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80-557: XvMC was the first UNIX equivalent of the Microsoft Windows DirectX Video Acceleration (DxVA) API . Popular software applications known to take advantage of XvMC include MPlayer , MythTV , and xine . Each hardware video GPU capable of XvMC video acceleration requires a X11 software device driver to enable these features. There are currently three X11 Nvidia drivers available: a 2D-only open source but obfuscated driver maintained by Nvidia called nv,

160-402: A   b   c   d   e {\displaystyle a\ b\ c\ d\ e} is exactly equivalent to a DFT of eight real numbers a   b   c   d   e   d   c   b {\displaystyle a\ b\ c\ d\ e\ d\ c\ b} (even symmetry), divided by two. (In contrast, DCT types II-IV involve

240-1063: A proprietary binary driver by Nvidia, and an open source driver based on reverse engineering of the binary driver developed by the Linux community called Nouveau . Nouveau is not pursuing XvMC support, the 2D nv driver does not support XvMC, and the official proprietary binary driver by Nvidia only supports MPEG-2 offloading (mo comp and iDCT) on hardware up to and including the GeForce 7000 series. VIA provides open source device drivers for some of its VIA Unichrome (S3 Graphics Chrome Series) hardware, supporting offloading of MPEG-2 and MPEG-4 ASP video. Thanks to VLD level of decoding VIA offloads much more decoding tasks from CPU than GPUs supporting iDCT or mo comp levels only. Keep in mind that not all devices are supported and there are some other caveats. Intel provides official open source device drivers which supports MPEG-2 offloading (mo comp and iDCT) on Intel's 8xx/9xx range of integrated graphics chips. Although ATI

320-426: A videotelephone scene with image quality comparable to an intra-frame coder requiring 2-bit per pixel. In 1979, Anil K. Jain and Jaswant R. Jain further developed motion-compensated DCT video compression, also called block motion compensation. This led to Chen developing a practical video compression algorithm, called motion-compensated DCT or adaptive scene coding, in 1981. Motion-compensated DCT later became

400-474: A Capture DDI for video capture. The DDIs it shares with DXVA 1.0 are also enhanced with the ability to use hardware acceleration of more operations. Also, the DDI functions are directly available to callers and need not be mediated by the video renderer. As such, a program can also create a pipeline for simply decoding the media (without rendering) or post-processing and rendering (without decoding). These features require

480-607: A DCT algorithm, an image (or frame in an image sequence) is divided into square blocks which are processed independently from each other, then the DCT blocks is taken within each block and the resulting DCT coefficients are quantized . This process can cause blocking artifacts, primarily at high data compression ratios . This can also cause the mosquito noise effect, commonly found in digital video . DCT blocks are often used in glitch art . The artist Rosa Menkman makes use of DCT-based compression artifacts in her glitch art, particularly

560-576: A context (resources permitting). Both "backend" and "frontend" subpicture behavior are supported. XvMC acceleration is supported in: XvMC have been removed in Mesa 22.3. Even though XvMC currently only supports hardware acceleration of motion compensation (mo comp) and inverse discrete cosine transform (iDCT), (and Variable-Length Decoding for VIA Unichrome GPU), additional video decoding processes could be passed on to modern GPUs which could be accelerated via GPU fragment programs. XvMC could be extended in

640-401: A continuous extension at the boundaries (although the slope is generally discontinuous). This is why DCTs, and in particular DCTs of types I, II, V, and VI (the types that have two even boundaries) generally perform better for signal compression than DFTs and DSTs. In practice, a type-II DCT is usually preferred for such applications, in part for reasons of computational convenience. Formally,

720-406: A data point or the point halfway between two data points (2 choices per boundary), for a total of 2 × 2 × 2 × 2 = 16 possibilities. Half of these possibilities, those where the left boundary is even, correspond to the 8 types of DCT; the other half are the 8 types of DST. These different boundary conditions strongly affect the applications of the transform and lead to uniquely useful properties for

