Computer system for statistical multiplexing of bitstreams

• US 6,754,241 B1
• Filed: 01/05/2000
• Issued: 06/22/2004
• Est. Priority Date: 01/06/1999
• Status: Expired due to Term

• Current Assignee: SRI International, Inc.
• Original Assignee: Sarnoff Corporation (SRI International, Inc.)
• Inventors: Lee, Xiaobing, Krishnamurthy, Ravi, Sethuraman, Sriram, Chiang, Tihao
• Primary Examiner(s): Chin, Wellington
• Assistant Examiner(s): HO, CHUONG T
• Application Number:
  US09/478,128
• Time in Patent Office: 1,630 Days
• Field of Search: 370/537, 370/538, 370/539, 370/540, 370/536, 370/468, 370/577, 370/434, 370/435, 370/234, 370/235, 370/532-535, 370/477, 348/385, 348/387, 348/419, 348/500, 348/423.1, 382/232, 382/234
• US Class Current: 370/537
• CPC Class Codes: H04N 19/115 Selection of the code volume for a coding unit prior to coding
• CPC Class Codes: H04N 19/14 Coding unit complexity, e.g. amount of activity or edge presence estimation H04N19/146 takes precedence
• CPC Class Codes: H04N 19/15 by monitoring actual compressed data size at the memory before deciding storage at the transmission buffer
• CPC Class Codes: H04N 19/152 by measuring the fullness of the transmission buffer
• CPC Class Codes: H04N 19/159 Prediction type, e.g. intra-frame, inter-frame or bidirectional frame prediction
• CPC Class Codes: H04N 19/172 the region being a picture, frame or field
• CPC Class Codes: H04N 19/177 the unit being a group of pictures [GOP]
• CPC Class Codes: H04N 19/179 the unit being a scene or a shot
• CPC Class Codes: H04N 19/42 characterised by implementation details or hardware specially adapted for video compression or decompression, e.g. dedicated software implementation H04N19/635 takes precedence
• CPC Class Codes: H04N 19/61 in combination with predictive coding
• CPC Class Codes: H04N 21/2365 Multiplexing of several video streams
• CPC Class Codes: H04N 21/23655 Statistical multiplexing, e.g. by controlling the encoder to alter its bitrate to optimize the bandwidth utilization
• CPC Class Codes: H04N 21/238 Interfacing the downstream path of the transmission network, e.g. adapting the transmission rate of a video stream to network bandwidth; Processing of multiplex streams hybrid fiber coaxial [HFC] networks for downstream channel allocation for video distribution H04L12/2801; flow control in packet networks H04L47/10; real-time communication protocols in data switching networks H04L65/00; scheduling or organising the servicing of application requests H04L67/60
• CPC Class Codes: H04N 21/4347 Demultiplexing of several video streams

Abstract

A PC-type computer has a system bus (e.g., a PCI bus) configured with a main CPU board, a statistical multiplexing (stat-mux) board, and a plurality of video/audio encoder boards, each configured to receive and compress a corresponding video/audio stream. The stat-mux board performs statistical multiplexing on the different compressed bitstreams to transmit multiple bitstreams over individual shared communication channels. Although each of the boards is configured to the system bus, each encoder board has a digital signal processor (DSP) with a synchronized serial interface (SSI) output port that is directly connected to an SSI input port on a DSP on the stat-mux board (which, in one embodiment, has four such DSPs each with six such SSI input ports). As such, (up to 24) compressed video/audio bitstreams generated on the various encoder boards can be transmitted directly to the stat-mux board without having to go through the system bus. In this way, the computer system can provide statistical multiplexing of low-latency video/audio bitstreams without having to suffer the processing delays associated with conventional transmission over PCI system buses.

