POW-R (Psychoacoustically Optimized Wordlength Reduction) is a set of commercial

dithering Dither is an intentionally applied form of noise used to randomize quantization error, preventing large-scale patterns such as color banding in images. Dither is routinely used in processing of both digital audio and video data, and is often ...

and

noise shaping Noise shaping is a technique typically used in digital audio, image, and video processing, usually in combination with dithering, as part of the process of quantization or bit-depth reduction of a digital signal. Its purpose is to increase the ap ...

algorithm In mathematics and computer science, an algorithm () is a finite sequence of rigorous instructions, typically used to solve a class of specific Computational problem, problems or to perform a computation. Algorithms are used as specificat ...

s used in

digital audio Digital audio is a representation of sound recorded in, or converted into, digital form. In digital audio, the sound wave of the audio signal is typically encoded as numerical samples in a continuous sequence. For example, in CD audio, sa ...

bit-depth reduction. Developed by a

consortium A consortium (plural: consortia) is an association of two or more individuals, companies, organizations or governments (or any combination of these entities) with the objective of participating in a common activity or pooling their resources for ...

of four companies – ''The POW-R Consortium'' – the algorithms were first made available in 1999 in digital audio hardware products. POW-R is now licensed for use by many companies, particularly those in the

digital audio workstation A digital audio workstation (DAW) is an electronic device or application software used for Sound recording and reproduction, recording, editing and producing audio files. DAWs come in a wide variety of configurations from a single software pro ...

(DAW) arena, where it currently has significant

market share Market share is the percentage of the total revenue or sales in a market that a company's business makes up. For example, if there are 50,000 units sold per year in a given industry, a company whose sales were 5,000 of those units would have a ...

History

POW-R was developed between 1997 and 1998 after an unfavorable change in the licensing terms of a leading bit-depth reduction algorithm of the time prompted some of its licensees to put together a consortium to develop a viable alternative algorithm. Formed by four audio engineering companies: Lake Technology (

Dolby Labs Dolby Laboratories, Inc. (often shortened to Dolby Labs and known simply as Dolby) is an American company specializing in audio noise reduction, audio encoding/compression, spatial audio, and HDR imaging. Dolby licenses its technologies to ...

), Weiss Engineering, Millennia Media and Z-Systems, the consortium set out with the goal to create 'the most sonically transparent dithering algorithm possible'. In 1999, the first products containing POW-R were released by consortium companies. Other companies became interested in using POW-R in their products, and the algorithms are now licensed to a number of leading DAW vendors including

Apple An apple is an edible fruit produced by an apple tree (''Malus domestica''). Apple fruit tree, trees are agriculture, cultivated worldwide and are the most widely grown species in the genus ''Malus''. The tree originated in Central Asia, wh ...

, Avid (

Digidesign Avid Audio (formerly Digidesign) is an American digital audio technology company. It was founded in 1984 by Peter Gotcher and Evan Brooks. The company began as a project to raise money for the founders' band, selling EPROM chips for drum mach ...

Sonic Studio Sonic Studio is an American company manufacturing digital audio production tools for engineering professionals. The company was created when Sonic Solutions divested itself of its audio product lines in order to concentrate on DVD and multimedia� ...

, Ableton,Ableton ‘What’s new’
/ref> Magix / Sequoia / Samplitude, and others.

Reception

One of the first products to include POW-R was a hardware dithering unit from Weiss engineering; in a review of this product in 1999, mastering engineer

Bob Katz Bob Katz is an American audio mastering engineer and author of a popular book on audio mastering. Katz has mastered three Grammy Award–winning albums and one nominated album. Projects he has worked on have received Grammys and acclaim from audi ...

spoke highly of the new algorithm declaring it 'an incredible achievement'.

Technical details

Technically, the entire POW-R suite is not noise shaping; rather, the original POW-R algorithm is based on narrow-band Nyquist dither, while other POW-R algorithms include noise shaping and white noise.Manufacturer's POW-R Data Sheet
/ref> Unlike noise-shaping algorithms based on an ‘

Absolute threshold of hearing The absolute threshold of hearing (ATH) is the minimum sound level of a pure tone that an average human ear with normal hearing can hear with no other sound present. The absolute threshold relates to the sound that can just be heard by the organis ...

’ model (i.e. the quietest sound that can be heard on otherwise silent conditions), POW-R has been designed to give optimal performance at normal listening levels. Here, optimal performance means maximizing the apparent

dynamic range Dynamic range (abbreviated DR, DNR, or DYR) is the ratio between the largest and smallest values that a certain quantity can assume. It is often used in the context of signals, like sound and light. It is measured either as a ratio or as a base-1 ...

of the resultant signal while simultaneously minimizing the audible effects of the dither and quantization noise which, if this is not achieved, are typically tonal in nature. Since noise audibility depends on the nature of the audio being processed, the POW-R algorithm is made available in three variants, optimized respectively for simple program such as

spoken word Spoken word refers to an oral poetic performance art that is based mainly on the poem as well as the performer's aesthetic qualities. It is a late 20th century continuation of an ancient oral artistic tradition that focuses on the aesthetics of ...

, limited dynamic range program such as rock music, and wide dynamic range program such as

orchestral music An orchestra (; ) is a large instrumental ensemble typical of classical music, which combines instruments from different families. There are typically four main sections of instruments: * bowed string instruments, such as the violin, viola, ce ...

. Each algorithm moves the noise to those frequencies where its audible effect for the particular audio type is minimized. The graph to the right shows the

frequency response In signal processing and electronics, the frequency response of a system is the quantitative measure of the magnitude and phase of the output as a function of input frequency. The frequency response is widely used in the design and analysis of sy ...

of the orchestral music algorithm variant (POW-R3, a 9th order

filter Filter, filtering or filters may refer to: Science and technology Computing * Filter (higher-order function), in functional programming * Filter (software), a computer program to process a data stream * Filter (video), a software component tha ...

History

Reception

Technical details

See also

References

Further reading