Search Results: Distortion

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Intermodulation distortion (audio): IMD results when two or more signals of different frequencies are mixed together and additional signals are formed at frequencies that are not, in general, at harmonic frequencies (integer multiples) of either source signal. Intermodulation causes spurious emissions that can create minor to severe interference to other operations on the signal. Although IMD may…; See Distortion
Delta Sigma audio encoding (DSD): Process for sampling an input signal. In the realm of digital content, this approach is generally seen as applied to sound, where it is often described as "oversampling." The delta-sigma (some say "sigma delta") converter digitizes the audio signal with a very low bit depth (generally 1-bit) but a very high sampling rate. The oversampling…; See LPCM
Total harmonic distortion: Although applicable to other waveforms, in the context of library- and archive-related digitization, THD is generally discussed in terms of sound. The total harmonic distortion of a signal is defined as the ratio of the sum of the powers of all harmonic components to the power of the fundamental frequency (the lowest frequency in a…; See Also Distortion; Noise
Sampling rate (audio): Sampling rate or sampling frequency defines the number of samples per second (or per other unit) taken from a continuous signal to make a discrete or digital signal. For time-domain signals like the waveforms for sound (and other audio-visual content types), frequencies are measured in in hertz (Hz) or cycles per second. The Nyquist–Shannon sampling…
Display Aspect Ratio (DAR): Display Aspect Ratio (DAR) is the ratio between the width and height of the frame at the time of playback. DAR is a metadata field present in most audiovisual containers (though absent in some, including AVI) that is used by playback software and platforms to properly render the width and height of the frame proportionally…; See Also Aspect ratio; Storage Aspect Ratio (SAR); Pixel Aspect Ratio (PAR)
Noise, digital audio: Noise has a number of meanings in terms of sound. This definition pertains to the measurement of noise in digitizing equipment, as when the International Association of Sound and Audiovisual Archives (IASA) specifies pass-fail values for the measurement of THD plus noise (THD+N). Different methods are used by different organizations to measure the…; See Also Aliasing; Artifact (defect); Dither; Distortion; Noise; Signal to noise ratio
Distortion, geometric: Distortion in which the true geometry of an object is not properly represented in the digital image, e.g., barrel (sides of a square bulge out) or pincushion (sides of a square curve inward). Some factors that can cause geometric distortion include: system optics, sensor defects, or mis-position of the image plane relative to the…; See Distortion
Archival master file: File that represents the best copy produced by a digitizing organization, with best defined as meeting the objectives of a particular project or program. In some cases, an archive may produce more than one archival master file. The terms used to name types of files vary within the digital library and digital archiving…; See Also Archival primary file; Production master file; Production primary file; Derivative file
Printed halftone: Most photographs, paintings, or similar pictorial works reproduced in books, magazines and newspapers are printed as halftones. In a halftone, the continuous tones of the picture being reproduced are broken into a series of equally spaced dots of varying size, printed with only one color of ink. The outcome exploits an optical illusion: the…
Production master file: Files produced by processing the content in one or more archival master or primary files, resulting in a new file or files with levels of quality that rival those of the archival master. The first type of processing consists of the assembly of a set of segments into a unified reproduction of an…; See Also Archival master file; Archival primary file; Production primary file; Derivative file
File format: Set of structural conventions that define a wrapper, formatted data, and embedded metadata, and that can be followed to represent images, audiovisual waveforms, texts, etc., in a digital object. The wrapper component on its own is often colloquially called a file format. The formatted data may consist of one or more…; See Also Wrapper; Bitstream; Encoding; Digital file; Object (PREMIS term)
Informational and artifactual value: This pairing provides a rough-and-ready conceptual frame for some of the discussions of the Federal Agencies Digitization Working Groups. The distinction between informational and artifactual is most easily discerned in the case of textual materials (roughly speaking, the text as compared to images of pages) and more difficult in the case of pictorial materials (the…; See Also Virtual replica; Physical replica; Museum-quality facsimile or print
Closed captions: Timed text information intended for display over a timeline, in synchronization with image and sound essence. Closed captions, unlike open captions, can be turned on or off in a media viewer (if the viewer supports this functionality). Closed captions offer limited font, color and position choices, and are aligned to a fixed grid. When present,…; See Also Open captions; Subtitles; Teletext
Virtual replica: A copy that represents the entirety of a physical item in image form. Microfilm copies of books (especially brittle books), newspapers, and manuscripts are one type of virtual replica, and they have been a staple output of library and archive preservation programs for many years. Most digital copies produced by libraries and archives today…; See Also Physical replica; Museum-quality facsimile or print; Copy negatives and transparencies; Interpositives, duplicate negatives and transparencies
Pixel Aspect Ratio (PAR): PAR (Pixel Aspect Ratio) is the ratio between the width and the height of each individual pixel that makes up a video frame. Pixels within a frame are all of a uniform size, and while they may be square, they often are not. If the pixels are square, the PAR value is 1:1 or 1,…; See Also Aspect ratio; Storage Aspect Ratio (SAR); Display Aspect Ratio (DAR)
Color: Color is one of the most difficult areas in digital imaging to specify, digitally encode, and reproduce, and for the verification that specifications have been met. The primary reason it is so challenging is that color is a perceptual phenomenon and cannot be described in an absolute and objective manner as can many other…; See Also Color model; Gamut; Spectral power distribution; Metamerism
Storage Aspect Ratio (SAR): SAR (Storage Aspect Ratio) is the width and height of a video frame expressed as a ratio. For example, a video frame with a width of 720 pixels and height of 480 pixels (720x480) would have a SAR of 3:2. SAR can be calculated with the following equation: SAR = DAR / PAR Note that some…; See Also Pixel Aspect Ratio (PAR); Display Aspect Ratio (DAR); Aspect ratio
Audio description: Audio description, also known as video description in Federal Communications Commission (FCC) rules, provides access to visual information by means of audio-narrated description of key visual elements in a video program for audience members who are blind or have a visual impairment. Best practices for audio description from the FCC\'s Disability Advisory Committee (DAC) state…; See Video description
Wrapper: A term often used by digital content specialists to name a file format that encapsulates its constituent bitstreams and includes metadata that describes the content within. Archetypal examples include WAVE and TIFF. Files that are instances of these wrappers are distinguished in terms of their underlying bitstreams, e.g., WAVE files may contain (a) linear pulse…; See Bundling file format
Structured audio: Dynamically constructed sound resulting from the processing of data through combinations of software and hardware. Such software includes sequencers and trackers that use data to control when individual sound elements should start and stop, to set values for attributes such as volume and pitch, and for other effects that should be applied to the…; See Waveform (sound)

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Federal Agencies Digitization Guidelines Initiative

Search Results: Distortion

Federal Agencies
Digitization Guidelines Initiative