Image coding method and apparatus and image decoding method and apparatus

Abstract

An image coding and decoding technology for compressing motion pictures which makes use of critical point filter technology and that includes detection of scene changes to provide more accurate decoding. An image input unit acquires key frames. A scene change detector detects when there is a scene change between key frames, and notifies a matching processor to that effect. The matching processor then skips generation of correspondence data between those key frames. A stream generator generates a coded data stream in a manner that key frames and associated correspondence data are incorporated when there is no scene change, while key frames and associated correspondence disable data are incorporated when there is a scene change. This allows a decoder to more accurately decode the data stream and take account of scene changes.

1 . An image coding apparatus, comprising: 
 An image input unit, which receives key frame data comprising a plurality of key frames, wherein each key frame has an intended timing;    a scene change detector which detects when key frames bracket a scene change therebetween, wherein a key frame before the scene change is referred to as a before key frame and a key frame after the scene change is referred to as an after key frame;    a correspondence data generator which generates correspondence data for key frames;    a disable data generator which generates disable data, wherein the disable data indicates a prohibition of correspondence for the key frames which bracket a scene change; and    a stream generator which generates a data stream incorporating correspondence data for key frames which do not bracket a scene change and disable data for key frames which bracket a scene change,    wherein the before key frame is to be output a plurality of times from an intended timing of the before key frame until a predetermined change timing and the after key frame is to be output a plurality of times from the predetermined change timing until an intended timing of the after key frame.    
     
     
         2 . An image coding apparatus according to  claim 1 , wherein the disable data comprises ratio data that indicates a temporal positional relation of the scene change between the key frames which bracket the scene change and the predetermined change timing is the temporal position of the scene change.  
     
     
         3 . An image coding apparatus according to  claim 1  wherein the data stream is formed in a manner such that the correspondence data and the disable data differ in at least part of the data values thereof and thus both can be identified thereby.  
     
     
         4 . An image coding apparatus according to  claim 1 , wherein said correspondence data generator extracts critical points in respective key frames, and performs a pixel-based matching computation based on a correspondence relation between the critical points.  
     
     
         5 . An image coding apparatus according to  claim 4 , wherein said correspondence data generator further multiresolutionalizes respective key frames by extracting critical points thereof, and specifies a correspondence relation between the critical points by performing the pixel-based matching computation in sequence starting from a coarse level of multiresolution.  
     
     
         6 . An image coding apparatus according to  claim 1 , wherein said correspondence data generator computes a matching between key frames using a multiresolutional critical point filter.  
     
     
         7 . An image coding method, comprising: 
 receiving key frame data comprising a plurality of key frames, wherein each key frame has an intended timing;    detecting when two key frames bracket a scene change therebetween;    generating correspondence data for at least key frames which do not bracket a scene change; and    generating disable data indicating prohibition of correspondence for key frames which bracket a scene change;    generating a data stream incorporating correspondence data for key frames which do not bracket a scene change and disable data for key frames which bracket a scene change, wherein the before key frame is to be output a plurality of times from an intended timing of the before key frame until a predetermined change timing and the after key frame is to be output a plurality of times from the predetermined change timing until an intended timing of the after key frame.    
     
     
         8 . An image coding method according to  claim 7 , wherein the disable data comprises ratio data that indicates a temporal positional relation of the scene change between the key frames which bracket the scene change and the predetermined changetiming is the temporal position of the scene change.  
     
     
         9 . An image coding method according to  claim 7  wherein the correspondence data and the disable data are generated so that the type of data can be identified.  
     
     
         10 . An image decoding apparatus, comprising: 
 a key frame data unit which receives key frame data, wherein the key frame data comprises a plurality of key frames and each key frame has an intended timing;    a stream input unit which receives an input data stream including correspondence data for the key frames;    an intermediate image generator which generates intermediate frames between key frames, based on the correspondence data and key frame data;    a scene change detector which detects a scene change between key frames based on the input data stream, wherein a key frame that is before a scene change is referred to as a before key frame while a key frame that is after the scene change is referred to as an after key frame; and    an output unit which outputs key frames and intermediate frames wherein, when a scene change is detected, the intermediate image generator outputs the before key frame a plurality of times from the intended timing of the before key frame until a predetermined timing and outputs the after key frame a plurality of times from the predetermined timing until the intended timing of the after key frame.    
     
     
         11 . An image decoding apparatus according to  claim 10 , wherein said scene change detector detects the scene change based on the presence in the data stream of disable data, which has a different data structure than the correspondence data.  
     
     
         12 . An image decoding method according to  claim 11 , wherein the disable data comprises ratio data that indicates a temporal positional relation of the scene change between the two key frames which bracket the scene change and the predetermined timing is the temporal position of the scene change.  
     
     
         13 . An image decoding method, comprising: 
 receiving key frame data, wherein the key frame data comprises a plurality of key frames and each key frame has an intended timing;    receiving an input data stream including at least correspondence data between key frames;    generating one or more intermediate frames between key frames, based on the correspondence data and key frame data;    detecting a scene change between key frames based on the input data stream, wherein a key frame that is before a scene change is referred to as a before key frame while a key frame that is after the scene change is referred to as an after key frame; and    outputting key frames and intermediate images wherein, when a scene change is detected, the before key frame is output a plurality of times from the intended timing of the before key frame until a predetermined timing and the after key frame is output a plurality of times from the predetermined timing until the intended timing of the after key frame.    
     
     
         14 . An image decoding method according to  claim 11 , wherein the scene change is detected based on the presence in the input data stream of disable data, which has a different data structure than the correspondence data.  
     
     
         15 . An image decoding method according to  claim 14 , wherein the disable data comprises ratio data that indicates a temporal positional relation of the scene change between the key frames which bracket the scene change and the predetermined timing is the temporal position of the scene change.  
     
     
         16 . A physical computer readable medium including computer executable instructions which, when executed on a computing device, cause the computing device to perform the functions of: 
 receiving key frame data comprising a plurality of key frames, wherein each key frame has an intended timing;    detecting when two key frames bracket a scene change therebetween;    generating correspondence data for at least key frames which do not bracket a scene change; and    generating disable data indicating prohibition of correspondence for key frames which bracket a scene change;    generating a data stream incorporating correspondence data for key frames which do not bracket a scene change and disable data for key frames which bracket a scene change, wherein the before key frame is to be output a plurality of times from an intended timing of the before key frame until a predetermined change timing and the after key frame is to be output a plurality of times from the predetermined change timing until an intended timing of the after key frame.    
     
     
         17 . A physical computer readable medium including computer executable instructions which, when executed on a computing device, cause the computing device to perform the functions of: 
 receiving key frame data, wherein the key frame data comprises a plurality of key frames and each key frame has an intended timing;    receiving an input data stream including at least correspondence data between key frames;    generating one or more intermediate frames between key frames, based on the correspondence data and key frame data;    detecting a scene change between key frames based on the input data stream, wherein a key frame that is before a scene change is referred to as a before key frame while a key frame that is after the scene change is referred to as an after key frame; and    outputting key frames and intermediate images wherein, when a scene change is detected, the before key frame is output a plurality of times from the intended timing of the before key frame until a predetermined timing and the after key frame is output a plurality of times from the predetermined timing until the intended timing of the after key frame.