Stream demultiplexing device

• US 6,728,271 B1
• Filed: 08/22/2000
• Issued: 04/27/2004
• Est. Priority Date: 08/24/1999
• Status: Expired due to Term

• Current Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Kawamura, Osamu, Kajimura, Toshiyuki
• Primary Examiner(s): Patel, Ajit
• Assistant Examiner(s): Blount, Steven
• Application Number:
  US09/649,072
• Time in Patent Office: 1,344 Days
• Field of Search: 370/536, 370/389, 370/311, 370/337, 370/428, 370/429, 370/503, 370/516, 370/535, 370/538, 370/540, 370/542, 370/543, 370/544, 455/343.1, 725/151, 725/139, 725/131, 725/68, 725/100, 725/89, 380/212, 348/726
• US Class Current: 370/536
• CPC Class Codes: H04H 40/18 Arrangements characterised by circuits or components specially adapted for receiving
• CPC Class Codes: H04J 3/047 Distributors with transistors or integrated circuits
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

In a stream demultiplexing device, a synchronous clock signal is supplied to a header processing unit only when a header is being inputted and processed in the header processing unit, and supplied to a payload processing unit only when a payload is being inputted and processed in the payload processing unit. By such cutting off the synchronous clock signal supply to the header processing unit and the payload processing unit while they are not active, power consumption in the stream demultiplexing device is reduced.

Claims

1. A stream demultiplexing device for demultiplexing a plurality of elementary streams from a transport stream in which the plurality of elementary streams are time-division multiplexed, the transport stream including a plurality of transport packets that each contain a payload carrying a data portion taken from one of the plurality of elementary streams, the stream demultiplexing device comprising:

a storing unit having a plurality of storage areas each for storing a different one of the plurality of elementary streams;

a signal generating unit for generating a synchronous clock signal;

a payload processing unit for obtaining, after the stream demultiplexing device starts receiving a present transport packet, a payload of the present transport packet and transferring a data portion in the obtained payload to a storage area in the storing unit that corresponds to an elementary stream from which the data portion was taken, in accordance with the synchronous clock signal supplied from the signal generating unit; and

a first clock supply controlling unit for stopping the supply of the synchronous clock signal to the payload processing unit when the payload processing unit finishes transferring the data portion, and resuming the supply a predetermined time period after the stream demultiplexing device starts receiving a transport packet that follows the present transport packet.

2. The stream demultiplexing device of claim 1,

wherein the payload of each transport packet in the transport stream further carries an identifier identifying the elementary stream from which the data portion in the payload was taken,

wherein the payload processing unit includes:

a formatting unit for extracting the data portion from the payload of the present transport packet, after the stream demultiplexing device starts receiving the present transport packet; and

a filtering unit holding a plurality of identifiers in advance, for transferring the extracted data portion to the storing unit if an identifier in the payload of the present transport packet matches any of the plurality of identifiers, and rejecting the data portion if the identifier in the payload does not match any of the plurality of identifiers,

wherein the first clock supply controlling unit includes

a stopping unit for stopping the supply of the synchronous clock signal to the payload processing unit when the filtering unit rejects the data portion, and

wherein the first clock supply controlling unit resumes the supply which was stopped by the stopping unit, the predetermined time period after the stream demultiplexing device starts receiving the following transport packet.

3. The stream demultiplexing device of claim 1,

wherein the plurality of elementary streams include a video stream generated by encoding a video signal and an audio stream generated by encoding an audio signal, and

wherein after the video stream and the audio stream have been reconstructed in the storing unit from the data portions transferred by the payload processing unit, the video stream and the audio stream are decoded using a dedicated decoder outside the stream demultiplexing device.

4. The stream demultiplexing device of claim 1,

wherein each transport packet in the transport stream further contains a header carrying an identifier identifying the elementary stream from which the data portion in the payload was taken,

the stream demultiplexing device further comprising:

a header processing unit for obtaining, when the stream demultiplexing device starts receiving the present transport packet, a header of the present transport packet and analyzing the obtained header to determine the elementary stream from which the data portion in the payload of the present transport packet was taken, in accordance with the synchronous clock signal supplied from the signal generating unit; and

a second clock supply controlling unit for stopping the supply of the synchronous clock signal to the header processing unit when the header processing unit finishes analyzing the header, and resuming the supply when the stream demultiplexing device starts receiving the following transport packet,

wherein the payload processing unit transfers, based on the analysis by the header processing unit, the data portion in the payload of the present transport packet to the corresponding storage area in the storing unit.

