In previous works, the authors proposed a hierarchical bandwidth limitation technique based on the Karhunen-Lòeve Transform (KLT) to reduce the bandwidth for multichannel audio transmission. The subjective results proved that this technique could be used to reduce the overall bandwidth without significant audio quality degradation. Further study found that the transform matrix varied considerably over time for many recordings. In this paper, the KLT matrix was calculated based on short-term signals and updated adaptively over time. The perceptual effects of the adaptive KLT process were studied using a series of listening tests. The results showed that adaptive KLT resulted in better spatial quality than non-adaptive KLT but introduced some other artefacts.
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