Waves Support & Service: IDR Frequently Asked Questions

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Increased Digital Resolution (IDR)
Any digital signal processing that alters the original digits (e.g. mixing, gain changes, EQ, dynamic processing, etc.) generally increases the number of bits required to represent the signal, and even when processing signals that started life as 16 bits, it is normal to process at at least 24 bits resolution. However, as soon as the resolution is pulled back down to 16 bits by rounding or truncation (by removing the bottom 8 bits), the resulting rounding error produces an audible distortion at low signal levels, and a permanent loss of digital resolution that can never be recovered. If the audio signal is repeatedly processed and truncated back to 16 bits, the losses accumulate, causing a loss of the tonal subtleties of low-level sounds within a mix.

There are two ways around this problem :

[1] Do all intermediate processing and storage using at least 20 or 24 bits, to avoid or minimize resolution loss.

[2] Proper dithering. Adding a precisely controlled amount of noise (termed "dither") can convert the low-level nonlinear distortion caused by truncation, into a simple steady hiss, thereby removing all traces of low-level nonlinearity, but at the expense of an increased background noise. The perceived level of this noise can be greatly reduced by optimizing the shaping of the overall noise to match the ear's frequency-dependent sensitivity curves.

Waves IDR is a dithering technology designed for use at every stage of digital signal processing to which the signal is subject. It is for this reason that every Waves digital signal processing Plug-in, starting with the version 1.1 release of the Waves Q10 parametric equalizer incorporates Waves IDR.

Plug-ins intended for intermediate processing, such as the Q10 (parametric equalizer) version 1.1 and the C1 (Compressor/Limiter) incorporate the basic IDR options. Plug-ins designed to be at the final stage of processing (for mastering applications) such as the L1-Ultramaximizer (Peak limiter/Re-Quantizer) will include wider options for IDR, to allow for precise "fine-tuning" at the mastering stage.

A choice of two IDR technologies to meet different user needs, is offered on Waves Plug-in products :

Type 1
This is the 'purist' technology. It is designed for no nonlinear distortion or modulation noise at low levels, and combines optimal dither noise with psychoacoustic noise shaping.

When signals are subjected to several stages of processing and quantizing back to 16 bits, the design of resolution-enhancement must satisfy different requirements to technology designed just for one-stage use. If applied several times in succession, a digital resolution enhancement technology optimized for one-stage CD mastering can produce unwanted side-effects.

Waves IDR1 technology, however, is the first optimized for use at every processing stage, allowing for the effects of cascading and subsequent signal processing. IDR1 is also optimized to cause minimal side effects when used with stereo signals.

IDR1 is the recommended choice for use with 16 bit files processing and high quality mastering applications. It can also be used to enhance the resolution of 20 bit files to obtain even further improvement of sound quality.
Type 2
IDR2 also uses dither with a similar noise-shaping curve, but the dither is of a unique kind designed to minimize the amount of noise added, thereby giving a lower noise level than the IDR1 process, but at the expense of some low level distortion.

IDR2 is recommended for use with very low resolution files (8 or 12 bits) for multimedia applications, yielding audio quality for these resolutions superior to any other current methodologies. Nevertheless, the technology of IDR2 does have some advantages over IDR1 for high quality mastering as well, and it is a user choice whether the ultimate in low distortion of IDR1 is preferred, or the additional reduction in noise of IDR2.

IDR technology was specifically designed for use under Digidesign's Sound Designer II environment by Michael Gerzon, a world authority in psychoacoustics and a gold medalist of the AES. The design is a result of his long-term researches, dating back to 1982, with many of the other leading experts in digital resolution enhancement technologies.