Video compression and encoding method
A method of compressing video data having at least one frame having at least one block and each block having an array of pixels is provided. The method transforms the pixels of each block into coefficients and creates an optimal transmission order of the coefficients. The method also optimizes the speed of processing compressed video data by partitioning the data bitstream and coding each partition independently. The method also predicts fractional pixel motion by selecting an interpolation method for each given plurality or block of pixels depending upon at least one metric related to each given block and varies the method from block to block. The method also enhances error recovery for a current frame using a frame prior to the frame immediately before the current frame as the only reference frame for lessening quality loss during data transmission. Enhanced motion vector coding is also provided.
1. A method for intra prediction for use in block based video compression/decompression algorithms comprising the steps of:
using an encoder to subdivide each image into a set of partitions;
using an encoder to provisionally encode each partition using a plurality of different prediction modes in which pixels in the current partition are predicted by previously decoded pixels within the same image from the row above and the column to the left of the current partition, said provisional encoding done by giving each pixel in the partition a predicted value using one of a plurality of equations, wherein at least one of said plurality of equations comprises the following equation:
X ij =L 1 +A j −C;
wherein i and j represent a row and column position of X ij within a partition, whereby there is a row of pixels above and a column of pixels to the left of said partition, L i is a pixel from said column to the left of said partition in a same row of X ij , A j is a pixel from said row above said partition in a same column as of X ij , C is a pixel on the intersection of the row above and column left to the partition;
using an encoder to select and encode the optimal mode for each partition using a conditional probability distribution and;
using an encoder to transmit the selected optimal mode within a bitstream.
2. The method of claim 1 , wherein the conditional probability distribution is defined by a table of constants.
3. The method of claim 1 , further comprising the step of updating the probability distribution on a per frame basis according to statistics gathered relating to the frequencies or conditional frequencies of each mode in at least one prior frame.
4. The method of claim 1 , wherein the probability distribution is a fixed baseline distribution.
5. The method of claim 1 , wherein the probability distribution is updated for an image only when the number of bits used to update the probability distribution plus the number of bits required to encode all the prediction modes within the image using the updated probability distribution is less than the number of bits required to encode all the prediction modes using either the baseline probability distribution or the unchanged probability distribution from the previous frame.
6. The method of claim 1 , wherein selecting the optimal mode for a partition is based on a metric that combines the cost of the modes with error scores of the modes, where the cost of an intra prediction mode of a partition is calculated using Shannon cost of each mode calculated by the conditional probability distribution of the intra prediction modes for the partition and the error score of the mode is calculated using the differences between the predicted pixels values and the actual pixel values for the partition.
7. The method of claim 3 , further comprising the steps of:
Multiplying the cost of each mode with a constant;
Adding the multiplied cost of each mode to the error score for the mode; and
Selecting the intra prediction mode with lowest combined score for the partition.