Buffer underrun errors are encountered when copying files to a CD in a CDR, CD-RW. Several things might cause a buffer underrun error. This document explains what the error means and describes possible causes and steps that should be taken to avoid this error.
Introduction to CD writing
CD writing is a real time process that must be run constantly at the selected recording speed, without interruptions. The CD recorder’s buffer is constantly filled with a reserve of data waiting to be written so that small slow downs or interruptions in the flow of data from the computer do not interrupt writing.
Buffer underrun explanation and instructions
A buffer underrun error means that the flow of data from hard disk to CD recorder was interrupted long enough for the CD recorder’s buffer to be emptied, and writing was halted. If this occurs during an actual write operation rather than a test, your recordable disk might be ruined.
Possible causes of buffer underrun errors
- "Dumb" thermal recalibration
- Fragmented hard drive
- Sector size at 32 KB instead of 16 KB
- Not enough space in the temporary directory
- Slow source devices
- Source devices that transfer data in bursts
- Incorrect recorder controller settings
- Inability of the devices to sync properly
- Overall system configuration
- Computer unable to allow fast enough data transfer
- Old device drivers
- Any program that may activate on its own
- Anti-virus software
- Screen savers
- System agents
- TSR (terminate and stay resident) software
- System sounds
- Animated icons
Files to be recorded
- Recording many small files
- Damaged source files (data loss)
- Trying to record files in use by the system or other applications
- Copying from a CD that is scratched, dirty, or damaged
- Recorder malfunctioning
Troubleshooting steps to try
- Switch the CD-Writer to use 1x write speed.
- Disable the "write on the fly" feature in the Easy CD Creator program.
- Run the Scandisk utility.
- Run the Defrag utility (full optimization).
- Run a virus check using a virus protection program.
- Close other programs and TSRs that might be running on the system.
- Disable Power Management in the BIOS.
- Disable Power Management in the Windows Control Panel.
Checks and prevention
- Press the CTRL + ALT + DELETE keys to bring up the Close Programs window and end task on everything but the items Explorer and Systray before opening the CD-Writer software.
- Defragment your hard drives at least once a week to prevent files from being scattered across the hard drive.
- Do not record across a network. Copy the desired files to your local hard drive.
- Disc to disc copying requires a SCSI-2 or ATAPI CD-ROM drive. A 6x speed is recommended.
- Copying audio requires a source CD-ROM that supports digital audio extraction.
- Make sure that your hard drive does Smart Thermal Recalibration (that is, that it will not recalibrate if the CPU is being used).
- Record at a slower speed.
- Write a .ISO image to the hard drive first, if you have enough drive space.
- Always set audio to write at 1x.
- Keep the CDs, the recorder, and your source CD-ROM dust-free.
- Do not try to copy empty directories, zero byte files, or files that might be in use by the system at the time.
- More than 10,000 very small files should be written to a .ISO image first or recorded at 1x.
- Source files need to be in the best shape possible, preferably not too old, and not missing any bits or data.
- The temporary directory should always have space free that is at least twice the size of the largest file that you are recording.
Other information about buffer underruns
- If you are constantly encountering buffer underrun errors when trying to write to the CD-Writer, you can select "Test before writing" in the software used for writing to the CD-Writer. This will perform a simulated write of the exact file set you have chosen. Since this process is not actually writing on the disc, it will not ruin the CD if there is a failure.
- Other types of drives such as zips, slower CD-ROMs, and network drives do not have a high enough sustained transfer rate and/or access rate to keep the CD-Writer’s buffer full during a writing session. When writing from these types of devices, you must select the Write To The Hard Drive First option in the CD-Writer software and free enough hard drive space for the amount of data that you will be recording to the CD.
- Check documentation or contact the manufacturer of your hard drive to make sure that the hard drive has an average access time of 19 ms or lower, and that it will postpone Thermal Recalibration until the drive is not being accessed.
- Use the "Write To Hard Drive First" option in the CD-Writer software to lessen the number of accesses to be done to the hard drive and remove the strain of writing the .ISO image on the fly during a writing session. Even if you are writing the .ISO image to the same drive that is the source for the files in question, this will improve the chances of a successful write.
- To avoid getting buffer underrun errors during writing, disable any background applications running in Windows (screen savers, virus checkers, print managers, video managers, and system monitors).