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modified discrete cosine transformation (MDCT)

The Modified Discrete Cosine Transformation

(MDCT) is a modified DCT transformation and works with an overlap of 50 % in the time-frequency conversion. The overlap of 50 % means that the reproduced signal

deviates from the original signal during a transformation from the frequency to the time domain and a reverse transformation from the time to thefrequency domain. Only by partially taking into account the previous and subsequent blocks is reproduction possible and the artifacts of the codec

are eliminated. The MDCT transformation is used in Advanced Audio Coding (AAC), among other applications, where it works with two different block lengths. The long blocks are based on 2,048 samples, the short ones on 256 samples. This technique achieves a higher frequency and time resolution in AAC compression compared to MP3.

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Englisch: modified discrete cosine transformation - MDCT
Updated at: 23.06.2019
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