Abstract: An encoder that encodes a current block in a picture includes circuitry and memory. Using the memory, the circuitry: performs a first transform on a residual signal of the current block using a first transform basis to generate first transform coefficients; and performs a second transform on the first transform coefficients using a second transform basis to generate second transform coefficients and quantizes the second transform coefficients, when the first transform basis is the same as a predetermined transform basis; and quantizes the first transform coefficients without performing the second transform, when the first transform basis is different from the predetermined transform basis.

Abstract: An encoder that encodes a current block in a picture includes circuitry and memory. Using the memory, the circuitry: determines whether to use intra prediction for the current block; and when determining to use intra prediction, (i) performs a first transform on a residual signal of the current block using a first transform basis to generate first transform coefficients; and (ii-1) performs a second transform on the first transform coefficients using a second transform basis to generate second transform coefficients and quantizes the second transform coefficients, when an intra prediction mode of the current block is a predetermined mode or when the first transform basis is same as a predetermined transform basis; and (ii-2) quantizes the first transform coefficients without performing the second transform when the intra prediction mode is different from the predetermined mode and the first transform basis is different from the predetermined transform basis.

Abstract: When intra prediction is to be used, an encoder determines whether an adaptive basis selection mode is to be used and whether a size of the current block matches a determined size. When the adaptive basis selection mode is to be used and the size matches the determined size, the encoder fixes the first transform basis for the current block to a first determined transform basis in the adaptive basis selection mode, and generates first transform coefficients by performing first transform of residual signals of the current block using the first determined transform basis; quantizes the first transform coefficients when an intra prediction mode for the current block is a determined mode; and generates second transform coefficients by performing second transform of the first transform coefficients using a second transform basis, and quantizes the second transform coefficients, when the intra prediction mode is not the determined mode.

Abstract: An encoder which encodes a current block of a picture includes a processor and memory. Using the memory, the processor: determines whether intra prediction is to be used for the current block; and when it is determined that intra prediction is to be used for the current block, generates first transform coefficients by performing first transform of residual signals of the current block using a first transform basis; quantizes the first transform coefficients when an intra prediction mode for the current block is a determined mode and the first transform basis is different from a determined transform basis; and generates second transform coefficients by performing second transform of the first transform coefficients using a second transform basis, and quantizes the second transform coefficients, when the intra prediction mode for the current block is not the determined mode or when the first transform basis matches the determined transform basis.

Abstract: An encoder includes circuitry and memory. Using the memory, the circuitry: generates a reconstructed image by encoding and decoding an original image; performs, on a current block included in the reconstructed image, filter processing that is applied to all pixels in the current block, when an edge intensity of the current block is lower than a threshold; and skips the filter processing on the current block when the edge intensity of the current block is higher than the threshold.

Abstract: An encoder which encodes a current block to be encoded in an image includes: a determiner which (i) determines which one of intra processing and inter processing is applied to the current block, and (ii) when the intra processing is applied to the current block, determines whether an intra prediction mode for the current block is a non-directional prediction mode; and a frequency transformer which transforms the current block using a first transform basis when the intra prediction mode for the current block is the non-directional prediction mode, and transforms the current block using a second transform basis when the intra prediction mode for the current block is not the non-directional prediction mode. The first transform basis is a predefined fixed basis or a basis determined based on a coding parameter.

Abstract: An encoder which performs frequency transform on a current block to be encoded in an image includes: a size determiner which determines whether or not the current block has a size smaller than or equal to a threshold size; a basis selector which selects a basis for the current block from among a plurality of frequency transform bases when the current block has a size larger than the threshold size; and a frequency transformer which (i) transforms the current block using a fixed frequency transform basis when the current block has a size smaller than or equal to the threshold size and (ii) transforms the current block using a basis selected by the basis selector when the current block has a size larger than the threshold size.

Abstract: Provided is a communication device which can easily provide a function to enable signal cross-reference among a plurality of voice signals having different frequency ranges and to enhance the quality of voice communications, at a low cost. In the communication device, a band expansion unit (104) expands a narrow band voice signal to a broad frequency range voice signal; a gain control unit (105) controls a gain of a downstream voice signal using an upstream voice signal as a reference signal; an echo canceler (109) cancels an echo component contained in the upstream voice signal using the downstream voice signal as a reference signal; a down-sampling unit (111) generates a narrow band reference signal by performing a band conversion to convert a broad band voice signal to a narrow band voice signal; and an up-sampling unit (112) generates a broadband reference signal by performing band conversion to convert a narrow band voice signal to a broadband voice signal.