Claims

1. A computer system adapted to (1) generate a compressed bitstream for each of a plurality of independent input data streams and (2) combine the resulting plurality of compressed bitstreams into a single multiplexed output data stream, the computer system comprising:

(a) one or more encoding sub-systems, each encoding sub-system adapted to receive a different one of the independent input data streams and generate a corresponding compressed bitstream;

(b) a central processing sub-system adapted to receive at least one of the independent input data streams and generate a corresponding compressed bitstream;

(c) a statistical multiplexing (stat-mux) sub-system adapted to combine the compressed bitstreams from the one or more encoding sub-systems and from the central processing sub-system into the single multiplexed output data stream; and

(d) a system bus connected to each encoding sub-system, to the central processing sub-system, and to the stat-mux sub-system, wherein;

each encoding sub-system is further connected directly to the stat-mux sub-system such that the compressed bitstream from said each encoding sub-system is transmitted directly to the stat-mux sub-system without being transmitted over the system bus;

each compressed bitstream generated by the central processing sub-system is transmitted to the stat-mux sub-system via the system bus;

each input data stream has a specified desired latency level;

at least two input data streams can have different specified desired latency levels; and

the stat-mux sub-system is adapted to apply statistical multiplexing taking into account the corresponding specified desired latency level for each input data stream to;

generate and transmit control signals back to each encoding sub-system and to the central processing sub-system to control encoding processing used to generate the corresponding compressed bitstreams from the corresponding input data streams; and

control how the resulting compressed bitstreams are combined to form the single multiplexed output data stream.

2. The invention of claim 1, wherein the computer system comprises two or more such encoding sub-systems, each adapted to generate a different compressed bitstream for a different, independent input data stream.

3. The invention of claim 2, wherein the two or more different compressed bitstreams generated by the two or more encoding sub-systems can have different specified desired latency levels.

4. The invention of claim 1, wherein the central processing sub-system is adapted to generate simultaneously two or more different compressed bitstreams from two or more different, independent input data streams.

5. The invention of claim 4, wherein the two or more different compressed bitstreams generated by the central processing sub-system can have different specified desired latency levels.

6. The invention of claim 1, wherein each input data stream is a different audio/video stream.

7. The invention of claim 1, wherein the one or more compressed bitstreams generated by the one or more encoding sub-systems have lower specified desired latency levels than the one or more compressed bitstreams generated by the central processing sub-system.

8. The invention of claim 1, wherein:

each encoding sub-system has a synchronized serial interface (SSI) output port;

the stat-mux sub-system has an SSI input port for each SSI output port in the one or more encoding sub-systems; and

each compressed bitstream generated by a corresponding encoding sub-system is transmitted from the SSI output port of the encoding sub-system to the corresponding SSI input port of the stat-mux sub-system.

9. The invention of claim 1, wherein the system bus is a PCI bus.

10. The invention of claim 1, wherein each encoding sub-system and the central processing sub-system generate statistics about the corresponding compressed bitstreams and transmit those statistics to the stat-mux sub-system for use in performing the statistical multiplexing.

11. The invention of claim 1, wherein:

the computer system comprises two or more such encoding sub-systems, each adapted to generate a different compressed bitstream for a different, independent input data stream;

the two or more different compressed bitstreams generated by the two or more encoding sub-systems can have different specified desired latency levels;

the central processing sub-system is adapted to generate simultaneously two or more different compressed bitstreams from two or more different, independent input data streams;

the two or more different compressed bitstreams generated by the central processing sub-system can have different specified desired latency levels;

each input data stream is a different audio/video stream;

the compressed bitstreams generated by the encoding sub-systems have lower specified desired latency levels than the compressed bitstreams generated by the central processing sub-system;

each encoding sub-system has a synchronized serial interface (SSI) output port;

the stat-mux sub-system has an SSI input port for each SSI output port in the one or more encoding sub-systems;

each compressed bitstream generated by a corresponding encoding sub-system is transmitted from the SSI output port of the encoding sub-system to the corresponding SSI input port of the stat-mux sub-system;

the system bus is a PCI bus; and

each encoding sub-system and the central processing sub-system generate statistics about the corresponding compressed bitstreams and transmit those statistics to the stat-mux sub-system for use in performing the statistical multiplexing.