising and seeing if we can improve this experience.

That calculated metric:
[Video buffer underrun] / [Video first frame] * ( [Video first frame] / [Total Video first frame] ) * 1000