System and method for transporting a compressed video and data bit stream over a communication channel

• US 6,181,711 B1
• Filed: 10/10/1997
• Issued: 01/30/2001
• Est. Priority Date: 06/26/1997
• Status: Expired due to Term

• Current Assignee: Cisco Systems, Inc.
• Original Assignee: Cisco Systems, Inc.
• Inventors: Wu, Fang, Zhang, Ji, Chen, Wen H.
• Primary Examiner(s): FELBER, JOSEPH LEON
• Application Number:
  US08/947,480
• Time in Patent Office: 1,208 Days
• Field of Search: 370/465, 370/468, 370/545, 370/522, 370/537, 370/538, 370/203, 370/210, 370/484
• US Class Current: 370/468
• CPC Class Codes: H04L 2012/5636 Monitoring or policing, e.g. compliance with allocated rate, corrective actions
• CPC Class Codes: H04L 2012/5664 Support of Video, e.g. MPEG
• CPC Class Codes: H04L 2012/5671 Support of voice
• CPC Class Codes: H04L 2012/5672 Multiplexing, e.g. coding, scrambling
• CPC Class Codes: H04M 11/062 using different frequency bands for speech and other data
• CPC Class Codes: H04N 19/40 using video transcoding, i.e. partial or full decoding of a coded input stream followed by re-encoding of the decoded output stream
• CPC Class Codes: H04N 21/234381 by altering the temporal resolution, e.g. decreasing the frame rate by frame skipping
• CPC Class Codes: H04N 21/23614 Multiplexing of additional data and video streams arrangements for simultaneous broadcast of plural pieces of information H04H20/28
• CPC Class Codes: H04N 21/2365 Multiplexing of several video streams
• CPC Class Codes: H04N 21/2383 Channel coding or modulation of digital bit-stream, e.g. QPSK modulation arrangements for detecting or preventing errors in the information received by adapting the channel coding H04L1/0009; analogue front ends or means for connecting modulators, demodulators or transceivers to a transmission line H04L27/0002
• CPC Class Codes: H04N 21/2385 Channel allocation H04N21/266 takes precedence; Bandwidth allocation H04N21/24 takes precedence ; allocation of channels according to the instantaneous demands of the users in time-division multiplex systems H04J3/1682; admission control, resource allocation in open networks H04L12/5692; arrangements for maintenance or administration in data switching networks involving bandwidth and capacity management H04L41/0896; negotiating bandwidth in wireless networks H04W28/16
• CPC Class Codes: H04N 21/4347 Demultiplexing of several video streams
• CPC Class Codes: H04N 21/6373 for rate control , e.g. request to the server to modify its transmission rate flow control in packet networks H04L47/10
• CPC Class Codes: H04N 21/6377 directed to server one-way streaming services wherein the source is controlled by the destination H04L65/613
• CPC Class Codes: H04N 21/6379 directed to encoder , e.g. for requesting a lower encoding rate
• CPC Class Codes: H04N 21/658 Transmission by the client directed to the server
• CPC Class Codes: H04Q 11/0478 Provisions for broadband connections

Abstract

Digitally compressed video/audio bit streams, when transmitted over digital communication channels such as digital subscriber loop (DSL) access networks, ATM networks, satellite, or wireless digital transmission facilities, can be corrupted due to lack of sufficient channel bandwidth. This invention describes schemes to ensure lossless transmission of bit streams containing pre-compressed video signals within the communication channels. The schemes herein comprises a rate conversion system that converts the bit rate of a pre-compressed video bit stream from one bit rate to another, and that is integrated with a digital communication channel, and a means to convey the maximum channel transmission rate to the rate conversion system to allow satisfactory transmission of the bit stream from the input of the rate converter through the transmission facility.

Claims

1. An apparatus for modifying a bit rate of a bit stream to use an available bandwidth of a channel, the apparatus comprising:

a bit rate converter having an input, a control input and an output, the input coupled to receive a first bit stream with a first bit rate, the bit rate converter for converting the first bit stream to a second bit stream having a second bit rate, different from the first bit rate, the second bit stream being provided at the output of the bit rate converter; and

a transmitter having an input, a control output, and an output for transmitting data over the channel, the input of the transmitter coupled to the output of the bit rate converter to receive the second bit stream, the output of the transmitter coupled to the channel, the control output of the transmitter being coupled to the control input of the bit rate converter to send a control signal indicating a value for the second bit rate, the transmitter sending the second bit stream over the channel.