800-482: A function over a finite domain , such as the DFT or DCT or a Fourier series , can be thought of as implicitly defining an extension of that function outside the domain. That is, once you write a function f ( x ) {\displaystyle f(x)} as a sum of sinusoids, you can evaluate that sum at any x {\displaystyle x} , even for x {\displaystyle x} where

880-693: A half-sample shift in the equivalent DFT.) Note, however, that the DCT-I is not defined for N {\displaystyle N} less than 2, while all other DCT types are defined for any positive N . {\displaystyle N.} Thus, the DCT-I corresponds to the boundary conditions: x n {\displaystyle x_{n}} is even around n = 0 {\displaystyle n=0} and even around n = N − 1 {\displaystyle n=N-1} ; similarly for X k . {\displaystyle X_{k}.} The DCT-II

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960-398: A hardware-specific format. Any number of buffers can be created for use with a particular context (resources permitting). XvMC provides video acceleration starting at one of two places in the video pipeline . Acceleration starting at the first point, which we shall call the "Motion Compensation" level, begins after the inverse quantization and IDCT at the place where motion compensation

1040-475: A hybrid DCT- FFT algorithm), Advanced Audio Coding (AAC), and Vorbis ( Ogg ). Nasir Ahmed also developed a lossless DCT algorithm with Giridhar Mandyam and Neeraj Magotra at the University of New Mexico in 1995. This allows the DCT technique to be used for lossless compression of images. It is a modification of the original DCT algorithm, and incorporates elements of inverse DCT and delta modulation . It

1120-399: A length-one DFT (odd length) of a single number a  , corresponds to a DCT-V of length N = 1. {\displaystyle N=1.} ) Using the normalization conventions above, the inverse of DCT-I is DCT-I multiplied by 2/( N  − 1). The inverse of DCT-IV is DCT-IV multiplied by 2/ N . The inverse of DCT-II is DCT-III multiplied by 2/ N and vice versa. Like for

1200-475: A scaling can be chosen that allows the DCT to be computed with fewer multiplications. The DCT-II implies the boundary conditions: x n {\displaystyle x_{n}} is even around n = − 1 / 2 {\displaystyle n=-1/2} and even around n = N − 1 / 2 ; {\displaystyle n=N-1/2\,;} X k {\displaystyle X_{k}}

1280-414: Is a more effective lossless compression algorithm than entropy coding . Lossless DCT is also known as LDCT. The DCT is the most widely used transformation technique in signal processing , and by far the most widely used linear transform in data compression . Uncompressed digital media as well as lossless compression have high memory and bandwidth requirements, which is significantly reduced by

1360-567: Is a more modern video acceleration API which support the video acceleration features of modern GPUs. DirectX Video Acceleration DirectX Video Acceleration ( DXVA ) is a Microsoft API specification for the Microsoft Windows and Xbox 360 platforms that allows video decoding to be hardware-accelerated . The pipeline allows certain CPU -intensive operations such as iDCT , motion compensation and deinterlacing to be offloaded to

1440-664: Is a widely used transformation technique in signal processing and data compression . It is used in most digital media , including digital images (such as JPEG and HEIF ), digital video (such as MPEG and H.26x ), digital audio (such as Dolby Digital , MP3 and AAC ), digital television (such as SDTV , HDTV and VOD ), digital radio (such as AAC+ and DAB+ ), and speech coding (such as AAC-LD , Siren and Opus ). DCTs are also important to numerous other applications in science and engineering , such as digital signal processing , telecommunication devices, reducing network bandwidth usage, and spectral methods for

1520-478: Is also possible using 2 N signal followed by a multiplication by half shift. This is demonstrated by Makhoul . Some authors further multiply the X 0 {\displaystyle X_{0}} term by 1 / N {\displaystyle 1/{\sqrt {N\,}}\,} and multiply the rest of the matrix by an overall scale factor of 2 / N {\textstyle {\sqrt {{2}/{N}}}} (see below for

1600-509: Is by far the most commonly used format for the recording, compression and distribution of video content, used by 91% of video developers, followed by HEVC which is used by 43% of developers. Multidimensional DCTs (MD DCTs) have several applications, mainly 3-D DCTs such as the 3-D DCT-II, which has several new applications like Hyperspectral Imaging coding systems, variable temporal length 3-D DCT coding, video coding algorithms, adaptive video coding and 3-D Compression. Due to enhancement in

