Testing and Writing

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About Data Transfer

The writing of a recordable CD or DVD is a continuous process in Disc at Once and Track at Once modes. The system has to maintain a high data transfer rate to the recorder. If the transfer rate cannot be maintained, the writing will fail. Recordable discs can usually be written at different speeds, depending on the capability of the drive, and the type of recordable media. The data transfer rate is dependent on the speed of recording and the type of track written (CD-ROM mode 1, CD-ROM mode 2, CD-Audio, or DVD).

For external images, the required transfer rate depends on the selected sector size. 2048 bytes/sector is comparable to ISO; 2336 bytes/sector is comparable to CD-ROM XA; 2352 bytes/sector is comparable to CD digital audio. DVD media always use 2048 bytes per sector, but operate at a much higher speed level that CD media. 1x DVD speed is equal to about 7.5x CD speed.

Writing a DVD disc therefore demands a lot from the system with respect to data transfer rate. If the required transfer rate cannot be maintained, a buffer underrun error will occur. Buffering GEAR creates the virtual image of the project that is written to CD-R(W) just before actually writing it. An interruption in the flow of data to your CD-recorder would cause a write failure and the loss of your disc. To ensure a steady flow of data GEAR fills buffers with data. As GEAR writes data to the CD-R(W), the GEAR information window provides you with information on the percentage of each track written to CD-R(W) and the percentage of data remaining in the buffer. The read and write buffer size ranges typically from 256 KB to 1 MB. The read buffer is filled from the drive interface buffer in blocks of its size. A similar process applies to the write buffer, in this case the drive interface buffer is filled from the write buffer and then written to the CD or DVD.

Testing

Before you start recording your disc there are several tests you can perform to ensure successful writing:

1. Verifying your project

2. Testing transfer rate

3. Test-mode recording


Verifying a project:

When you verify a project, GEAR checks the size, date, and time stamp for each file in the track or project. If there are discrepancies, it usually means a file has been updated since it was loaded into the project and GEAR prompts you to update the project. GEAR automatically verifies a project before starting the writing of the disc. However, you can always verify a project manually: With the project you want to verify open, choose Verify Volume from the Project menu. If verify reported that files and/or directories have changed since being loaed into your project, update the project by reloading the reported files and directories. As GEAR verifies the track or project, the status of the verification is reported in the GEAR information window. If you selected `Verify after write' in the Recorder Settings, GEAR automatically verifies the written disc against the project on hard disk. Test write GEAR project You are advised to check your system's performance before you start writing, especially for the first few discs you will write. GEAR tests whether it can read all the information from your hard disk and write it to the CD recorder. The data is not actually written to the disc.

Testing Transfer Rate:

Open the project you want to test Click on Test next to the Output Device panel at the bottom of the main screen or select Test Write from the Recorder menu. A GEAR dialog appears where you can choose to write the CD-R(W) immediately after a successful test. No data is transferred to the recorder during this process. If parts of the image cannot be read fast enough, GEAR warns you. For tips on improving your system's performance see See Improving System Performance. Some recorders do not support test-mode recording.

Improving System Performance

You can try any of the following to optimize your system's performance: Close any other software applications you are running in the background. e.g. Anti-virus software, screen savers, or any other software that may attempt to access the hard disk while GEAR is recording. Use a defragmentation utility to defragment your hard disk. Check to see whether your hard disk does recalibration. Check to see if your SCSI termination is correct. An incorrect SCSI termination can cause delays on the SCSI bus. Use a physical image instead of a virtual image.

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