Abstract: The present invention concerns a method for transcoding a N bits word into a M bits word with M<N. The invention is applicable in various fields and more particularly in the display field. The method comprises the following steps: -breaking down the N bits word into an exponent part and a mantissa part having each a size which varies according to the value of said N bits word, the size of the mantissa part increasing with the value of said N bits word, and -encoding the exponent part of the N bits word into a variable number of bits A and removing, if need be, least significant bits of the mantissa part in order to obtain a mantissa with a variable number of bits B, with A+B=M.

Abstract: The gravity centred coding shall be improved with respect to false contour effect disturbances on plasma display panels for example. Therefore, there is provided a GCC code (gravity center coding) and a motion amplitude of a picture or a part of a picture. Furthermore, there is provided at least one sub-set code of the GCC code. The video data are coded with the GCC code or the at least one sub-set code depending on the motion amplitude. Thus, it is possible to reduce the number of coding levels if the motion increases. A further improvement can be obtained by using texture information for selecting the GCC code.

Abstract: The present invention is particularly useful in the field of plasma display panels (PDPs) or other display devices wherein each video level is represented by a combination of bits according to a specific coding. In this case, when the algorithms used to improve picture quality are based on data stored in memories such as look-up tables (LUTs), the size of such tables may be quite huge. To improve picture quality in PDPs, an algorithm using metacode LUTs has been developed, using data stored in look-up tables. The invention proposes a way to reduce the amount of look-up tables needed for implementing metacodes. According to the invention, only some look-up tables of low size are stored and the other ones are achieved by extrapolation.

Abstract: Overheating while enabling a full flexibility in the display usage should be avoided. This object is solved by a method for avoiding the overheating of a driver circuit in a plasma display panel wherein the driver circuit receives serially display data in form of a sequence of sub-field data bits and forwards parallelly the display data in the form of data blocks each consisting of a predefined number of sub-field data bits, the method comprising the steps of counting sub-field data bits the value of which differs from that of a neighbouring or preceding sub-field data bit and providing a respective counting signal indicative of heat contributions of sub-field data bits and, if said counting signal is above a pregiven threshold, taking countermeasures for reducing said temperature.

Abstract: The invention relates to a method and apparatus for processing video pictures, in particular for large area flicker effect and false contour effect reduction. This method concerns a new coding called Parallel Peak Coding. The general idea of the Parallel Peak Code is to have almost always the same energy in two packets of light and to encode the code words for these two packets differently so that changes in sub-field code word will not appear in the two packet code words simultaneously.

Abstract: Response fidelity problems appear for some specific video levels at PDP borders. The reason is that some cells at the border of the PDP panel are not completely closed and pollute when switched ON neighbouring cells being OFF. Therefore, it is suggested to encode the video levels in the border area in a specific way. Especially, for critical sub-fields within the code it is forbidden to insert a binary 0 between two binary 1. Thus, the neighbourhood of critical sub-fields being ON and OFF is avoided. Preferably, the specific border coding is performed under the control of an average power management and codewords being not used are recreated by dithering.

Abstract: The invention relates to a method for processing video pictures data for display on a display device having a plurality of luminous elements corresponding to the pixels of a video picture. The invention is related to every kind of display devices based on the principle of duty cycle modulation (pulse width modulation) of light emission and comprising a data driver. The aim of this method is to reduce the data driver overheating by optimizing the dithering of the pixel values of the video pictures. According to the invention, the pixel values used for dithering are chosen for reducing the state changes between successive bits of subfield code words of adjacent luminous elements.

Abstract: A picture quality when reducing the brightness or the contrast of the picture on a plasma panel shall be improved. For this purpose there is provided a driving apparatus including brightness/contrast control means for receiving video input data for modifying the video levels of the video input data in accordance with external adjustment data and for outputting modified video data. First power measurement means measure a power level of the modified video data and supply a first power level. Second power measurement means measure a power level of the video input data and supply a second power level. Generator means generate a third power level comprised between the first power level and the second power level or equal to the larger one to data processing means. The data processing means calculate the maximum number of sustain pulses per frame applicable to the modified video data on the basis of the third power level and control the display of the modified video data on the plasma display panel.

Abstract: The luminous elements of the three colours red, green and blue of a plasma video display have different time responses. Therefore, a coloured trail/edge appears behind and in front of the edges of a moving object. In order to reduce the disturbing character of such coloured trails/edges, correcting the video data for blue and red phosphor elements to compensate for the different time responses discolor them. Then only a discolored trail/edge appears which is less disturbing.

Abstract: The invention relates to a new method for power level control of a display device and an apparatus for carrying out the method. Classically, the contrast/brightness control and the power management (based on an average power level control) are made independently. These two controls can be contradictory. According to the invention, the power level mode and more particularly the number of sustain pulses within the video frame is selected as a function of the average power level (APL) of the picture to be displayed and the picture control signal representing the desired contrast and/or brightness value.