2. The apparatus of claim 1, wherein the second bit rate is less than the available channel bandwidth.

3. The apparatus of claim 1, wherein the transmitter is an xDSL transmitter that allows reliable transmission of the second bit stream and wherein the channel is a twisted copper wire.

4. The apparatus of claim 3, wherein the xDSL line condition determines the second bit rate.

5. The apparatus of claim 3, wherein the channel includes a physical medium and an xDSL receiver, the physical medium coupling the xDSL transmitter to the xDSL receiver.

6. The apparatus of claim 5, wherein the xDSL is a rate adaptive digital subscriber loop (RADSL) and the apparatus further comprises initialization logic coupled to the xDSL transmitter, the physical medium and the xDSL receiver for determining the available bandwidth of the channel and for providing a rate control signal to the xDSL transmitter indicating the available bandwidth of the channel, and wherein the xDSL transmitter provides the rate control signal to the bit rate converter.

7. The apparatus of claim 1, wherein the transmitter is an RADSL transmitter that includes a multiplexer and synchronization control, an interleaver, a constellation encoder, and a DAC and analog signal processor coupled in series.

8. The apparatus of claim 1, wherein the transmitter includes an ATM cell converter, the channel is an ATM network, and the second bit rate is about equal to an available connection capacity from the ATM network.

9. The apparatus of claim 8, wherein the apparatus further comprises an external rate controller having an output for providing a rate control signal specifying a desired bit rate, the output of the external rate controller coupled to the control input of the bit rate controller.

10. The apparatus of claim 8, wherein the external rate controller has an input coupled to the ATM network to to receive a signal indicating a connection capacity of the ATM network.

11. The apparatus of claim 8 further comprising an ATM cell de-converter having an input and an output, the input of the ATM cell de-converter coupled to receive ATM cells, the output of the ATM cell de-converter coupled to the input of the bit rate converter, the ATM cell de-converter for converting ATM cells to a compressed bit stream.

12. The apparatus of claim 8 wherein the ATM cell converter includes an ATM segmentation and re-assembly device.

13. The apparatus of claim 8 further comprising:

an RADSL receiver having an input and an output, the input of the RADSL receiver coupled to a physical medium included in the channel.

14. The apparatus of claim 1 wherein the bit rate converter further comprises:

a decoder and extractor having an input and an output for decoding data streams and extracting timing and programming information;

a modification unit having an input and an output for changing the number of bits in the bit stream, the input of the modification unit coupled to the output of the decoder and extractor; and

an encoder having an input and an output for performing coding on a bit stream, the input of the encoder coupled to the output of the modification unit.

15. The apparatus of claim 14 wherein the decoder and extractor further comprises:

a demultiplexer having an input and an output for extracting a video elementary stream; and

an elementary stream bit parser having an input and an output, the input of the elementary stream bit parser coupled to the demultiplexer, the elementary stream bit parser for dividing the video elementary stream into components, the output of the elementary stream bit parser coupled to the modification unit.

16. The apparatus of claim 14 wherein the modification unit further comprises:

a first modification unit for reducing the number of bits needed for discrete cosine transform coefficients;

a second modification unit for reducing the number of bits needed for motion vectors; and

a third modification unit for reducing the number of bits needed for auxiliary information.

17. The apparatus of claim 14 wherein the encoder performs variable length encoding on the bit stream received.

18. The apparatus of claim 14 wherein the bit rate converter further comprises:

a separation unit having an input and a plurality of outputs for dividing the bit stream into a plurality of sub-bit streams, at least one of the plurality of outputs of the separation unit coupled to the input of the decoder and extractor for processing by the decoder and extractor; and

a combining unit having a plurality of inputs and an output for combining a plurality of sub-bit streams into a single bit stream, at least one input of the combining unit coupled to the output of the encoder.

