Method for bidirectionally transmitting digital video signal and digital video signal bidirectional transmission system

• US 5,701,581 A
• Filed: 12/23/1994
• Issued: 12/23/1997
• Est. Priority Date: 12/28/1993
• Status: Expired due to Term

• Current Assignee: Hitachi Denshi Kabushiki Kaisha
• Original Assignee: Hitachi Denshi Kabushiki Kaisha
• Inventors: Murata, Nobuo, Tanabe, Kazuhiro, Eto, Yoshizumi, Nisikawa, Hiroyuki
• Primary Examiner(s): Kostak, Victor R.
• Assistant Examiner(s): Miller, John W.
• Application Number:
  US08/361,724
• Time in Patent Office: 1,096 Days
• Field of Search: 348/15, 348/16, 348/17, 348/14, 348/13, 348/12, 348/143, 348/211, 348/212, 348/6, 370/62, 370/105.1, 370/109, 370/68, 370/66, 370/58.1, 370/29, 455/5.1
• US Class Current: 348/14.13
• CPC Class Codes: H04N 21/2381 Adapting the multiplex stream to a specific network, e.g. an Internet Protocol [IP] network transmission of MPEG streams over ATM H04L12/5601
• CPC Class Codes: H04N 21/4223 Cameras H04N23/00 takes precedence
• CPC Class Codes: H04N 21/4381 Recovering the multiplex stream from a specific network, e.g. recovering MPEG packets from ATM cells transmission of MPEG streams over ATM H04L12/5601
• CPC Class Codes: H04N 23/66 Remote control of cameras or camera parts, e.g. by remote control devices
• CPC Class Codes: H04N 7/141 between two video terminals, e.g. videophone telephonic communication systems combined with television receiver for reception of entertainment or information matter H04M11/085
• CPC Class Codes: H04N 7/142 Constructional details of the terminal equipment, e.g. arrangements of the camera and the display
• CPC Class Codes: H04N 7/147 Communication arrangements, e.g. identifying the communication as a video-communication, intermediate storage of the signals selecting H04Q
• CPC Class Codes: H04N 7/181 for receiving images from a plurality of remote sources
• CPC Class Codes: H04N 7/183 for receiving images from a single remote source

Abstract

In a video signal transmission method and system wherein a signal containing a video signal is bidirectionally transmitted and received in a substantially real time in video appliances coupled via a transmission path to each other, a digital signal containing a digital video signal is time-compressed, and a transmission operation is controlled in such a manner that a transmission period and a no transmission period are alternately produced in a preselected period. Then, the time-compressed digital signal is transmitted to the transmission path during the transmission period, whereas another digital signal transmitted via the transmission path from the video appliance on the counter side is received during the no transmission period. Then, the received digital signal is time-expanded to reproduce the original signal.

Claims

1. A video signal transmission method wherein digital signals including at least digital video signals are bidirectionally transmitted and received in substantially real time between first and second video appliances coupled via a transmission path, said first and second video appliances each including a transmitting and receiving apparatus, said method comprising the steps of:

dividing a first digital signal of said first video appliance into a plurality of predetermined periods, and time-axis compressing said first divided signal to produce a first divided and compressed digital signal repeating a signal period and a no signal period alternately, said first divided and compressed signal being transmitted on said transmission path;

controlling said transmitting and receiving apparatus of said first video appliance to generate a first transmission period and a second transmission period alternately on said transmission path, said first transmission period being longer than said second transmission period, so that said first divided and compressed digital signal of said first video appliance is transmitted to said second video appliance in said first transmission period of said transmission path;

receiving said first divided and compressed digital signal from said first video appliance at said second video appliance; and

time-axis expanding said first divided and compressed digital signal to reproduce said first digital signal at said second video appliance;

wherein the period of said first divided and compressed digital signal is synchronized with that of said first transmission period; and

wherein when each of said predetermined periods into which said first digital signal is divided is Tf, said first transmission period is a period defined by one of the following equations;

space="preserve" listing-type="equation">(a) Tf=n×

Tn,

space="preserve" listing-type="equation">(b) Tf=n×

Tn+m×

Tm,

space="preserve" listing-type="equation">(c) Tf=n×

Tn+m×

Tm+k×

Tk, and

space="preserve" listing-type="equation">(d) Tf=Σ

(ni×

Ti),

where symbols Tn, Tm, Tk, Ti denote said first transmission period, and symbols n, m, k, ni, i represent positive integers other than 0.

