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Method and device for executing reverse discrete cosine transform

An inverse discrete cosine and discrete cosine transform technology, applied in code conversion, special data processing applications, image data processing, etc., can solve the problem of decoder size and power consumption limitations

Inactive Publication Date: 2004-06-09
SAMSUNG ELECTRONICS CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

At the same time, decoders are limited in size and power consumption since they are usually placed in mobile communication devices such as mobile phones and personal digital assistants (PDAs).

Method used

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  • Method and device for executing reverse discrete cosine transform
  • Method and device for executing reverse discrete cosine transform
  • Method and device for executing reverse discrete cosine transform

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Embodiment Construction

[0037] Fig. 4 shows "" in the DCT matrix that appears when decoding an MPEG4 stream obtained by encoding MPEG4 test motion pictures (Akiyo, Foreman and Mobile) with different quantization parameters (Qp) before one IDCT step. DCT coefficients" distribution. Here, the smaller the Qp is, the lower the compression ratio is, and encoding can be performed at a higher transmission rate. It has been proved that about 30% of the element values ​​in the DCT matrix are concentrated in a certain area (2×2, 4×4) of a DCT matrix. This is due to the fact that in the general distribution of DCT matrix element values, these values ​​are all concentrated in a low frequency band. However, the smaller the Qp, ie the better the image quality, the wider the distribution of values ​​of the elements of the DCT matrix from the low frequency band to the high frequency band.

[0038] FIG. 5 shows a graph of the occurrence probabilities of different numbers of non-zero element values ​​in a DCT matrix...

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Abstract

A method and apparatus for fast inverse discrete cosine transform (IDCT) are provided. The fast IDCT method includes: (a) searching all elements of a discrete cosine transform (DCT) matrix in a predetermined order for non-zero elements; and (b) calculating the restored value of each element of a restoration matrix, by 2 dimensional-inverse DCT (2D-IDCT) transforming the non-zero elements of the DCT matrix by using the symmetry of an IDCT formula. According to the method and apparatus, unnecessary computation for 0's that are the majority of elements in a DCT matrix can be reduced to the minimum in performing the IDCT transform. In addition, even when the number of elements having effective values is large in a DCT matrix, the amount of computation is greatly reduced by using the symmetry of a DCT formula such that the method shows an excellent performance when statistically compared to the conventional fast DCT algorithms.

Description

[0001] This application claims priority from Korean Patent Application No. 02-72388 filed on November 20, 2002, the entire disclosure of which is hereby incorporated by reference. technical field [0002] The present invention relates to a method and apparatus for performing a fast discrete cosine transform (DCT). Background technique [0003] Digital data compression, in particular, the compression of video signals is an integral part of various multimedia application environments. However, since a video signal contains a large amount of information that must be processed, there are many limitations in efficiently transmitting, storing or manipulating the data. In order to address these limitations, international standards such as Moving Picture Experts Group (MPEG)-2, MPEG-4, H.263, H.26L, etc. specify compressed stream syntax and decoding processes. [0004] Compression methods can be classified into lossless compression methods and lossy compression methods. If lossles...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G06F17/14G06T9/00H03M7/30H04N1/41H04N19/102H04N19/134H04N19/176H04N19/189H04N19/44H04N19/503H04N19/60H04N19/61H04N19/625
CPCG06F17/147H04N19/132H04N19/625
Inventor 车尚昌安钟学
Owner SAMSUNG ELECTRONICS CO LTD
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