Abstract: Systems and methods for controlling compression of image data by a quality controller include obtaining a desired target number of bits to be generated from compression of a current image area using a predetermined compression protocol, determining a calculated quantisation level based on the desired number of bits using a predetermined relationship between the number of bits and quantisation level, selecting a discrete quantisation level from a plurality of predetermined discrete quantisation levels based on the calculated quantisation level, determining a predicted number of bits that would result from compression of the current image area at the selected discrete quantisation level using the predetermined relationship, determining whether the predicted number of bits exceeds the desired number of bits and, if not, providing to an encoder information to enable the encoder to determine a set of compression parameters associated with the selected discrete quantisation level.

Abstract: The present invention relates to a method of decoding a video bitstream, the method comprising the steps of: receiving a bitstream representing: residual samples produced by subtracting encoder filtered motion compensated prediction samples from image samples; and motion vectors used in forming the motion compensated prediction samples; the encoder filtering process conducted on the motion compensated prediction samples at an encoder having at least one parameter; using said motion vectors to provide motion compensated prediction samples from a previously reconstructed image; decoder filtering said motion compensated prediction samples in accordance with said at least one parameter; and adding said filtered motion compensated prediction samples to said residual samples to reconstruct images. A system and apparatus corresponding to this method are also disclosed.

Abstract: The present invention relates to a method of decoding a video bitstream, the method comprising the steps of: receiving a bitstream representing: residual samples produced by subtracting encoder filtered motion compensated prediction samples from image samples; and motion vectors used in forming the motion compensated prediction samples; the encoder filtering process conducted on the motion compensated prediction samples at an encoder having at least one parameter; using said motion vectors to provide motion compensated prediction samples from a previously reconstructed image; decoder filtering said motion compensated prediction samples in accordance with said at least one parameter; and adding said filtered motion compensated prediction samples to said residual samples to reconstruct images. A system and apparatus corresponding to this method are also disclosed.

Abstract: In video coding or decoding, coding blocks in a current frame are predicted from blocks in previously encoded frames with prediction samples and associated information organised in a prediction unit. A decision on which prediction unit type to consider for coding is made upon analysis of the distribution of a sum of absolute difference or other function of the residual signal over the block.

Abstract: A video decoder has a transform mode and a transform skip mode and in the transform skip mode a residual prediction mode is selected. A compressed bit-stream is entropy-decoded to obtain a block of quantised values. An inverse quantiser operates in the transform mode to form transform coefficients and in the transform skip mode to form differential residual values. In the transform mode an inverse transform is performed to form residual values. In the transform skip mode residual prediction is used perform residual prediction using high accuracy locally decoded residual value. The residual value is then down-scaled to obtain the reconstructed residual. A block predictor is formed from decoded image values at the same precision at which video samples are stored in the frame memory.

Abstract: In video coding or decoding, coding blocks in a current frame are predicted from blocks in previously encoded frames with prediction samples and associated information organised in a prediction unit. A decision on which prediction unit type to consider for coding is made upon analysis of the distribution of a sum of absolute difference or other function of the residual signal over the block.

Abstract: For a video sequence including a composite image having a foreground image and a transparency mask, a video encoder determines whether the transparency mask is the same as a transparency mask of a preceding image. Where the transparency mask is not the same, the transparency mask is encoded as an image. The encoder then transmits the encoded foreground image, any encoded transparency mask and a flag signifying whether the encoded transparency mask for a preceding image is to be used in association with the encoded foreground image of the current image.

Abstract: For a video sequence having at least one composite image comprising a foreground and a transparency mask, a video encoder transmits the encoded foreground image and the encoded transparency mask together with a flag signifying whether or not the encoded transparency mask is to be decoded as a binary transparency mask. Clipping values may be signalled to the decoder for use in clipping of a decoded binary transparency mask.

Abstract: In video encoding, where image values are transformed to provide transform coefficients and transform coefficients are quantised to derive a compressed bitstream, an ID profile is selected at the encoder and used with a representative image intensity to scale image values in the block. The selected ID profile is signalled to the decoder with the compressed bitstream. At the decoder, the ID profile is extracted from the compressed bitstream and—after performing inverse quantisation and an inverse transform to form image values—those image values are inverse scaled.

Abstract: A video decoder has a transform mode and a transform skip mode and in the transform skip mode a residual prediction mode is selected. A compressed bit-stream is entropy-decoded to obtain a block of quantised values. An inverse quantiser operates in the transform mode to form transform coefficients and in the transform skip mode to form differential residual values. In the transform mode an inverse transform is performed to form residual values. In the transform skip mode residual prediction is used perform residual prediction using high accuracy locally decoded residual value. The residual value is then down-scaled to obtain the reconstructed residual. A block predictor is formed from decoded image values at the same precision at which video samples are stored in the frame memory.