Calculating burn times

[Steve]

I'm trying to figure out if it's possible to know how long a given CD burner will take to burn a full (700 MB) CD. For example, I know my 52x can do one in about 2:40 (160 seconds), and I know that 1x=150 KB/s.

Say I wanted to pick up a 16x CD burner for whatever reason. I know 16x150=2400 KB/s, so let's call that 2.4 MB/s (I know, that's not exact but close enough for rough estimation). If I were to divide 700 MB by 2.4 MB/s I'd get 292 seconds (I think) or almost 5 minutes. Does that sound right? Am I doing it right?

 

[artikk]

Originally posted by: sm8000
I'm trying to figure out if it's possible to know how long a given CD burner will take to burn a full (700 MB) CD. For example, I know my 52x can do one in about 2:40 (160 seconds), and I know that 1x=150 KB/s.

Say I wanted to pick up a 16x CD burner for whatever reason. I know 16x150=2400 KB/s, so let's call that 2.4 MB/s (I know, that's not exact but close enough for rough estimation). If I were to divide 700 MB by 2.4 MB/s I'd get 292 seconds (I think) or almost 5 minutes. Does that sound right? Am I doing it right?

The theoratical math behind the concept is correct but you never know what in real life will happen. There will alwyas be slight changes in the final results. Different burners sometimes might burn a LITTLE faster/better or slower. Just my opinion.

 

[spidey07]

sounds right.

Although calculus would involve calulating the rate of change of the CD's angular velocity relative to linear write speed. The bits/sec (length) write is constant but the disc rotates at different speeds.

you're doing arithmatic.

 

[Steve]

Yeah, that's about as advanced as my math gets I do remember that rotational speed increases as the laser burns further out to the edge in order to maintain a constant data rate.

However it seems my math may be more flawed than that. By my formula, my 52x ought to burn a full disc in 90 seconds. It doesn't, even though Nero says it's maintaining a burn speed of 52x.

I remember my friend's old 4x burner taking 20 minutes to burn a disc, so 5 minutes on a 16 sounds right there....I don't know, how else could I estimate a typical, average burn time for a _x burner?

 

[sniperruff]

the "x" rating does not work that way. for example, a 48x burner probably will not burn a cd at half the time as a 24x cd burner.

lets say a burner is 52x, it only burns at 52x around the outer edge (or is it inner?) of a CD.

 

[TuxDave]

Looks about right to me...

 

[95SS]

80/speed = time is my general rule, plus time for TOC and finalizing.

 

[Kelvrick]

You'll have to factor in how long it takes the drive to spin up too.

Like, my NEC 3520 burns a 4.7gb disc in 7:17 seconds at 12x and 6:31 at 16x. Almost no difference except buffer hits towards the end at 16x.

 

[Steve]

Originally posted by: sniperruff
the "x" rating does not work that way. for example, a 48x burner probably will not burn a cd at half the time as a 24x cd burner.

lets say a burner is 52x, it only burns at 52x around the outer edge (or is it inner?) of a CD.

I think I'd heard that too, and I think it's the outer edge. I thought the 1x=150KB/s rate was constant, but maybe not when it comes to burning.

 

[TerryMathews]

Originally posted by: sniperruff
the "x" rating does not work that way. for example, a 48x burner probably will not burn a cd at half the time as a 24x cd burner.

lets say a burner is 52x, it only burns at 52x around the outer edge (or is it inner?) of a CD.

You're right, but you're also wrong.

You are correct in that a 48x drive will not burn twice as fast as a 24x drive, assuming it's not an uber 48x drive. Your reason is wrong however.

A 12x drive will burn twice as fast as a 6x drive. The difference there is that newer, faster drives have hit a RPM speed limit for discs. Not just burners either, readers too. Some manufacturers label it as CAV or constant angular velocity, but basically all drives > 40x do it.

Above a certain RPM, discs explode. It's just a simple fact. That RPM is lower than is necessary to achieve 48x on the inner track of a CD assuming a normal design (Not multi-beam, etc.)

You are correct in that only the outer edge hits that maximum speed. It's marketing speak. In the old days, the drives adjusted their angular velocity as the outer edge was reached to ensure a consistent burn speed. Run your burner at a low enough speed now and you'll probably notice the same behavior. From one perspective, these 'newer' drives are simpler. They don't adjust their speed as they burn - it's flat out with regards to RPM. That may be true of all the speeds, I've never honestly tested in a newer drive.

