Hey guys, Eric Tarr here for theproaudiofiles.com. In this video I’ll be discussing how to
use dithering as the very stage of mastering. So far I’ve been using the Ozone 5 plugin
to master my song. Here’s what I’ve got so far.
[song being mastered with iZotope Ozone 5]
Dithering is one of the most complicated concepts in the mastering process. This is because the result
the result of dithering is to actually add noise to your signal to make it sound better. This might
be a little counterintuitive because normally noise is a bad thing with audio. But the
thing to understand is the addition of noise is inevitable. Whenever you’re printing
a track whether you use dithering or not. With dithering, you at least have control
over the noise to make it almost impossible to hear. Without dithering you run the risk
that this noise could be audible to your listeners.
So why does noise come in whenever you’re printing a track? This is because the signal
that you’re printing is going from a higher bit-depth to a lower bit-depth. Whenever this
happens, the resolution or detail of the signal is reduced. In other words, your computer
has to round up, or approximate the amplitude of this signal to fit the lower bit-depth.
Now the resolution of the CD Wav file is 16-bit. Which is plenty of resolution for playback
purposes of audio. So this is usually the bit-depth that you want to print to whenever
you’re bouncing a song from your DAW. Although 16-bit is sufficient for playback purposes,
there are advantages for recording at a higher bit-depth, such as 24-bit for processing purposes.
Nonetheless, whether you record at 16 or 24 bit, you still need to use dithering. And
here’s why. Your digital audio workstation is going to process the audio signals internally
at 32-bit floating point regardless of whether you record signals in your DAW at 16 or 24
bit. Essentially your DAW is automatically giving you a higher resolution for internal
processing. And this is a good thing.
So there’s always gonna be the need to have this final conversion necessary to go from
32-bit down to 16-bit. And then the round off of the resolution. This approximation
is like adding noise to your signal because sometimes the amplitude gets rounded up, and
sometimes it gets rounded down by a small amount. Without dithering, these rounding
errors are correlated with your audio signal, or in other words, they’re related independent
on your audio signal. Assuming your signal contains a lot of energy within a frequency
range that’s easy to hear, the rounding errors could also be within a frequency range
that’s easy to hear. However when you use dithering, you are intentionally adding noise
that’s going to be difficult for the listener to hear. This is because dither noise can
be shaped, it can be in a frequency in a range that is difficult for humans to perceive.
So let’s take a look at the dithering capabilities of Ozone. Right now I’m working inside of
the maximizer module of Ozone 5. Here you’ll find the dithering capabilities of the plugin.
Right now I have dithering turned off. Therefor if I was to print the audio from my session,
I’d actually be adding in noise that’s correlated with the signal of my song. This
is exactly what I want to avoid and why I’m gonna be using dithering.
So I’ll go ahead and turn dithering on. Right off the bat I’m gonna be adding in
noise now that’s uncorrelated with my song and more difficult to hear. Alright, now I’m
using the MBIT algorithm but there are several other algorithms to use as well. Alright,
inside of each algorithm you actually have several parameters for shaping that noise
to make it even less audible. In order to demonstrate these I’m gonna switch over
to the dither plot here, so you can see the frequency spectrum of the noise that I’m
adding in. Right now I have the noise shaping turned off, so this is noise that has a flat
frequency response. I can go ahead and turn on the noise shaping here, see what happens.
I’m scooping out some of the energy of the noise that’s in the frequency range that’s
most audible for human hearing. There’s gonna be more energy of the noise in the low
frequencies and the really high frequencies. As I turn on noise shaping even higher, you
can see that more and more high frequency noise gets added in. This is gonna be very
difficult for humans to hear. Alright, so I can go all the way up to ultra. Ok, you
can also change the bit depth that you’re working with. Now if you’re gonna be printing
to 16-bit audio, you just want to leave it on that. But if you’re using DVD audio then
you might want to use 24. You can also use, if I turn 8-bit audio, that all of a sudden
the noise becomes more audible. But I’m gonna switch it back to 16-bit here. And you
can change the dither amount, whether you want it to be extra dither, or none, low.
I’m gonna just leave it on normal for now. Alright, show you some of these other algorithms.
Again, you can have noise shaping. Each algorithm has its own type of noise shaping. It’s
pretty much up to you to decide what you want to use. For the most part, they’re all gonna
be better than working without dither. But, the more and more noise shaping that you use,
it’s gonna put the energy in these high frequencies — it’s gonna be difficult
to hear. In this case you can change the number of bits, the amplitude of the noise that you’re
adding in from 1-bit to 2-bit. And so on. Switch back here. You can see as you get into
more of these complicated algorithms and noise shaping, primarily focusing the energy in
the high frequencies. Switch over to noise 2.
Alright, so last thing I’ll demonstrate then is this DC Filter. I usually almost always
click this one. What this is gonna do is make sure that there’s no offset going to my
speakers. So that my speakers are at a steady state point of no energy, rather than having
them either pushed forward and then oscillating or pushed back. And that’s the DC Offset
that you want to filter out. And that’s all there really is to the dithering module
of Ozone 5.
That concludes the series I have on mastering with Ozone 5. I hope that you have a good
idea now about how to use this very powerful tool for mastering your own tracks. Take care
guys.
[mastered song]