Stmicroelectronics S.r.l.

Microelectronics S.r.l.

Maria Luisa Sacchi

Danilo Pietro Pau

Luca Bortot

Daniele Bagni

Mattia De Bei

Gian Antonio Mian

A method of producing an output bitstream of coded digital video data with a bit-rate different from the bit-rate of an input bitstream includes dividing the input bitstream into a sequence of coded data and a sequence of control bits. The sequence of control bits is modified as a function of the desired bit-rate of the output bitstream that is different from the bit-rate of the input bitstream. An output sequence of control bits is produced. The method further includes decoding the sequence of coded data producing an intermediate sequence of data, and quantizing with a pre-established step and coding the intermediate sequence of data producing an output sequence of coded data. The output sequences producing the output bitstream are merged with the desired bit-rate.

Method of varying the bit rate of the data stream of coded video pictures

A method for measuring the activity of a macroblock of a video picture in the direct cosine transform domain of values assumed by a selected component of the video signal includes dividing the macroblock into blocks of data in the discrete cosine transform domain before quantization, and separately storing each block of data in a memory. The method further includes reading each block of data stored in the memory for obtaining respective coefficients, and multiplying an absolute value of each coefficient by a selected mask of words comprising a number of words not exceeding a number of words forming each block. The results of the multiplications are summed for producing an activity coefficient for each block. A first activity coefficient of the macroblock is calculated corresponding to a sum of the activity coefficients produced for each block. A normalized activity value of the macroblock is calculated as the ratio between a sum of double the first activity coefficient with a mean activity coefficient relative to a preceding coded frame, and a sum of double the mean activity coefficient with the first activity coefficient.

Measurement of activity of video image by DCT and filtering of the prediction error coefficients

An algorithm based on a pre-analysis implements an efficient constant bit-rate control with a reduced requirement on a buffer memory capacity. The pre-analysis is on at least one slice (GOS) of the current whole picture, and/or on a mix of information on the pre-analysis of a slice of the preceding picture and on the actual encoding data of the preceding whole picture. The pre-analysis may be carried out by precoding the GOS with a constant reference quantizer or by entropy computation. The local control of the bit-rate is implemented by an integrative-proportional controller.

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Milan, Italy

Maria Luisa Sacchi