How do burners work exactly?

[billyellis]

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.

 

[ManQu]

Wiki Quote :- Theoretical versus practical writing speed
Almost all of the modern CD/DVD burning software support selection of the speed at which the portable disc is written to. However, the option a user choses only defines the theoretical maximum of disc burning process.
There are other factors that influence the time taken for a disc to be written to:Resources available to the program: Reading or writing data on a disc consumes moderate to high level of system resources (including memory and CPU resources), and running other programs at the same time may force the CD/DVD drive to choose a lower speed automatically, to accommodate with the available resources.
Disc quality: Optical disc recorders detect the available speed options based on the data which is available on the disc itself; however, some low quality discs make a high speed option available to the software, while the burning process can never reach that speed in act.
The reading and writing process does not happen at a steady speed. Both CD and DVD store data with constant linear velocity, so outer tracks contain more data per radian than inner tracks. During reading and writing, data flow speed varies based on the position of the laser under the disc.

 

[ManQu]

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

Recorder Unique Identifier
Owing to pressure from the music industry, as represented by the IFPI and RIAA, Philips developed the Recorder Identification Code (RID) to allow media to be uniquely associated with the recorder that has written it. This standard is contained in the Rainbow Books. The RID-Code is the opposite[clarification needed] of the Source Identification Code (SID), an eight character supplier code that is placed on every CD-ROM.

The RID-Code consists of a supplier code (e.g. "PHI" for Philips), a model number and the unique ID of the recorder.

 

[dividebyzero]

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.

 

[mailpup]

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.

 

[billyellis]

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.

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?

 

[SNGX1275]

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.