Combined intraframe and interframe transform coding system

A method for processing image signals to reduce the amount of data utilized to represent images where the images are defined by a sequence of frames where each frame includes a two-dimensional array of blocks where each block includes a two-dimensional array of digital signals representing the portion of an image within the block, the steps comprising,

• transforming the digital signals to transform coefficients for each block for each of a plurality frames in the sequence of frames,
• forming variable predicted transform coefficients for each block of a first frame using variable prediction factors determined for each block,
• comparing said predicted transform coefficients with corresponding transform coefficients of a corresponding block of a second frame to provide transform coefficient difference signals for each of the coefficients in each of the blocks of said second frame,
• processing said transform difference signals for each block to form processed difference signals having a controlled range of values,
• coding said processed difference signals to form statistically coded signals such that the more frequently occurring values of coded signals are represented by shorter code lengths and the less frequently occurring values of coded signals are represented by longer code lengths,
• storing said coded signals in a buffer memory.

A method for processing image signals to reduce the amount of data utilized to represent images where the images are defined by a sequence of frames where each frame includes a two-dimensional array of blocks where each block includes a two-dimensional array of digital signals representing the portion of the image within the block, the steps comprising,

• transforming the digital signals to transform coefficients for each block for each of a plurality frames in the sequence of frames,
• forming predicted transform coefficients for each block of a first frame,
• comparing said predicted transform coefficients with corresponding transform coefficients of a corresponding block of a second frame to provide transform coefficient difference signals for each of the coefficients in each of the blocks of said second frame,
• processing said transform difference signals for each block to form processed difference signals having a controlled range of values, determined by a feedback signal said processing including selecting a subset of said difference signals for each block with a selection threshold controlled by a threshold signal,
• coding said processed difference signals to form statistically coded signals such that the more frequently occurring values of coded signals are represented by shorter code lengths and the less frequently occurring values of coded signals are represented by longer code lengths,
• storing said coded signals in a buffer memory, thereby increasing the fullness of said buffer memory up to the currently filled capacity which is equal to or less than the maximum capacity of said buffer memory,
• unloading said coded signals from said buffer memory, thereby reducing the currently filled capacity of said memory,
• adaptively determining said feedback signal as a function of the difference between the currently filled capacity and the maximum capacity of said buffer memory.

An apparatus for processing image signals to reduce the amount of data utilized to represent images where the images are defined by a sequence of frames where each frame includes a two-dimensional array of digital signals representing the image, said apparatus comprising,

• means for transforming the digital signals to form transform coefficients for each of a plurality of frames in the sequence of frames,
• means for forming predicted transform coefficients for a first frame using variable prediction factors,
• means for comparing said predicted transform coefficients with corresponding transform coefficients of a second frame to provide transform coefficient difference signals for each of the coefficients of said second frame,
• means for processing said transform difference signals to form processed difference signals having a controlled range of values,
• means for coding said processed difference signals to form statistically coded signals such that the more frequently occurring values of coded signals are represented by shorter code lengths and the less frequently occurring values of coded signals are represented by longer code lengths.

A apparatus for processing image signals to reduce the amount of data utilized to represent images where the images are defined by a sequence of frames where each frame includes a two-dimensional array of blocks where each block includes a two-dimensional array of digital signals representing the portion of an image within the block, said apparatus comprising,

• means for transforming the digital signals to transform coefficients for each block for each of a plurality frames in the sequence of frames,
• means for forming variable predicted transform coefficients for each block of a first frame using variable prediction factors determined for each block,
• means for comparing said predicted transform coefficients with corresponding transform coefficients of a corresponding block of a second frame to provide transform coefficient difference signals for each of the coefficients in each of the blocks of said second frame,
• means for processing said transform difference signals for each block to form processed difference signals having a controlled range of values,
• means for coding said processed difference signals to form statistically coded signals such that the more frequently occurring values of coded signals are represented by shorter code lengths and the less frequently occurring values of coded signals are represented by longer code lengths,
• means for storing said coded signals in a buffer memory.