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Another disc speed question... Math included

post #1 of 6
Thread Starter 
If I have a player capable of 16 times speed and i use 16 X discs and I have one hour of material at XP mode....
It should take only 3.75 minutes why does it take closer to nine or 10 minutes if I have something that's on a disk that's full what exactly does the time speed mean?
post #2 of 6
Are you using one of your newer Panasonic DVDRs? If so the top speed of it's burner is 8x no matter how fast the DVD says. Also if you use the recommended silent burn feature I believe it tops out at 4 or maybe 6x. I use silent because I believe it's easier on the drive, I also feel the likelihood of a failed burn is less.
post #3 of 6
From the DIGITAL FAQ web site:

http://www.digitalfaq.com/guides/media/dvd-media-concepts.htm

Quote:
The x speeds.
The x in a burning speed means almost nothing. It is not a multiplication of anything, especially when Z-CLV and P-CAV burning is involved. As you surpassed 4x speeds, time savings diminishes quickly, especially between 8x-16x speeds. Speeds range on several factors, including disc type, burning method, and the drive itself.

1x DVD burn takes approximately 55-60 minutes
2x DVD burn takes approximately 25-30 minutes
2.4x DVD burn takes approximately 20-25 minutes
4x DVD burn takes approximately 14-16 minutes
6x DVD burn takes approximately 9-12 minutes
8x DVD burn takes approximately 8-9 minutes
12x DVD burn takes approximately 7-8 minutes
16x DVD burn takes approximately 6-7 minutes

Zonal burning.
It's pretty much impossible, at least with current hardware, to spin a disc at 16x from start to finish. Blame physics. With 4x and slower media, the drive spun up to the burn speed, and burned 4x from beginning to end, using the CLV (constant linear velocity) burning method. The disc also had a uniform look on the burned dye.

With the advent of 8x media, Z-CLV (zonal constant linear velocity) and P-CAV (partial constant angular velocity) were introduced. Z-CLV starts at a speed like 4x, then at a certain point in the media, jumps to 6x, then 8x, etc., until it reaches the maximum speed. Sometimes a 16x Z-CLV burn will only burn a few hundred MB at 16x, which is why x speeds mean almost nothing anymore. P-CAV is similar, but does not jump speed. It increases velocity from 4x to 4.5x to 5x, etc., until it reaches it's top speed. Much like Z-CLV, it may not hit max speed until the last 30 seconds worth of burning. This is why a 12x burn is almost an identical wait time to the speed of a 16x burn.

Yeah, the x speed ratings are mostly a marketing ploy I guess.
post #4 of 6
It's because "16X" is the PEAK transfer speed of the DVD, not the average or constant speed.

There's a lot less data per rotation on the innermost part of the disk compared to the outermost part of the disk. Because of that, you only hit the peak speed when recording the very outermost part of the disk - the inner tracks are much slower. And since recording starts at the innermost part of the disk you'll never actually hit the peak speed at all unless you burn the entire disk.
post #5 of 6
Thread Starter 
Thank you church AV guy, that was a great reaponse
post #6 of 6
I noticed the time difference between 8x disks and 16x disks was less than two minutes, and was CERTAINLY not the 50% that I was expecting. you're not the only one who was confused. Someone else posted this for me when I asked, so I figured I should do it for you. smile.gif
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