Television – Monitoring – testing – or measuring
Reexamination Certificate
2001-02-06
2003-10-14
Kostak, Victor R. (Department: 2611)
Television
Monitoring, testing, or measuring
C348S700000, C348S722000
Reexamination Certificate
active
06633329
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to the monitoring of errors in video signals, and more particularly to the detection of frozen fields in video that has been encoded according to an analog television standard.
Companies that distribute video over compressed pathways, such as satellite or digital cable distributors, have hundreds of channels that need to be monitored for defects. These companies need an automated method of monitoring for such defects. One of the most common of these errors is frozen fields, in which the video ceases to change, or is black, due to equipment failure. The current instrument that is used to detect such an error is the Tektronix PQM300 Picture Quality Monitor manufactured by Tektronix, Inc. of Beaverton, Oreg., United States of America which uses a single-ended measurement algorithm described in U.S. patent application Ser. No. 09/152,495 entitled “Picture Quality Measurement Using Blockiness” and filed Sept. 10, 1998. However this single-ended blockiness measurement does not decide whether the blockiness being detected is caused by unacceptable CODEC deformation of the image or is the natural result of blockiness that exists within the video. A method for detecting blockiness caused by DCT-based CODECs is described in U.S. patent application Ser. No. 09/518,430 entitled “Blockiness Period Detection of DCT-Based CODECs” filed Mar. 3, 2000.
However if the frozen video is at any point in analog encoded format, such as NTSC or PAL, the chrominance variations inherent in these standards cause even visually identical fields to be significantly different on a pixel by pixel basis. Enough so that a measurement that determines the difference between two otherwise identical fields while not yielding false positives on similar, but non-identical, fields is extremely computationally expensive. This variance remains even if the video stream is subsequently converted back into a digital format. For example comparing field one of one frame to field one of the next frame results in indications of differences between the fields due to artifacts of the analog encoding process that are 180° out of phase due to the color phase clocking, even though the fields are otherwise identical—frozen.
What is desired is a means of detecting frozen fields in video data that has been at some point analog encoded.
BRIEF SUMMARY OF THE INVENTION
Accordingly the present invention provides a frozen field detection technique for previously analog encoded video data by obtaining a difference between each field and its nth subsequent field where the color phasing of the analog encoding standard is identical. Then when the difference is essentially zero, a frozen field indicator is initiated to indicate the presence of frozen fields in the video signal.
The objects, advantages and other novel features of the present invention are apparent from the following detailed description when read in conjunction with the appended claims and attached drawing figures.
REFERENCES:
patent: 4214263 (1980-07-01), Kaiser
patent: 5119191 (1992-06-01), Van den Heuvel
patent: 6122433 (2000-09-01), McLaren
patent: 6259480 (2001-07-01), Yamauchi et al.
patent: 6377297 (2002-04-01), Janko et al.
patent: 02-000115766 (2000-04-01), None
Janko Bozidar
Maurer Steven D.
Gray Francis I.
Kostak Victor R.
Tektronix Inc.
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