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QuickTime Graphics Codec
QuickTime Graphics is a lossy video compression and decompression algorithm (codec) developed by Apple Inc. and first released as part of QuickTime 1.x in the early 1990s. The codec is also known by the name Apple Graphics and its FourCC SMC. The codec operates on 8-bit palettized RGB data. The bit-stream format of QuickTime Graphics has been reverse-engineered and a decoder has been implemented in the projects XAnim and libavcodec. Technical Details The input video that the codec operates on is in an 8-bit palettized RGB colorspace. Compression is achieved by conditional replenishment and by reducing the palette from 256 colors to a per-4×4 block adaptive palette of 1-16 colors. Because Apple Video operates in the image domain without motion compensation, decoding is much faster than MPEG-style codecs which use motion compensation and perform coding in a transform domain. As a tradeoff, the compression performance of Apple Graphics is lower. The decoding complexity ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
System Management Controller
The System Management Controller (SMC) is a subsystem of Intel Macintosh computers. It is similar in function to the older SMU or PMU of PowerPC based Macintosh computers. Overview The SMC has roles in controlling thermal and power management, battery charging, video mode switching, sleep and wake, hibernation, and LED indicators. It also enables enforcement of the macOS End User License, allowing macOS to identify when it is running on non-Apple hardware. See also * Embedded controller (EC) * Power management integrated circuit (PMIC) * Power Management Unit (PMU) * System Management Unit (SMU) * Apple T2 The Apple T2 (Apple's internal name is T8012) security chip is a system on a chip (SoC) tasked with providing security and controller features to Apple's Intel based Macintosh computers. It is a 64-bit ARMv8 chip and runs bridgeOS. T2 has its ow ... References {{reflist External linksEFI and SMC firmware updates for Intel-based Macs Products introduced in 2006 Macint ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Run-length Encoding
Run-length encoding (RLE) is a form of lossless data compression in which ''runs'' of data (consecutive occurrences of the same data value) are stored as a single occurrence of that data value and a count of its consecutive occurrences, rather than as the original run. As an imaginary example of the concept, when encoding an image built up from colored dots, the sequence "green green green green green green green green green" is shortened to "green x 9". This is most efficient on data that contains many such runs, for example, simple graphic images such as icons, line drawings, games, and animations. For files that do not have many runs, encoding them with RLE could increase the file size. RLE may also refer in particular to an early graphics file format supported by CompuServe for compressing black and white images, that was widely supplanted by their later Graphics Interchange Format (GIF). RLE also refers to a little-used image format in Windows 3.x that is saved with the fil ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
S3 Texture Compression
S3 Texture Compression (S3TC) (sometimes also called DXTn, DXTC, or BCn) is a group of related lossy texture compression algorithms originally developed by Iourcha et al. of S3 Graphics, Ltd. for use in their Savage 3D computer graphics accelerator. The method of compression is strikingly similar to the previously published Color Cell Compression, which is in turn an adaptation of Block Truncation Coding published in the late 1970s. Unlike some image compression algorithms (e.g. JPEG), S3TC's fixed-rate data compression coupled with the single memory access (cf. Color Cell Compression and some VQ-based schemes) made it well-suited for use in compressing textures in hardware-accelerated 3D computer graphics. Its subsequent inclusion in Microsoft's DirectX 6.0 and OpenGL 1.3 (via the GL_EXT_texture_compression_s3tc extension) led to widespread adoption of the technology among hardware and software makers. While S3 Graphics is no longer a competitor in the graphics accelerator ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Smacker Video
Smacker video is a video file format (with the ''.SMK'' file extension) developed by Epic Games Tools, and primarily used for full-motion video in video games. Smacker uses an adaptive 8-bit RGB palette. RAD's format for video at higher color depths is Bink Video. The Smacker format specifies a container format, a video compression format, and an audio compression format. Since its release in 1994, Smacker has been used in over 2300 games. Blizzard used this format for the cinematic videos seen in its games '' Warcraft II'', ''StarCraft'' and '' Diablo I''. The format has been reverse engineered and implemented in libavcodec. A non-commercial SourceForge project ''libsmacker'' released an open source decoder in 2013.SourceForge projeclibsmacker/ref> Technical details File format (container) Smacker defines its own container format. A Smacker file can contain a Smacker video track and up to seven audio tracks. Each audio track can have either one channel (mono) or two channels ( ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Microsoft Video 1
Microsoft Video 1 or MS-CRAM is an early lossy video compression and decompression algorithm (codec) that was released with version 1.0 of Microsoft's Video for Windows in November 1992. It is based on MotiVE, a vector quantization codec which Microsoft licensed from Media Vision. In 1993, Media Vision marketed the Pro Movie Spectrum, an ISA board that captured video in both raw and MSV1 formats (the MSV1 processing was done in hardware on the board). Compression algorithm Microsoft Video 1 operates either in an 8-bit palettized color space or in a 15-bit RGB color space. Each frame is split into 4×4 pixel blocks. Each 4×4 pixel block can be coded in one of three modes: skip, 2-color or 8-color. In skip mode, the content from the previous frame is copied to the current frame in a conditional replenishment fashion. In 2-color mode, two colors per 4×4 block are transmitted, and 1 bit per pixel is used to select between the two colors. In 8-color mode, the same scheme applie ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Apple Video