2. A video signal transmission method as claimed in claim 1, wherein said predetermined period Tf is set to a period of one frame period of said video signal multiplied by any positive integer other than 0.

3. A video signal transmission method as claimed in claim 1, wherein said predetermined period Tf is set to a period of one field period of said video signal multiplied by any positive integer other than 0.

4. A video signal transmission method as claimed in claim 1, wherein said predetermined period Tf is set to a period of one scanning line of said video signal multiplied by any positive integer other than 0.

5. A video signal transmission method wherein digital signals including at least digital video signals are bidirectionally transmitted and received in substantially real time between first and second video appliances coupled via a transmission path, said first and second video appliances each including a transmitting and receiving apparatus, said method comprising the steps of:

dividing a first digital signal of said first video appliance into a plurality of predetermined periods, and time-axis compressing said first divided signal to produce a first divided and compressed digital signal repeating a signal period and a no signal period alternately, said first divided and compressed signal being transmitted on said transmission path;

controlling said transmitting and receiving apparatus of said first video appliance to generate a first transmission period and a second transmission period alternately on said transmission path, said first transmission period being longer than said second transmission period, so that said first divided and compressed digital signal of said first video appliance is transmitted to said second video appliance in said first transmission period of said transmission path;

receiving said first divided and compressed digital signal from said first video appliance at said second video appliance; and

time-axis expanding said first divided and compressed digital signal to reproduce said first digital signal at said second video appliance;

wherein in at least one of said first and second video appliances, said method further comprises the step of adding a synchronization signal to said transmitted divided and compressed digital signal at a predetermined position in said transmitted divided and compressed digital signal in each transmission period; and

wherein in at least one of said first and second video appliances, said method further comprises the steps of;

detecting said synchronization signal from said received divided and compressed digital signal; and

stopping transmission of said divided and compressed digital signal for a predetermined time in a case of no detection of said synchronization signal in a predetermined detection repetition pattern within at least a predetermined time.

6. A video signal transmission method wherein digital signals including at least digital video signals are bidirectionally transmitted and received in substantially real time between first and second video appliances coupled via a transmission path, said first and second video appliances each including a transmitting and receiving apparatus, said method comprising the steps of:

dividing a first digital signal of said first video appliance into a plurality of predetermined periods, and time-axis compressing said first divided signal to produce a first divided and compressed digital signal repeating a signal period and a no signal period alternately, said first divided and compressed signal being transmitted on said transmission path;

controlling said transmitting and receiving apparatus of said first video appliance to generate a first transmission period and a second transmission period alternately on said transmission path, said first transmission period being longer than said second transmission period, so that said first divided and compressed digital signal of said first video appliance is transmitted to said second video appliance in said first transmission period of said transmission path;

receiving said first divided and compressed digital signal from said first video appliance at said second video appliance; and

time-axis expanding said first divided and compressed digital signal to reproduce said first digital signal at said second video appliance;

wherein at each of said first and second video appliances, said method further comprises the step of transmitting a signal having a level substantially equal to an average value of said digital signals of said transmission period when no signal is transmitted in said transmission period.

7. A video signal transmission method as claimed in claim 6, further comprising the step of discriminating a high level and a low level based on a predetermined reference value from said received divided and compressed digital signal;

wherein said reference value is set to a value which is lower than an average value of said digital signals by a value corresponding to an attenuation amount of said digital signal in said transmission path.

