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SMPTE Journal ( Volume: 85, Issue: 2, February 1976)
[ACTIVE]

Differential Phase and Gain Measurements in Digitized Video Signals

Metadata

Publisher
SMPTE — White Plains, NY, USA
Doc Type
Journal Article
Content Type
Original Research
Abbreviated Title
J SMPTE
Volume
85, No. 2, pp. 76–79
Abstract
The peculiar nature of the standard test signal currently used in analog television system evaluation treats a digitized video signal in such a way that the true performance of the system under test (VTRs in particular) is not revealed. The common test signal for measuring DP and DG in a VTR is a 20-IRE-unit subcarrier superimposed either on a 100-IRE-unit ramp signal or on a stair-step signal. Experience has shown that even though the VTR circuits are only fractionally loaded, the results of DP and DG measurements may be easily interpreted for fully loaded (saturated color) operation. This is not true for combined analog and digital systems because quantizing errors, once introduced, have a fixed peak value so that they actually represent a smaller and smaller proportion of the signal as the signal is made greater. Standard measurements of DP and DG in high-quality digital systems can be so misleading as to show errors of more than 8% DG and 5° DP. Two improvements in measuring techniques are proposed: first, the subcarrier amplitude of the test signal should be doubled to 40 IRE units peak-to-peak, and second, the subcarrier phase should be made random during the ramp or stair-step. These changes will not eliminate the problem but will make meaningful measurements easier to obtain.
Publication Date
1976-02-01
DOI
10.5594/J13299
ISSN
Print: 0036-1682
Link
https://doi.org/10.5594/J13299
Author(s)
Michael O. FelixAmpex Corp., 401 Broadway, Redwood City, CA 94063
Copyright
© 1976 Society of Motion Picture and Television Engineers, Inc.

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Michael O. Felix; Differential Phase and Gain Measurements in Digitized Video Signals, SMPTE Journal ( Volume: 85, Issue: 2, February 1976); SMPTE, 1976. Available at https://doi.org/10.5594/J13299
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Michael O. Felix; Differential Phase and Gain Measurements in Digitized Video Signals, SMPTE Journal ( Volume: 85, Issue: 2, February 1976); SMPTE, 1976. Available at https://doi.org/10.5594/J13299

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Michael O. Felix; Differential Phase and Gain Measurements in Digitized Video Signals, SMPTE Journal ( Volume: 85, Issue: 2, February 1976); SMPTE, 1976. Available at https://doi.org/10.5594/J13299
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<span class="citation">Michael O. Felix; <cite>Differential Phase and Gain Measurements in Digitized Video Signals</cite>, SMPTE Journal ( Volume: 85, Issue: 2, February 1976); SMPTE, 1976. Available at <a href="https://doi.org/10.5594/J13299" target="_blank" rel="noopener">https://doi.org/10.5594/J13299</a></span>

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Preview:
Michael O. Felix; Differential Phase and Gain Measurements in Digitized Video Signals, SMPTE Journal ( Volume: 85, Issue: 2, February 1976); SMPTE, 1976
doi: 10.5594/J13299
url: https://doi.org/10.5594/J13299
Snippet:
<li>
Michael O. Felix; <cite id="bib-10-5594-j13299">Differential Phase and Gain Measurements in Digitized Video Signals</cite>, SMPTE Journal ( Volume: 85, Issue: 2, February 1976); SMPTE, 1976
<span class="doi">10.5594/J13299</span>
</li>

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