Koninklijke Philips Corporation N.V.

Daniel Snook

Jean Gobert

Fran&ccedil;oise Groliere

Françoise Groliere

Marc Drieux

The present invention relates to an encoding method processing video object planes (VOPs) of I, P or B type and including a dynamic allocation of said VOPs. According to said method, for each input frame a preliminary forward motion estimation is carried out between current and previous frames. Current and previous motion fields are then used to evaluate a coherence factor, expressed as connected to the sums of local differences within current and previous motion field. According to the value of the coherence factor with respect to an empirically determined threshold, a decision is finally taken on the type of the frame to be coded.

Video encoding method

The MPEG-4 standard describes four prediction modes: a direct prediction mode, a bidirectional prediction mode, a forward prediction mode, and a backward prediction mode. These modes may be used for the encoding of a block on the basis of a past reference frame and a future reference frame. Thus, for the encoding of a given block, the invention provides an advantageous strategy leading to the choice of a well adapted prediction mode among the four possible ones. The proposed strategy works in favor of the direct mode and gives criteria to be satisfied when using this particular prediction mode.

Video encoding-method

In the Improved PB-frames mode, one of the options of the H.263&plus; Recommendation, a macroblock of a B-frame may be encoded according to a forward, a backward or a bidirectional prediction mode. The invention relates to a method of encoding a sequence of pictures defining a strategy for the choice of a prediction mode among the three possible ones in the encoding of B-macroblock. This strategy is based upon SAD(Sum of Absolute Difference) calculations and motion vectors coherence and allows to use backward prediction when scene cuts occur. In the proposed strategy, the SAD of the bidirectional prediction is not necessarily derived when the motion is non linear allowing less calculation and reduction in CPU burden. The invention also relates to an encoding system for carrying out said method and including a computer-readable medium storing instructions that allow the implementation of this method.

Low bit rate video coding method and system

In the Improved PB-frames mode, one of the options of the H.263&plus; Recommendation, a macroblock of a B-frame may be encoded according to a forward, a backward or a bidirectional prediction mode. The invention relates to a method of encoding a sequence of pictures defining a strategy for the choice of a prediction mode among the three possible ones in the encoding of B-macroblock. This strategy is based upon SAD(Sum of Absolute Difference) calculations and motion vectors coherence and allows to use backward prediction when scene cuts occur. The calculations are here performed on original pictures allowing less calculation and reduction in CPU burden. The invention also relates to an encoding system for carrying out said method and including a computer-readable medium storing instructions that allow the implementation of this method.

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Paris, France

Daniel Snook