System stream creating apparatus which adjusts system clock reference based on total number of pictures to be stored and decoded during certain time period

Abstract

A system stream creating apparatus including: a stream data transfer unit for extracting a piece of picture data having a size of a payload from the video stream data and storing it into a fixed-length pack; a header data generating unit for writing a system clock reference (SCR) in a pack header; a condition judging unit for judging, when the SCR is written, whether a difference between (1) a total number of pieces of picture data to be stored in the video decoder buffer up to the SCR and (2) a total number of pieces of picture data to be decoded by the decoding apparatus up to a unit time before the SCR has reached a predetermined value; and a-stop/resume control unit for, when the judgement is positive, causing the header data generating unit not to write the SCR and causing the stream data transfer unit to stop storing the piece of video stream data, and after having done these, causing a time updating unit to update the SCR then causing the condition judging unit to judge, and when the judgement is negative, causing the header data generating unit to write the SCR and causing the stream data transfer unit to resume storing the piece of video stream data.

What is claimed is:  
     
         1 . A system stream creating apparatus for creating a system stream, the system stream being a sequence of fixed-length packs, each pack storing a piece of video stream data, the video stream data being a sequence of picture data, the system stream creating apparatus comprising: 
 a stream data transfer unit operable to extract a piece of picture data having a size of a payload from the video stream data and store the piece of picture data into a fixed-length pack;    a header data generating unit operable to write a specified time in a header of the pack storing the piece of picture data, the specified time indicating a time when the piece of picture data of the pack is to be input to a video decoder buffer of a decoding apparatus;    a condition judging unit operable to judge, when the header data generating unit writes the specified time, whether a difference between (1) a total number of pieces of picture data to be stored in the video decoder buffer up to the specified time and (2) a total number of pieces of picture data to be decoded by the decoding apparatus up to a unit time before the specified time has reached a predetermined value;    a time updating unit operable to update the specified time; and    a stop/resume control unit operable to, when the condition judging unit judges that the difference has reached the predetermined value, cause the header data generating unit not to write the specified time and cause the stream data transfer unit to stop storing the piece of video stream data, and when having caused the header data generating unit not to write and having caused the stream data transfer unit to stop storing, cause the time updating unit to update the specified time and cause the condition judging unit to judge whether the difference calculated using the updated specified time has reached the predetermined value, and when the condition judging unit makes the judgement negatively, cause the header data generating unit to write the specified time and cause the stream data transfer unit to resume storing the piece of video stream data.    
     
     
         2 . The system stream creating apparatus of  claim 1 , wherein 
 the decoding apparatus decodes one piece of picture data every video frame cycle,    the unit time is one second, and    the predetermined value is lower than a result of a division of one second by one video frame cycle.    
     
     
         3 . A recorder system comprising: 
 the system stream creating apparatus of  claim 2;  and    a recording apparatus which records a system stream generated by the system stream creating apparatus onto a record medium.    
     
     
         4 . The recorder system of  claim 3  further comprising: 
 a reading apparatus which reads the system stream from the record medium; and  
 a decoding apparatus which decodes the system stream read by the reading apparatus.  
 
     
     
