Image signal recording and reproducing system with use of bandwidth compression coding

Abstract

A recording and reproducing system for digitizing the image signal and compression coding the signal by in-field and inter-field, or in-frame and inter-frame coding, wherein the inter-field or inter-frame coding is used as the primary coding method, in field or in-frame coding is applied at a regular interval, and when scene changes are detected, in-field or in-frame coding is mandatorily applied to the field or frame immediately after the scene change. Furthermore, a new in-field or in-frame coding cycle is started at the field or frame immediately after the scene change to absorb the increased information resulting from in-field or in-frame coding by increasing the compression ratio of the inter-field or inter-frame coding means within the period to the next in-field or in-frame coded field or frame. The generation of additional information is further reduced and the increase in information produced by the field or frame immediately after the scene change is absorbed by a data substitution, specifically by absorbing the increase in information generated by the field or frame immediately after the scene change by using the same data as that of the immediately preceding field or frame for the field or frame immediately before or after the scene change.

What is claimed is:  
     
       1. A signal processing system comprising: 
       (1) a coding means for digitizing an image signal and coding the digitized image signal in units of a predetermined data length, said coding means comprising an intra-unit coding means for coding the digitized image signal in said units of said predetermined data length  of each unit using only the digitized image signal contained in said each unit and an inter-unit coding means for coding the digitized image signal over two successive units  of each unit using the digitized image signals contained in plural units including said each unit; and  
       (2) a scene change detection means for detecting scene changes,  
       wherein said coding means performs coding for the digitized image signal by said intra-unit coding means at a cycle having a length equal to a predetermined number of said units of said predetermined data length, while coding a remaining digitized image signal by said inter-unit coding means, and also mandatorily performs coding, by said intra-unit coding means, for a unit immediately after a scene change, when said scene change is detected by said scene change detection means, and  
       wherein a compression ratio of said inter-unit coding means is increased during one cycle of said intra-unit coding means corresponding to the detected scene change, thereby absorbing an increase of information due to the mandatory coding by said intra-unit coding means.  
     
     
       2. The signal processing system according to claim  1  wherein a new cycle of said intra-unit coding means is started from a unit immediately after the scene change is detected. 
     
     
       3. The signal processing system according to claim  1  wherein an indication code is added to the unit immediately after the scene change is discriminate it from other units coded during said cycle. 
     
     
       4. The signal processing system according to claim  2  wherein an indication code is added to the unit immediately after the scene change to discriminate it from other units coded during said cycle. 
     
     
       5. A signal processing system comprising: 
       (1) a coding means for digitizing an image signal and coding the digitized image signal in units of a predetermined data length, said coding means comprising an intra-unit coding means for coding the digitized image signal in said units of said predetermined data length  of each unit using only the digitized image signal contained in said each unit and an inter-unit coding means for coding the digitized image signal over two successive units  of each unit using the digitized image signals contained in plural units including said each unit; and  
       (2) a scene change detection means for detecting scene changes,  
       wherein said coding means performs coding for the digitized image signal by said intra-unit coding means at a cycle having a length equal to a predetermined number of said units of said predetermined data length, while coding a remaining digitized image signal by said inter-unit coding means, and also mandatorily performs coding, by said intra-unit coding means, for a unit immediately after a scene change, when said scene change is detected by said scene change detection means, and  
       wherein coding for at least one unit related to the unit immediately after the scene change is performed using data of a unit immediately preceding said at least one unit, thereby suppressing an increase of information due to the mandatory coding by said intra-unit coding means.