detail information

The specifications of this drive tell us that it should write DVD±R at 16x and DVD+RW/-RW at 8x/6x. In this part, we will measure the write time for various types of DVD+R/RW and DVD-R/RW discs. We will also focus on write quality and media compatibility.

DVD-Writing performance:

In this test we will measure the time for writing to DVD±R discs. We used Nero Burning Rom to burn an ISO compilation containing 4480MB of data. We used the Disc-At-Once write method.

For these DVD writing tests, the Plextor PX-755A was set to the following.

⋅         PoweRec on
⋅         Auto Strategy on
⋅         All media had been stored in the Auto Strategy database prior to writing the disc.

DVD+R

DVD-R

Look below for the results.

The results are about average when compared to other drives.

Write quality:

You should first notice that this is not a scientific and professional way to test the discs. But according to our testing done in recent months, we would conclude that there is a clear link between the quality reported when scanning the disc and the playability of the disc in different devices. Also notice that different drives report different amounts of errors. K-Probe was designed to work with Lite-On DVD-Writers, so we recommend using a DVD-Writer from Lite-On. In this test we use a Lite-On SHW-16H5S DVD-Writer, as already said; remember that scans done with a Lite-On DVD-ROM or Lite-On combo drive can't be compared with the results obtained with a Lite-On DVD-Writer. Also remember that different PI/PO ECC sum settings along with different reading speeds in K-Probe will affect the result, we use these settings;  PI (Parity Inner) set to summarize 8 ECC blocks, PIF (Parity Inner Failures) set to summarize 1 ECC block, reading speed: 4X CLV (Constant Linear Velocity). Setting the PI sum to 8 and the PIF sum to 1 will give a result that we may compare to the standards for DVD+R/RW and DVD-R/RW.

But what is a good scan? That is a discussion that we don't think will end soon, as different drives report different amount of errors, some players are more picky about media than others, and so on. But as a comparison we present you with a scan from two pressed DVD discs:

This scan shows the results from a pressed DVD-Video disc (GoldenEye).

This scan shows the result from a pressed DVD-Video disk (The Green Mile). Notice the error jump when shifting to the second layer (the error level actually drops from the end of the first layer to the beginning of the second layer).

If you read below, you will see that both the pressed DVD-discs are well within the standards.

Download the ECMA 267 Standard for DVD-ROM, the ECMA 337 Standard for DVD+R/RW and the ECMA 338 Standard for DVD-R/RW at http://www.ecma-international.org if you want to look at the standards for yourself. Here is some data from the ECMA standards (same for DVD-ROM, DVD-R/RW and DVD+R/RW):

Random errors:

A row of an ECC Block that has at least 1 byte in error constitutes a PI error. In any 8
consecutive ECC Blocks the total number of PI errors before correction shall not exceed 280.

Here we see that a PI error is defined as a row in an ECC block having 1 byte or more containing errors and that the sum of PI errors in 8 ECC blocks after each other should not exceed 280 PI errors.

But what is a row and what is an ECC block? Again we refer to the ECMA standards. We do not copy and paste everything, but if you're interested, look in the ECMA standards. A row is 182 bytes long where the last 10 bytes contain PI (Parity Inner) information. An ECC block is 208 rows long where the last 16 rows contain the PO (Parity Outer) information. This gives us a maximum possible PI error amount of 208 errors per block and for 8 blocks after each other this sum is of course 8 times higher, giving a maximum possible amount of 1664 PI-8 errors. In practical use, a disc with 1664 PI-8 errors is unreadable.

According to our tests the specified max PI-8 sum of 280 for good discs seems to be a good guideline, as some readers have problems reading discs when the PI-8 errors is over 300 and most players starts to have problems when the PI-8 error level reaches 600 or more.

But what are the PIF errors that K-Probe reports? They are Parity Inner Failures, meaning errors left after PI correction. Only the ECMA 337 standard describes the Parity Inner Failures. So how is a Parity Inner Failure defined? Here is what the ECMA 337 states:

'If a row of an ECC Block as defined in 13.3 contains more than 5 erroneous bytes, the row is said to be 'PI-uncorrectable"."

In theory, an ECC block may in the worst case have 208 PIF since every ECC block is 208 rows long. But the ECMA 337 standard goes further and specifies the max amount of accepted PI Failures (uncorrectable errors) allowed on a good disc:

'In any ECC Block the number of PI - uncorrectable rows should not exceed 4."  

This means that when the PIF sum is set to 1, the maximum error value should not exceed 4. The theoretical maximum value for PIF is 208 errors.

But what makes a disc unreadable? A POF (Parity Outer Failure) error will make the disc unreadable, but K-Probe does not display the POF's.

Notice that there are other aspects such as disc reflectivity, jitter, tracking errors and so on that also will affect the readability of a DVD disc - but for this we do not have measuring equipment available.

Also, another note is that we have scanned the discs at 4X CLV speed, by lowering the speed to 2X(DVD-R/RW)/2.4X(DVD+R/RW) or 1X the amount of reported errors may drop on some discs. We scanned at 4X CLV due to lower speeds taking too much time.

To see if there is a connection between the reported amount of errors and readability of the discs we also include the reading curve from a NEC ND-3540A DVD-Writer. The reason why we have changed the reader is that some companies disliked that we used a modified firmware to obtain 16x reading speed. So to please them, we are now using a drive that reads DVD+R/-R media at 16x as default. A small speed reduction near the end is still accepted on good discs, but serious reading problems or reading failures is a bad sign.

Easier explanation on how to read the test results.

Maybe this got too technical, and you are wondering what to look for in KProbe reports?

Use this as a guideline for good discs:

• PI (Parity Inner): No larger areas on the disc should exceed 280 PI-8 errors, do not worry too much about high single spikes that exceed 280.
• PIF (Parity Inner Failures): No larger areas on the disc should exceed 4 PIF-1 errors, do not worry too much about high single spikes that exceed 4.

And as always; lower is better

And look at the reading curve; if it looks clean with no dips it should be good, a small slowdown near the end is accepted.

DVD+R media compatibility and write quality:

In these tests we will be using a Lite-On SHW-16H5S with firmware LS0T along with K-Probe to measure the disc quality. We will also be using the NEC ND-3540A with firmware 1.03 along with CD-Speed for our read-back tests. 

For these DVD writing tests, the Plextor PX-755A was set to the following.

⋅         Power Rec on
⋅         Auto Strategy on
⋅         All media had been stored in the Auto Strategy database prior to writing the disc.

A very good burn to start our tests. Recommended!

The burn quality is excellent but the PX-755A slowed down the burn to 12x.

A very good result from this difficult to handle media.

No surprises here, an excellent result from the Verbatim 8x media manufactured by Taiyo Yuden. Highly recommended!

Once again the result is excellent. Highly recommended!

Another excellent burn from the Plextor media manufactured by Taiyo Yuden. Highly recommended!

The PI errors are extremely low. Considering this media was burned faster than its rated speed, we have another excellent result. Highly recommended!

Once again we have an excellent result. Highly recommended!

Once again we have a very good result from the BenQ media manufactured by Daxon.

To finish off our DVD+R tests, we have another good result from the TDK 16x media.

DVD+ReWritable media:

We used the same test procedures as in our DVD+R tests.
Below are our obtained results

PI errors are high but are well within specification at the start of the disc. PIF errors are fairly low and our read-back test is perfect. The result is good.

The result is very good.

To sum it up: So far the Plextor PX-755A writes DVD+R with very good to excellent quality. DVD+RW write quality is also good.

On the next page you will find the DVD-R/RW writing results...