How does DCT provide energy compaction?

[mathew.paul]

How does DCT provide energy compaction...?? Isn't that one of the reasons, along with it being purely real, why it is extensively used in several image and video compression algorithms..?? would a DST give the same compression ??

- matt

 

[radheshbhat]

Re: DCT

may be a useful link : https://www.dsprelated.com/showmessage/34432/1.php

 

[buenos]

DCT

there are other methods, like DST, DFT, DHT (haar) , DWHT (walsh-hadamard), or KLT but the DCT is the most popular, because it produces real output, good for natural pictures, and it compresses the rest of the signal energy into some coefficients.

 

[itsthetimetodisco]

Re: DCT

DCT can provide energy compaction because of the way its basis function is formed. Just like we have cos(0) = 1 and cos(90) = 0, likewise the energy of the subblock of image gets concentrated to the low frequency coefficients and the high frequency coefficients have magnitude tending towards zero.
(on a smilar idea, DST will not be useful as sin(0) = 0 and sin(90) = 1, which is not helpful for compression as then we will need all 64 coefficienst in zigzag scanning and entropy coding).

 

[Ralph80]

Re: DCT

See this DCT conversion example