Abstract: The invention concerns a video processing for improving the picture quality of picture which are displayed on display devices like plasma display panels and all kind of display devices based on the principle of duty cycle modulation of light emission and for reducing the average power dissipation. The basic idea behind the invention is to generate only the required amount of sustain pulses that effectively produce light and to avoid generating unnecessary sustain pulses. To this end, the video range of the input video is increased in order to be equal to a nominal range, 255 in the case of a 8-bit coding, and a power level mode with a reduced number of sustain pulses is selected to keep constant the brightness of the image. The number of sustain pulses that do not produce light is reduced.

Abstract: The invention relates to a method for power level control of a display device and an apparatus for carrying out the method. Classically, a power level mode defining a subfield organization to be used for subfield coding is selected as a function of the average power level of the picture to be displayed for keeping constant the power consumption of the display device. According to the invention, it is proposed to select the power level mode as a function of the input frame frequency in such a way as to have as little as possible deviations from nominal peak white and full white values at the same time that an overloading of the panel power supply is prevented. More particularly, the number of sustain pulses within the video frame and selected by the power level mode is modified as a function of the input frame frequency.

Abstract: The invention relates to a method and a device for encoding the luminance value of a pixel of a picture into a subfield code word in a display device. It can be applied to every display device using a PWM (Pulse Width Modulation) technology and subfields for displaying video picture. It can be used to compensate for any luminance problem that can be estimated. The general idea of the recursive coding is to encode one sub-field after the other in order to be able to compensate for problems occurring on one sub-field with the other sub-fields. More particularly, the bits of a subfield code word are computed recursively one after the other such that the defects (e.g. line load and/or linearity) in the light emission or luminance generated by a bit of the subfield code word can be compensated by the following bits of the subfield code word.

Abstract: The present invention relates to a coding method intended to improve the performance of GCC coding based on the temporal centre of gravity of displayed video codes. According to the invention, the number of video levels that can be selected in order to implement the GCC coding is increased by increasing the number of subfields in the video level display frame. This increase in the number of subfields is made possible by simultaneously addressing the cells of at least two adjacent rows of the PDP during at least two subfields of the video image display frame.

Abstract: The invention relates to a method for processing video data to be displayed on a display device having a plurality of luminous elements corresponding to the pixels of a video picture, wherein an error diffusion step is applied to at least a part of said video data to refine the grey scale portrayal of said video picture, said error diffusion step comprising, for each current pixel of said part of video picture, a step of truncating the value of the corresponding video data and a step of diffusing the truncation error to at least one neighboring pixel. According to the invention, a noise is inserted on the error before and/or after its diffusion to the neighbouring cells. Owing to this principle no static pattern should be visible, improving the overall picture quality.

Abstract: The present invention relates to a method and an apparatus for processing video pictures especially for dynamic false contour effect and dithering noise compensation. The main idea of this invention is to divide the picture to be displayed in areas of at least two types, for example low video gradient areas and high video gradient areas, to allocate a different set of GCC (for Gravity Center Coding) code words to each type of area, the set allocated to a type of area being dedicated to reduce false contours and dithering noise in the area of this type, and to encode the video levels of each area of the picture to be displayed with the allocated set of GCC code words. In this manner, the reduction of false contour effects and dithering noise in the picture is optimized area by area.

Abstract: A method for processing video data for display on a display device having a plurality of luminous elements comprising: applying a dithering function based on single ones of said luminous elements to at least part of said video data to refine the grey scale portrayal of video pictures of said video data, computing at least one motion vector from said video data, and changing at least one of the phase amplitude, spatial resolution and temporal resolution of said dithering function in accordance with said at least one motion vector when applying the dithering function to said video data.

Abstract: The invention relates to a method for optimizing brightness in a display device having a plurality of luminous elements corresponding to the pixels of a picture, wherein the time duration of a video frame or video field is divided into a plurality of sub fields during which the luminous elements can be activated for light emission with sustain pulses corresponding to a sub field code word which is used for brightness control, the total number of sustain pulses being determined in view of a selected power mode function of picture load the method including the following steps: setting a threshold value in relation to the picture load, comparing, for a frame, the number of the current sustain pulse to said threshold value, if the number of the current sustain pulses is below the threshold value, the sustain pulses are generated at a fixed frequency, if the number of the current sustain pulses is above the threshold value, the sustain pulses are generated at an evolving frequency.

Abstract: The present invention relates to a method for processing video pictures for display on a display device comprising a plurality of lines constituted by luminous elements called cells corresponding to the pixels of a picture, wherein the time duration of a video frame is divided into a plurality of sub-field periods during which the cells can be activated for light emission, a sub-field period being divided into an addressing period wherein the plurality of lines is scanned line by line, a sustaining period and an erasing period, wherein, in the addressing period, the addressing time is different from one line to an other. The invention is mainly used in PDP technology.

Abstract: The invention relates to a method for driving a display panel comprising a matrix array of cells which could be “ON” or “OFF”, wherein, to display an image, a video frame is divided into N sub-fields, each sub-field comprising at least an addressing period and a sustaining period, the addressing period being constituted either by a selective writing period or a selective erasing period and the duration of the sustaining period corresponding to the weight associated with said sub-field. According to the invention, the sub-fields successively alternate between a sub-field with a selective writing period and a sub-field with an erasing period. The invention is applicable to PDPs.