Wednesday 22 February 2012

SCEE audio team prepare for the zombie apocalypse

I love this pic!

A couple of months ago our London Studio audio team took part in the 2.8 hours later event, defending London from the undead hoards dressed as the Scooby Doo crew.

As valiant as they were, they weren't able to hold back the zombie masses for long, and eventually succumbed to wandering the streets of London looking for brains.

Left to right: Joanna Orland, Joe Thwaites, Nick Ward-Foxton, Alastair Lindsay and Malin Arvidsson

On a related note, I wanted to go to this talk at the Cambridge University Science Festival, but they'd sold out before I had a chance to reserve tickets :-(

Monday 20 February 2012

All In The Mix

This is a transcript of a talk I did on game audio mixing at the Brighton Develop Conference, in the UK in July 2010.

Remember, this was written to accompany a Keynote presentation, but I can't post that here, so you'll have to imagine it.  It looked awesome ;-)

All In The Mix

What's the difference between LKFS and LUFS?

As part of my work, I've been reading a lot about audio loudness standards recently.

There seems to be a bit of confusion between LKFS and LUFS, so I thought I'd explain the difference between these two measurements.

So, the short answer to the question, what's the difference between LKFS and LUFS is.....nothing.  Not any more anyway.  They used to be different but now they are effectively the same thing.

Here's the long answer:

About 4 or 5 years ago, the ITU (International Telecommunications Union) released a paper, 'ITU-R BS.1770 - Algorithms to measure audio programme loudness and true-peak audio level.'  It described a way to measure the average loudness of a piece of audio and gave you a value for the audio as a whole.  The units it used were LKFS, which stands for Loudness, K-Weighted, referenced to digital Full Scale, averaged out over the duration of the piece.

The EBU (European Broadcasting Union), took this and ran with it.  However, over time they discovered a problem.  It was too easy for long quiet sections of audio to bring down the average measurement.  So they released a paper, 'EBU R128 - Loudness normalisation and permitted maximum level of audio signals', containing a few modifications.

They introduced some new units, namely LUFS (Loudness Units, relative to digital Full Scale), LU (Loudness Units), and LRA (Loudness Range, a measurement of the dynamic range, measured in LU).  The LRA measurement was actually developed by TC Electronics, who are part of the EBU PLOUD group.

The big change was the introduction of a gate that would stop data being taken into account if the level dropped below a certain threshold.  Because consumers judge the loudness of any particular piece of audio based on the loud parts, what the EBU called the foreground loudness, this gate would ignore any data that was 8 LU below the ungated measurment, so quiet sections would not skew the overall measurement.

So, at that point, there was a difference between LKFS and LUFS.  LKFS was the ungated measurement, and LUFS was the measurement that included the effects of the gate.  Generally, on your average TV programme (over a period of say 20-30 minutes), the difference between the LKFS and LUFS measurements is usually between 1-2 LU.

However, in March 2011, the ITU updated their paper with ITU-R BS.1770-2, incorporating the changes the EBU recommended in it's paper R128, namely the gate.  Both the ITU and the EBU agreed that they would both change the threshold of the gate to -10 LU.

So, as of March 2011, LKFS = LUFS.  The EBU were hoping that the ITU would drop LKFS and adopt the EBU's LUFS units, as Florian Camerer, the chair of the EBU's PLOUD group told me that the ITU spec doesn't follow standard naming conventions for units.  However, they didn't, so we're stuck with both of them.

Personally I find it a lot easier to speak of LUFS, as it's easier to describe the differences in material as being 3 LU, as opposed to 3 L_lowercase K_.  But hey!  Anything is better than nothing!

How does this blogging thing work then?

I've been thinking about starting a blog for years now, but never got round to it.  Working for SCEE I'm constrained over what aspects of my work I can talk about publicly.  However, over the years I've done a ton of talks at various conferences, mainly the Game Developer's Conference and the UK's Develop Brighton Conference, as well as various talks at UK universities, on all aspects of audio for videogames.

So, I'm going to start posting them here, as well as any other stuff I happen to find interesting at any particular point.

Watch this space!