1680-615: Is even around k = 0 {\displaystyle k=0} and odd around k = N . {\displaystyle k=N.} Because it is the inverse of DCT-II up to a scale factor (see below), this form is sometimes simply referred to as "the inverse DCT" ("IDCT"). Some authors divide the x 0 {\displaystyle x_{0}} term by 2 {\displaystyle {\sqrt {2}}} instead of by 2 (resulting in an overall x 0 / 2 {\displaystyle x_{0}/{\sqrt {2}}} term) and multiply

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1760-677: Is even around n = 0 {\displaystyle n=0} and odd around n = N ; {\displaystyle n=N;} X k {\displaystyle X_{k}} is even around k = − 1 / 2 {\displaystyle k=-1/2} and even around k = N − 1 / 2. {\displaystyle k=N-1/2.} The DCT-IV matrix becomes orthogonal (and thus, being clearly symmetric, its own inverse) if one further multiplies by an overall scale factor of 2 / N . {\textstyle {\sqrt {2/N}}.} A variant of

1840-543: Is even or odd), since the corresponding DFT is of length 2 ( N − 1 ) {\displaystyle 2(N-1)} (for DCT-I) or 4 N {\displaystyle 4N} (for DCT-II & III) or 8 N {\displaystyle 8N} (for DCT-IV). The four additional types of discrete cosine transform correspond essentially to real-even DFTs of logically odd order, which have factors of N ± 1 / 2 {\displaystyle N\pm {1}/{2}} in

1920-440: Is now called the type-II DCT (DCT-II), as well as the type-III inverse DCT (IDCT). Since its introduction in 1974, there has been significant research on the DCT. In 1977, Wen-Hsiung Chen published a paper with C. Harrison Smith and Stanley C. Fralick presenting a fast DCT algorithm. Further developments include a 1978 paper by M. J. Narasimha and A. M. Peterson, and a 1984 paper by B. G. Lee. These research papers, along with

2000-710: Is optimal in the decorrelation sense). As explained below, this stems from the boundary conditions implicit in the cosine functions. DCTs are widely employed in solving partial differential equations by spectral methods , where the different variants of the DCT correspond to slightly different even and odd boundary conditions at the two ends of the array. DCTs are closely related to Chebyshev polynomials , and fast DCT algorithms (below) are used in Chebyshev approximation of arbitrary functions by series of Chebyshev polynomials, for example in Clenshaw–Curtis quadrature . The DCT

2080-469: Is planned for the future. (Now all hardware has support for MPEG-2 acceleration on iDCT and mo comp levels). There are no device drivers which support XvMC on Matrox hardware, (although Matrox Parhelia hardware has support for MPEG-2 acceleration on mo comp level). Binary device driver by S3 only supports MPEG-2 offloading in initial 2.0.16 driver on Chrome 20 GPUs. This is from X-Vxvideoideo Motion Compensation - API specification v. 1.0 XvMC extends

2160-1144: Is probably the most commonly used form, and is often simply referred to as "the DCT". This transform is exactly equivalent (up to an overall scale factor of 2) to a DFT of 4 N {\displaystyle 4N} real inputs of even symmetry where the even-indexed elements are zero. That is, it is half of the DFT of the 4 N {\displaystyle 4N} inputs y n , {\displaystyle y_{n},} where y 2 n = 0 , {\displaystyle y_{2n}=0,} y 2 n + 1 = x n {\displaystyle y_{2n+1}=x_{n}} for 0 ≤ n < N , {\displaystyle 0\leq n<N,} y 2 N = 0 , {\displaystyle y_{2N}=0,} and y 4 N − n = y n {\displaystyle y_{4N-n}=y_{n}} for 0 < n < 2 N . {\displaystyle 0<n<2N.} DCT-II transformation

