Video encoding-method
AssigneeKoninklijke Philips Electronics N.V.
InventorDaniel Snook
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Abstract
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.
Claims4
A method of encoding a sequence of pictures, each picture being partitioned into non-overlapping blocks of pixels, the method comprising, for a block (Y) belonging to a picture (P1) to be encoded on the basis of a past reference frame (P0) and a future reference frame (P2), hereafter referred to as a block to be encoded, at least the steps of:
- deriving for a block (Z) in the future reference frame with the same location as the block to be encoded, an optimum motion vector (MV) on the basis of the past reference frame and a corresponding optimum prediction block (X) in the past reference frame;
- deriving the sum of absolute difference between the block in said future reference frame with the same location as the block to be encoded and the optimum prediction block in the past reference frame, hereafter referred to as SADref;
- deriving for the block to be encoded, a forward motion vector (MVf) on the basis of the optimum motion vector and a corresponding forward prediction block (W) in the past reference frame
- deriving the sum of absolute difference between the block to be encoded and the forward prediction block, hereafter referred to as SADf;
- deriving for the block to be encoded, a backward motion vector (MVb) on the basis of the optimum motion vector and a corresponding backward prediction block (V) in the future reference frame;
- deriving the sum of absolute differences between the block to be encoded and the backward prediction block, hereafter referred to as SADb;
- encoding the block to be encoded according to a direct prediction mode if one of the following conditions is satisfied:
- the spatial coordinates of the optimum motion vector are within a given range (I);
- the deviation of SADref towards SADb is smaller than a given threshold;
- the deviation of SADref towards SADf is smaller than a given threshold.
Dependencies are inferred from the claim text.