Multiplexing transmission apparatus for image signal and multiplexing system

• US 5,371,535 A
• Filed: 01/15/1993
• Issued: 12/06/1994
• Est. Priority Date: 01/30/1992
• Status: Expired due to Fees

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Takizawa, Masaaki
• Primary Examiner(s): Britton, Howard W.
• Application Number:
  US08/005,211
• Time in Patent Office: 690 Days
• Field of Search: 348/15, 348/17, 348/473, 348/588, 348/722, 348/518, 348/519, 370/62
• US Class Current: 348/14.1
• CPC Class Codes: H04N 7/15 Conference systems
• CPC Class Codes: H04N 7/181 for receiving images from a plurality of remote sources

Abstract

A compact and low-cost multiplexing apparatus for a plurality of high-efficiency encoded image signals is capable of improving an image quality and of shortening a transmission delay time. The multiplexing apparatus for an image signal includes delay compensating circuits provided corresponding to a plurality of image terminals, for storing image encoded signals sent from the respective image terminals; a control circuit for performing a control to form a large frame signal from small frame signals whose number is equal to at the most the number of image signal sources, by detecting frame head codes from input/outputs of the delay compensating circuits, thereby not being duplicated from a plurality of delay compensating circuits, and also adding circuit for adding a frame start code to each of large frames. Even when the frame rates are different between terminals, since all of the image encoded signals are not decoded but multiplexed, deterioration of image qualities and transmission delays can be reduced. Since apparatuses for encoding/decoding images can be omitted, the entire multiplexing apparatus can be made compact.

Claims

1. A multiplexing system of a image signal, wherein image signals transmitted from an plurality of television cameras are multiplexed to be outputted into a reproducing apparatus, comprising:

a plurality of television cameras arranged at different positions from each other;

a plurality of encoding circuits connected to the respective television cameras, for variable-length-encoding image information sent from the respective television cameras;

a multiplexing apparatus for multiplexing outputs derived from said plural encoding circuits, said multiplexing apparatus being arranged by a plurality of delay compensating circuits for temporarily storing a small frame constructed of a plurality of image signals which are transmitted from the plural television cameras via the variable-length encoding circuits, a plurality of frame head code detecting circuits for detecting frame start codes (PSC) from the respective small frames, removing circuits for removing the PSC from the respective small frames read out from the delay compensating circuits; and

a control circuit connected to each of said frame head code detecting circuits, for detecting whether or not a new small frame has been written into the respective delay compensating circuits, and for executing such a control to form a large frame which is sent out to a transmission path by employing either the small frames all of which have been stored into said delay compensating circuits, or a small frame of a predetermined dummy signal in response to the detection result; and

a reproducing apparatus connected via said transmission path to said multiplexing apparatus, said reproducing apparatus reproducing an image, while the image is reconstructed, when there are the small frames of the transmitted image signal, by employing said small frames, and also when there is said dummy signal, by again employing the small frames which have been transmitted during the previous transmission.

2. A multiplexing system of an image signal as claimed in claim 1, wherein said delay compensating circuits are constructed of a plurality of FIFO memories corresponding to the image information sent from said television cameras, and said frame head code detecting circuits and said removing circuits are provided at input units and output units of said plural FIFO memories, respectively.

3. A multiplexing system of an image signal, wherein image signals transmitted from a plurality of television cameras are multiplexed to be outputted into a reproducing apparatus, comprising:

a LAN (local area network) for mutually transmitting and receiving data; and

a plurality of transmission/reception terminals connected to said LAN, for performing a television conference, each of said transmission/reception terminals being constructed of;

a plurality of television cameras for each converting light reflected from an object to be imaged into an electric signal;

a plurality of variable-length-encoding circuits connected to the respective television cameras, for variable-length-encoding image information sent out from the television cameras;

a multiplexing apparatus for multiplexing outputs derived from said plural encoding circuits, said multiplexing apparatus being arranged by a plurality of delay compensating circuits for temporarily storing a small frame constructed of a plurality of image signals which are transmitted from the plural television cameras connected to each of said transmission/reception terminals via the variable-length encoding circuits, a plurality of frame head code detecting circuits for detecting frame start codes (PSC) from the respective small frames, removing circuits for removing the PSC from the respective small frames read out from the delay compensating circuits; and

a control circuit connected to each of said frame head code detecting circuits, for detecting whether or not a new small frame has been written into the respective delay compensating circuits, and for executing such a control to form a large frame which is sent out to said from a plurality of small frames by employing either the small frames all of which have been stored into said delay compensating circuits, or a small frame of a predetermined dummy signal in response to the detection result; and

a reproducing apparatus connected via said transmission path to said multiplexing apparatus, said reproducing apparatus reproducing an image, while the image is reconstructed, when there are the transmitted small frames, by employing said transmitted small frames, and when there is no relevant small frame, by again employing the small frames which have been transmitted during the previous transmission.

4. A multiplexing apparatus of an image signal, connected to a plurality of television cameras, for multiplexing encoded image signals from the respective television cameras, comprising:

a plurality of delay compensating circuits for temporarily storing a small frame constructed of a plurality of image signals which are transmitted from the plural television cameras via the variable-length encoding circuit;

a plurality of frame head code detecting circuits for detecting frame start codes (PSC) from the respective small frames;

a plurality of removing circuits for removing the PSC from the respective small frames read out from the delay compensating circuits; and

a control circuit connected to each of said frame head code detecting circuits, for detecting whether or not a new small frame has been written into the respective delay compensating circuits, and for executing such a control to form a large frame which is sent out to a transmission path, from a plurality of small frames.

5. A multiplexing apparatus of an image signal as claimed in claim 4, wherein said delay compensating circuits are constructed of a plurality of FIFO memories corresponding to the image information sent from said television cameras, and said frame head code detecting circuits and said removing circuits are provided at input units and output units of said plural FIFO memories, respectively.