| 摘要 |
A digital image compression system, capable of supporting full motion digital video, encodes the signals within a frame and further compresses by comparison with adjacent frames to eliminate temporal redundancy. In the encoding stage, an input signal is inspected and pixels identified as one of: 1) High frequency, low intensity elements of small spatial areas (1-2 pixels) (pixels 'c'); 2) Intermediate frequency elements of low intensity, larger spatial area than 1) (pixels 'd'); 3) Low frequency, high intensity elements represented by large spatial areas (pixels 'a'); 4) Isolated high intensity areas representing boundaries such as at the edge of objects (pixels 'b'). The four types of pixel are encoded as follows: 1) As zero (or if a row of zeroes is present, by run length encoding); 2) By run length encoding (for example with 8 bits for intensity and 4 bits for duration); 3) By run length encoding; 4) By 8 bits per pixel. Temporal redundancy reduction may be effected by the apparatus of Figure 3 (not shown) where the pixels in a current (b) and preceding (a) frame memory are compared by simultaneous clocking and the coordinates of and nature of any differences are temporarily recorded (c). 1) Area marked (a) representative of large spatial dimention of high intensity : (Run length encode). 2) Area marked (b) representative of boundary areas, with small sptial dimensions and high intensity. (Encode as 8 bit intensity value). 3) Area marked (c) representative of low intensity & small spatial dimension (Encode in 1 bit as zero) 4) Area marked (d) representative of medium intensity, intermediate spatial dimension. (run length endode.) |
