MPEG frame add/drop multiplexer with bandwidth controller

• US 6,466,592 B1
• Filed: 11/02/1998
• Issued: 10/15/2002
• Est. Priority Date: 11/02/1998
• Status: Expired due to Term

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Chapman, John T.
• Primary Examiner(s): TON, DANG T
• Application Number:
  US09/184,784
• Time in Patent Office: 1,443 Days
• Field of Search: 370/537, 370/535, 370/503, 370/507, 370/508, 370/516, 370/521, 370/477, 370/538, 370/480, 370/252, 370/254, 370/229, 370/465, 370/337, 370/351, 370/352, 375/371, 375/362, 348/426, 348/385, 348/465, 709/240, 709/247, 380/212, 380/217, 380/239, 380/269
• US Class Current: 370/537
• CPC Class Codes: H04N 21/235 Processing of additional data, e.g. scrambling of additional data or processing content descriptors
• CPC Class Codes: H04N 21/23608 Remultiplexing multiplex streams, e.g. involving modifying time stamps or remapping the packet identifiers
• CPC Class Codes: H04N 21/6118 involving cable transmission, e.g. using a cable modem
• CPC Class Codes: H04N 21/6168 involving cable transmission, e.g. using a cable modem

Abstract

An add/drop multiplexer in a cable network multiplexes data from different sources together on a common cable television channel without corrupting MPEG time stamps. An idle insertion circuit coupled to a first data source inserts, if necessary, a selectable guaranteed minimum number of idle frames into a first bit stream. If the number of naturally occurring idle frames is above the guaranteed minimum number, the idle insertion circuit does not force idle frames into the first bit stream. A multiplexer is coupled between the idle insertion circuit and a second data source and replaces data with idles in the first bit stream from the second data source. The idles inserted into the bit stream are used to control the amount of bandwidth allocated to the second data source.

Claims

1. A circuit for combining bit streams from different sources onto a common channel in a cable network, comprising:

a multiplexer having a first input receiving a first bit stream from a first data source with a selectable guaranteed minimum percentage of idles, a second input receiving data from a second source, and an output generating a multiplexed bit stream from the first and second source onto a common channel on the cable network; and

an output controller monitoring the first bit stream and enabling the multiplexer to insert data from the second source over idles detected in the first bit stream, the selectable minimum percentage of idles in the first bit stream providing the second source with a guaranteed minimum bandwidth for broadcasting data on the cable network.

2. A circuit according to claim 1 wherein the multiplexed bit stream is and formatted into MPEG frames.

3. A circuit according to claim 1 wherein the first source comprises a head end and the second source comprises an MPEG data source each broadcasting over the cable network.

4. A circuit according to claim 3 wherein the cable network includes a cable link broadcasting the multiplexed bit stream to multiple cable modems at remote subscriber locations.

5. A circuit according to claim 1 wherein the first bit stream includes MPEG time stamps, data packets and idles, the idles inserted at predetermined minimum time periods when no time stamps exist in the first bit stream or when there are no data packets are available from the first source and no time stamps exist in the first bit stream.

6. A circuit according to claim 1 including an idle insertion circuit that inserts the selectable minimum percentage of idles into the first bit stream.

7. A circuit for combining bit streams from different sources onto a common channel in a cable network, comprising:

a multiplexer having a first input receiving a first bit stream from a first data source with a selectable guaranteed minimum percentage of idles, a second input receiving data from a second source, and an output generating a multiplexed bit stream from the first and second source onto a common channel on the cable network;

an output controller monitoring the first bit stream and enabling the multiplexer to insert data from the second source over idles detected in the first bit stream, the selectable minimum percentage of idles in the first bit stream providing the second source with a guaranteed minimum bandwidth for broadcasting data on the cable network; and

an idle insertion circuit that inserts the selectable minimum percentage of idles into the first bit stream, wherein the idle insertion circuit includes the following;

an MPEG framer receiving both time stamps from a time stamp generator and data packets from a packet queue and outputting the first bit stream;

a counter circuit coupled to the MPEG framer for counting frames in the first bit stream and initiating the MPEG framer to insert a predetermined number of idles in the first bit stream; and

a masking circuit coupled between the counter and the MPEG framer preventing the MPEG framer from inserting idles when time stamps occur in t first bit stream.

8. A circuit according to claim 7 including a register for loading a selectable idle number into the counter.

9. A circuit according to claim 7 including a multiplexer coupling one of the time stamp generator and the packet queue to the framer, according to occurrences of time stamps in the first bit stream.

