Abstract: A variable bitrate coding method includes an iterative process including a first analysis pass and a second prediction pass. Further, followed by a last control step for adjusting a stepsize with respect to a target bitrate. A picture re-arrangement step is also provided between the analysis and prediction steps of one iteration, in order to encode with an improved quality the picture sequence. This coding method is applicable to MPEG-2 encoders for storage media with limited capacity.

Abstract: The bit rate of a data stream having the following characteristics is modified. The data stream includes control words, each of which defines when a data portion of the data stream has to be read from an input buffer at a receiving end. An MPEG video stream has such characteristics. It is calculated, for at least one future instant in time (Tfut), within which bounds (Rmax, Rmin) the bit rate (R) of the data stream can be modified at that future instant of time, so as to cause neither underflow nor overflow of the input buffer. The bit rate is modified at a future instant in time within the bounds (Rmax, Rmin) which have been calculated for the future instant in time. This allows a fast modification of the bit rate which generally contributes to the quality of the data comprised in the data stream.

Abstract: The variable bitrate coding method according to the invention comprises an iterative process including a first analysis pass and a second prediction pass and followed by a last control step for adjusting said stepsize with respect to said target bitrate. According to the invention, a picture re-arrangement step is provided between the analysis and prediction steps of one iteration, in order to encode with an improved quality the picture sequence.

Abstract: The variable bitrate coding method according to the invention includes an iterative process including a first coding pass and a second prediction pass. The coding pass allows for a picture coding of a sequence with a constant quantization stepsize (and quality) and the prediction pass allows for a matching of the stepsize to the wanted target bitrate. After some iterations, a last step allows for a finer adjustment of said stepsize with respect to said target bitrate.

Abstract: A data compression assembly has several data-compression channels (DCC). The data-compression channels may be, for example, encoders which encode different programs in accordance with an MPEG standard. A data-compression channel comprises a data compressor (CMP) and a buffer-memory space (BUF). The data compressor compresses input data (D) so as to obtain compressed data (Dc). The buffer-memory space temporarily stores the compressed data and provides the compressed data in the form of an output data stream (DS). Indications (IND) of compressed-data quality (Q[Dc]) versus extent of compression (E[CMP]) are established for respective data-compression channels. A total output bit rate (Rtot) is partitioned over respective output data streams in dependence on these indications. The extent of compression in respective data-compression channels is controlled individually on the basis of output data stream bit rate (R) and amount of compressed data (F) stored in the buffer memory space.

Abstract: The variable bitrate coding method according to the invention comprises an iterative process including a first coding pass and a second prediction pass. The coding pass allows for a picture coding of a sequence with a constant quantization stepsize (and quality) and the prediction pass allows for a matching of the stepsize to the wanted target bitrate. After some iterations, a last step allows for a finer adjustment of said stepsize with respect to said target bitrate.

Abstract: The variable bitrate coding method according to the invention comprises an iterative process including a first analysis pass and a second prediction pass. The analysis pass allows for a picture coding of a sequence with a constant quantization stepsize (and quality) and the prediction pass allows for a matching of the stepsize to the wanted target bitrate. After some iterations, a last step allows for a finer adjustment of said stepsize with respect to said target bitrate.

Abstract: The variable bitrate coding method according to the invention comprises an iterative process including a first analysis pass and a second prediction pass. The analysis pass allows for a picture coding of a sequence with a constant quantization stepsize (and quality) and the prediction pass allows for a matching of the stepsize to the wanted target bitrate. After some iterations, a last step allows for a finer adjustment of said stepsize with respect to said target bitrate.

Abstract: The variable bitrate coding method according to the invention comprises an iterative process including a first analysis pass and a second prediction pass and followed by a last control step for adjusting said stepsize with respect to said target bitrate. According to the invention, a picture re-arrangement step is provided between the analysis and prediction steps of one iteration, in order to encode with an improved quality the picture sequence. Application: MPEG-2 encoders for storage media with limited capacity.

Abstract: A variable bitrate coding method includes an iterative process including a first analysis pass and a second prediction pass. Further, followed by a last control step for adjusting a stepsize with respect to a target bitrate. A picture re-arrangement step is also provided between the analysis and prediction steps of one iteration, in order to encode with an improved quality the picture sequence. This coding method is applicable to MPEG-2 encoders for storage media with limited capacity.

Abstract: A method for variable-length encoding of images includes a quantization step followed by a variable-length encoding step, whereafter the signals obtained are stored in a buffer memory. The quantization step used is computed on the basis of a feedback parameter, which is a decreasing function of the filling level of the buffer memory, and a feedforward parameter, which is a function of the quantity of information in the image. Advantageously, the feedforward parameter includes at least a multiplicative factor which is a decreasing function of the saturation of one of the chrominance components U or V in the current block or macroblock with respect to the rest of the image. An encoding device is also described.

Abstract: A device for encoding digital signals corresponding to images which are subdivided into blocks has a first encoding channel including a discrete cosine transform circuit. In addition to this first encoding channel the device has a second encoding channel which encodes the differences between the original coefficients present at the output of the discrete cosine transform circuit and the same coefficients after quantization and inverse quantization. This second channel encodes the differences after they are quantized with a finer quantization step than in the first encoding channel. The device further includes a prediction channel including a motion compensation stage, that uses both the inverse quantized coefficients coded in the first encoding channel and the inverse quantized coefficients coded in the second encoding channel to produce a predicted digital signal. This predicted digital signal is subtracted from the digital signal to be encoded by the device.