Data compression

Comparison of spectrograms of audio in an uncompressed format and several lossy formats. The lossy spectrograms show bandlimiting of higher frequencies, a common technique associated with lossy audio compression.
Solidyne 922: The world's first commercial audio bit compression sound card for PC, 1990
Processing stages of a typical video encoder

Process of encoding information using fewer bits than the original representation.

- Data compression
Comparison of spectrograms of audio in an uncompressed format and several lossy formats. The lossy spectrograms show bandlimiting of higher frequencies, a common technique associated with lossy audio compression.

84 related topics

Alpha

A picture showing scratches on the readable surface of a CD-R. Music and data CDs are coded using error correcting codes and thus can still be read even if they have minor scratches using error detection and correction.

Information theory

Scientific study of the quantification, storage, and communication of digital information.

Scientific study of the quantification, storage, and communication of digital information.

A picture showing scratches on the readable surface of a CD-R. Music and data CDs are coded using error correcting codes and thus can still be read even if they have minor scratches using error detection and correction.

Important sub-fields of information theory include source coding, algorithmic complexity theory, algorithmic information theory and information-theoretic security.

Comparison of spectrograms of audio in an uncompressed format and several lossy formats. The lossy spectrograms show bandlimiting of higher frequencies, a common technique associated with lossy audio compression.

Transform coding

Comparison of spectrograms of audio in an uncompressed format and several lossy formats. The lossy spectrograms show bandlimiting of higher frequencies, a common technique associated with lossy audio compression.

Transform coding is a type of data compression for "natural" data like audio signals or photographic images.

Lovelace's description from Note G.

Codec

Device or computer program which encodes or decodes a data stream or signal.

Device or computer program which encodes or decodes a data stream or signal.

Lovelace's description from Note G.

In contrast, audio codecs for recording or broadcast can use high-latency audio compression techniques to achieve higher fidelity at a lower bit-rate.

The PNG image PNG-Gradient.png viewed with a hex editor application for Ubuntu.

Portable Network Graphics

Raster-graphics file format that supports lossless data compression.

Raster-graphics file format that supports lossless data compression.

The PNG image PNG-Gradient.png viewed with a hex editor application for Ubuntu.
A demonstration of the colour depth in a PNG file, in bits per channel. Left: 8 bits, Right: 16 bits. Note the artifacts, adjusted contrast for clarity.
Example with several types of image content
251px
PNG's filter method 0 can use the data in pixels A, B, and C to predict the value for X.
A PNG with 256 colors, which is only 251 bytes large with pre-filter. The same image as a GIF would be more than thirteen times larger.
An illustration of Adam7 interlacing over a 16×16 image.
An APNG (animated PNG) file (displays as static image in some web browsers)
Composite image comparing lossy compression in JPEG with lossless compression in PNG: the JPEG artifacts can be easily visible in the background of this kind of image data, where the PNG image has solid color.

The motivation for creating the PNG format was the realization that, on 28 December 1994, the Lempel–Ziv–Welch (LZW) data compression algorithm used in the Graphics Interchange Format (GIF) format was patented by Unisys.

Dolby Digital

A Dolby Digital Penthouse Soundhead mounted on a mid-1950s vintage Kalee model 20 projector
A photo of a 35 mm film print featuring all four audio formats (or quad track)- from left to right: Sony Dynamic Digital Sound (SDDS) (blue area to the left of the sprocket holes), Dolby Digital (grey area between the sprocket holes labelled with the Dolby Double-D logo in the middle), analog optical sound (the two white lines to the right of the sprocket holes), and the DTS time code (the dashed line to the far right)
The former Dolby Digital logo, entitled "Aurora", that was sometimes shown at the start of broadcasts, feature films, and video games
The old Dolby Digital logo
A Dolby home theater badge on a laptop computer

Dolby Digital, originally synonymous with Dolby AC-3, is the name for what has now become a family of audio compression technologies developed by Dolby Laboratories.

MPEG-4 Part 2

Video compression format developed by the Moving Picture Experts Group (MPEG).

Video compression format developed by the Moving Picture Experts Group (MPEG).

Most of the video compression schemes standardize the bitstream (and thus the decoder) leaving the encoder design to the individual implementations.

MPEG-4 SLS

MPEG-4 SLS, or MPEG-4 Scalable to Lossless as per ISO/IEC 14496-3:2005/Amd 3:2006 (Scalable Lossless Coding), is an extension to the MPEG-4 Part 3 (MPEG-4 Audio) standard to allow lossless audio compression scalable to lossy MPEG-4 General Audio coding methods (e.g., variations of AAC).

High-definition television

High-definition television (HD or HDTV) describes a television system providing a substantially higher image resolution than the previous generation of technologies.

High-definition television (HD or HDTV) describes a television system providing a substantially higher image resolution than the previous generation of technologies.

Early HDTV broadcasting used analog technology, but today it is transmitted digitally and uses video compression.

Stadium seating rows closer to digital cinema screens offer significantly more immersive experiences.

Digital cinema

This article focuses on digital projection and distribution in cinemas.

This article focuses on digital projection and distribution in cinemas.

Stadium seating rows closer to digital cinema screens offer significantly more immersive experiences.
Texas Instruments, DLP Cinema Prototype Projector, Mark V, 2000
AMC Theatres former corporate headquarters in Kansas City, prior to their 2013 move to Leawood, Kansas.
Broadcasting antenna in Stuttgart

Its main basis is the modified discrete cosine transform (MDCT), a lossy audio compression algorithm.

Two bits of entropy: In the case of two fair coin tosses, the information entropy in bits is the base-2 logarithm of the number of possible outcomes; with two coins there are four possible outcomes, and two bits of entropy. Generally, information entropy is the average amount of information conveyed by an event, when considering all possible outcomes.

Entropy (information theory)

Average level of "information", "surprise", or "uncertainty" inherent to the variable's possible outcomes.

Average level of "information", "surprise", or "uncertainty" inherent to the variable's possible outcomes.

Two bits of entropy: In the case of two fair coin tosses, the information entropy in bits is the base-2 logarithm of the number of possible outcomes; with two coins there are four possible outcomes, and two bits of entropy. Generally, information entropy is the average amount of information conveyed by an event, when considering all possible outcomes.

Information theory is useful to calculate the smallest amount of information required to convey a message, as in data compression.