10. A preconditioning circuit for generating a bit stream on a cable network, comprising:

a packet queue containing data packets from a data source;

a time stamp generator generating time stamps establishing time references in the bit stream;

an idle insertion circuit coupled to both the packet queue and the time stamp generator that generates the bit stream by combining the data packets with the time stamps while guaranteeing a selectable minimum number of idle frames.

12. A preconditioning circuit according to claim 10 including the following:

a modulator for modulating the bit stream into an intermediate frequency; and

a frequency converter for converting the intermediate frequency into a cable TV channel frequency.

13. A preconditioning circuit according to claim 12 including a cable TV link coupled to the idle insertion circuit for carrying the bit stream to multiple cable modems in remote cable TV subscriber locations.

11. A preconditioning circuit for generating a bit stream on a cable network, comprising:

a packet queue containing data packets from a data source;

a time stamp generator generating time stamps establishing time references in the bit stream; and

an idle insertion circuit coupled to both the packet queue and the time stamp generator that generates the bit stream by combining the data packets with the time stamps while guaranteeing a selectable minimum number of idle frames, wherein the idle insertion circuit includes the following;

a framer coupled to both the time stamp generator and the data queue and outputting a bit stream;

a counter coupled to the framer; and

a masking circuit coupled between the counter and the framer preventing the framer from inserting the idle frames over the time stamps.

14. A preconditioning circuit according to claim 11 including the following:

a multiplexer multiplexing data packets from a second data source with the bit stream from the idle insertion circuit; and

a data output controller monitoring the bit stream from the idle insertion circuit and enabling the second source to output data through the multiplexer when idles appear in the bit stream.

15. A cable network, comprising:

a first data source generating a first bit stream;

a second data source generating data packets;

a cable link coupling the first data source to the second data source;

an idle insertion circuit coupled to the first data source that inserts a minimum number of idle bits into the first bit stream;

a multiplexer circuit coupled between the idle insertion circuit and the second data source replacing idle bits in the first bit stream with data packets from the second data source, the minimum number of idle bits guaranteeing the second data source a minimum amount of bandwidth on the cable network.

16. A cable network according to claim 15 wherein the multiplexer generates an MPEG bit stream broadcast over the same TV channel on the cable link.

17. A cable network according to claim 16 wherein the idle insertion circuit is programmable to selectively vary the minimum bandwidth allocated to the second source.

18. A method for multiplexing multiple MPEG bit streams onto a common TV channel in a television cable network, comprising:

counting occurrences of MPEG frames in an MPEG bit stream;

identifying when a predetermined number of the MPEG frames have occurred in the MPEG bit stream;

detecting whether a time stamp exists in a next MPEG frame in the MPEG bit stream;

inserting an MPEG idle frame into the next MPEG frame when the predetermined number of MPEG frames have occurred and the time stamp is not detected; and

replacing idle frames in the MPEG bit stream with data packets from a second data source thereby forming a multiplexed MPEG bit stream and guaranteeing the second source a guaranteed portion of the multiplexed MPEG bit stream.

19. A method according to claim 18 including inserting the MPEG idle frame after the next MPEG time frame when the time stamp is the next MPEG time frame.

20. A method for multiplexing multiple MPEG bit streams onto a common TV channel in a television cable network, comprising:

counting occurrences of MPEG frames in an MPEG bit stream;

identifying when a predetermined number of the MPEG frames have occurred in the MPEG bit stream;

detecting whether a time stamp exists in a next MPEG frame in the MPEG bit stream;

inserting an MPEG idle fame into the next MPEG frame when the predetermined number of MPEG frames have occurred and the time stamp is not detected;

replacing idle frames in the MPEG bit stream with data packets from a second data source thereby forming a multiplexed MPEG bit stream and guaranteeing the second source a guaranteed portion of the multiplexed MPEG bit stream;

inserting the MPEG idle frame after the next MPEG time frame when the time stamp is the next MPEG time frame;

modulating the multiplexed MPEG bit stream onto a TV channel;

transmitting the modulated MPEG bit stream on the cable television network to multiple cable modems at remote subscriber locations;

demodulating the modulated MPEG bit stream at the subscriber locations;

sending the demodulated MPEG bit stream from the first source and demodulated data packets from the second source over a LAN to a personal computer.

