Hints for Producing Good Discs
Discs must be perfectly clean when recording. One of the most common problems is a speck of dust on the disc while recording. The speck will block the recording beam and create a “void”, where there are no “pits”. This will show up in the test results typically as E22 errors. Since data discs should not have E22 errors, this can be a fatal flaw.
Recording speed matters. Higher speed often gives poorer results. Everybody wants to go as fast as possible, and modern writers can record at very high speeds. Burning software typically defaults to the highest possible record speed. But if you want the best quality results, the highest speeds are not the best choice.
The best recording speed will depend on the writers and media you are using. Each different combination will have a different optimum speed, and produce different results.
Because of various compromises that must be made to cover a very wide range of possible recording speeds, we find that the optimum speed is close to the middle of the drive’s range. For instance, with the writers and media we use, we find that 16X recording gives the best results for CDs, and 6X recording produces the best results with DVDs, even though the drive is capable of 48X (CD) and 18X (DVD) recording.
If you are producing discs where quality matters, and there is a high cost of failure, it is well worthwhile to discover the optimum writing speed for your system. You can see a more detailed analysis at http://www.mscience.com/hispeed.html.
Compatibility between writer and media. There is no “best” media or writer, but some combinations work better than others. The trick is to find the combination that works best for you. Also keep in mind that the media will vary from batch to batch, so what worked in the past may not work now. The only way to find out what combination of writer, media and write speed works best is to try as many combinations as you can and measure the results.
How to Choose the Best Media
The number one issue is compatibility between the writer and the media. There isn’t necessarily a “best” writer or “best” media; some combinations work better than others. The writer’s laser power and write strategy must match the type of media used. Both media and writers have evolved over the years, so there are many opportunities for mis-match.Most major brands will produce good results with modern writers. But anybody can make a bad batch. The media is pretty consistent within a batch, so if there is a manufacturing defect, every disc will be bad. We have received bad batches from most major manufacturers. Defects range from stamper defects to bubbles in the plastic, to dirty discs and dye layer coating problems. We have had to change brands several times over the years when a particular brand’s process changed. You can use CDX or DVX to determine the best type of media for your application: Record a full disc at the speed you wish to use in production. It is important to record the whole disc, because media defects are more common at the outside of the disc. Then measure error rates and analog signal parameters. Low error rates (Grade A or B) are a good indication of recording quality, but you can learn more by also making analog “pit geometry” measurements. Beta, for instance is a function of the writers laser power. Negative Beta indicates that the laser power is insufficient for the type of media or the speed used. It is commonly seen that the Beta will drop as the recording radius increases, due to the increased writing speed. In this case, you can try a lower recording speed.
Reflectivity and I3 (or Resolution) are also good indicators of recording quality. Recordable discs have low reflectivity due to adsorption of the laser beam by the dye layer. If reflectivity is too low, the resultant signals will be too small to be decoded reliably.Recording speed also makes a big difference. Again, your results will depend on the combination of writer and media, but try each type of media at different speeds to see what works best. In general, the lowest and highest speeds will not work best. Recorders are optimized for high speed, so some compromise is made at the lowest speeds. The highest speeds are also problematic, as higher laser power is required and faster servos. With our writers and media, we get the best results at 16X on CDs, and 6X on DVDs. Check out http://www.mscience.com/hispeed.html for more information about the risks of high-speed recording.
You can also discover which is the lowest cost media that gives satisfactory results. Try several different types of media in your burners and see which works best. Cost is not necessarily an indicator of good media quality. If you can get as good or better results with lower cost media, you can save money.