Abstract: A method is provided of coding a video sequence as a video stream having a base layer and one or more refinement layers destined for users having different user profiles. A visual object is coded in at least one of the refinement layers codes, which is distinct from visual objects coded in the base layer or in another of the refinement layers. The visual object corresponds to semantic content destined specifically for the users of one of the profiles.

Abstract: In order to detect a fade in a sequence of images, a luminance level is calculated for each of the images of a window (termed a detection window) that is N consecutive images in length, and for the image preceding the detection window. A difference of luminance level between the luminance level of the current image and the luminance level of the image preceding the current image is calculated. This is done for each of the N images of the detection window. The presence of a fade for the detection window is deduced if, for at least k images of the detection window, the difference of luminance level is greater than a predefined threshold, with 2<=k<=N.

Abstract: The invention relates to a method for detecting a fade in a sequence of images which comprises the following steps: calculating, for each of the images of a window N consecutive images in length, termed the detection window, and for the image preceding the detection window, a luminance level on the basis of the luminance values associated with each of the pixels of each of the images; calculating, for each of the N images of the detection window, a difference of luminance level between the luminance level of the current image and the luminance level of the image preceding the current image; and deducing therefrom the presence of a fade for the detection window if, for at least k images of the detection window, said difference of luminance level is greater that a predefined threshold, with 2?k?N.

Abstract: A method is provided of coding a video sequence as a video stream having a base layer and one or more refinement layers destined for users having different user profiles. A visual object is coded in at least one of the refinement layers codes, which is distinct from visual objects coded in the base layer or in another of the refinement layers. The visual object corresponds to semantic content destined specifically for the users of one of the profiles.

Abstract: The invention relates to a device for coding video frame sequences, comprising means (1) for measuring the spatial activity of the video frames to be coded, means (1) for measuring the temporal activity of the video frames to be coded, means (2) for coding the frames as a frame structure or as a field structure. According to the invention, the means (2) for coding the frames as a frame structure or as a field structure are able to choose the field or frame structure dynamically as a function of the measurements of spatial and temporal activity of the said frame.

Abstract: The invention relates to a method for detecting a fade in a sequence of images which comprises the following steps: calculating, for each of the images of a window N consecutive images in length, termed the detection window, and for the image preceding the detection window, a luminance level on the basis of the luminance values associated with each of the pixels of each of the images; calculating, for each of the N images of the detection window, a difference of luminance level between the luminance level of the current image and the luminance level of the image preceding the current image; and deducing therefrom the presence of a fade for the detection window if, for at least k images of the detection window, said difference of luminance level is greater that a predefined threshold, with 2?k?N.

Abstract: A device and a method for coding video images by motion compensation. The device incorporates a coding unit and a filtering unit. A calculation unit for calculating a recursivity coefficient as a function of an estimated noise level and a prediction error, a measurement unit for measuring the intra-image correlation and the inter-image correlation, a selection unit for selecting a type of coding applied to the current input image as a function at least of the measurements of the inter-image correlation and of the measurements of the intra-image correlation and as a function of the estimated noise level, a coding unit for coding the current input image as a function of the type of coding selected.

Abstract: The invention relates to a device for coding video frame sequences, comprising means (1) for measuring the spatial activity of the video frames to be coded, means (1) for measuring the temporal activity of the video frames to be coded, means (2) for coding the frames as a frame structure or as a field structure. According to the invention, the means (2) for coding the frames as a frame structure or as a field structure are able to choose the field or frame structure dynamically as a function of the measurements of spatial and temporal activity of the said frame.

Abstract: The invention relates to a device and a method for coding video images by motion compensation. The device according to the invention incorporates incorporated means of coding and means of filtering. It comprises means of calculation of a recursivity coefficient as a function of an estimated noise level and of a prediction error, means of measurement of the intra-image correlation and of the inter-image correlation, means of selection of a type of coding applied to the current input image as a function at least of the measurements of the inter-image correlation and of the measurements of the intra-image correlation and as a function of the estimated noise level means of coding of the current input image as a function of the type of coding selected.

Abstract: The invention relates to a process for coding digital data of a video sequence for its transmission and a variable bit rate. It is characterized in that the bit rate regulation in respect of the image at the instant n is performed as a function of a bit rate prediction in respect of the transmission channel for the instant n+&tgr;, &tgr; being a constant time between the instant of storage of an image in the buffer of the coder and the instant of output of this image from the buffer of the decoder.

Abstract: A block based signal compression system, as for example for coding video signal, and employing quantization of codewords or transform coefficients includes circuitry for adaptively controlling the quantization. Adaptivity of quantization is made a function of several parameters. One parameter is coding cost or bandwidth, wherein coding cost is generated on a macroblock basis but averaged over a window of macroblocks centered on a macroblock currently to be quantized. Another parameter is block or macroblock motion attributes, wherein block motion attribut values are used to modify the quantizing function.