Douglas N Stevens

US Patent:

7876355, Jan 25, 2011

Filed:

Apr 17, 2006

Appl. No.:

11/405928

Inventors:

Douglas C. Stevens - Portland OR, US

Assignee:

Harmonic Inc. - San Jose CA

International Classification:

H04N 17/00

US Classification:

348180, 348615, 348559, 348189, 348700, 348701

Abstract:

Methods and apparatuses to detect presence of undesirable video abnormalities during, for example, video ingest or playback. These undesirable characteristics may include an average picture level that is less than a preset threshold value, or static input, in which the content does not change over a significant number of frames. Detection of abnormalities results in an alarm to a system operator. Analysis and alarm may occur automatically during processing of video data streams. The same abnormalities may be detected during playback of the image data.

US Patent:

50498800, Sep 17, 1991

Filed:

Apr 2, 1990

Appl. No.:

7/503009

Inventors:

Douglas C. Stevens - Portland OR

Assignee:

Tektronix, Inc. - Beaverton OR

International Classification:

H03M 746

US Classification:

341 63

Abstract:

A method of compressing a digitized waveform into a sequence of N-bit words includes selecting corresponding bit values from N data words and generating a value based thereon. A next N input words are selected and the corresponding bits are used to generate a next value. The process is continued for each significant bit of the input sequence and the generated value stream is run-length encoded to produce a compressed data output stream.

US Patent:

52145085, May 25, 1993

Filed:

Feb 14, 1992

Appl. No.:

7/834963

Inventors:

Douglas C. Stevens - Portland OR

Assignee:

Tektronix, Inc. - Wilsonville OR

International Classification:

H04N 1700

US Classification:

358139

Abstract:

Spatial bandwidth testing for digital data-compressed video systems is performed using a complex, or high entropy, test signal. A portion of the test signal is acquired as a control frame. This control frame is divided into a plurality of blocks. Each block is processed by a two-dimensional Discrete Fourier Transform (DFT). The test signal is input to a digital data-compressed video system and a corresponding portion of the output of the video system, a test frame, is acquired and processed in the same manner as the control frame. The resulting coefficient arrays from the control and test frames are compared to each other to obtain an output array of ratios for each block. The ratio of those coefficients corresponding to the predominant frequency of each block of the control frame are displayed as a three-dimensional gain plot. The ratio of those coefficients corresponding to low frequencies of each block of the control frame are displayed as a three-dimensional noise plot. The resulting plots provide an objective, visual indication of the characteristics of the digital data-compressed video system.

US Patent:

47542055, Jun 28, 1988

Filed:

Sep 22, 1986

Appl. No.:

6/909972

Inventors:

Calvin D. Diller - Hillsboro OR
Douglas C. Stevens - Portland OR

Assignee:

Tektronix, Inc. - Beaverton OR

International Classification:

G01R 1330
H01J 2970
G09G 302

US Classification:

315377

Abstract:

An instrument for providing a principal display representing the variation of a first quantity as a function of a second quantity, comprises a display screen. A visually distinct dot is generated on the display screen and is deflected along one of two orthogonal axes in dependence upon the value of the first quantity and along the other axis in dependence upon the value of the second quantity. The dot is additionally deflected to selected positions along the two axes to generate an auxiliary display of a marker and of an information-conveying character adjacent the marker. The position of the auxiliary display is adjustable along at least one of the axes.

US Patent:

53879252, Feb 7, 1995

Filed:

Mar 18, 1991

Appl. No.:

7/673167

Inventors:

Laurent A. Melling - Scappoose OR
Edward D. Wardzala - Portland OR
Douglas C. Stevens - Portland OR
John C. Reynolds - Aloha OR

Assignee:

Tektronix, Inc. - Wilsonville OR

International Classification:

G09G 114

US Classification:

345134

Abstract:

A test signal generator applies a test pattern to a device under test. The output of the device under test is displayed on a video picture monitor. The test signal generator inserts a cursor into the test pattern, the position of the cursor within the test pattern being variable. From the cursor the test signal generator also generates a trigger signal. The trigger signal may be used to trigger the horizontal sweep of a waveform display device to which the output of the device under device is input. By observing the picture monitor an operator may adjust the cursor to a position just prior to an anomaly in the displayed test pattern so that only that portion of the output waveform of the device under test in the vicinity of the cursor is displayed on the waveform display device.

US Patent:

54556201, Oct 3, 1995

Filed:

Jan 21, 1994

Appl. No.:

8/184156

Inventors:

Douglas C. Stevens - Portland OR
James L. Tallman - Beaverton OR

Assignee:

Tektronix, Inc. - Wilsonville OR

International Classification:

H04N 1700
H04N 1702

US Classification:

348184

Abstract:

A system for automatic generation of vector reference graticules for a vectorscope display acquires the active video portion of a video signal that includes a color bar test signal. The values for each color difference component at each reference color plateau for the acquired color bar test signal are averaged to provide horizontal and vertical displacement values for each reference color, including black. Graticule boxes are electronically generated and positioned for each reference color on a display according to the respective horizontal and vertical displacement values.

US Patent:

47438452, May 10, 1988

Filed:

Sep 17, 1986

Appl. No.:

6/908551

Inventors:

Calvin D. Diller - Hillsboro OR
Douglas C. Stevens - Portland OR

Assignee:

Tektronix, Inc. - Beaverton OR

International Classification:

G01R 1320

US Classification:

324121R

Abstract:

In an oscilloscope, a readout control circuit is adapted to create a horizontal cursor on an oscilloscope screen at a vertical level controlled by cursor level data generated by a microcomputer, and to cause the beam to form characters on the screen indicating a voltage represented by the vertical level of the cursor. Vertical offset and vertical gain parameters characterizing a vertical preamplifier system controlling display of a waveform are measured and utilized to determine the value of cursor level data needed to cause the readout control circuit to position the cursor on the screen to accurately reflect a selected voltage with respect to voltage magnitudes represented by points on the displayed waveform. The oscilloscope is adapted to measure peak magnitudes of a vertical preamplifier input signal, and the readout control circuit permits the oscilloscope to display a cursor on a screen at a level indicating the magnitude of the measured peak with respect to magnitudes represented by a displayed waveform.

US Patent:

52744450, Dec 28, 1993

Filed:

Mar 1, 1991

Appl. No.:

7/663220

Inventors:

Michael S. Overton - Beaverton OR
Bruce J. Penney - Portland OR
Douglas C. Stevens - Portland OR

Assignee:

Tektronix, Inc. - Wilsonville OR

International Classification:

H04N 1700
H04N 1702
H04N 1704

US Classification:

358139

Abstract:

A three-dimensional test signal for a video codec is generated by injecting a conventional foreground test signal at a predetermined location as a foreground component within a background test signal as a background component, the background component having a variable complexity. The three-dimensional test signal is input to the video codec and the output of the video codec is measured using conventional measurement instruments. The background component may be a pseudo-random noise signal, a zone plate signal or other variable complexity-type signal, with the foreground component occurring at greater intervals than the neighboring pixels used by the codec compression algorithm. The conventional measurement instruments display only the foreground component with distortions in the video codec caused by the complexity of the background component appearing in the display. A spectral display of the output of the video codec using a zone plate signal as the background component may also be used to characterize the video codec performance.