21. An electronic storage medium containing computer executable software for multiplexing multiple bit streams onto a common channel in a television cable network, comprising:

code for counting occurrences of frames in a bit stream;

code for identifying when a predetermined number of the frames have occurred in the bit stream;

code for detecting whether a time stamp exists in a next frame in the bit stream;

code for inserting an idle frame into the next frame when the predetermined number of frames have occurred and the time stamp is not detected; and

code for replacing idle frames in the bit stream with data packets from a second data source thereby forming a multiplexed bit stream and guaranteeing the second source a guaranteed portion of the multiplexed bit stream.

22. An electronic storage medium according to claim 21 including code for inserting the idle frame after the next frame when the next frame contains the time stamp.

23. An electronic storage medium according to claim 21 including:

code for modulating the multiplexed bit stream onto a channel;

code for transmitting the modulated bit stream on the television cable television network to multiple cable modems at remote subscriber locations;

code for demodulating the modulated bit stream at the subscriber locations; and

code for sending the demodulated bit stream from the first source and demodulated data packets from the second source to an endpoint.

24. A system for multiplexing multiple bit streams onto a common channel in a television cable network, comprising:

means for counting occurrences of frames in a bit stream;

means for identifying when a predetermined number of the frames have occurred in the bit stream;

means for detecting whether a time stamp exists in a next frame in the bit stream;

means for inserting an idle frame into the next frame when the predetermined number of frames have occurred and the time stamp is not detected; and

means for replacing idle frames in the bit stream with data packets from a second data source thereby forming a multiplexed bit stream and guaranteeing the second source a guaranteed portion of the multiplexed bit stream.

25. A system according to claim 24 including means for inserting the idle frame after the next frame when the next frame contains the time stamp.

26. A system according to claim 24 including:

means for modulating the multiplexed bit stream onto a channel;

means for transmitting the modulated bit stream on the cable television network to multiple cable modems at remote subscriber locations;

means for demodulating the modulated bit stream at the subscriber locations; and

means for sending the demodulated bit stream from the first source and demodulated data packets from the second source to an endpoint.

27. A system for combining bit streams from different sources onto a common channel, comprising:

a circuit having a first input receiving a first bit stream from a first data source with a selectable guaranteed minimum percentage of idles, a second input receiving data from a second source, and an output generating a multiplexed bit stream from the first and second source onto a common channel on a cable network, the circuit monitoring the first bit stream and enabling the insertion of data from the second source over idles detected in the first bit stream, the selectable minimum percentage of idles in the first bit stream providing the second source with a guaranteed minimum bandwidth for broadcasting data on the channel.

28. A system according to claim 27 wherein the multiplexed bit stream is formatted into MPEG frames.

29. A system according to claim 27 wherein the first source comprises a head end and the second source comprises an MPEG data source each broadcasting over a cable network.

30. A system according to claim 29 wherein the cable network includes a cable link broadcasting the multiplexed bit stream to multiple cable modems at remote subscriber locations.

31. A system according to claim 27 wherein the first bit stream includes MPEG time stamps, data packets and idles, the idles inserted at predetermined minimum time periods when no time stamps exist in the first bit stream or when there are no data packets available from the first source and no time stamps exist in the first bit stream.

32. A system according to claim 27 wherein the circuit inserts the selectable minimum percentage of idles into the first bit stream.

33. A circuit according to claim 32 wherein the circuit counts frames in the first bit stream, initiating the insertion of a predetermined number of idles in the first bit stream according to the number of counted frames, and prevents inserting idles whenever time stamps occur in the first bit stream.

34. A circuit according to claim 27 including a register for loading a selectable number of idles into the circuit.

35. A circuit according to claim 27 wherein the circuit modulates the multiplexed bit stream onto the channel and transmits the modulated bit stream on a cable television network to multiple cable modems at remote subscriber locations, the modulated bit stream demodulated one of the subscriber locations and the demodulated bit stream from the first source and the demodulated bit stream from the second source sent to an endpoint.

36. A cable modem, comprising:

a circuit for receiving a multiplexed bit stream on a common channel on a cable network, the multiplexed bit stream having a first bit stream from a first data source with a selectable guaranteed minimum percentage of idles and data from a second source, data from the second source inserted over idles detected in the first bit stream and the selectable minimum percentage of idles in the first bit stream providing the second source with a guaranteed minimum bandwidth for broadcasting data on the cable network.

37. A cable modem according to claim 36 wherein the multiplexed bit stream is modulated onto a TV channel.

38. A cable modem according to claim 37 wherein the modulated bit stream is demodulated by the circuit and the demodulated bit stream from the first source and the demodulated data from the second source sent to a computer.

39. A cable modem according to claim 38 wherein the modulated bit stream is transmitted on the cable television network to multiple cable modems at different remote subscriber locations.