Digital watermarking technique

Abstract

A watermarking system allowing both sufficiently high quality of watermarked moving pictures and enhanced ease of watermark detection is disclosed. A watermark level of a watermark to be embedded into a picture of data is changed depending on the picture type of a selected block of frequency component data, and then a watermark having the watermark level is inserted into the selected block of frequency component data. Therefore, a moving-picture can be effectively embedded with a digital watermark without substantially reducing the quality of image and the digital watermark can be detected reliably. A relative proportion of watermark levels of I-picture, B-picture, and P-picture is preferably set to 10:7:5.

1 - 6 : (Cancelled)  
   
   
       7 : A method for inserting a watermark into a selected block of frequency component data in a picture of data having one of a plurality of picture types, comprising the steps of: 
 a) storing a reference watermark;    b) determining a picture type of the selected block of frequency component data;    c) changing a watermark level of the reference watermark depending on the picture type of the selected block of frequency component data to produce a watermark to be used; and    d) inserting the watermark to be used into the selected block of frequency component data.    
   
   
       8 : The method according to  claim 7 , wherein the picture types are Intra-frame coding picture (hereafter, I-picture), Inter-frame Predictive coding picture (hereafter, P-picture) and Bidirectionally Predictive coding picture (hereafter, B-picture), wherein a relative proportion of watermark levels of I-picture, B-picture, and P-picture is 10:7:5.  
   
   
       9 : The method according to  claim 7 , wherein, in the step (c), the watermark level of the reference watermark is changed depending on both the picture type of the selected block of frequency component data and the selected block.  
   
   
       10 : (Cancelled)  
   
   
       11 : A system for inserting a watermark into a selected block of frequency component data in a picture of data having one of a plurality of picture types, comprising: 
 a memory storing a reference watermark;    a determiner for determining a picture type of the selected block of frequency component data;    a multiplier for multiplying a watermark level of the reference watermark by a factor varying depending on the picture type of the selected block of frequency component data to produce a watermark to be used; and    an inserting section for inserting the watermark to be used into the selected block of frequency component data.    
   
   
       12 : The system according to  claim 11 , wherein the picture types are Intra-frame coding picture (hereafter, I-picture), Inter-frame Predictive coding picture (hereafter, P-picture) and Bidirectionally Predictive coding picture (hereafter, B-picture), wherein a relative proportion of factors corresponding to I-picture, B-picture, and P-picture is 10:7:5.  
   
   
       13 : The system according to  claim 11 , wherein the multiplier multiplies a watermark level of the reference watermark by a factor varying depending on both the picture type of the selected block of frequency component data and the selected block.  
   
   
       14 - 15 : (Cancelled)  
   
   
       16 : A digital watermarking method comprising the steps of: 
 at a watermark inserting section for inserting a watermark into a selected block of frequency component data in a picture of data having one of a plurality of picture types,    storing a reference watermark;    determining a picture type of the selected block of frequency component data;    changing a watermark level of the reference watermark depending on the picture type of the selected block of frequency component data to produce a watermark to be used; and    inserting the watermark to be used into the selected block of frequency component data, and    at a watermark detecting section for detecting a watermark from a selected block of frequency component data in a picture of data having one of a plurality of picture types,    storing the reference watermark;    determining a picture type of the selected block of frequency component data;    changing a watermark level of the reference watermark depending on the picture type of the selected block of frequency component data to produce a watermark to be used;    extracting a watermark from the selected block in the picture of data;    selecting a watermark of a type depending on a picture type of the selected block; and    determining whether the stored watermark is embedded in the selected block, based on an extracted watermark with a selected watermark.    
   
   
       17 : (cancelled)  
   
   
       18 : A digital watermarking system comprising: 
 a watermark inserting device for inserting a watermark into a selected block of frequency component data in a picture of data having one of a plurality of picture types;    a watermark detecting device for detecting a from a selected block of frequency component data in of data having one of a plurality of picture types,    wherein    the watermark inserting device comprises:    a first memory storing a reference watermark;    a first determiner for determining a picture type of the selected block of frequency component data;    a first multiplier for multiplying a watermark level of the reference watermark by a factor varying depending on the picture type of the selected block of frequency component data to produce a watermark to be used; and    an inserting section for inserting the watermark to be used into the selected block of frequency component data, and    the watermark detecting device comprises:    a second memory storing the reference watermark;    a second determiner for determining a picture type of the selected block of frequency component data;    a second multiplier for multiplying a watermark level of the reference watermark by a factor varying depending on the picture type of the selected block of frequency component data to produce a watermark to be used;    an extractor for extracting a watermark from the selected block in the picture of data;    a selector for selecting a watermark of a type depending on a picture type of the selected block; and    a third determiner for determining whether the stored watermark is embedded in the selected block, based on an extracted watermark with a selected watermark.