How to Calculate Current Real RPM of a CD/DVD Drive (Not Nominal RPM) Programmatically ?

Question

2.50/5 (2 votes)

See more:

Hi
Have you ever use some tools like Nero CD Speed Test, Opti Drive Controller, or DvdInfo?
In these applications you can get real RPM of a drive. I mean it is said that drives at the speed X have RPM Y but it's a nominal or maybe ideal RPM if you set your drive at a speed and get the RPM with these tools you will see it's a bit different and changes continuously.

For some calculation in my project I need to know the exact RPM at any time I want.
I've tested one method: reading a sector twice - from medium (not cached reading) - many times and calculating elapsed time between two reading, finally get median value. But it's a far different value from values which standard testing tools report (like tools I mentioned). For example for 24X speed, RPM should be near 5100 but any method I tested reported a strange RPM.

So how can I calculate RPM?

Thanks

Posted 3-Apr-14 9:29am

Coder-123456

Add a Solution

Comments

[no name] 3-Apr-14 22:23pm

What's the point? Unless these programs have access to the drive firmware then they are guessing the rpm. The rpm changes continuously with head position. Statistical methods if possible can only guess what the rpm was some time back. Actually no because statistical methods that use data transfer rate, seek time etc are collecting data that has nothing to do with rpm. A lot of mistaken assumptions here. Quite a bizarre question.

1 solution

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

bling · Answer 1 · 2014-04-04T06:10:00

I do not know if this will work. This assumes it is possible to read a whole track at once.

Read a single sector. Measure the time from IO request to arrival of the data.

Read a whole track (as a single request). Measure the time from IO request to arrival of the last sector.

For "N" sectors, the time difference between the first and second measurement should be the time to read N-1 sectors (while also cancelling any setup time for the read requests).

N times this number, divided by N-1 should be the time for a whole rotation. The reciprocal of that is your RPM. Don't forget to adjust from milliseconds to minutes.