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 processing, image, and video processing, usually in combination with dithering, as part of the process of Quantization (signal processing), quantization or Audio bit depth, bit-dep ...

algorithm In mathematics and computer science, an algorithm () is a finite sequence of Rigour#Mathematics, mathematically rigorous instructions, typically used to solve a class of specific Computational problem, problems or to perform a computation. Algo ...

s used in

digital audio Digital audio is a representation of sound recorded in, or converted into, digital signal (signal processing), digital form. In digital audio, the sound wave of the audio signal is typically encoded as numerical sampling (signal processing), ...

bit-depth reduction. Developed by a

consortium A consortium () 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 achieving a ...

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 pr ...

(DAW) arena, where it currently has significant

market share Market share is the percentage of the total revenue or sales in a Market (economics), 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 ...

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. (Dolby Labs or simply Dolby) is a British-American technology corporation specializing in audio noise reduction, audio encoding/compression, spatial audio, and high-dynamic-range television (HDR) imaging. Dolby li ...

), 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 a round, edible fruit produced by an apple tree (''Malus'' spp.). Fruit trees of the orchard or domestic apple (''Malus domestica''), the most widely grown in the genus, are agriculture, cultivated worldwide. The tree originated ...

, 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 machin ...

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), also known as the absolute hearing threshold or auditory threshold, 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 absolu ...

’ 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 Dynamics (from Greek δυναμικός ''dynamikos'' "powerful", from δύναμις ''dynamis'' " power") or dynamic may refer to: Physics and engineering * Dynamics (mechanics), the study of forces and their effect on motion Brands and ent ...

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 is an oral poetic performance art that is based mainly on the poem as well as the performer's aesthetic qualities. It is a 20th-century continuation of an oral tradition, ancient oral artistic tradition that focuses on the aesthetic ...

, 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: * String instruments, such as the violin, viola, cello, a ...

. 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 (waves), phase of the output as a function of input frequency. The frequency response is widely used in the design and ...

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

filter Filtration is a physical process that separates solid matter and fluid from a mixture. Filter, filtering, filters or filtration may also refer to: Science and technology Computing * Filter (higher-order function), in functional programming * Fil ...

History

Reception

Technical details

See also

References

Further reading