19. An apparatus for bandwidth sharing between a first stream and a second stream, the apparatus comprising

a first bit rate converter having an input and an output, the input of the first bit rate converter coupled to receive the first stream, the first bit rate converter for changing a bit rate of the first stream to a first bit rate;

a second bit rate converter having an input and an output, the input of the second bit rate converter coupled to receive the second stream, the second bit rate converter for changing a bit rate of the second stream to a second bit rate; and

a multiplexer having a first input, a second input and an output, the first input of the multiplexer coupled to output of the first bit rate converter, the second input of the multiplexer coupled to output of the second bit rate converter, the multiplexer determining an intended bit rate profile for the first stream and allocating bandwidth to the first stream, and allocating any remaining bandwidth to the second stream.

20. The apparatus of claim 19 further comprising:

a transmitter having an input and an output for transmitting data over the channel, the transmitter having its input coupled to the output of the multiplexer to receive a mixed bit stream, the transmitter sending the mixed bit stream over the channel such that bit errors occur at a rate no more than a predetermined value.

21. The apparatus of claim 19, wherein the first stream is a compressed video bit stream and the second stream is a TCP/IP based data stream.

22. A method for modifying a bit rate of a bit stream to use an available bandwidth of a channel, the method comprising the steps of:

determining the bandwidth of the channel;

receiving the bit stream;

converting the bit stream to have a bit rate less than or equal to the bandwidth of the channel wherein converting the bit stream includes modifying data in the bit stream; and

transmitting the converted bit stream over the channel.

23. The method of claim 22 wherein the step of transmitting includes the step of sending the converted bit stream over a rate adaptive digital subscriber loop.

24. The method of claim 22 wherein the step of converting is controlled by a rate control signal from a RADSL transmitter.

25. The method of claim 22 wherein the step of determining the bandwidth of the channel is performed by initialization logic signaling an RADSL transmitter, a physical medium and a RADSL receiver.

26. The method of claim 22 wherein the step of transmitting the converted bit stream over the channel comprises ATM segmentation and re-assembly.

27. The method of claim 22 wherein the step of converting is controlled by a rate control signal from an ATM network.

28. The method of claim 22 further comprising the step of converting ATM cells to the bit stream before the bit stream is received.

29. The method of claim 22 wherein the step of transmitting the converted bit stream over the channel comprises the steps of:

converting the bit stream to ATM cells; and

sending the converted bit stream over a rate adaptive digital subscriber loop.

30. The method of claim 22 wherein the step of converting the bit stream to have a bit rate less than or equal to the bandwidth of the channel comprises the steps of:

decoding data streams and extracting timing and programming information;

modifying the number of bits in the bit stream; and

encoding the bit stream.

31. The method of claim 30 wherein the step of decoding data streams and extracting timing further comprises the steps of:

demultiplexing to extract a video elementary stream; and

parsing the video elementary stream to divide the video elementary stream into components.

32. The method of claim 30 wherein the step of modifying the number of bits in the bit stream further comprises the steps of:

reducing the number of bits needed for discrete cosine transform coefficients;

adjusting the number of bits needed for motion vectors; and

reducing the number of bits needed for auxiliary information.

33. The method of claim 30 wherein the step of encoding performs variable length encoding on the bit stream received.

34. The method of claim 30 further comprising the steps of:

separating a bit stream into a plurality of sub-bit streams for the steps of decoding, modifying and encoding; and

combining the plurality of sub-bit streams after decoding, modifying and encoding.

35. A method for bandwidth sharing between a first stream and a second stream, the method comprising the steps of:

bit rate converting the first stream to produce a converted first stream;

bit rate converting the second stream to produce a converted second stream; and

multiplexing between the converted first stream and the converted second stream based on an intended bit rate profile for the first stream and allocating bandwidth to the converted first stream, and allocating any remaining bandwidth to the converted second stream.

36. The method of claim 35 further comprising the step of transmitting the multiplexed data stream over a channel such that bit errors occur at a rate no more than a predetermined value.

37. The method of claim 35, wherein the first stream is a compressed video bit stream and the second stream is a TCP/IP based data stream.