2240-458: Is to be applied. The second point, which we shall call the "IDCT" level, begins before the IDCT just after the inverse quantization. Rendering is done by presenting the library with a target XvMCSurface and up to two reference XvMCSurfaces for the motion compensation, a buffer of 8x8 blocks and a command buffer which describes how to use the 8x8 blocks along with motion compensation vectors to construct

2320-544: Is widely implemented in digital signal processors (DSP), as well as digital signal processing software. Many companies have developed DSPs based on DCT technology. DCTs are widely used for applications such as encoding , decoding, video, audio, multiplexing , control signals, signaling , and analog-to-digital conversion . DCTs are also commonly used for high-definition television (HDTV) encoder/decoder chips . A common issue with DCT compression in digital media are blocky compression artifacts , caused by DCT blocks. In

2400-412: Is widely used in many applications, which include the following. The DCT-II is an important image compression technique. It is used in image compression standards such as JPEG , and video compression standards such as H.26x , MJPEG , MPEG , DV , Theora and Daala . There, the two-dimensional DCT-II of N × N {\displaystyle N\times N} blocks are computed and

2480-423: The DFT , the normalization factor in front of these transform definitions is merely a convention and differs between treatments. For example, some authors multiply the transforms by 2 / N {\textstyle {\sqrt {2/N}}} so that the inverse does not require any additional multiplicative factor. Combined with appropriate factors of √ 2 (see above), this can be used to make

X-Video Motion Compensation - Misplaced Pages Continue

2560-586: The Enhanced Video Renderer (EVR) present in MF. The DXVA is used by software video decoders to define a codec-specific pipeline for hardware-accelerated decoding and rendering of the codec. The pipeline starts at the CPU which is used for parsing the media stream and conversion to DXVA-compatible structures. DXVA specifies a set of operations that can be hardware-accelerated and device driver interfaces (DDIs) that

2640-602: The GPU . DXVA 2.0 allows more operations, including video capturing and processing operations, to be hardware-accelerated as well. DXVA works in conjunction with the video rendering model used by the video card . DXVA 1.0, which was introduced as a standardized API with Windows 2000 ( DirectX 7 ), and is currently available on Windows 98 or later, can use either the overlay rendering mode or VMR 7/9 . DXVA 2.0, available only on Windows Vista , Windows 7 , Windows 8 and later OSs, integrates with Media Foundation (MF) and uses

2720-635: The Media Foundation topology loader to create a full media playback pipeline. DXVA 1.0 is emulated using DXVA 2.0. DXVA 2.0 does not include the COPP DDI, rather it uses PVP for protected content. Windows 7 implements DXVA-HD if the driver complies with WDDM 1.1. DXVA2 implementations come in two variants: native and copy-back . With native implementation, the decoded video stays in GPU memory until it has been displayed. The video decoder must be connected to

2800-715: The Windows Display Driver Model drivers, which limits DXVA 2.0 to Windows Vista , Windows Server 2008 , Windows 7 , Windows Server 2008 R2 and Windows 8 . On Windows XP and Windows 2000 , programs can use DXVA 1.0. DXVA 2.0 allows Enhanced Video Renderer as the video renderer only on Vista, Windows 7, and Windows 8. (With Windows XP, DXVA-Rendering is possible with VMR9 and the well-known Overlay Mixer.) DXVA integrates with Media Foundation and allows DXVA pipelines to be exposed as Media Foundation Transforms ( MFTs ). Even decoder pipelines or post-processing pipelines can be exposed as MFTs, which can be used by

2880-624: The X video extension (Xv) and makes use of the familiar concept of the XvPort. Ports have attributes that can be set and queried through Xv. In XvMC ports can also have hardware motion compensation contexts created for use with them. Ports which support XvImages (i.e. they have an "XV_IMAGE" port encoding as described in the Xv version 2.2 API addendum) can be queried for the list of XvMCSurface types they support. If they support any XvMCSurface types an XvMCContext can be created for that port. XvMCContext describes

2960-503: The graphic driver can implement to accelerate the operations. If the codec needs to do any of the defined operations, it can use these interfaces to access the hardware-accelerated implementation of these operations. If the graphic driver does not implement one or more of the interfaces, it is up to the codec to provide a software fallback for it. The decoded video is handed over to the hardware video renderer, where further video post-processing might be applied to it before being rendered to

