Dither - Ozone 8 Help Documentation

May 2024 · 7 minute read

Overview

Ozone contains a comprehensive set of dithering tools that allows you to prepare studio-quality audio for CD and other formats by effectively converting and dithering audio to 24, 20, 16, 12, or 8 bits. Note that the dither tool is independent of the Maximizer module.

dither panel

Key Features

Controls

View/Enable Dither panel

dither button

BIT DEPTH

Sets the target bit depth for the audio. When mastering for a CD, for example, you would want this set to 16 bit.

DITHER AMOUNT

This sets the number of bits or amount of dither that will be used. The dithering amount can be varied among Off, Medium, and Strong.

Note about Dither Amount options

The Off and Low settings can leave some non-linear quantization distortion or dither noise modulation, while the strong setting completely eliminates the non-linear distortion at the expense of a slightly increased noise floor. In general, the medium dither amount is a good choice.

HARMONIC SUPPRESSION

If, for some reason, any dithering noise is undesirable, simple truncation remains the only option. Truncation results in harmonic quantization distortion that adds overtones to the signal and distorts the timbre.

In this case you can click the Harmonic Suppression button to slightly alter the truncation rules, moving the harmonic quantization distortion away from overtones of audible frequencies.

This option doesn’t create any random dithering noise oor. Instead it works more like truncation, but with better tonal quality in the resulting signal.

LIMIT PEAKS

Dither noise is random in nature, and has a very low amplitude. However, after noise shaping, especially in aggressive dithering modes, the high-frequency dither noise is significantly amplified, and the overall dither signal can show spurious peaks (up to -60 dB FS for a 16-bit quantization).

If such high peaks are undesirable, you can click the Limit Peaks button to e ectively suppress the spurious peaks in the noise-shaped dither.

AUTO-BLANKING

Selecting this option will completely mute dither output (i.e. dither noise) when the input signal is completely silent (0 bits of audio) for at least 0.7 seconds.

NOISE SHAPING

Selects the amount of noise shaping that is applied during the dithering process. Noise shaping pushes the noise necessary for dithering into less audible frequency ranges, allowing for greater dithering with less perceived noise.

You can control the aggressiveness of this shaping, ranging from Off (no shaping) through Max (roughly 14 dB of audible noise suppression).

Different amounts of noise shaping will have subtle e ects on the sound quality of the dither process, so experiment with the di erent settings with your particular program material.

FILTER DC OFFSET

Activates a high-pass filter with a 1 Hz cutoff frequency.

DC offset (direct current offset) is a defect in the recording when the waveform’s average voltage is above or below zero. Audio signals are normally represented by an alternating current whose average value is zero. Some malfunctions in the recording equipment can result in a direct current leaking into the signal. Thus, the recorded waveform appears to be above or below the zero line.

In FFT (Fast Fourier Transform) analyzers, the DC offset is represented with energy at zero frequency (0 Hz). A DC offset can be removed with a high-pass filter. It is important to distinguish DC offset from waveform asymmetry. Asymmetry skews the waveform shape towards positive or negative levels, but the average current stays at zero. Unlike DC offset, asymmetry has no particular energy near 0 Hz and can be reduced using phase rotation filters.

Note

The DC Offset Filter runs in real-time before the Maximizer. The Maximizer module must be in signal chain to enable DC offset filtering.

Meters

BIT METER

dither bit meter

This can be an invaluable resource for monitoring the digital activity of your program material, including viewing:

The bit meter monitors the state of bits in a digital signal.

In general, you want to see activity on each of the bits (except the top one, see below for explanation), meaning that over a period of a few seconds each of the bits in the outside columns should be lit. You should also click on the meter periodically to reset the peak hold of the outside columns, as something like DC offset would toggle a lower bit once (lighting the outside column), but would never toggle it after that since the bit is being held.

If you’re dithering down, you only want to see 16, 12, or 8 bits lit (corresponding to the output bit depth of the dither).

Note that the bit meter is not a level meter. Instead, it shows which bits are being used. If a bit is used (goes from 1 to 0 or vice versa), the position for that bit is lit.

The main use of the bit meter is to look for problems or discontinuities in the digital signal. Some examples of problems are shown below:

Why the Top Bit Will Never Light Up in the Bit Meter

When samples are stored as a binary number, negative samples are specially encoded. Since the binary representation of negative numbers is not intuitive, Ozone takes the absolute value of each sample before plotting it on the bit meter. Since the most significant bit is only set when a sample is negative, this bit will never light up. We simply included the top bit as placeholder for completeness.

BIT METER RESET

Click here to reset the bit meter and start its display over with the program material’s current playback point.

NOISE SHAPING CURVE

This graph shows the noise-shaping profile curve, as displayed across the frequency spectrum. The graph displays the general frequency curve of the specific dither noise pro le that is used, depending on the algorithm.

DC OFFSET METER

When the DC Offset Filter is on, the DC Offset meter shows the amount of the DC that is being removed.

More information about Dithering

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