8. A video signal transmission system wherein digital signals containing at least digital video signals and digital audio signals are bidirectionally transmitted and received in substantially real time in first and second video appliances coupled via a transmission path, said first and second video appliances each including a transmitting and receiving apparatus, said first video appliance comprising:

means for producing a first digital signal by time-division multiplexing at least said digital video signal and said digital audio signal;

means for dividing said first digital signal into a plurality of predetermined periods and time-axis compressing said first divided digital signal in order to produce a first divided and compressed digital signal repeating a signal period and a no signal period alternately;

means for transmitting said first divided and compressed digital signal to said second video appliance through said transmission path;

means for controlling said transmitting and receiving apparatus of said first video appliance to generate a first transmission period and a second transmission period alternately on said transmission path, said first transmission period being longer than said second transmission period, and controlling said transmitting means so that said first divided and compressed digital signal of said first video appliance is transmitted to said second video appliance in said first transmission period of said transmission path;

means for receiving a second divided and compressed digital signal from said second video appliance;

means for time-axis expanding said second divided and compressed digital signal to reproduce a second digital signal; and

means for separating said time-axis expanded second digital signal to reproduce at least a digital video signal and a digital audio signal;

wherein said second video appliance comprises;

means for producing a second digital signal by multiplexing at least said digital video signal and said digital audio signal;

means for dividing said second digital signal into a plurality of predetermined periods and time-axis compressing said second divided digital signal in order to produce said second divided and compressed digital signal repeating a signal period and a no signal period, alternately;

means for transmitting said second divided and compressed digital signal to said transmission path;

means for controlling said transmitting and receiving apparatus and said transmitting means to transmit said second divided and compressed digital signal in said second transmission period to said first video appliance through said transmission path;

means for receiving said first divided and compressed digital signal from said first video appliance;

means for time-axis expanding said first divided and compressed digital signal to reproduce a first digital signal; and

means for separating said time-axis expanded digital signal to reproduce said digital video signal and said digital audio signal;

wherein said first video appliance further comprises means for adding a synchronization signal to said transmitted first divided and compressed digital signal at a predetermined position in said transmitted divided and compressed digital signal in each transmission period; and

wherein said second video appliance further comprises;

means for detecting said synchronization signal from said received first divided and compressed digital signal; and

means for stopping transmission of said second divided and compressed signal when said synchronization signal is not detected within a predetermined time.

9. A video signal transmission method wherein digital signals including at least digital video signals are bidirectionally transmitted and received in substantially real time between first and second video appliances coupled via a transmission path, said first and second video appliances each including a transmitting and receiving apparatus, said method comprising the steps of:

dividing a first digital signal of said first video appliance into a plurality of predetermined periods, and time-axis compressing said first divided signal to produce a first divided and compressed digital signal repeating a signal period and a no signal period alternately, said first divided and compressed signal being transmitted on said transmission path;

controlling said transmitting and receiving apparatus of said first video appliance to generate a first transmission period and a second transmission period alternately on said transmission path, said first transmission period being longer than said second transmission period, so that said first divided and compressed digital signal of said first video appliance is transmitted to said second video appliance in said first transmission period of said transmission path;

receiving said first divided and compressed digital signal from said first video appliance at said second video appliance;

time-axis expanding said first divided and compressed digital signal to reproduce said first digital signal at said second video appliance;

dividing a second digital signal of said second video appliance into a plurality of predetermined periods, and time-axis compressing said second divided digital signal to produce a second divided and compressed digital signal repeating a signal period and a no signal period alternately;

controlling said transmitting and receiving apparatus of said second video appliance so that said second divided and compressed digital signal of said second video appliance is transmitted to said first video appliance in said second transmission period of said transmission path;

receiving said second divided and compressed digital signal from said second video appliance at said first video appliance; and

time-axis expanding said second divided and compressed digital signal to reproduce said second digital signal at the first video appliance;

wherein said first divided and compressed digital signal of said first video appliance is a signal in which a video signal for one picture image from said first video appliance is divided into a plurality of said predetermined periods; and

wherein said method further comprises the step of adding a first signal representing predetermined phase information relating to said video signal from said first video appliance to said first divided and compressed digital signal at a predetermined position in said first divided and compressed digital signal.

