Inappropriate temporal speed of quantization noise is known to be the reason for the so-called pre-echo artifacts in perceptual audio coding. These artifacts occur when a transient signal is being coded in a spectral representation because the quantization noise is spread out over the entire window length of the filterbank and, in this way, is not masked by the signal. A novel approach to the pre-echo problem is presented, allowing to shape the quantization noise in time. The technique is shown to also work efficiently in the case of pitched signals (e.g., speech) where traditional block switching schemes do not offer a solution.
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