3040-525: The DCT lossy compression technique, capable of achieving data compression ratios from 8:1 to 14:1 for near-studio-quality, up to 100:1 for acceptable-quality content. DCT compression standards are used in digital media technologies, such as digital images , digital photos , digital video , streaming media , digital television , streaming television , video on demand (VOD), digital cinema , high-definition video (HD video), and high-definition television (HDTV). The DCT, and in particular

3120-403: The DCT blocks found in most digital media formats such as JPEG digital images and MP3 audio. Another example is Jpegs by German photographer Thomas Ruff , which uses intentional JPEG artifacts as the basis of the picture's style. Like any Fourier-related transform, DCTs express a function or a signal in terms of a sum of sinusoids with different frequencies and amplitudes . Like

3200-450: The DCT with slightly modified definitions. The N real numbers   x 0 ,   …   x N − 1   {\displaystyle ~x_{0},\ \ldots \ x_{N-1}~} are transformed into the N real numbers X 0 , … , X N − 1 {\displaystyle X_{0},\,\ldots ,\,X_{N-1}} according to one of

3280-618: The DCT, is used in Advanced Video Coding (AVC), introduced in 2003, and High Efficiency Video Coding (HEVC), introduced in 2013. The integer DCT is also used in the High Efficiency Image Format (HEIF), which uses a subset of the HEVC video coding format for coding still images. AVC uses 4 x 4 and 8 x 8 blocks. HEVC and HEIF use varied block sizes between 4 x 4 and 32 x 32 pixels . As of 2019 , AVC

X-Video Motion Compensation - Misplaced Pages Continue

3360-388: The DCT-I matrix orthogonal but breaks the direct correspondence with a real-even DFT . The DCT-I is exactly equivalent (up to an overall scale factor of 2), to a DFT of 2 ( N − 1 ) {\displaystyle 2(N-1)} real numbers with even symmetry. For example, a DCT-I of N = 5 {\displaystyle N=5} real numbers

3440-511: The DCT-II, is often used in signal and image processing, especially for lossy compression, because it has a strong energy compaction property. In typical applications, most of the signal information tends to be concentrated in a few low-frequency components of the DCT. For strongly correlated Markov processes , the DCT can approach the compaction efficiency of the Karhunen-Loève transform (which

3520-651: The DCT-IV, where data from different transforms are overlapped , is called the modified discrete cosine transform (MDCT). The DCT-IV implies the boundary conditions: x n {\displaystyle x_{n}} is even around n = − 1 / 2 {\displaystyle n=-1/2} and odd around n = N − 1 / 2 ; {\displaystyle n=N-1/2;} similarly for X k . {\displaystyle X_{k}.} DCTs of types I–IV treat both boundaries consistently regarding

3600-483: The DFT, a DCT operates on a function at a finite number of discrete data points . The obvious distinction between a DCT and a DFT is that the former uses only cosine functions, while the latter uses both cosines and sines (in the form of complex exponentials ). However, this visible difference is merely a consequence of a deeper distinction: a DCT implies different boundary conditions from the DFT or other related transforms. The Fourier-related transforms that operate on

3680-480: The GPU is not fast enough to copy its memory back to the CPU's memory. Native mode is advantageous unless there is a need for customized processing, as the additional copy-back operations will increase GPU memory load. Inverse discrete cosine transform A discrete cosine transform ( DCT ) expresses a finite sequence of data points in terms of a sum of cosine functions oscillating at different frequencies . The DCT, first proposed by Nasir Ahmed in 1972,

3760-449: The boundary conditions are responsible for the "energy compactification" properties that make DCTs useful for image and audio compression, because the boundaries affect the rate of convergence of any Fourier-like series. In particular, it is well known that any discontinuities in a function reduce the rate of convergence of the Fourier series, so that more sinusoids are needed to represent

