Computer Expert Witness
Graham Dilloway CITP MBCS
Computer Expert Witness

Chartered IT Professional and Member of British Computer Society

Listed in Register of Expert Witnesses

Member of the Academy of Experts

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Computer and CD Equipment

My expert witness report indicated that CD equipment was unlikely to be able to mass produce counterfeit CD discs.

The Defendant was charged with copying music CDs after computer equipment and counterfeit CDs were seized from his home.  The defendant said that he had copied CDs for his family and had not been operating a commercial copying operation.

I produced a computer expert witness report that showed the capabilities of the CD writing equipment seized from the Defendant.

Note:   This report is reproduced exactly as it was when served excepting that company and personal names have been removed.


1. This report was prepared by Graham Dilloway of 39 Conham Hill Bristol BS15 3AW. I am a Member of the British Computer Society, the chartered professional body for the computer industry in the UK. I am a member of the Academy of Experts and of the Expert Witness Institute. I have worked with computers for 30 years. This work has all involved the implementation and configuration of computers, their operating systems and the core software applications of a computer environment (e.g. word processors and spreadsheets). I have worked with personal computers almost exclusively for more than fifteen years.


2. Part of my instructions are contained in a letter, dated 3 May 2002, from Solicitor S, that says, in part, "… indicate the rate at which it would have been possible to produce counterfeit CDs using the said equipment".

3. Further instructions were agreed in a telephone conversation with the solicitors on 23 May 2002 and I understand these further instructions to be:

"The "said equipment" referred to above is a Mitsumi CD Writer drive model number CR4804TE.

The report should explain the meaning of "buffer under run" when writing CDs and should describe steps that might reduce the effect of "buffer under run"".

Speed of Writing CDs.

4. Appendix A contains text copied from an Internet web site at and describes the meaning of "speed" when used to describe a CD drive.

5. The document says, "Regular audio CD players can play an entire audio CD in 74 minutes" and that some CD writers can "... write CD-RW disks at 4X, or 600 KB per second. It will write an entire 74 minute CD-RW in about 18 minutes (74 minutes divided by 4)".

6. Appendix B contains a specification for the Mitsumi CR4804TE CD Writer copied from the Mitsumi web site at

7. The specification for the Mitsumi drive says, "Transfer rates write: CD-R, 4x Speed: 600 Kb/sek, CD-RW, 4x Speed: 600 Kb/sek".

8. The specification for the Mitsumi drive says that this drive will write CDs at "4X" speed and the web site says that "4X" speed drive will write a full 74 minute CD in about 18 minutes.

Buffer Under Run

9. Appendix C contains a description of "buffer under run" copied from a Sony web site at

10. A summary of the description of "buffer under run" from the Sony web site would be that the computer fails to provide data to the CD Writer drive fast enough. This causes an error in the write process that may be audible when listening to the CD.

11. The article from the Sony web site describes steps that can be taken to reduce the risk of a "buffer under run". The description refers to a specific Sony drive but the steps described are relevant to all CD Writers. One of the steps described is, "Reduce the write speed of the CD-R/CD-RW drive."

12. For example, a CD Writer that usually runs at "4X" speed and suffers "buffer under run" errors might not produce errors if it was run at "2X" speed.

13. A CD Writer running at "2X" speed will write a full 74 minute CD in about 36 minutes.


14. A Mitsumi CR4804TE CD Writer will write a full CD in about 18 minutes in normal circumstances.

15. A "buffer under run" error can occur if the computer is unable to provide data to the drive quickly enough.

16. It may be possible to avoid "buffer under run " errors by running a "4X" drive at "2X" speed and writing a full CD in about 36 minutes.

17. This expert witness statement consisting of 3 pages each signed by me is true to the best of my knowledge and belief and I make it knowing that, if it is tendered in evidence, I shall be liable to prosecution if I have willfully stated in it anything that I know to be false or do not believe to be true.

Graham Dilloway
Expert Witness

39 Conham Hill


BS15 3AW

27 May 2002

Appendix A – CD Drive Speeds


What do the speed ratings (e.g., 6x4x32) mean for CD writers?