Apple Video is a lossy video compression and decompression algorithm (codec) developed by Apple Inc. and first released as part of QuickTime 1.0 in 1991. The codec is also known as QuickTime Video, by its FourCC RPZA and the name Road Pizza. (The codename "Road Pizza" is a reference to the idea that "when you run over an animal, you're basically compressing it on the freeway".) When used in the AVI container, the FourCC AZPR is also used. The bit-stream format of Apple Video has been reverse-engineered and a decoder has been implemented in the projects XAnim and Libavcodec. Technical Details The codec operates on 4×4 blocks of pixels in the RGB colorspace. Each frame is segmented into 4×4 blocks in raster-scan order. Each block is coded in one of four coding modes: skip, single color, four color, or 16 color. Colors are represented by 16 bits with a bit-depth of 5 bit for each of the three components red, green, and blue, a format known as RGB555. Because Apple Video op ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Color Cell Compression
Color Cell Compression is a lossy compression, lossy image compression algorithm developed by Campbell et al., in 1986, which can be considered an early forerunner of modern texture compression algorithms, such as S3 Texture Compression and Adaptive Scalable Texture Compression. It is closely related to Block Truncation Coding, another lossy image compression algorithm, which predates Color Cell Compression, in that it uses the dominant luminance of a block of pixels to partition said pixels into two representative colors. The primary difference between Block Truncation Coding and Color Cell Compression is that the former was designed to compress grayscale images and the latter was designed to compress color images. Also, Block Truncation Coding requires that the standard deviation of the colors of pixels in a block be computed in order to compress an image, whereas Color Cell Compression does not use the standard deviation. Both algorithms, though, can compress an image down to ef ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Block Truncation Coding
Block Truncation Coding (BTC) is a type of lossy image compression technique for greyscale images. It divides the original images into blocks and then uses a quantizer to reduce the number of grey levels in each block whilst maintaining the same mean and standard deviation. It is an early predecessor of the popular hardware DXTC technique, although BTC compression method was first adapted to color long before DXTC using a very similar approach called Color Cell Compression. BTC has also been adapted to video compression. BTC was first proposed by Professors Mitchell and Delp at Purdue University. Another variation of BTC is Absolute Moment Block Truncation Coding or AMBTC, in which instead of using the standard deviation the first absolute moment is preserved along with the mean. AMBTC is computationally simpler than BTC and also typically results in a lower Mean Squared Error (MSE). AMBTC was proposed by Maximo Lema and Robert Mitchell. Using sub-blocks of 4×4 pixels gives a co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Color Quantization
In computer graphics, color quantization or color image quantization is quantization applied to color spaces; it is a process that reduces the number of distinct colors used in an image, usually with the intention that the new image should be as visually similar as possible to the original image. Computer algorithms to perform color quantization on bitmaps have been studied since the 1970s. Color quantization is critical for displaying images with many colors on devices that can only display a limited number of colors, usually due to memory limitations, and enables efficient compression of certain types of images. The name "color quantization" is primarily used in computer graphics research literature; in applications, terms such as ''optimized palette generation'', ''optimal palette generation'', or ''decreasing color depth'' are used. Some of these are misleading, as the palettes generated by standard algorithms are not necessarily the best possible. Algorithms Most standar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Indexed Color
In computing, indexed color is a technique to manage digital images' colors in a limited fashion, in order to save computer computer data storage, memory and Hard disk drive, file storage, while speeding up display refresh and file transfers. It is a form of Vector quantization#Use in data compression, vector quantization compression. When an image is encoding, encoded in this way, color information is not directly carried by the image pixel data, but is stored in a separate piece of data called a color lookup table (CLUT) or Palette (computing), palette: an array of color specifications. Every element in the array represents a color, indexed by its position within the array. Each image pixel does not contain the full specification of its color, but only its index into the ''palette''. This technique is sometimes referred as pseudocolor or indirect color, as colors are addressed indirectly. History Early graphics display systems that used 8-bit indexed color with frame buffers ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pulse-code Modulation
Pulse-code modulation (PCM) is a method used to digitally represent analog signals. It is the standard form of digital audio in computers, compact discs, digital telephony and other digital audio applications. In a PCM stream, the amplitude of the analog signal is sampled at uniform intervals, and each sample is quantized to the nearest value within a range of digital steps. Alec Reeves, Claude Shannon, Barney Oliver and John R. Pierce are credited with its invention. Linear pulse-code modulation (LPCM) is a specific type of PCM in which the quantization levels are linearly uniform. This is in contrast to PCM encodings in which quantization levels vary as a function of amplitude (as with the A-law algorithm or the μ-law algorithm). Though ''PCM'' is a more general term, it is often used to describe data encoded as LPCM. A PCM stream has two basic properties that determine the stream's fidelity to the original analog signal: the sampling rate, which is the number of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Color Quantization
In computer graphics, color quantization or color image quantization is quantization applied to color spaces; it is a process that reduces the number of distinct colors used in an image, usually with the intention that the new image should be as visually similar as possible to the original image. Computer algorithms to perform color quantization on bitmaps have been studied since the 1970s. Color quantization is critical for displaying images with many colors on devices that can only display a limited number of colors, usually due to memory limitations, and enables efficient compression of certain types of images. The name "color quantization" is primarily used in computer graphics research literature; in applications, terms such as ''optimized palette generation'', ''optimal palette generation'', or ''decreasing color depth'' are used. Some of these are misleading, as the palettes generated by standard algorithms are not necessarily the best possible. Algorithms Most standar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