5. The stream demultiplexing device of claim 4,

wherein the payload processing unit includes

a plurality of processing subunits each for processing a payload in accordance with the synchronous clock signal supplied from the signal generating unit,

wherein the header processing unit includes

a selecting unit for selecting one of the plurality of processing subunits which is to process the payload of the present transport packet, based on an identifier in the header of the present transport packet, and

wherein the first clock supply controlling unit stops the supply of the synchronous clock signal to the other processing subunits when the selecting unit selects the processing subunit, and resumes the supply when the selected processing subunit finishes transferring the data portion and the stream demultiplexing device starts receiving the following transport packet.

6. The stream demultiplexing device of claim 4,

wherein the header processing unit includes:

a reading unit for reading an identifier from the header of the present transport packet;

a holding unit for holding a predetermined tuning identifier in advance; and

a judging unit for judging whether the identifier read by the reading unit matches the tuning identifier held in the holding unit, and notifying the read identifier to the payload processing unit if the read identifier matches the tuning identifier,

wherein the first clock supply controlling unit includes

a stopping unit for stopping the supply of the synchronous clock signal to the payload processing unit when the judging unit in the header processing unit judges that the read identifier does not match the tuning identifier, and

wherein the first clock supply controlling unit resumes the supply which was stopped by the stopping unit, the predetermined time period after the stream demultiplexing device starts receiving the following transport packet.

7. The stream demultiplexing device of claim 4,

wherein the payload of each transport packet in the transport stream further carries an identifier identifying the elementary stream from which the data portion in the payload was taken,

wherein the payload processing unit includes:

a formatting unit for extracting the data portion from the payload of the present transport packet, after the stream demultiplexing device starts receiving the present transport packet; and

a filtering unit holding a plurality of identifiers in advance, for transferring the extracted data portion to the storing unit if an identifier in the payload of the present transport packet matches any of the plurality of identifiers, and rejecting the data portion if the identifier in the payload does not match any of the plurality of identifiers,

wherein the first clock supply controlling unit includes

a stopping unit for stopping the supply of the synchronous clock signal to the payload processing unit when the filtering unit rejects the data portion, and

wherein the first clock supply controlling unit resumes the supply which was stopped by the stopping unit, the predetermined time period after the stream demultiplexing device starts receiving the following transport packet.

8. The stream demultiplexing device of claim 7,

wherein the header processing unit corresponds to a stage preceding the payload processing unit,

wherein the predetermined time period is a period taken for the header processing unit to obtain and analyze a header, and

wherein the first clock supply controlling unit has a counter that starts counting in accordance with the synchronous clock signal when the stream demultiplexing device starts receiving each transport packet in the transport stream, in order to monitor a lapse of the predetermined time period.

9. The stream demultiplexing device of claim 4,

wherein stuffing data is present after each transport packet in the transport stream,

wherein the second clock supply controlling unit stops the supply of the synchronous clock signal to the header processing unit when the header processing unit finishes analyzing the header of the present transport packet, prohibits the supply while the stream demultiplexing device is receiving the payload of the present transport packet and stuffing data following the present transport packet, and resumes the supply when the stream demultiplexing device starts receiving the following transport packet, and

wherein the first clock supply controlling unit stops the supply of the synchronous clock signal to the payload processing unit when the payload processing unit finishes transferring the data portion of the present transport packet, prohibits the supply while the stream demultiplexing device is receiving the stuffing data following the present transport packet, and resumes the supply the predetermined time period after the stream demultiplexing device starts receiving the following transport packet.

