Also referred to as simply watermarking, a pattern of bits inserted into a digital image, audio or video file that identifies the file’s copyright information (author, rights, etc.). The name comes from the faintly visible watermarks imprinted on stationery that identify the manufacturer of the stationery. The purpose of digital watermarks is to provide copyright protection for intellectual property that’s in digital format.
Unlike printed watermarks, which are intended to be somewhat visible, digital watermarks are designed to be completely invisible, or in the case of audio clips, inaudible. Moreover, the actual bits representing the watermark must be scattered throughout the file in such a way that they cannot be identified and manipulated. And finally, the digital watermark must be robust enough so that it can withstand normal changes to the file, such as reductions from lossy compression algorithms.
Satisfying all these requirements is no easy feat, but there are a number of companies offering competing technologies. All of them work by making the watermark appear as noise – that is, random data that exists in most digital files anyway. To view a watermark, you need a special program that knows how to extract the watermark data.
Watermarking is also called data embedding and information hiding.
A commonly used term in the telecommunications industry. Waveform is a graphical representation of a signal as a plot of amplitude versus time, i.e., the shape of a wave.
- wave table synthesis
A technique for generating sounds from digital signals. Wave table synthesis stores digital samples of sound from various instruments, which can then be combined, edited, and enhanced to reproduce sound defined by a digital input signal. Wave table synthesis reproduces the sound of musical instruments better than Frequency Modulation (FM) synthesis. The MIDI standard supports […]
A circular, elliptical or rectangular metal tube or pipe through which electromagnetic waves are propagated in microwave and RF communications. The wave passing through the medium is forced to follow the path determined by the physical structure of the guide.
A mathematical function used in compressing images. Images compressed using wavelets are smaller than JPEG images and can be transferred and downloaded at quicker speeds. Wavelet technology can compress color images from 20:1 to 300:1, grayscale images from 10:1 to 50:1.
- wavelet compression
The lossy compression of an image by converting it into a set of mathematical expressions.