         5 . A system stream creating apparatus for creating a system stream, the system stream being a sequence of fixed-length packs, each pack storing a piece of video stream data, the video stream data being a sequence of picture data, the system stream creating apparatus comprising: 
 a stream data transfer unit operable to extract a piece of picture data having a size of a payload from the video stream data stored in a video buffer and store the piece of picture data into a fixed-length pack;    a header data generating unit operable to write a specified time in a header of the pack storing the piece of picture data, the specified time indicating a time when the piece of picture data of the pack is to be input to a video decoder buffer of a decoding apparatus;    a condition judging unit operable to judge, when a piece of picture data having a size of payload is extracted from the video buffer and stored into a fixed-length pack, whether an amount of data stored in the video buffer would be lower than or equal to a predetermined value if the piece of picture data having the size of payload were stored into the video buffer, using a model of change in the amount of data stored in the video buffer, the model being made on an assumption that picture data is input to the video buffer every certain time and a piece of picture data included in each pack is output from the video buffer at a specified time written in a header of each pack;    a time updating unit operable to update the specified time; and    a stop/resume control unit operable to, when the condition judging unit judges that the amount of data would be lower than or equal to the predetermined value, cause the header data generating unit not to write the specified time and cause the stream data transfer unit to stop storing the piece of picture data, and when having caused the header data generating unit not to write and having caused the stream data transfer unit to stop storing, cause the time updating unit to update the specified time and cause the condition judging unit to judge whether the amount of data stored in the video buffer would be lower than or equal to the predetermined value, and when the condition judging unit judges that the amount of data would exceed the predetermined value, cause the header data generating unit to write the specified time and cause the stream data transfer unit to resume storing the piece of picture data.    
     
     
         6 . The system stream creating apparatus of  claim 5 , wherein the certain time is a video frame cycle or a slice cycle.  
     
     
         7 . The system stream creating apparatus of  claim 6  further comprising: 
 a picture number judging unit operable to judge, when the stream data transfer unit stores a next piece of picture data into the pack, whether a total number of pieces of picture data in the pack has reached a predetermined number; and  
 a transfer control unit operable to, when the picture number judging unit has judged positively, cause the stream data transfer unit to stop storing the next piece of picture data and store dummy data into the pack.  
 
     
     
         8 . The system stream creating apparatus of  claim 7 , wherein 
 the transfer control unit causes the stream data transfer unit to store the next piece of picture data into another pack.    
     
     
         9 . The system stream creating apparatus of  claim 8  further comprising: 
 a video encoding unit operable to generate picture data by compressing a video signal when the picture number judging unit has judged negatively, and generating as many next start codes as correspond to remaining space of the pack as the dummy data when the picture number judging unit has judged positively, wherein  
 the stream data transfer unit stores either the picture data or the next start codes generated by the video encoding unit into the pack.  
 
     
     
         10 . A system stream creating apparatus for creating a system stream, the system stream being a sequence of fixed-length packs the system stream creating apparatus comprising: 
 a video encoding unit operable to generate picture data and when having generated a last piece of picture data of a GOP, generate as many next start codes as correspond to remaining space of a pack which stores the last piece of picture data; and    a stream data transfer unit operable to store either the picture data or the next start codes generated by the video encoding unit into a fixed-length pack.    
     
     
         11 . A system stream creating apparatus for creating a system stream, the system stream being a sequence of fixed-length packs, each pack storing a piece of either video stream data or audio stream data, the video stream data being a sequence of picture data, the audio stream data being a sequence of audio frames, the system stream creating apparatus comprising: 
 a stream data transfer unit operable to extract either a piece of picture data having a size of a payload from the video stream data or an audio frame from the audio stream data and store the extracted picture data or audio frame into a fixed-length pack; and    a transfer control unit operable to control the stream data transfer unit so that a group of audio frames provided through a plurality of channels and having the same presentation time in common are stored in a group of packs which have been generated successively.    
     
     
         12 . The system stream creating apparatus of  claim 11  further comprising: 
 a header data generating unit operable to write a specified time into a header of a pack, the specified time indicating a time when either a piece of picture data or an audio frame included in the pack is to be input to a decoding apparatus, wherein  
 when a difference between a presentation time of the audio frame and the specified time written in the header of the pack, is lower than a certain value, the transfer control unit causes the stream data transfer unit to store the audio frame into the pack.  
 