10. A video signal transmission method as claimed in claim 9, wherein said second divided and compressed digital signal of said second video appliance is a signal in which a video signal for one picture image from said second appliance is divided into a plurality of said predetermined periods;

and

wherein said method further comprises the step of adding a second signal representing predetermined phase information relating to said video signal from said second appliance to said second divided and compressed digital signal at a predetermined position in said second divided and compressed digital signal.

11. A video signal transmission method as claimed in claim 9, wherein said method further comprises the steps of:

detecting said first signal representing said predetermined phase information at said second video appliance; and

making synchronization of a predetermined phase of said second divided and compressed digital signal as a reference of signal processing of said second video appliance on the basis of said detected first signal representing said predetermined phase information, appliance is made shorter than said first transmission period; and

wherein a time duration of said second divided and compressed digital signal of said second video appliance is made shorter than said second transmission period.

12. A video signal transmission method as claimed in claim 9, wherein said first signal representing said predetermined phase information is selected from phases of a vertical scanning period of a video signal, a field period of a video signal, a frame period of a video signal, and phases equal to these periods multiplied by any integer.

13. A video signal transmission method wherein digital signals including at least digital video signals are bidirectionally transmitted and received in substantially real time between first and second video appliances coupled via a transmission path, said first and second video appliances each including a transmitting and receiving apparatus, said method comprising the steps of:

dividing a first digital signal of said first video appliance into a plurality of predetermined periods, and time-axis compressing said first divided signal to produce a first divided and compressed digital signal repeating a signal period and a no signal period alternately, said first divided and compressed signal being transmitted on said transmission path;

controlling said transmitting and receiving apparatus of said first video appliance to generate a first transmission period and a second transmission period alternately on said transmission path, said first transmission period being longer than said second transmission period, so that said first divided and compressed digital signal of said first video appliance is transmitted to said second video appliance in said first transmission period of said transmission path;

receiving said first divided and compressed digital signal from said first video appliance at said second video appliance; and

time-axis expanding said first divided and compressed digital signal to reproduce said first digital signal at said second video appliance;

wherein a ratio of said first transmission period to said second transmission period is selected to be 2;

1; and

wherein said first transmission period and said second transmission period correspond to twelve scanning line periods and six scanning line periods, respectively, of a video signal.

14. A video signal transmission system wherein digital signals containing at least digital video signals and digital audio signals are bidirectionally transmitted and received in substantially real time in first and second video appliances coupled via a transmission path to each other,

said first video appliance comprising:

means for producing a first digital signal by multiplexing of at least said digital video signal and said digital audio signal;

means for dividing said first digital signal into plurality of predetermined periods and time-axis compressing said first divided signal in order to produce a first transmission signal repeating a signal period and a no signal period, alternately;

means for transmitting said first transmission signal to said transmission path; and

means for controlling said first and second video appliances to generate a first transmission period and a second transmission period alternately in said transmission path, and controlling said transmitting means so that said first transmission signal is synchronized with said first transmission period and is transmitted to said second video appliance in said first transmission period;

said second video appliance comprising;

means for producing a second digital signal by multiplexing of at least said digital video signal and said digital audio signal;

means for dividing said second digital signal into a plurality of predetermined periods and time-axis compressing said second divided signal in order to produce a second transmission signal repeating a signal period and a no signal period alternately;

means for transmitting said second transmission signal to said transmission path; and

means for controlling said transmitting means so that said second transmission signal is synchronized with said second transmission period and is transmitted to said first video appliance in said second transmission period;

said first video appliance further comprising;

means for receiving said second transmission signal from said second video appliance;

means for time-axis expanding said second transmission signal to reproduce said second digital signal; and

means for time-division separating said time-axis expanded digital signal to reproduce at least the digital video signal and the digital audio signal; and

said second video appliance further comprising;

means for receiving said first transmission signal from said first video appliance;

means for time-axis expanding said received first transmission signal to reproduce said first digital signal; and

means for time-division separating said time-axis expanded digital signal to reproduce at least the digital video signal and the digital audio signal;

wherein said first video appliance is a television camera, and said second video appliance is a television camera controlling apparatus.