Disc Quality tests
Having recorded the maximum amount possible onto the Verbatim 8x DVD+R Double layer media at its rated recording speed of 8x and above to all available review drives with Nero CD-DVD Speed, the next stage of this review will concentrate on Disc Quality.
The first part of the Quality tests involved scanning all the pieces of Verbatim 8x DVD+R Double layer media recorded on each review recording device with the Plextor PX-755A using Plextools Q-Check tests to find out how many potential SUM8 (PI Errors) and Sum1 (PI Failures) a playback device would have to correct whilst playing or transferring the recorded media. This also enabled me to obtain which of the 5 recorded pieces of media most matched the average result. The average disc shown below was then subjected to a Beta and Jitter test. Although more tests are available I believe I am showing the most common factors in overall disc quality for the average user.
"As the whole purpose of reviewing media for our readers is to try and obtain a good idea of the average quality of a given media, I have come up with this new methodoligy for determing these factors. These are my own personal views and by no means as accurate as an Industry C.A.T.S device for measuring the quality of a disc but I believe I have come as close as I possibly can do with the equipment available to the average user."
I will expect that not every piece of media is capable of producing this
with such influences as excepted media/ hardware tolerance levels having an impact but I will expect the results not to consistently stray too far from set standards for a recommended media. It is also the sum of all tests that I use to determine the overall quality of the media and not one test alone.
The less Sum1 and Sum8 that are found on a media then in theory the better the chances are of good long term playback for this media without data loss becoming a significant problem. Thats not to say that recordings with high Sum1 and Sum8 levels will be bad - the error correction logic of DVD playback and transfer devices are capable of correcting many potential errors. There is just more chance they might be affected by such influences as dirt or fingerprints. Different scanning devices scan slightly differently but basic guidelines using a Plextor drive are that Sum8 should not exceed 280 for sustained periods and Sum1 should not exceed 4 for sustained periods. You don't want to see any reported POF's (Parity Outer Failures) as these normally should result in uncorrectable errors!
Jitter and beta must remain within set specifications for a Plextor scan (Beta should not exceed +15 or -5 for sustained periods with the more level the result the better). Jitter should stay within the lower half of the graph for best results. Reading devices with good jitter correction ability should be able to read higher reported levels better than those that don't.
Overview of Disc Quality results:
Taking into account all tests carried out during this stage of the review, it is clear to see that recording at the rated speed of 8x didn't dispaly any errors of any serious concern and that a good quality recording had been achieved on all devices. The BenQ DW 1640 however, achieved a very good overall level of quality Vs recording speed and the results from this drive could be considered the best of any tested recording devices overall. The Plextor PX-755A which managed 10x to some parts of the recording also produced very appealing quality. Anyone who uses Plextor drives and Power record will know all about the way the Plextor can adjust recordings to any media dependant on a disc to disc basis to obtain good quality recordings using correct laser power.
The Philips DVDR1660P1 achieved a very good level of quality even if it couldn't achieve 8x for both layers under present firmware. But lets not forget the Pioneer DVR 110. Under firmware 1.39 it achieved a very good level of quality in the Sum8 and Sum1 tests but the very quality concious may like to see Jitter lowered slightly on the second layer. The high but still within specification Sum8 values towards the end of the first layer of the NEC ND-4551A recording was the least favourable of any recording achieved during this review. Some work is needed towards the end of the first layer to reduce potential errors and bring it more in line with other results achieved.
"Please note that you will need a compatible drive for doing these scans such as the Plextor PX-755A I have used in this review for making my decisions on the potential quality of this media. Other drives you could try include BenQ, Liteon, NU TECH and ASUS branded writers, but only the Plextor drives with Q check functions offer the full range of tests."
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