     
     
         13 . A system stream creating method for creating a system stream, the system stream being a sequence of fixed-length packs, each pack storing a piece of video stream data, the video stream data being a sequence of picture data, the system stream creating method comprising: 
 a stream data transfer step for extracting a piece of picture data having a size of a payload from the video stream data and storing the piece of picture data into a fixed-length pack;    a condition judging step for judging, when a specified time, which indicates a time when the piece of picture data stored in a pack is to be input to a video decoder buffer of a decoding apparatus, is written in a header of the pack storing the piece of picture data, whether a difference between (1) a total number of pieces of picture data to be stored in the video decoder buffer up to the specified time and (2) a total number of pieces of picture data to be decoded by the decoding apparatus up to a unit time before the specified time has reached a predetermined value;    a specified time writing step for writing the specified time into the pack storing the piece of picture data when it is judged in the condition judging step that the difference has not reached the predetermined value; and    a specified time adjusting step for, when it is judged in the condition judging step that the difference has reached the predetermined value, updating the specified time, judging whether a difference between (1) a total number of pieces of picture data to be stored in the video decoder buffer up to the updated specified time and (2) a total number of pieces of picture data to be decoded by the decoding apparatus up to a unit time before the updated specified time has reached the predetermined value, and when the judgement is made negatively, writing the updated specified time into the pack storing the piece of picture data.    
     
     
         14 . A system stream creating method for creating a system stream, the system stream being a sequence of fixed-length packs, each pack storing a piece of video stream data, the video stream data being a sequence of picture data, the system stream creating method comprising: 
 a condition judging step for judging, when a piece of picture data having a size of payload is extracted from the video stream data in a video buffer and stored into a fixed-length pack, whether an amount of data stored in the video buffer would be lower than or equal to a predetermined value if the piece of picture data having the size of payload were stored into the video buffer, using a model of change in the amount of data stored in the video buffer, the model being made on an assumption that picture data is input to the video buffer every certain time and a piece of picture data included in each pack is output from the video buffer at a specified time written in a header of each pack;    a pack generation adjustment step for, when the condition judging step judges that the amount of data would exceed the predetermined value, updating a time when the piece of picture data is to be input to a video decoder buffer of a decoding apparatus and judging whether the amount of data stored in the video buffer would be lower than or equal to the predetermined value;    a pack generation step for, when either the condition judging step or the pack generation adjustment step judges that the amount of data would be lower than or equal to the predetermined value, storing the piece of picture data into the pack, and writing a specified time into a header of the pack storing the piece of picture data based on a time when the piece of picture data is extracted from the video buffer, the specified time indicating a time when the piece of picture data is to be input to the video decoder buffer.    
     
     
         15 . A system stream creating method for creating a system stream, the system stream being a sequence of fixed-length packs, each pack storing a piece of video stream data, the video stream data being a sequence of picture data, the system stream creating method comprising: 
 a video encoding step for generating picture data, and when having generated a last piece of picture data of a GOP, generating as many next start codes as correspond to remaining space of a pack which stores the last piece of picture data; and    a stream data transfer step for storing either the picture data or the next start codes generated by the video encoding unit into a fixed-length pack.    
     
     
         16 . A system stream creating method for creating a system stream, the system stream being a sequence of fixed-length packs, each pack storing a piece of either video stream data or audio stream data, the video stream data being a sequence of picture data, the audio stream data being a sequence of audio frames, the system stream creating method comprising: 
 a header data generating step for writing a specified time into a header of a pack, the specified time indicating a time when a piece of picture data or an audio frame included in the pack is to be input to a decoding apparatus;    a condition judging step for judging whether a difference between a presentation time of the audio frame and the specified time written in the header of the pack is lower than a certain value; and    a stream data transfer step for extracting an audio frame from the audio stream data and storing the extracted audio frame into the pack when the condition judging step makes a positive judgement, and for extracting a piece of picture data having a size of a payload from the video stream data and storing the extracted picture data into the pack when the condition judging step makes a negative judgement.    
     
