Idea: Remove mutual redundancy among successive pixels in a region of support (ROS) or neighborhood and encode only the new information. This method is based upon linear prediction. Let us start with 1-D linear predictors. An Nth order linear prediction of x(n) based on N previous samples is generated using a 1-D autoregressive (AR) model. … Read more
The H.264 standard uses its macroblock partitions to develop a tree-structured motion compensation algorithm. One of the problems with motion-compensated prediction has always been the selection of the size and shape of the block used for prediction. Different parts of a video scene will move at different rates in different directions or stay put. A … Read more
Motion-compensated prediction is accomplished by searching the previous picture for a block similar to the block being encoded. The enhanced reference picture selection mode allows the encoder to search more than one picture to find the best match and then use the best suited picture to perform motion-compensated prediction. Reference picture selection can be accomplished … Read more
In this mode, along with changes in the signalling of changes in quantization parameters, the quantization process is improved in several ways. In the baseline mode, both the luminanace and chrominance components in a block are quantized using the same quantizer. In the modified quantization mode, the quantizer used for the luminance coefficients is different … Read more
The variable length codes for inter and intra frames are designed with different assumptions. In the case of the inter frames it is assumed that the values of the coefficients will be small and there can be large numbers of zero values between nonzero coefficients. This is a result of prediction which, if successfully employed, … Read more
Temporal , SNR , and Spatial Scalability Mode Reference picture resampling allows a reference picture to be “warped” in order to permit the generation of better prediction. It can be used to adaptively alter the resolution of pictures during encoding Reduced – Resolution Update Mode This mode is used for encoding highly active scenes. The … Read more
Deblocking Filter Mode This mode is used to remove blocking effects from the 8×8 block edges. This smoothing of block boundaries allows for better prediction. This mode also permits the use of four motion vectors per macroblock and motion vectors that point beyond the edge of the picture Reference Picture Selection Mode This mode is … Read more
PB – frames and Improved PB – frames Mode The PB frame consists of a P picture and a B picture in the same frame. The blocks for the P frame and the B frame are interleaved so that a macroblock consists of six blocks of a P picture followed by six blocks of a … Read more
Syntax – Based Arithmetic Coding Mode In this mode the variable length codes are replaced with an arithmetic coder. The word length for the upper and lower limits is 16. The option specifies several different Cum Count tables that can be used for arithmetic coding. There are separate Cum Count tables for encoding motion vectors, … Read more
In this mode the motion vector range is extended to [−31.5, 31.5] , which is particularly useful in improving the compression performance of the algorithm for larger picture sizes. The mode also allows motion vectors to point outside the picture. This is done by repeating the edge pixels to create the picture beyond its boundary … Read more