After my morning run (a beautiful but hard 11 miles along the Southern California coast), I came to the studio to set up the room for a film mix that’s going to happen on Monday and Tuesday. Andy Hay, the go to guy in the world of independent film mixing and overall ace audio guy and I spent a couple of hours routing this and that, checking out the new near field monitors and making sure there was a hot microphone in the room for some lines that may have to be re-recorded.
And we got talking about film sound, monitor systems, the X Curve, DCP and…my favorite topic…high-resolution sound. I asked him if any films were being done in high-res audio. The answer is no, not that he’s aware of.
If you think going to the movies or listening to your favorite cinematic feature in your home theater delivers a great audio experience, you’re sadly mistaken. I thought that only music lovers are had fidelity problems…we’re getting great sound compared to film sound!
My mixing room is equipped with a THX certified set of JBL speakers…you know, the big ones with the horn drivers and a woofer for the low end. There is also a large subwoofer for the LFE (Low Frequency Enhancement) channel, my trusty TML Labs “Profunder” driven by 500 watts of Bryston power. Andy mixes “in the box”, which means that a surface controller makes changes to the Pro Tools sequences and plug ins. Mixers don’t want to mix dialog, music and effects with a mouse. Control surfaces use a simple Ethernet connection to allow the virtual faders on the computer monitor to be moved by the physical faders on the surface.
All audio for films is PCM at 48 kHz/24-bits. The actors are recorded by the production sound mixer at 48 kHz/24-bits, the foley and ADR (automatic dialog replacement) are recorded at 48 kHz/24-bits and the mix is output as part of a DCP (Digital Cinema Package) for final delivery with the visuals…at 48 kHz/24-bits PCM. Nothing high-resolution about any stage of the production. And it gets worse.
For “consistency”, there is an aggressive low pass filter applied to the full range audio before you get to hear the soundtrack. It’s called the “X-Curve”. Sounds pretty exotic, doesn’t it? How bad could a little high frequency rolloff be? After all, it’s only dialog, a little underscore and a few sound effects, right? It’s hugely bad…and I had no idea until today.
The X-Curve is based on the Film Academy curve. See the illustration below (which was borrowed and recreated from an interview with audio pioneer Loan Allen, on the editors guild website).
Figure 1 – The X-Curve and Academy Rolloff at the low and high end of the audio spectrum.
As you can see from the graph, the rolloff is very severe and basically removes any frequencies above 10 kHz. Along the way, the X-Curve attenuates more and more high frequency information…3 dB per octave up to 10 kHz and then 6 dB per octave. There’s no hope for high-fidelity in a movie house.
And do you think it’s any better at home? Nope…the studios that are preparing the 5.1 and stereo mixes for DVD or BD, are shackled with the same source material that was provided to the theater. Why bother thinking about better codecs and Dolby TrueHD for your movies when the content is already so compromised. I’ll have to do some checking with my engineer friends about the home theater world. But as far as I know, the same kind of rolloff (although a different curve) is applied to television programming.
It looks like it’s going to be a long struggle for film lovers looking for high-resolution audio on their soundtracks. There are a lot of theaters that would have to adopt a standard audio specification. There is the THX standard but this doesn’t apply to the non-THX theaters…too bad.
Will there come a day when 96 kHz/-24-bit surround mixes will happen in all movie theaters? Undoubtedly, yes. They’ve managed to adopt the DCP format as a digital standard for showing films digitally…let’s just hope the soundtracks are next.