The dct Reference Manual

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The dct Reference Manual

This is the dct Reference Manual, version 1.0.0, generated automatically by Declt version 4.0 beta 2 "William Riker" on Mon Aug 15 03:35:47 2022 GMT+0.

Table of Contents


1 Introduction

cl-dct

Build Status Coverage Status

Discrete cosine transform (DCT) is a signal processing algorithm that compresses a signal. It's similar to a Fourier transform. DCT is often used in speech recognition for computing MFCC features.

There are a number of different versions and implementations of DCT. This implementation mimics the one in Matlab. You should also get the same results in scipy with the command:

scipy.fftpack.dct([4., 3., 5., 10.], norm='ortho')

The idct() implementation is equivalent to the Matlab implementation and the scipy command:

scipy.fftpack.idct([4., 3., 5., 10.], norm='ortho')

This is an O(n²) implementation. O(n log(n)) implementations are also possible.


2 Systems

The main system appears first, followed by any subsystem dependency.


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2.1 dct

Discrete cosine transform.

Author

Ben Lambert <belambert@mac.com>

License

Apache-2.0

Version

1.0.0

Dependency

alexandria (system).

Source

dct.asd.

Child Component

src (module).


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3 Modules

Modules are listed depth-first from the system components tree.


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3.1 dct/src

Source

dct.asd.

Parent Component

dct (system).

Child Components

4 Files

Files are sorted by type and then listed depth-first from the systems components trees.


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4.1 Lisp


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4.1.1 dct/dct.asd

Source

dct.asd.

Parent Component

dct (system).

ASDF Systems

dct.


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4.1.2 dct/src/package.lisp

Source

dct.asd.

Parent Component

src (module).

Packages

dct.


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4.1.3 dct/src/dct.lisp

Dependency

package.lisp (file).

Source

dct.asd.

Parent Component

src (module).

Public Interface

5 Packages

Packages are listed by definition order.


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5.1 dct

Source

package.lisp.

Use List

common-lisp.

Public Interface

6 Definitions

Definitions are sorted by export status, category, package, and then by lexicographic order.


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6.1 Public Interface


6.1.1 Ordinary functions

Function: dct (array &key truncated)

Discrete cosine transform (DCT).
DCT-II taken from:
http://en.wikipedia.org/wiki/Discrete_cosine_transform#DCT-II
Further multiplied the X0 term by 1/√2 and multiply the resulting matrix by an overall scale factor of √(2/N) ...(?)

Package

dct.

Source

dct.lisp.

Function: idct (array)

Adapted from: http://www.mathworks.com/help/toolbox/signal/ref/idct.html

Package

dct.

Source

dct.lisp.


Appendix A Indexes


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A.1 Concepts


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A.2 Functions

Jump to:   D   F   I  
Index Entry  Section

D
dct: Public ordinary functions

F
Function, dct: Public ordinary functions
Function, idct: Public ordinary functions

I
idct: Public ordinary functions

Jump to:   D   F   I  

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A.3 Variables