3840-426: The callbacks for deinterlacing operations. The COPP (Certified Output Protection Protocol) DDI functions allow the pipeline to be secured for DRM-protected media , by specifying encryption functions. The ProcAmp DDI is used to accelerate post-processing video. The ProcAmp driver module sits between the hardware video renderer and the display driver, and it provides functions for applying post-processing filters on

3920-459: The concept of DCT to multidimensional signals. A variety of fast algorithms have been developed to reduce the computational complexity of implementing DCT. One of these is the integer DCT (IntDCT), an integer approximation of the standard DCT, used in several ISO/IEC and ITU-T international standards. DCT compression, also known as block compression, compresses data in sets of discrete DCT blocks. DCT blocks sizes including 8x8 pixels for

4000-506: The corresponding change in DCT-III). This makes the DCT-II matrix orthogonal , but breaks the direct correspondence with a real-even DFT of half-shifted input. This is the normalization used by Matlab , for example, see. In many applications, such as JPEG , the scaling is arbitrary because scale factors can be combined with a subsequent computational step (e.g. the quantization step in JPEG ), and

4080-432: The data are even about the sample a , in which case the even extension is dcbabcd , or the data are even about the point halfway between a and the previous point, in which case the even extension is dcbaabcd ( a is repeated). These choices lead to all the standard variations of DCTs and also discrete sine transforms (DSTs). Each boundary can be either even or odd (2 choices per boundary) and can be symmetric about

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4160-464: The data in the target XvMCSurface. When the pipeline starts at the iDCT level, Xv will perform the IDCT on the blocks before performing the motion compensation. A function is provided to copy/overlay a portion of the XvMCSurface to a drawable with arbitrary scaling. XvMCSubpictures are separate surfaces that may be blended with the target surface. Any number of XvMCSubpictures may be created for use with

4240-463: The decompressed video. The functions exposed by DXVA DDIs are not accessible directly by a DirectShow client, but are supplied as callback functions to the video renderer. As such, the renderer plays a very important role in anchoring the pipeline. DXVA support for H.264 was added in DirectX 9.0c . DXVA 2.0 enhances the implementation of the video pipeline and adds a host of other DDIs, including

4320-462: The denominators of the cosine arguments. However, these variants seem to be rarely used in practice. One reason, perhaps, is that FFT algorithms for odd-length DFTs are generally more complicated than FFT algorithms for even-length DFTs (e.g. the simplest radix-2 algorithms are only for even lengths), and this increased intricacy carries over to the DCTs as described below. (The trivial real-even array,

4400-538: The device. The resulting pipeline is usable in a DirectShow -compatible application. DXVA specifies the Motion Compensation DDI, which specifies the interfaces for iDCT operations, Huffman coding , motion compensation , alpha blending , inverse quantization , color space conversion and frame-rate conversion operations, among others. It also includes three sub-specifications: Deinterlacing DDI, COPP DDI and ProcAmp DDI. The Deinterlacing DDI specifies

4480-402: The discrete cosine transform is a linear , invertible function f : R N → R N {\displaystyle f:\mathbb {R} ^{N}\to \mathbb {R} ^{N}} (where R {\displaystyle \mathbb {R} } denotes the set of real numbers ), or equivalently an invertible N × N square matrix . There are several variants of

4560-775: The formulas: Some authors further multiply the x 0 {\displaystyle x_{0}} and x N − 1 {\displaystyle x_{N-1}} terms by 2 , {\displaystyle {\sqrt {2\,}}\,,} and correspondingly multiply the X 0 {\displaystyle X_{0}} and X N − 1 {\displaystyle X_{N-1}} terms by 1 / 2 , {\displaystyle 1/{\sqrt {2\,}}\,,} which, if one further multiplies by an overall scale factor of 2 N − 1 , {\displaystyle {\sqrt {{\tfrac {2}{N-1\,}}\,}},} , makes

4640-411: The function is even or odd at both the left and right boundaries of the domain (i.e. the min- n and max- n boundaries in the definitions below, respectively). Second, one has to specify around what point the function is even or odd. In particular, consider a sequence abcd of four equally spaced data points, and say that we specify an even left boundary. There are two sensible possibilities: either

