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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, is a widely used transformation technique in signal processing and data compression .
Transform coding dates back to the late 1960s, with the introduction of fast Fourier transform (FFT) coding in 1968 and the Hadamard transform in 1969. [ 34 ] An important image compression technique is the discrete cosine transform (DCT), a technique developed in the early 1970s. [ 16 ]
It is most easily applied to discrete cosine transform (DCT) based video coding standards, because the coding is performed in blocks. [8] As a way of exploiting temporal redundancy, motion estimation and compensation are key parts of video compression.
The modified discrete cosine transform (MDCT) is a transform based on the type-IV discrete cosine transform (DCT-IV), with the additional property of being lapped: it is designed to be performed on consecutive blocks of a larger dataset, where subsequent blocks are overlapped so that the last half of one block coincides with the first half of the next block.
The discrete cosine transform (DCT) is the most widely used transform coding compression algorithm in digital media, followed by the discrete wavelet transform (DWT). Transforms between a discrete domain and a continuous domain are not discrete transforms.
Motion compensation is one of the two key video compression techniques used in video coding standards, along with the discrete cosine transform (DCT). Most video coding standards, such as the H.26x and MPEG formats, typically use motion-compensated DCT hybrid coding, [1] [2] known as block motion compensation (BMC) or motion-compensated DCT (MC ...
The macroblock is a processing unit in image and video compression formats based on linear block transforms, typically the discrete cosine transform (DCT). A macroblock typically consists of 16×16 samples, and is further subdivided into transform blocks, and may be further subdivided into prediction blocks.
Block-artifacts are a result of the very principle of block transform coding. The transform (for example the discrete cosine transform) is applied to a block of pixels, and to achieve lossy compression, the transform coefficients of each block are quantized. The lower the bit rate, the more coarsely the coefficients are represented and the more ...