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Simple DCT problem

Hi all, I am new to DCT and now testing my FDCT and IDCT program. I found some of my high frequency DCT part is higher than low frequency DCT part. And I don't know whether it is correct. Where can I find example of 8*8 DCT input and output to test my code,thanks! BTW, my code's DCT in...

DCT

Hi, I am looking for some technical information rgarding DCT. Why DCT is used in image/video/audio instead of transform like FFT? What information we get after taking a DCT? Is DCT just the real part of FFT? Please send me some info regarding this. Thanking you ...

how to relate 8x8 DCT to 4x4 DCT?

Dear all, Can anybody tell me how to express 8x8 DCT in the form of 4x4 DCT? 8x8 DCT = function( 4x4 DCT) ??? Is there any simple relationship? Thanks a lot, -Walala ...

A question on DCT

HI all, I have a query on DCT. How does DCT gives energy compaction compared to DFT when it is applied to say an image? ~R ...

DCT in audio compression

After reading, what seems like a lot of material, I'm still in doubt why DCT isnt used in audio-compression. Seeing as DCT assumes mirror symmetry, my only idea for not validating DCT over MDCT is that with real-life signals you can rarely (if ever) expect a signal to have that property? Is that cor...

Computing DFT of a signal from its DCT coefficients?

Hello, I have the following question regarding obtaining the DFT of a signal directly from its DCT representation: Say we are given the N-point DCT coefficients Xdct(k) of some real-valued signal x(n), but what we really want is the N-point DFT of x(n), Xdft(k). I need to obtain the power ...

does the current DCT/IDCT hardware use the same architecture for both DCT and IDCT?

Dear all, I came across an interesting problem: for a device both encodes and decodes video, do the designers seperately design circuit for DCT and another circuit for IDCT? I suspect that they have one universal transform circuit, then with some modification, IDCT can be computed using the DC...

DCT Scalings

Hello All, I am trying to implement forward and inverse DCT based on Y. Arai, T. Agui, and M. Nakajima, "A Fast DCT-SQ Scheme for Images," Trans. of the IEICE, vol. E-71, no. 11, pp. 1095-1097, Nov. 1988 paper. Both flow graphs for the forward and inverse DCT are given in the paper. When I tr...

help with 10-point DCT

hello, i know that it is possible but i don't know how. radix-2 DCT are well covered but i can't find radix-5 references for DCT or FFT.... can anybody drop me the algorithm ? thanks in advance, YG ...

how is the discrete cosine transform matrix transform equivalent to the standard dct definition (DCT-II)

Can some one explain or point me to a paper with the proof of how the DCT matrix transformation Y=DCT(X) = AXA' (where A is the DCT transform matrix, X is the input data matrix, Y is the transformed data coeff's) A(u,v) = (1/N)^(1/2) for u =0 A(u,v) = (2/N)^(1/2) * cos(PI*(2v+1)*u/(2*N)) ...

challenge: how to do filtering in DCT domain?

Dear all, I guess this is a little simple... Don't largh at me if it is too simple... Basicall I have a 3x3 filter, let's say [ -0.1 0.2 -0.1; 0.2 0.6 0.2; -0.1 0.2 -0.1]; I want to do this in DCT domain......

DCT vs. DFT

Hi! Can anyone explain me, why you use DCT instead of DFT for transformation of image-data (like it is done for JPEG). I know that the DCT can be performed by a DFT with a post-rotation. But what are the advantages of the DCT compared to the DFT? Are there any benefits from the post-rotatio...

KLT & DCT

Hi We know that DCT is almost as good as KLT for a 1st order markov process. But under what cases ( if any) will they both KLT and DCT be the same. regards Abraham This message was sent using the Comp.DSP web interface on www.DSPRelated.com ...

FFT VS DCT

I see that all are asking why DCT is better than FFT or DFT. Where FFT is prepered than DCT? Why ? Is it only for phase information? _____________________________________ Do you know a company who employs DSP engineers? Is it already listed at http://dsprelated.com/employers.php ? ...

Re: Regarding DCT

Had written a simplistic dct implementation some time back in 'C'. May help. http://piyushkaul.tripod.com/dct_c.zip. Optimized 2D-DCT implemention src would also be available on net at many places. Regarding using dct2. What problem are you having? The syntax is B = dct2(A); Can't possib...

Fixed Point DCT

CONTEXT: I have implemented DCT's in fixed point (DCT-IV and DCT-II). Currently I allow one extra bit, each time there is an addition, to avoid overflow. For example for a size 64 transform there are 6 stages of decomposition in radix-2 and each stage involves addition, which means I need log2(...

Re: MDCT

Chris Felton wrote: > Couple reasons, first question is why is the DCT used instead of the > DFT (fast version of both transforms exist, image compression > literature is a good resource for DCT vs. DFT). This is mainly due to > the property of energy compaction. On average the DCT repre...

why DCT

Hi guys, I was curious to know why is it that DCT is used in image compression. why not FFT? ...

Input and output of 2-D DCT needed for any dimension

Hi friends, Can anybody send one example of 2-D DCT calculation with input and out put matrix for any dimension. Atleast send me input and output for 2-D DCt (4X4 or 8X8) any dimension. I need to finalize the algo for implementing in FPGA. Please kindly respond ASAP. R...

What is the most computation efficient hardware implementation method for DCT

What is the best way (in terms of reduced computation thus resulting in reduced power consumption) to implement DCT in hardware(iam interested in doing RTL and then synthesize with some technology library rather than doing an FPGA kind of implementation). I intend to implement 8x8 DCT with each elem...

