Jitter. The untold story

Now the truth can be revealed. What they don’t want you to know about jitter.

I wanted to do a little jitter testing so I stuck a mini DVD burned with a 600 MB file into my Liteon 165H6, and ran DVDscan. I intended to investigate how much more jitter DVDscan was reporting than CDspeed was reporting.

I had noticed previously that the jitter measurement was repeatable. Subsequent scans would show the same jitter. But not this time. Each time I scanned, the jitter increased. I thought I would see how high it would get but after 12 scans I realized this might take a lifetime.

So instead I decided to see what would happen if I re-loaded the DVD. I hit the “tray out” button and then the “tray in” button. This cured the problem. The jitter dropped to a normal level and stayed that way for 12 more scans. Apparently the disc didn’t get loaded correctly the first time. Maybe this only happens with mini DVDs, and I don’t know how ofter it happens, but I will be more suspicious of any scans in the future unless I verify the jitter doesn’t change between scans.

I made a movie for your viewing pleasure. Until it plays at a theater near you, you can click the link. Actually it’s a 260KB animated gif. You will see the jitter increase for 12 scans, then drop to a normal level and stay there. As I said earlier, I reloaded the disc after 12 scans.

I suppose the PIE/PIF scans were changing also as the jitter increased, but I didn’t record those. I have to leave something for the sequel, you know :slight_smile:

I suppose now every time I go to burn a DVD I’m going to wonder if the disc is loaded cockeyed. Now I wish I had never run this test :sad:

Do you always re-run tests without cycling the drive tray? I find it safer to [I]‘reset’[/I] a disc by opening/closing drive tray if I want to re-run tests on it to help ensure what you experienced does not occur.

I don’t usually re-run tests, but I don’t ever remember recycling the tray until this happened.

I’m just confused. My little testing episode raised questions but provided no answers. Maybe the best thing to do is hope it doesn’t cause any problems, and forget it ever happened. :slight_smile: