Method and apparatus for selecting image data to skip when encoding digital video

DETAILED DESCRIPTION A block and frame skipping technique decides which image regions, blocks or frames in a video frame or series of frames should be skipped.
Many of the blocks in a given video frame are very similar to blocks in previous frames and after motion compensation the pixel energy remaining in the blocks is very small.
As a result, either few or no bits are generated when encoding these low energy blocks.
Block skipping detects in advance which of the regions in a video frame will not produce any bits, so that the encoder can skip the encoding process for these blocks.
The energy threshold is dynamically adapted for every image frame according to the energy in the frame, a number of bits available for encoding the frame and the efficiency of the encoder.
The block skipping technique uses an iterative procedure to determine the optimal energy threshold.
Block skipping repeatedly discards the image block with the lowest energy and then recomputes the energy threshold.
The process is repeated until the energy threshold is less than that of the block with lowest energy among the remaining nondiscarded blocks.
The threshold at this point is referred to as the optimal energy threshold.
All image blocks whose pixel energy is below the optimal energy threshold are skipped.
Frame skipping predicts the distortion quality of an entire frame before encoding.
If the predicted frame quality is below a distortion threshold, more bits are assigned to that frame while other frames are skipped.
Block skipping and frame skipping provide more efficient bit rate control by not allocating bits to blocks or frames that should not be encoded.
Block and frame skipping reduce up to 90 percent of the computational complexity of the DCT/quantization procedure at the encoder.
Another benefit of the invention from previous decoding techniques is that the quality of the encoded video is guaranteed not to drop below a minimum pixel signal to noise ratio (PSNR), even throughout scene changes and high-motion video frames