Discrete Cosine Transform

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nlulani

Joined: 29 Nov 2004
Posts: 26
Helped: 1

31 Jan 2006 7:15 Discrete Cosine Transform

Hi all,
I have tried to implement fast DCT and fast IDCT in C by using separable property and taking 8X8 block at a time of an image. But results are a little bit strange. I see verticle and horizntal lines throughout the image. these lines seems to be obvious from the fact that I am taking one block at a time for DCT processing. However as per this assumption as I am increasing the size of a block from 8X8 to 16X16 or higher these lines get separated accordingly more.

But still I am searching for its solution. If anyone has come across the same problem and solved it then please let me know about it. I am attaching here the results for your convenience.

thanks and regards
Nitin

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kalyanram

Joined: 03 Jan 2005
Posts: 558
Helped: 346

01 Feb 2006 14:33 Re: Discrete Cosine Transform

Hi,
THis could be due to the Endianness od the system. I hope you are using the PC environment (i.e Intel based system...which is little endian) in this case the samples have their bytes swapped try reversinfg the byte order before transfoemation and before writing to the file. This could be the case as far as I can see.

~Kalyan.