Abstract: 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.

Abstract: A method and a transmission system for use in coding and Progressive Image Transmission (PIT), in which the transmitter at the initial stages of the transmission uses a Region Based Coding (RBC) scheme (905) in order to provide the receiver with an image of good visual quality at a high compression ratio, which the RBC is known to be able to provide. At a later stage of the transmission, when the visual quality of the RBC image is no longer superior to other compression techniques such as JPEG, the PIT switches (903) use a continuous tone compressor (907) for the further transmission, without losing the information contained in the RBC image already transmitted.