Embedding and extracting supplemental data in an information signal

Abstract

A method and an arrangement are disclosed for embedding supplemental data in an information signal such as a sigma-delta modulated audio signal. The encoded signal includes two or more channels, e.g. a left channel bit stream (z 1 ) and a right channel bit stream (z 2 ). The same supplemental data (w) is accommodated at corresponding predetermined bit positions, e.g. every M th bit position, of the bit streams. This allows detection and extraction of the supplemental data without the need for accommodating a sync pattern in the signal. At the receiving end, a sequence of M th bits from the first channel is compared with a corresponding sequence of M th bits from the second channel. If they are identical, the sequence is a candidate supplemental data sequence. This is done for different sequence positions (m) until the supplemental data has been found.

1 . A method of embedding supplemental data (W) in an information signal (z), comprising the step of embedding ( 3 , 4 ) supplemental data samples (w) at predetermined positions of said information signal, characterized in that the information signal comprises at least two signal channels (z 1 ,z 2 ), the method including the step of embedding the same supplemental data samples (w) at corresponding positions of said channels.  
     
     
         2 . A method as claimed in  claim 1 , wherein the channels are the left and right audio signal components of a stereo audio signal, the method comprising the steps of encoding ( 1 , 2 ) each channel (x 1 ,x 2 ) into a respective bit stream (y 1 ,y 2 ) and embedding ( 3 , 4 ) the same supplemental data bits (w) at corresponding bit positions of said bit streams.  
     
     
         3 . An arrangement for embedding supplemental data in an information signal comprising means ( 3 , 4 ) for embedding supplemental data samples (w) at predetermined positions of said information signal, characterized in that the information signal comprises at least two signal channels (z 1 ,z 2 ), said embedding means ( 3 , 4 ) being arranged to embed the same supplemental data samples (w) at corresponding positions of said channels.  
     
     
         4 . An arrangement as claimed in  claim 3 , wherein the channels are the left and right audio signal components of a stereo audio signal, the arrangement comprising means ( 1 , 2 ) for encoding each channel (x 1 ,x 2 ) into a respective bit stream (y 1 ,y 2 ) and embedding ( 3 , 4 ) the same supplemental data bits (w) at corresponding bit positions of said bit streams.  
     
     
         5 . A method of extracting supplemental data from an information signal comprising at least a first (z 1 ) and a second (z 2 ) channel each having identical supplemental data samples (w) embedded at predetermined signal sample positions, the method comprising the steps of: 
 comparing ( 52 ;  62 ) a first sequence of predetermined first channel signal samples spaced apart by said number (M) of signal samples with a corresponding second sequence of second channel signal samples, and    displacing ( 51 ;  65 ) said first and second sequence by one sample position, and repeating said comparison step for said displaced first and second sequence as long as the sequences are not identical.    
     
     
         6 . A method as claimed in  claim 5 , further comprising the step of storing ( 53 ;  63 ) the signal data samples that are identical in the sequences being compared.  
     
     
         7 . An arrangement for extracting supplemental data from an information signal comprising at least a first (z 1 ) and a second (z 2 ) channel each having identical supplemental data samples (w) embedded at predetermined corresponding signal sample positions, the arrangement comprising: 
 means ( 52 ;  62 ) for comparing a first sequence of predetermined first channel signal samples with a corresponding second sequence of second channel signal samples, and    means ( 51 ;  65 ) for displacing said first and second sequence by one sample position, and repeating said comparison step for said displaced first and second sequence as long as the sequences are not identical.    
     
     
         8 . An information signal having embedded supplemental data samples at predetermined positions of the signal, characterized in that the information signal comprises at least two channels and that the same supplemental data samples have been embedded at corresponding positions of said channels.  
     
     
         9 . A signal as claimed in  claim 3 , wherein the channels are the left and right audio signal components of a stereo audio signal, each component being encoded into a respective bit stream and the same supplemental data bits being embedded at predetermined bit positions of said bit streams.  
     
     
         10 . A storage medium having recorded thereon a signal as claimed in  claim 8  or  9 .