July 20, 2013

The Depths Of My Bits And The Rates Of My Samples...

by Chris Randall

Once I got past this dude's beard and the ImageLine logo that they splashed on someone else's video (the original isn't embeddable), I quickly realized that this is the single best explanation of bit depth, sample rate, and dither that anyone has bothered to make.

I've always thought that 48kHz (which puts the Nyquist frequency above 100% of the human race's hearing ability) and 24 bits (which puts the noise floor below that of most any instrument, recording method, and reproduction method) were perfectly acceptable values. This video pretty much says that's fine, although not for the reasons I thought.

Anyhow, if you're a musician that records digital audio, you owe it to yourself to spend a half hour watching this.


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Jul.22.2013 @ 9:51 AM
@speak_onion: a couple of reasons - 48k is the standard for broadcast so there could be one less conversion you'll have to do. Pushing the brickwall filter up a little more to 24k gives a hair more top-end headroom and since most mastering guys are going to process through an analog chain and capture the results before making the final 44.1 master, the "stay at 44.1 until the end" argument is rather moot.

Jul.22.2013 @ 10:43 AM
Chris Randall
44.1 is kind of arbitrary; it puts Nyquist at 20.5, which is technically 500Hz above the nominal threshold of human hearing. The thing is that quite a few people, especially young people, can hear over 20K. 48kHz puts Nyquist at 24kHz, which is _definitely_ above what anyone can hear, even the most Golden-Eared Gearslut. So you might as well just do 48K and be done with it.

Regarding playback, are you talking about a situation where someone bought a CD, put it in a CD player, and listened to that playback directly? That's... quaint.


Jul.22.2013 @ 10:52 AM
48 kHz gives a big more transition width to the antialiasing filter that you need in D/A conversion. A less steep filter can have less ringing.

This is assuming the "standard" antialiasing filter design, my understanding of which is probably up to the level of "Musical Applications for Microprocessors" which was published in 1980. I know that oversampling A/D and D/A convertors are a different issue, but I don't really know what is going on there.

Jul.22.2013 @ 5:19 PM
The video is very good - I think it gives reassurance that the theory will always be valid but maybe not the implementation - eg. jitter wasn't really covered or the fine details of the reconstruction.

I think it's worth considering some of the info in this video:

link [www.youtube.com]

Jul.22.2013 @ 5:32 PM
"48kHz puts Nyquist at 24kHz, which is _definitely_ above what anyone can hear, even the most Golden-Eared Gearslut"

So what happens when I sample a musical sounding prop, and pitch it down just one octave (which really isn't a massive shift - i know plenty of musicians who detune instruments to make kick drums etc)

Surely that 24kHz Nyquist frequency becomes 12kHz, which is well within even an aging rock stars hearing range...

Maybe it doesn't matter if your mics don't capture anything above 20kHz, but plenty of props resonate above 20kHz (eg anything metal) and there are mics available that capture frequencies above 20kHz (MKH80X0, Schoeps etc)

Imho the correct sample rate more depends on what you intend to do in terms of processing and manipulation, rather than making hard rules about the delivery sample rate.....

Jul.22.2013 @ 5:59 PM
Chris Randall
Assuming your DAW is set to 48k, Nyquist is _still_ 24k, no matter what you're doing with your pitching-down-fun-and-games. Which is why you hear no aliasing "pitching down" but almost instantly "pitching up."

All that said, if you're trying to impress dogs or a TEDx conference, knock yourself out. Otherwise, go write a good hook and some witty lyrics and quit worrying about it.


Jul.23.2013 @ 3:44 AM
Only a typo I'm sure, but isn't Nyquist for 44.1 22.05?

And something nice I've learned from this topic-

44100 is 2 squared times 3 squared times 5 squared times 7 squared

Jul.23.2013 @ 10:36 AM
I've always worked at 44.1. There were always instances where we had to make a CD, or import something from a CD, or something, and now it's habit. For the last 20 something years people have debated this. How much of your favorite music from that time was recorded at 44.1k and how much at 48k?

Jul.23.2013 @ 3:36 PM
That was great. Thanks for sharing.

Jul.23.2013 @ 7:36 PM
Ghost Gum
@bassling At the risk of sounding like a gearslutz beard stroker I read a comparison of that method of pitchshifting a long time ago, and the dude that wrote it got a high res file to null against the same thing done from 44.1 using some expensive pitchshift plugins... whether there's any detail left three octaves down is another question, but at least yer saving money on plugins!

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