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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 is appro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
System Management Controller
The System Management Controller (SMC) is a subsystem of Intel and Apple processor-based Macintosh computers. It is similar in function to the older SMU, PMU, or UAE of non-Intel 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 ... References {{reflist External linksEFI and SMC firmware updates for Intel-based Macs Products ... [...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 (sequences in which the same data value occurs in many consecutive data elements) are stored as a single data value and count, rather than as the original run. This is most efficient on data that contains many such runs, for example, simple graphic images such as icons, line drawings, Conway's Game of Life, and animations. For files that do not have many runs, RLE could increase the file size. RLE may also be used to refer to an early graphics file format supported by CompuServe for compressing black and white images, but was widely supplanted by their later Graphics Interchange Format (GIF). RLE also refers to a little-used image format in Windows 3.x, with the extension rle, which is a run-length encoded bitmap, used to compress the Windows 3.x startup screen. Example Consider a screen containing plain black text on a solid white background. There will be many long runs of white pixel ... [...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 market ... [...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 List_of_software_palettes#Adaptive_palettes, 8-bit palette (computing), palettized color space or in a List_of_monochrome_and_RGB_color formats#15-bit_RGB, 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 ... [...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#QuickTime 1.x, 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 Audio Video Interleave, AVI Digital container format, 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 Color depth, bit-depth of 5 bit for each of the three ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Color Cell Compression
Color Cell Compression is a 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 effectively 2 bit ... [...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 com ... [...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 standard ... [...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 memory and file storage, while speeding up display refresh and file transfers. It is a form of vector quantization compression. When an image is 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: 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 and color lookup tables include Shoup's SuperPaint (1973) and the video frame buffer described in 1975 by Kajiya, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pulse-code Modulation
Pulse-code modulation (PCM) is a method used to digitally represent sampled 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 regularly at uniform intervals, and each sample is quantized to the nearest value within a range of digital steps. 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 times per second that samples are taken; and the bit depth, which determines the ... [...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 standard ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
