Koninklijke Philips Corporation N.v.

U.S. Philips Corporation

Etienne Fert

Daniel Kaiser

Nicolas Bailleul

Pierre Gautier

Myriam Grandchamp

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.

Variable bitrate video coding method and corresponding video coder

Bit-rate modification

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.

Data compression assembly having several data-compression channels

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.

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.

Method of variable-length encoding of images and device for performing

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.

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Paris, France

Etienne Fert