DCT

DCT may refer to:

Biology

Computing and technology

Entertainment

Mathematics

Warships

Dct (File Format)

Introduction

A proprietary variable codec audio file format designed for dictation by NCH Software. It has dictation header information and can be encrypted (often required by medical confidentiality laws). A free dct player, Express Scribe Transcription is provided.

List of codecs supported in dct files.

Comments

The above are wave files - even if they have the mp3 codec they will have the ".wav" or ".dct" extension.

Discrete cosine transform

A discrete cosine transform (DCT) expresses a finite sequence of data points in terms of a sum of cosine functions oscillating at different frequencies. DCTs are important to numerous applications in science and engineering, from lossy compression of audio (e.g. MP3) and images (e.g. JPEG) (where small high-frequency components can be discarded), to spectral methods for the numerical solution of partial differential equations. The use of cosine rather than sine functions is critical for compression, since it turns out (as described below) that fewer cosine functions are needed to approximate a typical signal, whereas for differential equations the cosines express a particular choice of boundary conditions.

In particular, a DCT is a Fourier-related transform similar to the discrete Fourier transform (DFT), but using only real numbers. DCTs are equivalent to DFTs of roughly twice the length, operating on real data with even symmetry (since the Fourier transform of a real and even function is real and even), where in some variants the input and/or output data are shifted by half a sample. There are eight standard DCT variants, of which four are common.