10. The stream demultiplexing device of claim 9,

wherein a parity code is present after each transport packet in the transport stream,

wherein the stream demultiplexing device is connected to an error correcting device that (1) performs error correction on the transport stream using the parity code and (2) outputs to the stream demultiplexing device the corrected transport stream in which the stuffing data is present after each transport packet in place of the parity code, and

wherein the header processing unit and the payload processing unit respectively obtain the header and the payload of the present transport packet included in the corrected transport stream.

11. The stream demultiplexing device of claim 10,

wherein the error correcting device also outputs a packet start signal and a valid data signal to the stream demultiplexing device, the packet start signal showing a start of each transport packet in the corrected transport stream, and the valid data signal being active while each transport packet is being received by the stream demultiplexing device, and being inactive while the stuffing data after each transport packet is being received by the stream demultiplexing device,

the stream demultiplexing device further comprising

a stream preprocessing unit for storing part of the corrected transport stream received by the stream demultiplexing device while the valid data signal is active, into a buffer as the present transport packet,

wherein the first clock supply controlling unit and the second clock supply controlling unit specify, based on the packet start signal and the valid data signal, a time at which the stream demultiplexing device starts receiving the present transport packet, a time at which the second clock supply controlling unit resumes the supply of the synchronous clock signal to the header processing unit, and a time at which the first clock supply controlling unit resumes the supply of the synchronous clock signal to the payload processing unit, and control the supply of the synchronous clock signal to the header processing unit and the payload processing unit based on the specified times.

12. The stream demultiplexing device of claim 4,

wherein at least one of the plurality of elementary streams has been encrypted before being multiplexed in the transport stream,

wherein the header processing unit includes:

a reading unit for reading an identifier from the header of the present transport packet;

a holding unit for prestoring an identifier identifying the encrypted elementary stream; and

a judging unit for judging whether the identifier read by the reading unit matches the identifier in the holding unit,

the stream demultiplexing device further comprising;

a decrypting unit for obtaining, if the judging unit in the header processing unit judges that the read identifier matches the identifier in the holding unit, the payload of the present transport packet and decrypting the data portion in the obtained payload, in accordance with the synchronous clock signal supplied from the signal generating unit; and

a third clock supply controlling unit for stopping the supply of the synchronous clock signal to the decrypting unit when the decrypting unit finishes decrypting the data portion, and resuming the supply when the judging unit judges that an identifier in a header of the following transport packet matches the identifier in the holding unit,

wherein if the judging unit judges that the read identifier matches the identifier in the holding unit, the payload processing unit obtains the decrypted data portion generated by the decrypting unit and transfers the decrypted data portion to the storing unit, in accordance with the synchronous clock signal.

13. The stream demultiplexing device of claim 12,

wherein the decrypting unit corresponds to a stage preceding the payload processing unit and succeeding the header processing unit,

wherein the predetermined time period is a total period taken for the header processing unit to obtain and analyze a header and the decrypting unit to obtain a payload and decrypt a data portion therein, and

wherein the first clock supply controlling unit has a counter that starts counting in accordance with the synchronous clock signal when the stream demultiplexing device starts receiving each transport packet in the transport stream, in order to monitor a lapse of the predetermined time period.

14. The stream demultiplexing device of claim 13,

wherein stuffing data is present after each transport packet in the transport stream,

wherein the second clock supply controlling unit stops the supply of the synchronous clock signal to the header processing unit when the header processing unit finishes analyzing the header of the present transport packet, prohibits the supply while the stream demultiplexing device is receiving the payload of the present transport packet and stuffing data following the present transport packet, and resumes the supply when the stream demultiplexing device starts receiving the following transport packet, and

wherein the first clock supply controlling unit stops the supply of the synchronous clock signal to the payload processing unit when the payload processing unit finishes transferring the data portion of the present transport packet, prohibits the supply while the stream demultiplexing device is receiving the stuffing data following the present transport packet, and resumes the supply the predetermined time period after the stream demultiplexing device starts receiving the following transport packet.

15. The stream demultiplexing device of claim 14,

wherein a parity code is present after each transport packet in the transport stream,

wherein the stream demultiplexing device is connected to an error correcting device that (1) performs error correction on the transport stream using the parity code and (2) outputs to the stream demultiplexing device the corrected transport stream in which the stuffing data is present after each transport packet in place of the parity code, and

wherein the header processing unit and the payload processing unit respectively obtain the header and the payload of the present transport packet included in the corrected transport stream.

