Coding and decoding methods for coding and decoding a coded data stream representing at least one image split into blocks. The method includes, for a current block, determining if the current block is coded according to an intra coding mode or another coding mode, the intra coding mode using an intra prediction mode selected from a group of intra prediction modes, according to an intra prediction mode associated with a neighbouring block of the current block. When coded according to the intra coding mode, an intra prediction mode in the group is determined for the current block, according to an intra prediction mode associated with a previously decoded block of the image. The current block is decoded according to the determined intra prediction mode associated with the current block. When coded according to the other coding mode, the current block is decoded according to the other coding mode.

A coding method and a decoding method for decoding a coded data stream representative of at least one image that is split into blocks. For at least one current block of the image, an item of information indicating a coding mode of the current block is decoded from the data stream. When the coding mode of the current block corresponds to a first coding mode, the current block is decoded using a first determined quantization step to dequantize, in the transform domain, a prediction residue associated with the current block. When the coding mode of the current block corresponds to a second coding mode, the current block is decoded using a second determined quantization step to dequantize, in the spatial domain, a prediction residue associated with the current block. The first quantization step and the second quantization step are determined according to the same quantization parameter.

A coding method and a decoding method for decoding a coded data stream representative of at least one image that is split into blocks. For at least one current block of the image, an item of information indicating a coding mode of the current block is decoded from the data stream. When the coding mode of the current block corresponds to a first coding mode, the current block is decoded using a first determined quantization step to dequantize, in the transform domain, a prediction residue associated with the current block. When the coding mode of the current block corresponds to a second coding mode, the current block is decoded using a second determined quantization step to dequantize, in the spatial domain, a prediction residue associated with the current block. The first quantization step and the second quantization step are determined according to the same quantization parameter.

An intra frame bit rate allocation method being performed by a computer device comprising at least one processor, includes when a current frame of picture is an intra frame in a specified frame sequence, pre-encoding the current frame of picture; calculating a corresponding intra frame encoding cost and an inter frame encoding cost of the pre-encoding; and allocating an intra frame bit rate according to the calculated intra frame encoding cost and the inter frame encoding cost.

A further coding efficiency increase is achieved by, in hybrid video coding, additionally predicting the residual signal of a current frame by motion-compensated prediction using a reference residual signal of a previous frame. In other words, in order to further reduce the energy of the final residual signal, i.e. the one finally transmitted, and thus increase the coding efficiency, it is proposed to additionally predict the residual signal by motion-compensated prediction using the reconstructed residual signals of previously coded frames.

A further coding efficiency increase is achieved by, in hybrid video coding, additionally predicting the residual signal of a current frame by motion-compensated prediction using a reference residual signal of a previous frame. In other words, in order to further reduce the energy of the final residual signal, i.e. the one finally transmitted, and thus increase the coding efficiency, it is proposed to additionally predict the residual signal by motion-compensated prediction using the reconstructed residual signals of previously coded frames.

A bit rate control method includes the following operations: receiving a first target bit of a video to be coded; determining a second target bit for first coding tree units (CTUs) in CTUs of the video according to the first target bit; determining a fourth target bit of at least one fourth CTU in the CTUs according to an actual bit of at least one second CTU in the CTUs and a third target bit of at least one third CTU in the CTUs, in which the at least one second CTU is completely coded, the at least one third CTU is completely coded, and a coding of the at least one fourth CTU is not started; and sequentially adjusting at least one coding parameter for coding the video according to the second target bit, the third target bit, and the fourth target bit.

Techniques for selecting a coding mode for an image coding process are described. Coding modes can be selected through a coding mode transition state machine, a re-quantization process, selection of an optimal transform size, by skipping some quantization parameters, or by performing motion search.

Techniques for selecting a coding mode for an image coding process are described. Coding modes can be selected through a coding mode transition state machine, a re-quantization process, selection of an optimal transform size, by skipping some quantization parameters, or by performing motion search.

The invention relates to a method for decoding, comprising receiving a bitstream comprising encoded image data, forming from the bitstream in a computer memory a set of reference pixels having reference pixel values for intra-picture directional prediction, predicting a pixel value in a predicted image block (P) by intra-picture directional prediction by using values of one or more selected reference pixels (410, 420) in forming a predicted a pixel value, wherein the selected reference pixels (410, 420) are selected from a prediction direction with respect to the predicted pixel, and wherein the prediction direction between the reference pixel (410) and the predicted pixel can be a wide-angle prediction direction that forms an obtuse angle with top-left direction, repeating the pixel prediction for a number of pixels to form a predicted image block, and using the predicted image block (P) in decoding an image block from the bitstream to obtain a decoded image block. A corresponding method for decoding as well as a decoder, an encoder, computer program products for the same purpose, and a signal are provided.