Re: Fast 1-D DCT algorithms

Koen wrote: > Hi, > > Does anyone know of working and tested code (C/C++/pseudo/...) for > doing a fast 1-D DCT ? > I know about the Numerical Recipes code, but that has a rather > restrictive license... > I also have DCT and IDCT working already using the straight > implementat...

vlsi implementation of DCT

hi, i'm vlsi student. my project is on vlsi implementation of MDCT. can any one suggest me about the books and materials that i've to refer for the basics of DCT and MDCT. since i have to implement in FPGA can u suggest the best architecture for DCT and MDCT for vlsi implementation tha...

Fast 1D DCT Implementation in C/C++

Hi, Could anyone direct me to a very good 1D DCT Implementation in C/C++ My data is in sets of 8 numbers. Thanks a ton, Soumyadip. ...

DCT parallel using VHDL

Where can I find example of 8x8 dct input &output to test my code. I using input by Hexadecimal. nad also using multiply two's complement. ...

Example needed on 2-D DCT problem

Hi, I am working on verilog coding of 2-D DCT. To finalize the algorithm for hardware implementation, I need to work on 1 example to know the exact process. Can anybody send link having input and output, so that I could cross check it. Please help me ASAP. Regards, Raghavendra ...

[Question] Quantization step size for DCT coefficients

Hi, In any standard implementation of DCT, the DCT coefficients are quantized using Quantization Coefficients included in the JPEG file stream. Here where is the Quantization step size ? Do they vary in MPEG files Is it 2^(M-1) ? Is it M = 10. for JPEG files James Colin ...

what's the key properties of DCT/IDCT that lend it such wide use in image processing?

Dear all, Can anybody tell me what are the key properties of DCT/IDCT(2D) which lend it to the such wide use in image processing? I mean, why FFT, DHT, and other transformations are not used in image processing/compression? Book says that DCT resembles K-L transformation mostly, but how a...

8x8 DCT with Cordic algorithm

Hi all, I'm struggling to get my 8x8 DCT working with Cordic. With matrix multiplication it works fine. Have anyone done this with MatLab? I really appreciate any help available! If someone would be interested in taking a look I can send you my current solution that has some small bug but I...

DCT source code.

Dear All, I have DCT by B.G.Lee paper with me. I want to know whether source code for this algorithm is available on web?. If available where can I get ?. Regards, Ramya. ...

Re: DCT & IDCT algorithm problems

Hi, Finally whats the code? What are the mistakes? I cant figure it out. Could u explain? How to draw moving picures to pictures and then pictures to macroblocks? I am presently looking for MPEG4 Encoder and Decoder. Please give some information. Is there any opensources? Is it good to sta...

Image processing, DCT coefficients ordering

Hi guys, I am currently doing a project about the multiple description coding for a image using correlating transform. In one of the IEEE journals, the author describes the encoder as: “The coder is based on a modification of a standard JPEG coder. In our baseline encoder, each block of samp...

DCT lowpass filter coefficients

Hello, Does anyone know where I can find a good references that can recommend coefficients for a function that uses DCT for the transform and X coeffiecients to either lowpass filter a 1-D sample (8-pixels) or 2-D (8x8 pixels) sample of image data. thanks rainy ...

B.G. Lee DCT algorithm Implementation.

Hi all, I want to know whether the reference implementation of B.G.Lee's(Full name Given below) DCT algorithm was availabe on web ? If available, anyone please tell me the path or send me the code. Thanks in advance, Regards, Ramya. ****************************************************...

Re: which one is the most successful scheme to reduce blocky artifacts in low bit rate JPEG image?

"walala" wrote > Anybody give me some pointers? Thanks a lot in advance! Try http://citeseer.nj.nec.com/kim98fixedpoint.html BTW if you are using a coarse enough DCT approximation such that reconstruction gets you blocks you are better off using a transform like binDCT ... a fast inte...

Reasonablenes (NOT 'correctness') of using DCT in place of DFT

I've read ( 'have understood') that for real symmetric signals the DCT and DFT are equivalent. That got me thinking about a particular set of pseudo noise signals and how information is encoded. I'm interested in things loosely associated with speech recognition. Wouldn't be reasonable to...

JavaScript JPEG Implementation Help

Hello, For a bit of fun I am currently writing an implementation of a monochrome baseline DCT JPEG encoder in JavaScript. I am currently using the IJG DCT implementation and the standard quantization and Huffman tables described in ITU-T.81. However the resultant images don't appear correct, I fe...

Re: Video-equivalent of "pitch-shifting."

On Aug 27, 7:37 pm, Jerry Avins wrote: > Radium wrote: > > On Aug 26, 9:47 pm, Jerry Avins wrote: > > At first Radium wrote: > > > > > I want the actress to talk at the same speed, at a lower-pitch, and > > > > finish at the same-time without any low-pass filtering. > > > ...

Re: MDCT & IMDCT using FFT

Hi Brad, I haven't read the book you mention, but it looks like your code performs (asymptotically) four times as much work as is really needed to compute the MDCT. You lose a factor of two because you perform an FFT of size N instead of N/2, and you lose another factor of two because you pe...

how do I do DCT on a 100x100 image?

Let's say I have an image, which is 100 x 100. Each pixel is currently a real number, between 0 and 1. Totally there are 10000 pixels. The goal is to use DCT to reduce the 10000 pixels to hopefully 100 pixels, just like those DCTs in JPEG... Because there is an obvious pattern in the 10...

DCT reference software

Hi, Does anyone know of any reference software to perform a DCT on an image? Does the image have to be in a certain format? Thanks! ...