4720-496: The function with a given accuracy. The same principle governs the usefulness of the DFT and other transforms for signal compression; the smoother a function is, the fewer terms in its DFT or DCT are required to represent it accurately, and the more it can be compressed. (Here, we think of the DFT or DCT as approximations for the Fourier series or cosine series of a function, respectively, in order to talk about its "smoothness".) However,

4800-562: The future to support the same processes as the newer competing hardware video acceleration APIs like VDPAU , XvBA , and VAAPI : Besides not matching all of the features and function of DxVA (which is the Microsoft equivalent API for Windows ), and lacking support for other video formats than MPEG-2 in Linux device drivers from Intel and Nvidia , the XvMC API specification version 1.0 currently also has these other limitations: VA API

4880-408: The hardware, software and introduction of several fast algorithms, the necessity of using MD DCTs is rapidly increasing. DCT-IV has gained popularity for its applications in fast implementation of real-valued polyphase filtering banks, lapped orthogonal transform and cosine-modulated wavelet bases. DCT plays an important role in digital signal processing specifically data compression . The DCT

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4960-486: The implicit periodicity of the DFT means that discontinuities usually occur at the boundaries: any random segment of a signal is unlikely to have the same value at both the left and right boundaries. (A similar problem arises for the DST, in which the odd left boundary condition implies a discontinuity for any function that does not happen to be zero at that boundary.) In contrast, a DCT where both boundaries are even always yields

5040-400: The length, operating on real data with even symmetry (since the Fourier transform of a real and even function is real and even), whereas in some variants the input or output data are shifted by half a sample. There are eight standard DCT variants, of which four are common. The most common variant of discrete cosine transform is the type-II DCT, which is often called simply the DCT . This was

5120-457: The motion compensation type. Contexts may be "direct" or "indirect". For indirect contexts the X display server renders all video using the data passed to it by the client. For direct contexts the client libraries render the video with little or no interaction with the X display server. XvMCSurfaces are buffers into which the motion compensation hardware can render. The data in the buffers themselves are not client accessible and may be stored in

5200-442: The numerical solution of partial differential equations . A DCT is a Fourier-related transform similar to the discrete Fourier transform (DFT), but using only real numbers . The DCTs are generally related to Fourier series coefficients of a periodically and symmetrically extended sequence whereas DFTs are related to Fourier series coefficients of only periodically extended sequences. DCTs are equivalent to DFTs of roughly twice

5280-447: The original f ( x ) {\displaystyle f(x)} was not specified. The DFT, like the Fourier series, implies a periodic extension of the original function. A DCT, like a cosine transform , implies an even extension of the original function. However, because DCTs operate on finite , discrete sequences, two issues arise that do not apply for the continuous cosine transform. First, one has to specify whether

5360-538: The original 1974 Ahmed paper and the 1977 Chen paper, were cited by the Joint Photographic Experts Group as the basis for JPEG 's lossy image compression algorithm in 1992. The discrete sine transform (DST) was derived from the DCT, by replacing the Neumann condition at x=0 with a Dirichlet condition . The DST was described in the 1974 DCT paper by Ahmed, Natarajan and Rao. A type-I DST (DST-I)

5440-425: The original DCT as first proposed by Ahmed. Its inverse, the type-III DCT, is correspondingly often called simply the inverse DCT or the IDCT . Two related transforms are the discrete sine transform (DST), which is equivalent to a DFT of real and odd functions , and the modified discrete cosine transform (MDCT), which is based on a DCT of overlapping data. Multidimensional DCTs (MD DCTs) are developed to extend

5520-452: The point of symmetry: they are even/odd around either a data point for both boundaries or halfway between two data points for both boundaries. By contrast, DCTs of types V-VIII imply boundaries that are even/odd around a data point for one boundary and halfway between two data points for the other boundary. In other words, DCT types I–IV are equivalent to real-even DFTs of even order (regardless of whether N {\displaystyle N}

