# US 5,351,093 A · Phase alternating line video signal processing apparatus

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- Number: US 5,351,093 A
- Document ID: US5351093A
- Status: Granted
- Kind: A
- Application number: 08/060,084
- Filed: 1993-05-10
- Granted: 1994-09-27
- Earliest claimed: 1992-05-08
- Assignees: International Business Machines Corporation
- Inventors: David J. Brown; David C. Conway-Jones; Jong-Han Kim; Peter M. Smith
- Web page: https://patentgrep.com/patent/US5351093A

## CPC

- H04N 9/641: {Multi-purpose receivers, e.g. for auxiliary information (H04N9/642 takes precedence)}
- H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION

## Abstract

Signal processing apparatus comprises a chrominance subsampler (10) for sampling the U and V components of a PAL video signal in response to an enable signal. A counter (30) responsive to the horizontal synchronization component of the PAL video signal generates the enable signal upon detection of a predetermined number of horizontal synchronization pulses. Logic (60,70,80) responsive to the vertical synchronization component of the PAL video signal resets and disables the counter (30) upon detection of a vertical synchronization pulse. Logic (50,60,70,80) restarts the counter (30) from a reset state upon detection of a predetermined polarity in the V component of the PAL video signal.

## Claims

### Claim 1

Signal processing apparatus comprising:
a chrominance subsampler for sampling the U and V components of a PAL video signal in response to an enable signal;
a counter responsive to the horizontal synchronization pulses of the PAL video signal for generating the enable signal upon detection of a predetermined number of horizontal synchronization pulses of the PAL video signal;
first logic circuitry responsive to the vertical synchronization pulses of the PAL video signal for disabling the counter upon each detection of a vertical synchronization pulse of the PAL video signal; and
second logic circuitry for restarting the counter from a reset state upon detection of a predetermined polarity in the V component of the PAL video signal.

### Claim 2 (depends on 1)

Apparatus as claimed in claim 1 wherein said predetermined number is a multiple of two.

### Claim 3 (depends on 2)

Apparatus as claimed in claim 2 wherein said predetermined number is two.

### Claim 4 (depends on 1)

Apparatus as claimed in claim 1 wherein said counter is responsive to horizontal synchronization pulses corresponding to one field of each frame of the video signal.

### Claim 5 (depends on 1)

Apparatus as claimed in claim 1 wherein said predetermined polarity is positive.

### Claim 6

A method of subsampling a PAL video signal, the method comprising:
generating, via a counter, an enable signal upon detection of a predetermined number of horizontal synchronization pulses in the horizontal synchronization component of the PAL video signal;
sampling the U and V components of the video signal in response to the enable signal;
resetting and disabling the counter upon detection of a vertical synchronization pulse in the vertical synchronization component of the PAL video signal; and
restarting the counter from a reset state upon detection of a predetermined polarity in the V component of the PAL video signal.