Do you know all there is to know about Audio Rendering? Have you ever wonder what Dither really does?

 It´s funny but we´re sure there are plenty of incredibly talented Producers and Engineers that are able to make great sounding music but doesn’t know the first thing about Dither. Unfortunately, there is a lot of misinformation out there on this matter. It’s much more difficult than it should be to figure out what Dither really is if you should use it, and why.

The truth is that there is nothing fun about the technicalities of digital audio, sample rates, bit rates, bit depth, file formats, truncating bits, zeros, ones and the rest of all those terms and definitions. But, as Audio Engineers and Music Producers we have a responsibility to learn all about any new technology and if there´s a chance we can improve the quality of our productions, we should go for it. 

That´s why today, with Top Music Arts, we bring you a new article with all the details about a subject you all must have heard, and that is the Dithering. 

In Ableton Live as in many other DAWs you may have encountered this kind of options before, we´re going to try and clarify all there is to know about Dither here, always with some tips and guides to help along the way, so you all can optimize your rendering options and work at the best quality you possibly can!

Before we start talking about Dither, we need to review some fundamentals of audio rendering like the following…

Sample Rate

It´s the number of times the audio is sampled per second. For example, CD audio has a sample rate of 44100 Hz. This means that the audio is sampled 44100 times every second.

The sample rate is measured in Hertz, and that is a unit of frequency describing Cycles Per Second.

The Standard CD audio quality we are all used to uses a sample rate of 44.1 kHz (k means times 1000).

Sampling Rates range from 8000 Hz (very low quality) up to 192000 Hz (very hi quality). The disadvantage of working with very high sample rates is that they deliver some very large files, so you should consider that before working with all of your projects in the maximum sample rate. Maybe try choosing something like 48kHz, which is a higher quality that is the most usual. 

Bit Depth
 

 In digital audio, a value describes the resolution of the sound data that is captured and stored in an audio file. This attribute is what we call Bit depth.

 Any Audio clip with higher bit depth will have a more detailed sound recording quality.

Similarly, for image and video files, bit depth is used to determine the resolution of a picture. The higher the bit depth (24 bit versus 16 bit, for example) the better quality the image is in.

Bit Rate vs. Bit Depth

They may sound similar, but they are certainly not. Bit depth is often confused with Bitrate, which is measured in kilobits per second (Kbps) and is the data passing through per second when the sound is played back and is not the resolution of each separated sample that makes up the audio waveform (that´s Bit depth).

Bit Depth and Dynamic Range

Every recording has a degree of signal “bleeding” or interference in some way, called the noise floor, which we need to keep to a minimum through a sufficiently high bit depth. This can be achieved having the Dynamic Range, that is the difference between the loudest and the quietest points of our audio, much higher than the noise floor, allowing us to keep the hearable noise to a minimum.

We recommend you all to have this in mind when setting your input signals, before starting any recording process, especially if you have noise you can´t get rid of in your signal!

Bit depth also determines how loud a recording can be. For every 1-bit increase, the dynamic range increases by about 6 decibels. Audio CD formats use a bit depth of 16, which equates to 96 dB of dynamic range. If DVD or Blu-ray is used, the sound quality is higher because the bit depth is 24, which gives 144 dB of dynamic range. It also impacts the file size and format.

Having the right bit depth is a critical aspect to consider to reduce the amount of background noise.

Bit depth is often referred to as the Sample format or Audio Resolution of a Clip.

Bit Depth and Sound Quality

For bit depth, the unit of measure is binary digits commonly known by the term bits. And for every 1-bit increase, the accuracy doubles. The bit range is an important element that condition how good a recording will sound.

All the Mp3s you have in your music library that has been converted from Analog Audio to Digital Audio signals using Pulse Code Modulation (PCM) with a high bit depth contain a wider spectrum of frequencies than the ones encoded with low bit depths.

If the bit depth is too low, the recording is not going to be accurate, and a lot of quiet sounds are certainly going to be lost. Giving you a low-quality audio result. 

Bit depth is only relevant in the scope of a PCM signal. Lossy compression audio formats do not have bit depths.

Now that we´ve cleared that out of the way, let´s move on…

What is dither?

Dither is by definition a specific type of Low-level Noise that is added when converting the bit depth of an audio file in order to reduce Quantization Distortion Errors when we´re changing our audio bit depth.

You may be thinking, “But, isn´t noise a bad thing”, Dithering or to Dither is basically when we are adding noise to our audio signal, but this Noise is being added on purpose to trade a little bit of low-level hiss (harmonics) for a great deal of distortion. This distortion we´re mentioning here is first caused by using a fixed number of bits (16 bits, for example) to represent our sample points as accurate as possible.

In the analog world, there are infinite or continuous sample points available, although they are finite (accountable) in the digital world. 

The noise we add it´s really more similar to a random variation. Not the same as just adding white or pink noise to our signal.


If you want to know more about White and Pink noise, and also learn some mixing techniques, you can check our previous article about PINK NOISE - THE SECRET TECHNIQUE FOR VOLUME MIXING 

In fact, the word Dither means “nervous vibration” and it comes from how it was discovered. Engineers found that mechanical aircraft computers performed more accurately in flight than on the ground. The vibration from the plane’s engine actually helped increase the accuracy of the sticky moving parts in the machines.