     
         17 . A computer-readable record medium recording a program for creating a system stream, the system stream being a sequence of fixed-length packs, each pack storing a piece of video stream data, the video stream data being a sequence- of picture data, the program comprising: 
 a stream data transfer step for extracting a piece of picture data having a size of a payload from the video stream data and storing the piece of picture data into a fixed-length pack;    a condition judging step for judging, when a specified time, which indicates a time when the piece of picture data stored in a pack is to be input to a video decoder buffer of a decoding apparatus, is written in a header of the pack storing the piece of picture data, whether a difference between (1) a total number of pieces of picture data to be stored in the video decoder buffer up to the specified time and (2) a total number of pieces of picture data to be decoded by the decoding apparatus up to a unit time before the specified time has reached a predetermined value;    a specified time writing step for writing the specified time into the pack storing the piece of picture data when it is judged in the condition judging step that the difference has not reached the predetermined value; and    a specified time adjusting step for, when it is judged in the condition judging step that the difference has reached the predetermined value, updating the specified time, judging whether a difference between (1) a total number of pieces of picture data to be stored in the video decoder buffer up to the updated specified time and (2) a total number of pieces of picture data to be decoded by the decoding apparatus up to a unit time before the updated specified time has reached the predetermined value, and when the judgement is made negatively, writing the updated specified time into the pack storing the piece of picture data.    
     
     
         18 . A computer-readable record medium recording a program for creating a system stream, the system stream being a sequence of fixed-length packs, each pack storing a piece of video stream data, the video stream data being a sequence of picture data, the program comprising: 
 a condition judging step for judging, when a piece of picture data having a size of payload is extracted from the video stream data in a video buffer and stored into a fixed-length pack, whether an amount of data stored in the video buffer would be lower than or equal to a predetermined value if the piece of picture data having the size of payload were stored into the video buffer, using a model of change in the amount of data stored in the video buffer, the model being made on an assumption that picture data is input to the video buffer every certain time and a piece of picture data included in each pack is output from the video buffer at a specified time written in a header of each pack;    a pack generation adjustment step for, when the condition judging step judges that the amount of data would exceed the predetermined value, updating a time when the piece of picture data is to be input to a video decoder buffer of a decoding apparatus and judging whether the amount of data stored in the video buffer would be lower than or equal to the predetermined value;    a pack generation step for, when either the condition judging step or the pack generation adjustment step judges that the amount of data would be lower than or equal to the predetermined value, storing the piece of picture data into the pack, and writing a specified time into a header of the pack storing the piece of picture data based on a time when the piece of picture data is extracted from the video buffer, the specified time indicating a time when the piece of picture data is to be input to the video decoder buffer.    
     
     
         19 . A computer-readable record medium recording a program for creating a system stream, the system stream being a sequence of fixed-length packs, each pack storing a piece of video stream data, the video stream data being a sequence of picture data, the program comprising: 
 a video encoding step for generating picture data, and when having generated a last piece of picture data of a GOP, generating as many next start codes as correspond to remaining space of a pack which stores the last piece of picture data; and    a stream data transfer step for storing either the picture data or the next start codes generated by the video encoding unit into a fixed-length pack.    
     
     
         20 . A computer-readable record medium recording a program for creating a system stream, the system stream being a sequence of fixed-length packs, each pack storing a piece of either video stream data or audio stream data, the video stream data being a sequence of picture data, the audio stream data being a sequence of audio frames, the program comprising: 
 a header data generating step for writing a specified time into a header of a pack, the specified time indicating a time when a piece of picture data or an audio frame included in the pack is to be input to a decoding apparatus;    a condition judging step for judging whether a difference between a presentation time of the audio frame and the specified time written in the header of the pack is lower than a certain value; and    a stream data transfer step for extracting an audio frame from the audio stream data and storing the extracted audio frame into the pack when the condition judging step makes a positive judgement, and for extracting a piece of picture data having a size of a payload from the video stream data and storing the extracted picture data into the pack when the condition judging step makes a negative judgement.