Patent ID: 6556718
Filing Date: 2003-04-29
Classification: H04N

Abstract:
A method for coding video data according to a standard wherein non-Intra fields are identified among Intra fields and various coding options exist for the non-Intra fields including removal of temporal redundancy using a motion estimation algorithm and identification of predictor macroblocks providing approximation according to a prediction mode selectable among respective predicting modes of the different types of non-Intra fields, the method comprising the steps of:a) calculating a discrete cosine transform (DCT) for blocks of data of the predictor macroblocks according to a frame mode of decomposition with the blocks being composed of lines of data belonging to even lines semifield and to odd lines semifield, or in a field mode of decomposition with the blocks being composed of lines of data belonging to the same semifield; b) quantizing and coding the data resulting from the DCT carried out by blocks of data to be stored; c) computing for pixels of a current macroblock an absolute mean spread with respect to an average value (SMAp) and calculating an absolute mean spread (SMA&egr;) of a prediction error of each pixel of the current macroblock with respect to a common pixel of the predictor macroblock; d) selecting a coding option for the data of the current macroblock depending on the following conditions: {SMA&varepsilon;>SMApSMA&varepsilon;&GreaterEqual;Threshold1&AutoRightMatch;e) if at least one of the above two conditions in step d) are not satisfied, then determining whether the macroblock belongs to a field whose temporal redundancy with respect to a preceding field and/or successive field has been removed; f) if temporal redundancy has been removed, then inserting a relative predictor in a data stream together with motion vectors that characterizes the relative predictor according to a predicting mode chosen among a forward mode, a backwards mode, an interpolated mode, and a quantized prediction error; g) if temporal redundancy was not removed and the macroblock is recognized as belonging to a field containing temporal redundancy, then testing if the following conditions are met: {SMA&varepsilon;&it;â€ƒ&it;0>SMA&varepsilon;SMA&varepsilon;&it;â€ƒ&it;0&GreaterEqual;Threshold2&AutoRightMatch;where SMA&egr;0 is the absolute mean spread of the prediction error by using as a predictor of the current macroblock the macroblock identified by a null motion vector;h) if both the above conditions step g) are met, then motion compensation is carried out by inserting the relative predictor in the data stream together with the motion vectors that characterize the relative predictor according to a predicting mode chosen between a forward mode or a dual prime mode and a quantized prediction error; i) if the above conditions in step g) are not met, then motion compensation is not effected by inserting the prediction error when using as a predictor of the current macroblock the macroblock identified by the null motion vector in the data stream together with a null motion vector; j) calculating a complexity index of the single blocks of decomposition of the current macroblock according to a field mode and to a frame mode of the Intra type or of the error macroblock if the current macroblock is the non-Intra type, as a maximum value of a maximum absolute difference between any two adjacent pixels on a same line and on a same column of the block, and summing the maximum absolute differences of all the blocks defining a total complexity index of the relative macroblock; and k) identifying a minimum value of the complexity index for the same macroblock calculated in a frame mode and in a field mode, and calculating the DCT in the decomposition mode for which the minimum value of complexity index has been identified.