为什么在视频/图像压缩中DCT变换比其他变换更受青睐 [英] why DCT transform is preferred over other transforms in video/image compression

问题描述

我介绍了如何在图像和视频压缩标准中使用DCT（离散余弦变换）。

I went through how DCT (discrete cosine transform) is used in image and video compression standards.

但是，为什么仅DCT比dft或dst等其他转换更受青睐？

But why DCT only is preferred over other transforms like dft or dst?

推荐答案

因为 cos（0）为1，因此第一个（第0个）DCT-II的系数是要转换的值的平均值。这使得每个8x8块的第一个系数代表其组成像素的平均色调，这显然是一个很好的开始。随后的系数增加了更多的细节，从逐渐渐变的梯度开始，一直延伸到越来越复杂的图案，而且恰好碰巧前几个系数捕获了摄影图像中的大部分信号。

Because cos(0) is 1, the first (0th) coefficient of DCT-II is the mean of the values being transformed. This makes the first coefficient of each 8x8 block represent the average tone of its constituent pixels, which is obviously a good start. Subsequent coefficients add increasing levels of detail, starting with sweeping gradients and continuing into increasingly fiddly patterns, and it just so happens that the first few coefficients capture most of the signal in photographic images.

Sin（0）为0，因此DST以0.5或1的偏移量开始，并且第一个系数是平缓的土墩，而不是平坦的平原。这不太可能适合普通图像，结果是DST比DCT需要更多的系数来编码大多数块。

Sin(0) is 0, so the DSTs start with an offset of 0.5 or 1, and the first coefficient is a gentle mound rather than a flat plain. That is unlikely to suit ordinary images, and the result is that DSTs require more coefficients than DCTs to encode most blocks.

DCT恰好适合。真的就是全部。

The DCT just happens to suit. That is really all there is to it.

这篇关于为什么在视频/图像压缩中DCT变换比其他变换更受青睐的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！