MDCT exploits inter-frame aliasing cancellation to achieve critical sampling

Evidence

The MDCT analyses the signal in half-overlapping frames; that is, for windows of N samples the hop size is N/2 samples. The frequency partials of the MDCT represent sinusoids that are odd symmetric in the first half and even symmetric in the second half of the frame, as seen in Figure 15.10. For this reason, the individual MDCT frames generate temporal aliasing, which is countered by the opposite effect of the next frame. The real-valued amplitudes of the MDCT representation determine the amplitudes of the corresponding frequency components within the frame. — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 2116

Categorization

• DEFINE: Explains MDCT’s core mechanism: half-overlap frames whose odd/even symmetry generates aliasing that the next frame cancels.