Regular audio CD players can play an entire audio CD in 74 minutes. This speed is called 1X (pronounced "one ex"). The 1X speed corresponds to 150 kilobytes of data per second. A CD-ROM drive rated at 2X ("two ex") can read an entire CD in 37 minutes, or 300 KB per second, and so on.

The three numbers in the speed rating for a CD writer correspond to the speed of writing CD-R discs, writing CD-RW discs, and reading CDs respectively.

(CD-R write speed) x (CD-RW write speed) x (CD reading speed)

So, a 6x4x32 CD writer can....

... write CD-R disks at 6X, or 900 KB per second. It will write an entire 74 minute CD-R in about 12 minutes (74 minutes divided by 6).

... write CD-RW disks at 4X, or 600 KB per second. It will write an entire 74 minute CD-RW in about 18 minutes (74 minutes divided by 4).

... read any kind of CD at 32X, or 4800 KB per second. It will read an entire 74 minute CD in just over 2 minutes (74 minutes divided by 32).

Sometimes, companies will mix up the numbers, putting the read speed first and the write speeds afterward. It's easy to figure out which number is which. The highest number is the CD read speed, the middle number is the CD-R write speed, and the lowest number is the CD-RW write speed. Sometimes, the CD-R and CD-RW write speeds will be the same.


Appendix B – Mitsumi CD Writer Specification

CD-ReWriter CR 4804 TE


Supported formats: CD-DA, CD-ROM (Mode 1 und 2), CD ROM XA (Write 2, Form 1 und 2), Enhanced CD, Photo CD ( read only ), CD Text, Video CDRecording methods: Disk at once, Session at once, Track at once, Multisession, Packet WritingSupported sizes: CDs with 8 and 12 cm diameterCD-drawer: Tray-loadingInterface: IDE/EIDETransfer rates read: 24x Speed up to 3.600 Kb/secTransfer rates write: CD-R, 4x Speed: 600 Kb/sek, CD-RW, 4x Speed: 600 Kb/sekBurst transfer rates: IDE 16 Bit PIO Mode: 16,6 MB/sek, Multiword DMA Mode: 16,6 MB/sekData Transfer Mode: PIO: 0, 1, 2, 3, 4, DMA: 0, 1, 2 (Multiword)Access time: Random Access: 110 ms typical, Full stroke(00:02.00 - 60:00.00) 180 ms typicalData buffer: 2 MegabyteAudio: Audio out: 770 mVrms an 0 dB, Headphones: out 470 mVmrs at 1 kHz, Volume control left and right possible via softwareReliability: (MTBF)>50 000 hoursPower supply: DC +5V, 1,5A max, DC +12V, 3,0A maxAmbient conditions: Temperature: +5° bis +40° Celsius, Air humidity: 10 bis 80%, non-condensing



Appendix C – Buffer Under Run

What is a buffer under-run error?

This error occurs when the PC's data transfer rate is slower than the write speed to a CD-R/RW disc. Data is temporarily stored in a buffer (memory for temporarily storing data for processing) on the drive before it is written onto a disc. If the buffer becomes empty due to the speed difference, the write operation cannot continue and an error occurs. This error may be due to the PC's insufficient CPU power, but can be avoided by using the following method. On the other hand, if you use abCD (or packet writing software), write is based on packets (64 KB each) and therefore buffer under-run error can hardly occur.

· The DRU110A has the function for avoiding the Buffer Under Run Error.

· Before performing a data write, close all running applications which have nothing to do with it. Also, remove screen saver and memory-resident applications (system monitor, anti-virus application, etc.) as they may cause error as well.

· Reduce the write speed of the CD-R/CD-RW drive. For instance,CD-R: 12X > 8X > 4XCD-RW: 4XHigh Speed CD-RW: 10X > 4X

· Reboot the PC before performing a data write operation.

· Perform defragmentation (put related data into the same location) on the hard drive before performing a data write operation.

· Turn off the power management function of the hard drive.

· Create a data image on the hard drive first, and then write to the CD-R/CD-RW drive.