This is a question I see often: if the final form of the project is 44.1kHz or 48khz, why bother recording at high sample rates? There isn’t any one answer to that question, there are lots of answers. But I thought it might be useful to illustrate a reason by using a real world example…. And if you cannot be bothered reading all of this, then just remember this: Plugins LOVE dense data!
When I was working on a film last year called HOME BY CHRISTMAS I had the challenge of creating the sounds of memories – sometimes beautiful, happy romantic memories and other times the horrific memories of war, World War II to be exact. The film deals with the directors father telling stories about his experiences in WWII, first in the infantry and then as a prisoner of war. Before I started work I had a number of discussions with the director about how to approach the archival footage. One sequence in particular showed a distant battle at night with flashes of bombs going off and we realise this is memory and not ‘reality.’ So we didn’t want any full resolution dynamic explosions, and the scene ends with an introspective moment with her father in the garden of his house now, thinking about it all. So amongst other things I went looking for sounds that could evoke falling bombs and one of the elements I ended up using was a screech from a falling fireworks, except I processed the hell out of it. To start off with I pitched it down, way down. I sent it from SoundMiner into ProTools at 17% real speed, so what was a high fast screech became a long drawn out doppler that was almost vocal. But the problem then became the grain – the original recording was recorded on DAT quite a few years ago so was only 16bit 48k and pitching that much revealed the grain nastily. Partly to hide the grain but also to push the sound into memory I started playing around with processing it through various impulse responses – some were natural acoustics while others were weirder IRs (such as the Sanitarium collection) – with a little help in the final mix from the lovely reverbs at Park Road Post, the end result worked beautifully! But it made me think: I need some source material like that recorded at high resolution!!! And so the idea of recording the FIREWORKS library at 192kHz became a fixture in my mind.
Now the annoying thing is I don’t actually own a 192kHz interface, my ProTools HD2 rig has a 96io interface so I cant actually play or edit sounds at 192kHz. Back when i recorded the SEAL VOCALS library I actually recorded it at 192kHz but had no choice but to edit it at 96k, but this time I was determined to pursue the 192kHz from start to finish. So I called a favour in from a friend and rented his 192io for a week and set to and edited all the FIREWORKS material as well as recutting the SEAL VOCALS library (which will be a free update next week to anyone who bought SEAL VOCALS MAX)
Anyway once I had finished editing & output the FIREWORKS 192k library I started experimenting with plugins and tried some extreme pitch shifting. Using the plain old Digidesign Pitch AudioSuite plugin I took a sound with plenty of high frequency content and pitched it one octave down. Beautiful!! Totally continuous with no grain artefacts. Ok lets try 2 octaves… Wow!!! I was sold! Here is that first trial (a Predator firework) first at normal speed and then at -24 semitones down.
Heres another example (a Red Dragon firework) first at real speed, then one octave down, then two octaves down:
Heres a more percussive sound (a Solar Flare firework) – first at real speed, then 1 octave down, then 2 octaves down…
And a Might Cannon firework fired from inside a pipe, first at real speed, then one octave down, then two octaves down
Now obviously these examples are no longer full rez – the Soundcloud embed is limited to 128k MP3, if you go to the Soundcloud page they sound a bit better, but believe you me they do sound great!!! Apart from on their own such deeply altered sounds can also really contribute when layered with real sounds eg imagine a slow motion body fall and layering one of those Mighty Cannon hits pitched down two octaves! With real speed sounds layered on top your ear wont read the pitched layers as being altered due to masking, but the ooomph of thaose slwoed sounds is potentially VERY useful!
So apart from buying a 192io interface or one of the new Apogee Symphony interfaces, what use is all of this to you? Well there is a quick & dirty way to alter the playback speed of high resolution files in ProTools. If you go to the Workspace Browser in ProTools and find eg a 192kHz file, if you scroll across to the sample rate you will find it can be edited! So if I take a 192khz file and edit its sample rate to be 96kHz it will then play at half speed (one octave pitch shift) when it is imported into a 96kHz session! Now I haven’t compared this method with pitch shifting a sound in a 192kHz session and then exporting it to 96khz, but I will!
But as I mentioned at the head of this rant, the real moral of the story is that plugins LOVE dense data. Whether it is linear or variable pitch shifting or time stretching, the denser the data is in the source file, the more data the plugin has to use when interpolating. So even if your work session is 48kHz, if you intend to do some serious pitch manipulation it would be well worth your while recording the source files at 96khz or 192kHz and doing that processing in a 96khz session. Then transfer the processed files back into the 48k session for syncing/editing etc…