16. The stream demultiplexing device of claim 15,

wherein the error correcting device also outputs a packet start signal and a valid data signal to the stream demultiplexing device, the packet start signal showing a start of each transport packet in the corrected transport stream, and the valid data signal being active while each transport packet is being received by the stream demultiplexing device, and being inactive while the stuffing data after each transport packet is being received by the stream demultiplexing device,

the stream demultiplexing device further comprising

a stream preprocessing unit for storing part of the corrected transport stream received by the stream demultiplexing device while the valid data signal is active, into a buffer as the present transport packet,

wherein the first clock supply controlling unit and the second clock supply controlling unit specify, based on the packet start signal and the valid data signal, a time at which the stream demultiplexing device starts receiving the present transport packet, a time at which the second clock supply controlling unit resumes the supply of the synchronous clock signal to the header processing unit, and a time at which the first clock supply controlling unit resumes the supply of the synchronous clock signal to the payload processing unit, and control the supply of the synchronous clock signal to the header processing unit and the payload processing unit based on the specified times.

17. A stream demultiplexing device for demultiplexing a plurality of elementary streams from a transport stream in which the plurality of elementary streams are time-division multiplexed, the transport stream including a plurality of transport packets that each contain:

a payload carrying a data portion taken from one of the plurality of elementary streams; and

a header carrying an identifier identifying the elementary stream from which the data portion was taken, the stream demultiplexing device comprising;

a storing unit having a plurality of storage areas each for storing a different one of the plurality of elementary streams;

a signal generating unit for generating a synchronous clock signal;

a header processing unit for obtaining, when the stream demultiplexing device starts receiving a present transport packet, a header of the present transport packet and analyzing the obtained header to determine an elementary stream from which a data portion in a payload of the present transport packet was taken, in accordance with the synchronous clock signal supplied from the signal generating unit;

a payload processing unit for obtaining, after the stream demultiplexing device starts receiving the present transport packet, the payload of the present transport packet and transferring the data portion in the obtained payload to a storage area in the storing unit that corresponds to the elementary stream determined by the header processing unit, in accordance with the synchronous clock signal supplied from the signal generating unit;

a first clock supply controlling unit for stopping the supply of the synchronous clock signal to the payload processing unit when the payload processing unit finishes transferring the data portion, and resuming the supply a predetermined time period after the stream demultiplexing device starts receiving a transport packet that follows the present transport packet; and

a second clock supply controlling unit for stopping the supply of the synchronous clock signal to the header processing unit when the header processing unit finishes analyzing the header, and resuming the supply when the stream demultiplexing device starts receiving the following transport packet.

18. The stream demultiplexing device of claim 17,

wherein the header processing unit includes:

a reading unit for reading an identifier from the header of the present transport packet;

a holding unit for holding a predetermined tuning identifier in advance; and

a judging unit for judging whether the identifier read by the reading unit matches the tuning identifier held in the holding unit, and notifying the read identifier to the payload processing unit if the read identifier matches the tuning identifier,

wherein the first clock supply controlling unit includes

a stopping unit for stopping the supply of the synchronous clock signal to the payload processing unit when the judging unit in the header processing unit judges that the read identifier does not match the tuning identifier, and

wherein the first clock supply controlling unit resumes the supply which was stopped by the stopping unit, the predetermined time period after the stream demultiplexing device starts receiving the following transport packet.

19. The stream demultiplexing device of claim 17,

wherein the payload of each transport packet in the transport stream further carries an identifier identifying the elementary stream from which the data portion in the payload was taken,

wherein the payload processing unit includes:

a formatting unit for extracting the data portion from the payload of the present transport packet, after the stream demultiplexing device starts receiving the present transport packet; and

a filtering unit holding a plurality of identifiers in advance, for transferring the extracted data portion to the storing unit if an identifier in the payload of the present transport packet matches any of the plurality of identifiers, and rejecting the data portion if the identifier in the payload does not match any of the plurality of identifiers,

wherein the first clock supply controlling unit includes

a stopping unit for stopping the supply of the synchronous clock signal to the payload processing unit when the filtering unit rejects the data portion, and

wherein the first clock supply controlling unit resumes the supply which was stopped by the stopping unit, the predetermined time period after the stream demultiplexing device starts receiving the following transport packet.

