SVM question (1 Viewer)

[Mike Goad]

I have been slowly calibrating my RPTV myself & have been reading alot about disabling SVM. Could somebody tell me what exactly SVM is on a RPTV and why I should want to disable it?
Thanks in advance

 

[Joe Tilley]

MIke,SVM stands for scan velocity modulation,I cant remember what it dose but it will make an improvement in picture quilty when turned off.

You may wont to have this post moved to the TV area to get a quicker responce.

 

[BruceSpielbauer]

Mike:

Joe was correct. SVM stands for scan velocity modulation. I am no expert, but let me see if I can describe it, based on what I have read (and even seen). Technically, it reportedly changes the acceleration of the electron beam such that it makes thin, dark vertical lines thicker to compensate for the softness of these lines when near the limit of resolution of the set. Unfortunately it also introduces artifacts, as we shall see.

Think about one object (perhaps a dark, dark color of someone's shirt) which overlaps another (perhaps a light blue sky). In reality, there is not any "line" of separation. None. And, if you take a good photo, there is still no actual "line." Now, imagine a novice artist drawing that image. The first thing he or she often does it to "outline" that shape, by drawing the outer edges. Perhaps with a thin, black marker. Some of this shape would be vertical lines, correct? SVM affects this area.

Some manufacturers found a way to artificially introduce (or enhance) such non-existant borders, in a way, because it can actually deceive the eye into thinking we are seeing a "sharper" delineation between the two colors. One person on another forum quoted someone from a newsgroup who described it as outlining shapes, just like Saturday morning cartoons. This is one type of "edge enhancement." However, it is NOT a true image. It was not ther in the movie theater, it is not there if you are watching them film, and it is not what the director wanted. At first glance, it may deceive the eye into thinking you are seeing a "sharper" image (on that showroom floor, when the set next to it does not have it). It results in ringing, though. And, I have read, additional jaggies.

I have also said the effect can be similar, in a way, to the older special effects techniques of simply superimposing, (this is pre-blue screen, and pre-green screen advances). Often, especially in films of the 50s and 60s, a slightly articial "glow" or "false border" appeared around the "cut out edges" of the superimposed image. I recall this on films such as The Ten Commandments, Journey to the Center of the Earth (60s version), and many more. It was a minor distraction, to be certain. Now, most edge enhancement is NOT that obvious. But, think of it as a lesser version of the same final effect.

The problem can be compounded when one is watching a film which has been transferred by someone who ALSO thinks this is an improvement. This does happen, I am convinced. So, we have some technician who is transferring a film to DVD, and HE or SHE decides the transfer will look much sharper if he adds some edge enhancement. Then, you buy that DVD, and watch it on a large screen set where the manufacturer added yet another level of edge enhancement (SVM). Now, you have (perhaps) a double-thick width of magic markers surrounding shapes, as lines of demarcation (ouch!) Or, you have two conflicting or overlapping edge enhancement schemes, on almost (but not quite) overlaid on top of the other, resulting in a mish-mash of almost out of focus edges.

I JUST discussed the video transfer of the Star Wars, Episode I (Phantom Menace) (the DVD) with someone on another forum. Many have complained this DVD does have its own added edge enhancement. This was perhaps ten minutes ago. I am also convinced that the True Lies DVD (a Schwarzenager film) is guilty of a lot of edge enhancement.

Hope that this helps your understanding, in some way.

-Bruce