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How do burners work exactly?

By billyellis
Jan 6, 2010
  1. I know the basics, but based on my general understanding I am confused as to why a burning projects seems to start spinning slowly, then accelerate after a few minutes. As far as I have ever heard -
    http://computer.howstuffworks.com/cd-burner2.htm
    for example - the disc is read/written from the inside out.

    If that is the case, then the spin rate should be highest at the beginning and decelerate as the laser moves outward. But then why does a burn start quietly, then get louder and sound like the spinning rate has increased after several minutes? Is is related to the directory architecture being more complex to write than the data itself perhaps and needing a slower spin rate to achieve properly? Anyone know? Just curious.
     
  2. ManQu

    ManQu TS Rookie

     
  3. ManQu

    ManQu TS Rookie

    As a foot note ,I didnt know they had started tracking cd/dvd discs
    Wiki Quote :-
     
  4. dividebyzero

    dividebyzero trainee n00b Posts: 4,891   +1,258

    That information is already contained within commercially pressed discs. For example you can access basic information by ripping a disc with DVD Decrypter (or similar)- the information log will show the Source Media Implementation Identifier and in some cases the hardware involved.
    An easy way to ascertain if the movie you bought is bootleg is if this information comes up as a consumer program ( DVD Producer, Nero etc.) rather than commercial process (Sonic Scenarist for example). It would be a fairly straightforward process to include embedded hardware and firmware information.
     
  5. mailpup

    mailpup TS Special Forces Posts: 6,980   +362

    When you burn disks with data, burning isn't the only thing going on. At the end there is often a data verification mode. That can go at a much faster rate than burning so you will hear the drive spinning faster accordingly.
     
  6. billyellis

    billyellis TS Enthusiast Topic Starter Posts: 155

    I mean the actual burning process, not the verification at the end. Best conclusion I can make is that the first couple minutes are slow-burning the disc directory, and then it speeds up to start writing the binary data itself.

    Based on the paste above "DVD store data with constant linear velocity" which would imply a DEceleration of the spin as the laser moved outward, there still should be a very noticeable change in rotational velocity as the burn progresses. Maybe the spin rate does change and we simply can not detect an audible difference in drive noise? Seems unlikely, but what other answer could there be?
     
  7. SNGX1275

    SNGX1275 TS Forces Special Posts: 10,715   +397

    The initial slowness is because it is writing the lead in, and I believe the TOC, once that is completed it starts writing the data you want. My guess is it writes those at a slower speed to give it a better chance of being written properly.
     
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