Background
PCX is interested in selling DVDs that are good value. We are often approached by manufacturers and distributors to take on their media.
With vendors who have developed their own brand, we have wanted to find a way of quickly determining the appoximate quality of the disc. We found very early on that simply burning a few in a few different burners and playing them in a few players was not indicative of a disc's quality.
More recently we have adopted a method of burning the disc and testing it with a freeware software product that allows us to determine a rating system.
The average PI errors is what we use to evaluate the disc, where fewer errors indicate a better disc. This is far from a scientific process, however from experience it seems to work! PI errors are equivalent to reading retries and do not normally indicate blocks that can not be read.
Given the cursory nature of our testing, we look at ranges of Average PI errors to allocate a number of stars.
We would expect that if we were to test more discs from a batch, we would find some variation between discs and so the average result is what we are looking for.
The initial burn is verified and if the verify fails, we will try another few. We do not do the K-Probe tests on any disc that does not burn and verify without error.
How can I find a better disc?
In the end our experience in shipping many thousands of discs to hundreds of users is the real test of a disc. However we have some methods that we have developed to evaluate new disc offerings.
It is important to note that this testing is NOT statistically accurate, as we are testing only minute sample, it is simply an indicator for us when we are evaluating discs for resale. Simply a basic benchmark that we use to compare discs.
It is common to find an occasional disc that is 'bad' from any batch. Higher quality manufacturers have a lower proportion of 'bad' discs.
This is NOT a guarantee that you will get the same results. We strongly suggest that you perform the same or other testing to determine for yourself the quality of the media in your environment. This is because different burning and recording setups can affect disc compatibility
Here is an example (note that this is a general indicator and should not be taken to be the full story)
| Disc |
K-Probe
ave. errors |
Comment |
| Ritek DVD-R 4X |
0.55 |
This is a good disc |
| Ritek DVD-R 8X |
1.3 |
Good disc. |
| Princo DVD-R 4X inkjet burned at 4X |
14.0 |
This is an OK disc. |
| Anonymous DVD-R 4X burned at 4X |
67.0 |
Low quality disc!! |
We have found, based on this testing, that many of the most expensive discs are NO better than Ritek but are sold at substantially higher prices.
We have also discovered that lower cost discs can often be quite OK, but many are not.
It should be said that many people buy these
discs that we consider to be poor quality and have no problems, others may comment about some hesitation/pixelisation towards the end of the disc.
This is because there are blocks
that the DVD player can not read. If when the DVD was recorded it was also verified, then the bad blocks would be detected at this time.
Notably many people are not concerned about these 'slight imperfections' when recording video. Most importantly if you were using these discs for backup of data, then these bad blocks may mean that you can not access the files associated at all and so have effectively lost those data files.
Another attribute with regards to 'cheap' discs is their quality variability. We are often approached by vendors who can supply A-Grade, B-Grade and C-Grade discs. A common approach is to be offered a mix of A and B grade. This means that you may be getting say 1 in 5 discs that can not be successfully filled. This may not be a 'good deal' if you need to have no bad blocks on your DVDs. We sell only A-Grade discs!
Many of these discs will perform perfectly IF they are not filled, eg under 4GB are used. for a K-Probe graph of this kind of disc.
You may note an absence of discs that have less than a score of 3 stars. This is simply because we will not sell these discs.
We do not disclose information about the discs that are not acceptable to us.
Of course we are not implying that just because we do not sell a particular disc that it is in some way inferior. We do not plan to carry every brand of disc. We simply look to carry a range of good value discs and if we have a particular category covered, we do not feel the need to offer more disc makes.
PCX plans to include this kind of indicator with most DVD media over time.