# [opendtv] Re: Math of oversampling

*From*: Mark Schubin <tvmark@xxxxxxxxxxxxx>*To*: opendtv@xxxxxxxxxxxxx*Date*: Fri, 22 Apr 2005 13:20:06 -0400

>If a broadcaster uses a 1080p camera and broadcast as 480P and on the >reception end it is upconverted to 720P or stays 480P I understand that >because of oversampling both the 720P or 480P image would be better than >otherwise would be expected. What I would like to do is quantify this >value. How would you compare a straight thru 720P broadcast to one such >as that above. Would the 1080P>480P>720P route be 75% of the quality of >the 720P>720P>720P route? Would 1080P>480P>480P be 110% of 480P>480P>480P? > > The calculable quality is not betterness but potential sharpness. The psychovisual sensation of sharpness is proportional to the square of the area under a modulation-transfer-function (MTF) curve, a curve plotting contrast ratio against detail fineness. There are many factors contributing to the function (lens, aperture, etc.), but, for the purposes of your question, two "all-else-being-equal" (meaning an HD lens on an SD camera) factors will affect the sharpness: the number of samples in the imaging chip and the optical low-pass filtering. Even dealing with just the former involves significant math: http://www.cs.virginia.edu/~gfx/Courses/2003/ImageSynthesis/scribed_notes/09_sampling.pdf I understand that I can't include attachments on this list server, but, if anyone wants a diagram of the various contributions to MTF, contact me directly, and I'll send it. It's only about 70 KB. TTFN, Mark ---------------------------------------------------------------------- You can UNSUBSCRIBE from the OpenDTV list in two ways: - Using the UNSUBSCRIBE command in your user configuration settings at FreeLists.org - By sending a message to: opendtv-request@xxxxxxxxxxxxx with the word unsubscribe in the subject line.

**Follow-Ups**:**[opendtv] Re: Math of oversampling***From:*Bob Miller

**[opendtv] Re: Math of oversampling***From:*John Golitsis

**References**:**[opendtv] Math of oversampling***From:*Bob Miller

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