Image processing system

• US 4,984,083 A
• Filed: 06/28/1989
• Issued: 01/08/1991
• Est. Priority Date: 05/12/1986
• Status: Expired due to Term

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Ohtsubo, Hiroyasu, Masuda, Michio, Nishijima, Hideo, Ono, Koichi, Okamoto, Kaneyuki
• Primary Examiner(s): Shepperd, John W.
• Application Number:
  US07/373,630
• Time in Patent Office: 559 Days
• Field of Search: 358/183, 358/22
• US Class Current: 348/565
• CPC Class Codes: H04N 5/45 Picture in picture , e.g. displaying simultaneously another television channel in a region of the screen

Abstract

An image processing system comprising a first and second video signal sources providing a main-field video signal and sub-field video signal, respectively, means for compressing the sub-field video signal on the time axis, and a signal merging unit which merges the compressed sub-field video signal into the main-field video signal and delivers the resulting signal to a television receiver set, wherein the signal compressing means comprising a dual-port memory having a first and second ports and operating to compress the sub-field video signal on the time axis and store the compressed signal, and control means for controlling the reading and writing of the memory for the sub-field video signal, the control means comprising a first control section for writing the sub-field video signal into the first port of said memory, a second control section for transferring a signal from the first port to the second port, and a third control section for reading out a signal from the second port, said memory implementing the reading operation and writing operation in asynchronous manner.

Claims

1. An image processing system comprising:

a memory which is capable of storing four fields of sub-field video signals;

field discriminating means which discriminate odd-numbered and even-numbered fields of the sub-field video signals;

divider means for diving the discriminated sub-field video signals;

field discrimination means which discriminate odd-numbered and even-numbered fields of main-field video signals;

displaying period control means which outputs a displaying period signal of the sub-field video signals;

merging means which merges main-field video signals or sub-field video signals to output in accordance with the controlled displaying period signal;

write address control means for deciding an address area in the memory to write information in accordance with the discriminated sub-field video signals and the divided sub-field video signals and;

read address control means for deciding the read address area in the memory according to said discriminated main-field video signals, the displaying period signal and said divided sub-field video signals.

2. An image processing system according to claim 1, wherein each of said field discriminating means for main-field and sub-field video signals comprises:

a reversible counter which counts the number of horizontal sync signals inside or outside a vertical sync signal period of the image and sub-field video signals, means for presetting said reversible counter once in N periods (where N is a positive integer) of the vertical sync signal, sample-holding means which samples and holds the contents of said reversible counter immediately before presetting, second frequency-division means which implements frequency division for the vertical sync signal, and frequency-division phase control means which varies the frequency-division phase of said second frequency-division means in accordance with the output of said sample holding means.

3. An image processing system according to claim 2, further comprising:

a counter for counting the vertical sync signal or the output of said second frequency-division means, variation detection means which detect whether or not the output of said sample-holding means varies during a certain count period of said counter, and means for operating on said frequency-division phase only at the detection of variation by said variation detecting means.