Dithering Audio [How it Works. Explaining in the Pictures]

Audio Basis - articles about audio

Dithering audio is suppression method of non-linear audio distortions when bit depth is decreased. It is adding of special generated very low noise to signal. Dithering algoritm of AuI ConverteR 48x44 look for signal behavior. It allow minimize of noise influence to hearing and open minute details of music.

I will not tell about dithering mathematics. You can read it at other place. I'll just show what you get.

Case #1: without dithering

You have 24-bit or 32-bit (integer or float point) source. You need 16-bit source.

Pure modeled sine signal 24-bit or 32-bit (float point also)

Now we make 24-bit to 16-bit conversion without dithering. When 24-bit signal truncated to 16-bit rounding to nearest integer doing.

Pure sine after 24-bit to 16-bit truncation. Appear non-linear distortions

We see at this picture non-linear distortions ("wood of blue sticks"). Mid level of peaks of "sticks" about -135 dB.

These distortions increase and decrease with increasing and decreasing of useful signal. Other words - distortions correlate with useful signal.

Fact of existence these "sticks" and their correlation with useful signal give not very pleasant "digital sounding".

Case #2: with dithering audio

Now we will see 24-bit to 16-bit conversion with Audiophile Inventory's dithering audio alphaD.

In settings of AuI ConverteR 48x44 we set minimal value (Light) of Dithering mask depth... slider

Dithering audio settings of AuI ConverteR 48x44 - Light

Dithering audio settings of AuI ConverteR 48x44 - Light value (recommended)

That is result of 24 to 16 bit conversion

Conversion 24 to 16 bit with AuI's dithering audio alphaD

Now we see 2 things:

1. Mid level of peaks of noise about -145 dB.

2. The noise does not depend on the behavior of the signal. Now we loss "digital sounding".

If necessary we can add dithering intensivity for mask non-linear distortions by moving of Dithering mask depth... slider to right.

Attention!!! Non-traditional case!

Let's look to generated without dithering source 16-bit sine.

Source 16-bit sine generated without dithering

"Wood of sticks" again :)

Below we will see how does slider Dithering mask depth... position to signal spectrum. How it mask the non-linear distortions.

Source 16-bit sine generated without dithering after dithering level 0

We can mask source non-linear distortions with changing Dithering mask depth... slider position.

Watch: Demonstration of sound distortions without dithering for 8-bit signal

Watch: Andrey Subbotin talks about dither (en sub)

Resume

1. Dithering allow get more "transparent" sounding without "digits" :)

2. In common case recommended use Light position of slider Dithering mask depth... in Settings windows of AuI ConverteR 48x44.

3. We can mask non-linear distortions of 16-bit sources with moving slider Dithering mask depth... to 3 or 4 position (from left).