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)."
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.