EDIT: And to keep this on topic. You can't really calculate burn times anymore. In the old days, it was disc size / burn speed * 1.1 (to account for lead-in and lead-out). That always got me within a few seconds of the actual time. There's almost no point these days - that formula was when I had a 2x CD-R drive.

 

[Syringer]

Originally posted by: sniperruff
the "x" rating does not work that way. for example, a 48x burner probably will not burn a cd at half the time as a 24x cd burner.

lets say a burner is 52x, it only burns at 52x around the outer edge (or is it inner?) of a CD.

I would think it's inner..since that's where it spins the fastest since the circumference around there is smallest. Given that, I would think that manufacturers would want to advertise the highest speed possible.

 

[TerryMathews]

Originally posted by: Syringer

Originally posted by: sniperruff
the "x" rating does not work that way. for example, a 48x burner probably will not burn a cd at half the time as a 24x cd burner.

lets say a burner is 52x, it only burns at 52x around the outer edge (or is it inner?) of a CD.

I would think it's inner..since that's where it spins the fastest since the circumference around there is smallest. Given that, I would think that manufacturers would want to advertise the highest speed possible.

Nope.

 

[yhelothar]

Originally posted by: sm8000
Yeah, that's about as advanced as my math gets I do remember that rotational speed increases as the laser burns further out to the edge in order to maintain a constant data rate.

However it seems my math may be more flawed than that. By my formula, my 52x ought to burn a full disc in 90 seconds. It doesn't, even though Nero says it's maintaining a burn speed of 52x.

I remember my friend's old 4x burner taking 20 minutes to burn a disc, so 5 minutes on a 16 sounds right there....I don't know, how else could I estimate a typical, average burn time for a _x burner?

You got it backwards, along with TerryMatthews here. The rotational speed decreases as the laser burns farther out on the edge as the circumference is bigger thus passing through more data per RPM. In the center, it requires the cd to spin faster.

 

[Calin]

The audio CD rotates around 700 rpm for the center "tracks" and down to some 200 rpm on the outer edge. The idea is to keep a constant linear velocity (CLV) at the read head (laser) so the data is read at a constant data rate (every linear inch of the spiral on the disk contains just as much info as any other linear inch)
To improve the read speed, at first they used faster rotational speeds. After a while, as faster rotating disks produced vibrations and so on, they have "sectors" of CDROM radius that are processed at an linear velocity. If you use 2 sectors, on the inside sector the CDROM will spin at 700 to 450 rpm, at rating of 1x. On the second half of the drive, the CDROM will spin at 700 to 450 rpm, but at twice the linear disk speed, and so twice the data speed. This would be a 2x drive, even if its performance would be 1.5x (or less on CDROMs that are not written completely)

Calin

 

[notfred]

700mb is an 80 minute CD. That's 80 minutes at 1x. 40 minutes at 2x, 20 minutes at 4x, 10 minutes at 8x, 5 minutes at 16x, etc. You get the idea.

 

[Steve]

Originally posted by: notfred
700mb is an 80 minute CD. That's 80 minutes at 1x. 40 minutes at 2x, 20 minutes at 4x, 10 minutes at 8x, 5 minutes at 16x, etc. You get the idea.

If that's the idea, that data transmission rate is inversley (sp?) proportional to time constantly, then 32x is 2.5 minutes. My 52x does a full disc in 2.5 minutes, so either it's not true of burns or my burner is not doing 52x.

Calin, I think I understand your explanation of CLV, do you think you could elaborate on CAV for me?

 

[TerryMathews]

Originally posted by: virtualgames0

Originally posted by: sm8000
Yeah, that's about as advanced as my math gets I do remember that rotational speed increases as the laser burns further out to the edge in order to maintain a constant data rate.

However it seems my math may be more flawed than that. By my formula, my 52x ought to burn a full disc in 90 seconds. It doesn't, even though Nero says it's maintaining a burn speed of 52x.

I remember my friend's old 4x burner taking 20 minutes to burn a disc, so 5 minutes on a 16 sounds right there....I don't know, how else could I estimate a typical, average burn time for a _x burner?

You got it backwards, along with TerryMatthews here. The rotational speed decreases as the laser burns farther out on the edge as the circumference is bigger thus passing through more data per RPM. In the center, it requires the cd to spin faster.

No, I didn't. I said the speed adjusts in newer drives, and I am right. I didn't say the RPMs get faster, as a matter of fact I said they stayed the same which is 100% correct. How else can you explain that a drive will burn the inside at 20x and the outside at 48x?