A Novel Approach f IntraPrediction Mode Selection in H264在H.264幀內(nèi)預(yù)測模式選擇的新方法

1、a novel approach of intra-prediction mode selection for 4x4 in h.264(first_edition)2004.07.07 summer vacation seminarmyoung-seo kimcontents avc encoder overview introduction features luminance macroblock in a qcif frame 4x4 intra prediction example of profiling signaling i-prediction mode conclusion

2、 referencesavc encoder overviewidea issue!introduction in the upcoming h.264, intra-prediction for each 4x4 block is used to compress i-frame however, the full search algorithm to choose one of the 9 prediction modes is computationally expensive a novel approach of mode selection mode selection meth

3、od based on partial computation of the cost function ( cost16 = sad16 + 2r(qp) ), early termination and selective computation of highly probable mode using the selective search algorithm of each prediction modefeatures the basic image block unit h.264: 4x4 size mpeg-1/2/4 and h.261/3: 8x8 size some

4、advance features of h.264 4x4 integer dct intra-prediction in i-frame coding quarter-pixel motion compensation multiple reference frame and multiple block size for p-frame coding luminance macroblock in a qcif frame4x4 intra prediction (1-2) 4x4 block and its neighboring pixels 4x4 luma prediction m

5、ode4x4 intra prediction (2-2) a prediction mode is a way to generate 16 predictive pixel values (named a to p) using some or all of the neighboring pixels a to q mode 0: vertical prediction mode in which pixels a, e, i and m are predicted by a mode 1: horizontal prediction mode in which pixels a, b,

6、 c and d are predicted by i mode 2: dc prediction in which all pixels (a to p) are predicted by (a+b+c+d+i+j+k+l)/8 the other modes are similar except that the directions are differentexample of profiling prediction blocks p (4x4)signaling i-prediction mode (1-4) the choice of intra prediction mode

7、for each 4x4 block must be signaled to the decoder and this could potentially require a large number of bits to encode the prediction mode for each 4x4 block efficiently, the correlation between spatially adjacent blocks is exploited probability list! signaling i-prediction mode (2-4) for current bl

8、ock c, the encoder and decoder calculate the most probable prediction mode, the minimum of the prediction modes of a and b if either of these neighboring blocks is not available, the corresponding value a or b is set to 2 (dc prediction mode) in below figure, c is the current 4x4 block to be encoded

9、signaling i-prediction mode (3-4) the encoder sends a flag for each 4x4 block, prev_intra4x4_pred_mode if the flag is 1, the parameter most_probable_ prediction mode is used if the flag is 0, another parameter rem_intra4x4_ pred_mode is sent to indicate a change of mode rem_intra4x4_pred_mode curren

10、t most_probable_mode the prediction mode is set to rem_intra4x4_pred_mode+1signaling i-prediction mode (2-4) example blocks a and b have been predicted using mode 3 and 1 respectively. the most probable mode for block c is therefore 1 prev_intra4x4_pred_mode is set to 0 and so rem intra4x4_pred_mode

11、 is sent depending on the value of rem_intra4x4_pred_mode, one of the eight remaining prediction modes may be chosen conclusion although full search can achieve optimal prediction mode selection, its computationally expensive in fact, its a bottleneck in i-frame coding its highly desirable to develop fast intra-prediction mode selectionreferences performance comparison of the emerging h.264 video coding standard with the existing s