Audio is a Time-Based Medium
One of the first challenges you have when faced with an audio discovery project is determining just how much content you’re dealing with. In the rest of the e-discovery world, this is measured in gigabytes of data. That works okay, because with emails and word documents, even TIFF documents, there is a generally understand correlation between gigabytes and the number of pages in question. And this translates into the general work effort you’ll need to go through it all, either with or without a technology assist.
But audio and video are time-based media, and should be measured as such. Again, knowing how many hours you have to sift through will greatly determine the method you choose to perform the discovery. And the problem is that there is no easy correlation between file size and file length. Why not?
The answer is “bit rate.” Loosely translated, bit rate defines the number of bits that a given recording system uses to capture the audio and put it into the digital file. Bit rate is usually measured in Kbps, or kilo-bits per second, and can vary widely from 8Kpbs up to 128Kbps or even more.
If you hear people talk about “compression schemes” this is what they are referring to. Audio that is 8Kbps is much more highly compressed than 128Kbps. To illustrate, one Gbyte of audio encoded at 8Kbps contains 277 hours, while one Gbyte of audio at 128Kbps is only 17 hours. You can see from this example that gigabyte pricing for audio projects can have little relation to the amount of audio that you will have to review.
So the next time you are faced with a big project and your client (either internal or external) says “I’ve got 100 gigabytes of audio we need to review” you can be prepared to ask the most important follow up question.
“Okay, do you know what the bit rate is?”
They may not, but this at least starts the conversation down a different path, so you can jointly determine the number of hours in the project which is what really matters.