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Discussion Starter · #1 ·
When I recently installed a Hitachi SX-5500 LCOS, I noted that at 78", SOMETIMES during a scene change, for a fraction of a second (almost subliminal) I see black lines across a portion of the screen that appear as scan lines. Though it can happen at any type of scene, it seems most common on scene changes that would have an instant fade to black back to the next scene.


When projected to 60" the lines are less noticable, but probably because they are smaller. OK, I figured that this was due to the de-interlacing process when perhaps, something takes a split second (30th or 60th of a second?) to be processed to "catch up" with something else. That being the case, a progressive scan DVD, should not show these lines.


Well, I also see scenes in 5th Element Superbit in PS mode (Pioneer DV-47A) that display these lines, so it's not a de-interlacing artifact.


Because one doesn't want to fire up the projector to program the VCR or see on-screen menus while listening to music, I also incorporated a 7" LCD display into the HT. Now here's the rub... to my suprise, I also see these lines on the 7" display, so now I know it's not the Hitachi!


So what am I seeing??? Is this an artifact of fixed pixel devices? I never saw these before on any of my CRT or rear projection (45" Mitsubishi) units. I point it out to my wife and she said that maybe she thinks she saw it once. Now, I can't watch TV or movies without seeing it time after time.


If you want to look for this effect, one place to look is in the Fast and the Furious in the scene where the four cars are ready to race. At one point there is a scene with a white area for an instant (maybe representative of exhaust). Look for these lines in this white area. In the movie I don't see the lines but in the section of the commentary, trailers, or such (don't remember which and don't have the disc at this time), I get it everytime I play the scene. To make it even more confusing, on some movies, I don't see it everytime, even when playing the same scene. :confused:
 

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I occasionally see that same artifact with my setup. I've always assumed it's due to a single mis-tagged field in the MPEG stream at the scene change. I think it's tough for MPEG encoders to always get the 3:2 tags exactly right across a scene change. However, given that the DVD is mastered just once, but watched millions of times by millions of viewers, it's pretty shoddy work to not get the tags exactly right.


Dave
 

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It sound like film 3/2 pull down. Does your DVD player have 3/2 pull down? Some DVDs are flagged wrong (not F&F though) and will cause this but your player must not have this feature. Progressive scan does not guarantee 3/2 pull down. If you want to all but prevent this go to a HTPC and you will have the added benefit of a superior scalier to boot.
 

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The software DVD players used by HTPC's rely on the same flags that progressive DVD players do, so using a HTPC will not prevent this problem. It does happen very infrequently with the majority of DVD's however. Some discs (most Japanese Anime, for example) have got the problem in spades, but otherwise I've only seen it every now and then.


Dave
 

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Discussion Starter · #5 ·
Both the Hitachi and Pioneer have 3:2 pulldown, but because this occurs on broadcast television from digital cable (including such things as sit-coms and commercials) and movies and specials on DSS, I doubt that it is a 3:2 pulldown artifact.


Again, can anyone identify this phenonom?
 
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