Reduce Jaggy / Comb Effect

Dach wrote on 12/21/2009, 7:47 PM

I know this topic has been discuss before, but I am having no luck find past post. I am work on a project that is consisting of some pictures that originated as a PDF from a newspaper publisher. The images represent pages from their paper.

I am keyframming or panning across the image and on some I am experiencing some vertical lines jumping, being jagged, combing what every we want to call it.

Does anyone have any sure way to reduce or eliminate this effect? Is there a best file format, resolution, dpi, etc.

Thanks,

Chad

Comments

xberk wrote on 12/21/2009, 8:02 PM

Discussion on still images

Discussion above might shed some light.

Hellot wrote on 12/21/2009, 8:11 PM

Hey Dach. Sorry I don't have any help for you, but I'm having the same problem I think. A weird coincidence that I was just coming on here to ask the same question. I've rendered lots of things in vegas and have just ignored it. After being persuaded that Vegas is the best way to capture video, since it makes an exact copy of the footage, I noticed that it has a comb effect when theres movement even in the DVs native format. I've never had this problem with other software which leads me to believe that vegas is the problem. Others have said that the problem must lie in something else since vegas just makes an exact copy. Why doesn't the jagged edge or comb effect happen in windows movie maker for example?

musicvid10 wrote on 12/21/2009, 9:00 PM

Be sure you are rendering at Best.

johnmeyer wrote on 12/21/2009, 9:11 PM

The combing effects are perfectly normal and will not affect the way the video is displayed in the final version on DVD or, if you render back to DV tape, the way it will look if you play it from tape.

Vegas is working exactly as it should and you don't need to worry.

The reasons the lines show up is that a computer display shows, at the same moment in time, both fields that make up interlaced video frame. You can Google "interlace video" as others have suggested and get some really good tutorials on the subject. The short version is that all video shot on DV tape is interlaced. Interlacing refers to the fact that traditional video (now sometimes called SD) records every other line of video in one pass. This takes 1/60 of a second for NTSC video and 1/50 of a second for PAL. During the next 1/60 of a second it fills in the lines that were missed in the first pass. Thus, if there is horizontal motion in the video, you will get "herringbone" patterns in the video if you display it on a monitor that cannot paint odd fields at a different moment in time than even fields. This is what computer monitors do, so you will see these herringbones.

If the patterns bother you, you can change the quality of the Vegas preview window. There is a little icon at the top of the preview window. Change the quality from Best to Preview. This will display only the odd fields. While this only shows half the resolution, it completely eliminates the herringbones. This is what other software does by default and is why you don't see it when playing the video on other software. The final video will be encoded with the interlacing.

Some people see these artifacts and mistakenly believe that something is wrong, and they try very hard to remove the interlacing. This actually does need to be done when the video must be displayed on TV sets that don't support interlacing. However, this is best left to the TV set itself (or the DVD player, if it is equipped with the right software). Do not try to do it yourself.

Hellot wrote on 12/21/2009, 9:23 PM

Great explanation. I always thought that something was wrong. I'm going through the process of recapturing all my tapes through Vegas now.