Information processing apparatus and decoding control method

Abstract

Moving image stream data recorded on a recording medium includes title key managing data formed of sets of pointer information items indicating respective encipher data sections, and title keys decoding the respective encipher data sections indicated by the pointer information items. A playback apparatus stores the title key managing data recorded on the recording medium in a storage section. The playback apparatus detects change of the pointer information item included in the moving image stream data read from the recording medium. If the pointer information item has been changed, the playback apparatus obtains a title key corresponding to the pointer information item after change from the storage section, and executes decoding of the input moving image stream data by using the obtained title key.

1 . An information processing apparatus decoding a stream formed of at least one title, each title including a pointer information item indicating a type of the title and an encipher data section to be decoded by a decoding key corresponding to the pointer information item, comprising: 
 a storing unit which stores decoding key managing data formed of sets of pointer information items included in the input stream and decoding keys corresponding to the pointer information items;    a comparing unit which extracts a pointer information item included in the input stream, and compares the extracted pointer information item with a previously extracted pointer information item; and    a decoding unit which obtains a decoding key corresponding to the pointer information item included in the input stream from the stored decoding key managing data, and decodes an encipher data section included in the stream by using the obtained decoding key when the comparing unit determines that the extracted pointer information item is different from the previously extracted pointer information item, the decoding unit decoding the encipher data section included in the stream by using the obtained decoding key when the comparing unit determines that the extracted pointer information item agrees with the previously extracted pointer information item.    
   
   
       2 . An information processing apparatus according to  claim 1 , wherein 
 the pointer information items included in the decoding key managing data include all the pointer information items included in the input stream and all the decoding keys corresponding to the pointer information items.    
   
   
       3 . An information processing apparatus according to  claim 1 , wherein 
 the storing unit reads the decoding key managing data included in the input stream before executing the decoding means, and stores the read decoding key managing data.    
   
   
       4 . An information processing apparatus according to  claim 1 , further comprising: 
 a storage medium selectively provided in the information processing apparatus,    wherein the storing unit stores the decoding key managing data included in the input stream in the storage medium, and    the decoding unit obtains a decoding key corresponding to the pointer information item included in the input stream from the decoding key managing data stored in the storage medium, and decoding an encipher data section included in the stream by using the obtained decoding key in response to a condition that the extracted pointer information item is different from the previously extracted pointer information item, and decoding the encipher data section included in the stream by using the obtained decoding key in response to a condition that the extracted pointer information item agrees with the previously extracted pointer information item.    
   
   
       5 . An information processing apparatus according to  claim 1 , wherein 
 the decoding unit obtains a decoding key corresponding to the pointer information item included in the input stream from the stored decoding key managing data, and decoding an encipher data section included in the stream by using the obtained decoding key in place of a decoding key previously obtained, in response to a condition that the extracted pointer information item is different from the previously extracted pointer information item, and decoding the encipher data section included in the stream by using the decoding key previously obtained, in response to a condition that the extracted pointer information item agrees with the previously extracted pointer information item.    
   
   
       6 . A control method for decoding applied to an information processing apparatus decoding a stream formed of at least one title, each title including a pointer information item indicating a type of the title and an encipher data section to be decoded by a decoding key corresponding to the pointer information item, comprising: 
 storing decoding key managing data formed of sets of pointer information items included in the input stream and decoding keys corresponding to the pointer information items;    extracting an pointer information item included in the input stream, and comparing the extracted pointer information item with a previously extracted pointer information item; and    obtaining a decoding key corresponding to the pointer information item included in the input stream from the stored decoding key managing data, and decoding an encipher data section included in the stream by using the obtained decoding key when it is determined by the comparing that the extracted pointer information item is different from the previously extracted pointer information item, and decoding the encipher data section included in the stream by using the obtained decoding key when it is determined by the comparing that the extracted pointer information item agrees with the previously extracted pointer information item.    
   
   
       7 . A control method for decoding according to  claim 6 , wherein 
 the pointer information items included in the decoding key managing data include all the pointer information items included in the input stream and all the decoding keys corresponding to the pointer information items.    
   
   
       8 . A control method for decoding according to  claim 6 , wherein 
 the storing includes reading the decoding key managing data included in the input stream before executing the decoding, and storing the read decoding key managing data.    
   
   
       9 . A control method for decoding according to  claim 6 , wherein 
 the storing includes storing the decoding key managing data included in the input stream in a storage medium in the information processing apparatus, and    the decoding includes obtaining a decoding key corresponding to the pointer information item included in the input stream from the decoding key managing data stored in the storage medium, and decoding an encipher data section included in the stream by using the obtained decoding key in response to a condition that the extracted pointer information item is different from the previously extracted pointer information item, and decoding the encipher data section included in the stream by using the obtained decoding key in response to a condition that the extracted pointer information item agrees with the previously extracted pointer information item.    
   
   
       10 . A control method for decoding according to  claim 6 , wherein 
 the decoding includes obtaining a decoding key corresponding to the pointer information item included in the input stream from the stored decoding key managing data, and decoding an encipher data section included in the stream by using the obtained decoding key in place of a decoding key previously obtained, in response to a condition that the extracted pointer information item is different from the previously extracted pointer information item, and decoding the encipher data section included in the stream by using the decoding key previously obtained, in response to a condition that the extracted pointer information item agrees with the previously extracted pointer information item.