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

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.

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.

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.

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.

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.

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.

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.