20. The stream demultiplexing device of claim 19,

wherein the header processing unit corresponds to a stage preceding the payload processing unit,

wherein the predetermined time period is a period taken for the header processing unit to obtain and analyze a header, and

wherein the first clock supply controlling unit has a counter that starts counting in accordance with the synchronous clock signal when the stream demultiplexing device starts receiving each transport packet in the transport stream, in order to monitor a lapse of the predetermined time period.

21. A stream demultiplexing device for demultiplexing a plurality of elementary streams from a transport stream in which the plurality of elementary streams are time-division multiplexed, the transport stream including a plurality of transport packets that each contain:

a payload carrying a data portion taken from one of the plurality of elementary streams; and

a header carrying an identifier identifying the elementary stream from which the data portion was taken, wherein at least one of the plurality of elementary streams has been encrypted before being multiplexed in the transport stream, the stream demultiplexing device comprising;

a storing unit having a plurality of storage areas each for storing a different one of the plurality of elementary streams;

a signal generating unit for generating a synchronous clock signal;

a header processing unit for obtaining, when the stream demultiplexing device starts receiving a present transport packet, a header of the present transport packet and analyzing the obtained header to determine an elementary stream from which a data portion in a payload of the present transport packet was taken; and

a payload processing unit for obtaining, after the stream demultiplexing device starts receiving the present transport packet, the payload of the present transport packet and transferring the data portion in the obtained payload to a storage area in the storing unit that corresponds to the elementary stream determined by the header processing unit,

wherein the header processing unit includes;

a reading unit for reading an identifier from the header of the present transport packet;

a holding unit for prestoring an identifier identifying the encrypted elementary stream; and

a judging unit for judging whether the identifier read by the reading unit matches the identifier in the holding unit,

the stream demultiplexing device further comprising;

a decrypting unit for obtaining, if the judging unit in the header processing unit judges that the read identifier matches the identifier in the holding unit, the payload of the present transport packet and decrypting the data portion in the obtained payload, in accordance with the synchronous clock signal supplied from the signal generating unit; and

a clock supply controlling unit for stopping the supply of the synchronous clock signal to the decrypting unit when the decrypting unit finishes decrypting the data portion, and resuming the supply when the judging unit judges that an identifier in a header of a transport packet that follows the present transport packet matches the identifier in the holding unit,

wherein if the judging unit judges that the read identifier matches the identifier in the holding unit, the payload processing unit obtains the decrypted data portion generated by the decrypting unit and transfers the decrypted data portion to the storing unit.

22. A stream demultiplexing device for demultiplexing a plurality of elementary streams from a transport stream in which the plurality of elementary streams are time-division multiplexed, the transport stream including a plurality of transport packets that each contain:

a payload carrying a data portion taken from one of the plurality of elementary streams; and

a header carrying an identifier identifying the elementary stream from which the data portion was taken, the stream demultiplexing device comprising;

a storing unit having a plurality of storage areas each for storing a different one of the plurality of elementary streams;

a signal generating unit for generating a synchronous clock signal;

a payload processing unit for obtaining, after the stream demultiplexing device starts receiving a present transport packet, a payload of the present transport packet and transferring a data portion in the obtained payload to a storage area in the storing unit that corresponds to an elementary stream from which the data portion was taken,

wherein the payload processing unit includes

a plurality of processing subunits each for processing a payload in accordance with the synchronous clock signal supplied from the signal generating unit,

the stream demultiplexing device further comprising;

a header processing unit for selecting one of the plurality of processing subunits which is to process the payload of the present transport packet, based on an identifier in a header of the present transport packet; and

a clock supply controlling unit for stopping the supply of the synchronous clock signal to the other processing subunits when the header processing unit selects the processing subunit, and resuming the supply when the selected processing subunit finishes transferring the data portion of the present transport packet and the stream demultiplexing device starts receiving a transport packet that follows the present transport packet.