Guy Kuo
Supporting Actor
- Joined
- Mar 6, 1999
- Messages
- 581
Scan Velocity Modulation (SVM) and edge enhancement due to oversharpening are often both present in a display. While these "enhancments" are desired by less critical viewers, their presence produces geometric and ojbect edge artifcacts which are anathema to realistic depiction of images. The traditional method to look for SVM is comparison of the black and white portions of the lines in a Needle Pulse pattern. AVIA adds a right hand side needle pulse to help detect geometry distortions which would otherwise be missed using a traditional single pulse pattern as in VE. There is another, simpler way to tell if SVM is present.
When SVM is active, the horizontal movement of the electron beam is slowed during bright portions of the image. This slowing horizontally shrinks bright objects. Edge enhancement due to over-sharpening does not geometrically distort objects in this manner. We take advantage of this when comparing the line thickness in AVIA's Needle Pulses pattern, but some people seem to have difficulty with that method.
Display the AVIA Checkerboard 100 IRE pattern (Title 2Chapter 25) and you will see a checkerboard of black and white. The corners of the pattern actually just touch each exactly as in a real checkerboard, but if SVM is present this does not happen. You will notice that the white tiles don't touch the corners of each other if SVM is active. That's because SVM activity horizontally shrinks the white tiles (and hence stretches the black tiles) making the WHITE tiles fail to touch each other's corners. This makes for a quick and easy way to determine if SVM has actually been turned off should there be confusion over whether or not a poorly labeled service control changes sharpness vs SVM.
If the white tile corners touch each other, SVM is off. If the white tile corners fall short of each other horizontally, SVM is on.
------------------
Guy Kuo
Link Removed
Ovation Software, the Home of AVIA DVD
When SVM is active, the horizontal movement of the electron beam is slowed during bright portions of the image. This slowing horizontally shrinks bright objects. Edge enhancement due to over-sharpening does not geometrically distort objects in this manner. We take advantage of this when comparing the line thickness in AVIA's Needle Pulses pattern, but some people seem to have difficulty with that method.
Display the AVIA Checkerboard 100 IRE pattern (Title 2Chapter 25) and you will see a checkerboard of black and white. The corners of the pattern actually just touch each exactly as in a real checkerboard, but if SVM is present this does not happen. You will notice that the white tiles don't touch the corners of each other if SVM is active. That's because SVM activity horizontally shrinks the white tiles (and hence stretches the black tiles) making the WHITE tiles fail to touch each other's corners. This makes for a quick and easy way to determine if SVM has actually been turned off should there be confusion over whether or not a poorly labeled service control changes sharpness vs SVM.
If the white tile corners touch each other, SVM is off. If the white tile corners fall short of each other horizontally, SVM is on.
------------------
Guy Kuo
Link Removed
Ovation Software, the Home of AVIA DVD
