Efficient down-scaling of dct compressed images

摘要

In a method and a device for calculation of the Discrete Cosine Transform (DCT) only the DCT coefficients representing the first half and the second half of an original sequence are required for obtaining the DCT for the entire original sequence. The device and the method are therefore very useful when calculations of DCTs of a certain length is supported by hardware and/or software, and when DCTs of other sizes are desired. Areas of application are for example still image and video transcoding, as well as scalable image and/or video coding and decoding.