5600-570: The resulting matrix by an overall scale factor of 2 / N {\textstyle {\sqrt {2/N}}} (see above for the corresponding change in DCT-II), so that the DCT-II and DCT-III are transposes of one another. This makes the DCT-III matrix orthogonal , but breaks the direct correspondence with a real-even DFT of half-shifted output. The DCT-III implies the boundary conditions: x n {\displaystyle x_{n}}

5680-608: The results are quantized and entropy coded . In this case, N {\displaystyle N} is typically 8 and the DCT-II formula is applied to each row and column of the block. The result is an 8 × 8 transform coefficient array in which the ( 0 , 0 ) {\displaystyle (0,0)} element (top-left) is the DC (zero-frequency) component and entries with increasing vertical and horizontal index values represent higher vertical and horizontal spatial frequencies. The integer DCT, an integer approximation of

5760-425: The standard DCT, and varied integer DCT sizes between 4x4 and 32x32 pixels. The DCT has a strong energy compaction property, capable of achieving high quality at high data compression ratios . However, blocky compression artifacts can appear when heavy DCT compression is applied. The DCT was first conceived by Nasir Ahmed , T. Natarajan and K. R. Rao while working at Kansas State University . The concept

5840-424: The standard coding technique for video compression from the late 1980s onwards. A DCT variant, the modified discrete cosine transform (MDCT), was developed by John P. Princen, A.W. Johnson and Alan B. Bradley at the University of Surrey in 1987, following earlier work by Princen and Bradley in 1986. The MDCT is used in most modern audio compression formats, such as Dolby Digital (AC-3), MP3 (which uses

5920-402: The state of the motion compensation pipeline. An individual XvMCContext can be created for use with a single port, surface type, motion compensation type, width and height combination. For example, a context might be created for a particular port that does MPEG-2 motion compensation on 720 x 480 4:2:0 surfaces. Once the context is created, referencing it implies the port, surface type, size and

6000-400: The transform matrix orthogonal . Multidimensional variants of the various DCT types follow straightforwardly from the one-dimensional definitions: they are simply a separable product (equivalently, a composition) of DCTs along each dimension. For example, a two-dimensional DCT-II of an image or a matrix is simply the one-dimensional DCT-II, from above, performed along the rows and then along

6080-510: The various DCT types. Most directly, when using Fourier-related transforms to solve partial differential equations by spectral methods , the boundary conditions are directly specified as a part of the problem being solved. Or, for the MDCT (based on the type-IV DCT), the boundary conditions are intimately involved in the MDCT's critical property of time-domain aliasing cancellation. In a more subtle fashion,

6160-411: The video renderer with no intermediary processing filter. The video renderer must also support DXVA, which gives less freedom in the choice of renderers. With copy-back implementation, the decoded video is copied from GPU memory back to the CPU's memory. This implementation doesn't have the limitations mentioned above and acts similarly to a normal software decoder; however, video stuttering will occur if

6240-514: Was later described by Anil K. Jain in 1976, and a type-II DST (DST-II) was then described by H.B. Kekra and J.K. Solanka in 1978. In 1975, John A. Roese and Guner S. Robinson adapted the DCT for inter-frame motion-compensated video coding . They experimented with the DCT and the fast Fourier transform (FFT), developing inter-frame hybrid coders for both, and found that the DCT is the most efficient due to its reduced complexity, capable of compressing image data down to 0.25- bit per pixel for

6320-496: Was proposed to the National Science Foundation in 1972. The DCT was originally intended for image compression . Ahmed developed a practical DCT algorithm with his PhD students T. Raj Natarajan, Wills Dietrich, and Jeremy Fries, and his friend Dr. K. R. Rao at the University of Texas at Arlington in 1973. They presented their results in a January 1974 paper, titled Discrete Cosine Transform . It described what

6400-536: Was the first manufacturer to provide MPEG-2 acceleration in their graphic boards with the Rage 128 GPU, it has never provided documentation on how to use it. So no XvMC is available, and will probably never be. XvMC is supported on Radeon -4000 cards (which have UVD ) by Catalyst driver from 8.10 and higher at an experimental level (meaning that it doesn't work " out of the box ".) (See also X-Video Bitstream Acceleration ). Motion compensation support in other ATI/AMD hardware

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