Does this look right? Questions from a newbie with a NEC 3520

vbimport

#1

I created a data disc with my new 3520 using the Nero Test utility. The disc used was a Sony 8X DVD-R. The chart I got looked just like the attached chart. I don’t know how to post pictures of my own readouts so I borrowed this one from the Liggy firmware thread. The only difference was the type of disc used was a DVD-R not DVD+R (DVD-ROM). Is this indicative of a properly working DVD Burner? What’s with all the drop outs? Is there any way to fix this? I have noticed that when burning discs the 3520 seems to start at 4x and then about a 1/4 of the way through the disc moves to 6x and then after another 1/4 of the disc moves to 8x and so on. Why does this graph show a linear progression without the plateaus that I see when doing regular burns?

Thanks for helping a new guy out!

John


#2

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#3

All the “drop-outs” are where the burner stops to recalibrate the laser power. You’ll see mention of an AOPC or WOPC (optical power calibration) feature in the product specifications. This is fairly typical for many of today’s burners.

The graph you attached shows a transfer rate (green line) with a linear progression (actually, it looks more second order to me) because it is burning in constant angular velocity (CAV) mode. The rotational speed of the disc is fixed (at about 9000 rpm in this case) and the transfer rate varies as the laser moves across the disc. The circumference of the inner tracks is shorter than that of the outer tracks, but in CAV mode it completes one full rotation in the same amount of time (1/9000 minutes, or about 0.0067 seconds). Since it covers more distance in the same about of time (on the outer tracks) it can write more data in the same amount of time (higher transfer rate). The linear data density of the optical disc is constant over the entire surface (unlike magnetic data storage, where the data density frequently varies).

Your drive is burning in a zoned constant linear velocity (Z-CLV) mode. As the laser seeks towards the outer edge of the disc (optical discs burn from the hub towards the outer edge), the drive slows down the rotational speed of the disc to keep the linear speed (of the laser, with respect to the surface of the disc) constant. When the rotational speed reaches some lower threshhold, it jumps back to the higher speed, and the transfer rate goes into a higher zone (4x, 6x, 8x, etc.)

Yes, all this is completely normal.


#4

Ty:

That is the most scientifically precise response I have ever received to a post in any forum I have ever participated in and I presume I am somewhere in the hundredds at this point! Thanks for the insight! I realize now why I didn’t study engineering in college.

One other question, why is it that most people are posting smooth graphs without the drop outs? (See attached). They also seem to be achieving much better burn times (this was supposedly burned at 12x):



#5

The graph in your last post shows the results of a transfer rate test. This is reading a disc, not burning it.

DRF