The noise that Dithering adds to your tracks works the same way. It helps to increase the accuracy of your digital audio recordings.

How does it work?

What Dithering is basically doing is to add noise of a level less than the least-significant bit before rounding to 16 bits. The noise that´s added has the effect of spreading the many short-term errors across the audio spectrum as broadband noise, similar to white noise.

We can make small improvements to this dithering algorithm, such as shaping the noise to areas where it’s less objectionable, by changing the noise Type or also the Shape, depending on the DAW you are working with. But the process remains the same, one of simply adding the minimal amount of noise necessary to do the job and get a better result.

Why should we use Dither?

Dither is required for reducing the number of bits (down-sampling) in an audio file to help mask any quantization errors. To preserve information, that would be lost in the process otherwise. As we said Dither works by randomizing the quantization errors, the added noise has the effect of spreading the errors across the audio spectrum which makes them less noticeable and avoids unpleasant distortions.

If you’re converting a file from 24-bit to 16-bit, you need to get rid of or Truncate the 8 extra bits of information. The Truncation of bits (to discard them when reducing the word size) causes quantization distortion which can cause the Audio to sound brittle, and gritty, as well as shrink the stereo image.

Any Audio file that was correctly Dithered compared to one that wasn’t are going to be extremely different in quality results, the correctly Dithered version will always sound better, even to untrained ears.

Adding a quiet noise never hurt anybody, but hearing the effects of quantization errors can be quite alarming and frustrating. If you want to prevent this, you should always have in mind if you need to Dither before you render your Audio.

When should we use Dither?

A lot of producers we would recommend you all to only Dither once, Dither is noise that’s added and we shouldn’t be constantly adding noise to our Audio, shouldn´t we?

In order to minimize the quantization errors that are introduced when you are converting fixed bit depth audio files, you should use Dither every time you process a file in your DAW.

All modern DAWs (on their latest updated versions) process and calculate in 32-bit floating regardless of the source bit depth. This means that bit depth conversions are happening every time you process the Audio in any way like Freezing tracks, Bouncing in place and Consolidating regions.

Dither is not necessary when using resolutions that are high enough.

Using 32-bit floating point, for example, you can rest assured that your dynamic range is so wide, that the least-significant bit of your audio is practically so quiet, it’s not even perceptible anymore.

DAWs are not going to add Dither automatically, which means that bits are being truncated every time processes are happening inside your chosen software. You can prevent any conversion or need to Dither entirely by always working in 32-bit floating.

We´d even recommend you to send a 32-bit floating WAV file to your mastering engineer and leave the Dithering to them. You shouldn’t need to Dither until you finalize your master into a fixed point bit depth.

You’ll only need dithering when reducing the number of bits used to represent a signal. Therefore, when you reduce a 16-bit file to 8 bits, you’ll need dithering.

As a way to sum things up, here are some guidelines. Have them in mind, and dithering won’t ever cause you any trouble:

• Don’t change file types unless you absolutely have to. If you recorded at 24-bit/44.1kHz, just stay there! If for some reason you need to down-sample, be sure to use Dither during the conversion.
  
  
• Save Dithering for when your files are headed outside of your DAW. Dither only once when you need to render (export) your audio for external uses.
  
  
• If you’re sending your files for your Mastering, leave Dithering out if you can export with 32-bit float. In this case, the mastering process will take care of Dither for you. When you are exporting anything other than 32-bit float, you´ll have to dither. That includes when you bounce files that are the same bit-depth as the ones you recorded!

Dither Options in Ableton Live 10

Even though when working at 24 bits the audible artifacts of quantization errors are negligible, by working in 32 bit floating we can eliminate the need to add Dither during mixing and leave the one-time decision to be done in mastering.

For professional sound quality, record and render audio at a rate of at least 44.100 kHz and a depth of 24 bits. This way, any further processing such as mixing and editing will not result in any degradation.

If you must encode/record to MP3, aim for 320 kbps – 32bit float.

DAWs like Ableton Live and digital audio signal processors usually work at this resolution. So it’s possible and recommended to apply Dithering only when you have to deliver your audio as 16-bit values or lower. So don´t worry!

In Ableton Live 10, when you are next to Render or Export your Audio, you should check your settings, let´s go through them really quick: 

Here is the rendering window, as you can see there is a PCM section where you can choose to Encode or not, the Type of file (WAV or AIFF), the Bit Depth (mentioned previously in detail), and the Dither Options, where you can select which Dithering Mode will be used when you are rendering to any bit depth lower than 32-bit (preserving a large dynamic range).

As you can see here, when exporting as 32bit in Ableton Live, the dithering option is actually greyed out, because it’s not necessary, as mentioned above.

So, as we were saying, if your CPU can handle it always work at a 32-bit floating format, in any DAW you choose. Anyways it's good to know everything you need about Audio Rendering so here is another chart with more information about file sizes in different types of Qualities. For you to have in mind before choosing your audio file type to store your music or Export music.

File Sizes for Stereo Digital Audio Settings