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【速搜问答】编码变换是什么

问答 admin 2周前 (04-19) 19次浏览 已收录 0个评论

汉英对照:
Chinese-English Translation:

编码变换(trans coding;coding transform)是指将信号从一种编码方案向另一种编码方案的直接转换(无须将信号变回模拟形式)。

Transform coding (coding transform) refers to the direct conversion of a signal from one coding scheme to another (without changing the signal back to analog form).

编码变换(trans coding;coding transform)是指将信号从一种编码方案向另一种编码方案的直接转换(无须将信号变回模拟形式)。

Transform coding (coding transform) refers to the direct conversion of a signal from one coding scheme to another (without changing the signal back to analog form).

信源编码器首先是把信源信号转换成二进制信息序列,为了使欲传输的信源信息在传输速率一定的条件下更快,更多地传输,还要把数据进行压缩,也就是通过信源编码,去掉信息中大量多余部分,这样就可以极大地提高传输效率。

The source encoder first converts the source signal into binary information sequence. In order to make the source information to be transmitted faster and more under the condition of a certain transmission rate, it also needs to compress the data, that is, to remove a large number of redundant parts in the information through the source coding, which can greatly improve the transmission efficiency.

信道编码它是为了保证信息传输的可靠性、提高传输质量而设计的一种编码。它是在信息码中增加一定数量的多余码元,使码字具有一定的抗干扰能力,因此信道编码又称抗干扰编码。

Channel coding is designed to ensure the reliability of information transmission and improve the quality of transmission. It is to add a certain number of redundant symbols in the information code, so that the code word has a certain anti-interference ability, so the channel coding is also called anti-interference coding.

信息在传输过程中有来自各个方面的干扰。例如通信设备各个器件的缺陷和内部噪声;信道中存在的各种干扰,如高频信道的衰落,天电干扰等。所有这些干扰都会影响传输的可靠性,信道编码就是为了克服这些干扰、增加传输可靠性的一门通信胡。设计信道编码的目的,就是在编码效率一定的条件下,尽可能提高已编码信号的检错或纠错能力。或者说在保证一定的检错或纠错能力的条件下尽可能提高编码效率。

Information in the transmission process has interference from all aspects. For example, the defects and internal noise of each device of communication equipment; various interferences existing in the channel, such as fading of high frequency channel, radio interference, etc. All these interferences will affect the reliability of transmission. Channel coding is a communication method to overcome these interferences and increase the reliability of transmission. The purpose of designing channel coding is to improve the error detection or correction ability of the coded signal as much as possible under the condition of certain coding efficiency. In other words, the coding efficiency can be improved as much as possible under the condition of ensuring a certain ability of error detection or error correction.

工作原理

working principle

编码变换不是直接对空域图像信号进行编码,而是首先将空域图像信号映射变换到另一个正交矢量空间(变换域或频域),产生一批变换系数,然后对这些变换系数进行编码处理。变换编码是一种间接编码方法,其中关键问题是在时域或空域描述时,数据之间相关性大,数据冗余度大,经过变换在变换域中描述,数据相关性大大减少,数据冗余量减少,参数独立,数据量少,这样再进行量化,编码就能得到较大的压缩比。典型的准最佳变换有 DCT(离散余弦变换)、DFT(离散傅里叶变换)、WHT(Walsh Hadama 变换)、HrT(Haar 变换)等。其中,最常用的是离散余弦变换。

The coding transformation is not to encode the spatial image signal directly, but to map the spatial image signal to another orthogonal vector space (transform domain or frequency domain), generate a batch of transform coefficients, and then encode these transform coefficients. Transform coding is a kind of indirect coding method. The key problem is that when the data is described in time domain or spatial domain, the correlation between the data is large and the data redundancy is large. After the transform is described in the transform domain, the data correlation is greatly reduced, the data redundancy is reduced, the parameters are independent and the amount of data is small. In this way, the coding can get a larger compression ratio. The typical quasi optimal transforms are DCT (discrete cosine transform), DFT (Discrete Fourier transform), wht (Walsh hadama transform), HRT (Haar transform), etc. Among them, the most commonly used is the discrete cosine transform.

在编码变换中的比特分配中,分区编码是基于最大方差准则;阈值编码是基于最大幅度准则。变换编码是失真编码的一种重要的编码类型。

In the bit allocation of coding transformation, the partition coding is based on the maximum variance criterion, and the threshold coding is based on the maximum amplitude criterion. Transform coding is an important type of distortion coding.

一般来说,信号压缩是指将信号进行换基处理后,在某个正交基下变换为展开系数按一定量级呈指数衰减,具有非常少的大系数和许多小系数的信号,这种通过变换时限压缩的方法称为编码变换。

Generally speaking, signal compression means that the signal is transformed into a signal with very few large coefficients and many small coefficients under a certain orthogonal basis after base changing. This method of time limited compression is called coding transformation.

编码中实用的变换,不但希望能有最佳变换的性能,而且要有快速的算法。而卡一洛变换不存在快速算法,所以在实际的编码变换中不得不大量使用各种性能上接近最佳变换、同时又有快速算法的正交变换。正交变换可分为非正弦类和正弦类。非正弦类变换以沃尔什变换、哈尔变换、斜变换等为代表,其优点是实现时计算量小,但它们的基矢量很少能反映物理信号的机理和结构本质,变换的效果不甚理想。而正弦类变换以离散傅里叶变换、离散正弦变换、离散余弦变换等为代表,其最大优点是具有趋于最佳变换的渐近性质。例如,离散正弦变换和离散余弦变换已被证明是在一阶马氏过程下卡一洛变换的几种特例。由于这一原因,正弦类变换已日益受到人们的重视。

Practical transformation in coding, not only hope to have the best transformation performance, but also have a fast algorithm. However, there is no fast algorithm for Karnaugh transform, so we have to use a lot of orthogonal transform which has the best performance and fast algorithm. Orthogonal transformation can be divided into non sinusoidal transformation and sinusoidal transformation. The nonsinusoidal transform is represented by Walsh transform, Haar transform and skew transform. The advantage of nonsinusoidal transform is that it needs less computation, but their base vectors rarely reflect the mechanism and structural essence of physical signals, and the effect of the transform is not ideal. The sinusoidal transform is represented by discrete Fourier transform, discrete sine transform and discrete cosine transform, and its greatest advantage is that it has the asymptotic property of approaching the best transform. For example, discrete sine transform and discrete cosine transform have been proved to be some special cases of Karnaugh transform in first order Markov process. For this reason, sinusoidal transformation has been paid more and more attention.


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