6. Error Correction Tests
LiteOn LVW-5005 DVD Recorder - page 5
Error Correction Tests
Here, we try to simulate one of the most interesting problems
an average user frequently faces while using a DVD player, namely reading
accuracy of a DVD player when accessing a defective or scratched DVD or CD.
Of course, the performance of the drive here may be influenced
by the quality/precision of its mechanical parts (Optical Pickup Unit,
sufficient servo control, etc), as well as with the drive's reading strategy
under abnormal conditions, controlled by the main chipset and firmware commands.
In case of a reader and especially a high-priced stand-alone reader, we would expect a better control during the reading process. We tested LiteOn LVW-5005 with a number of pressed DVD-Video and AudioCD test discs. The ABEX series from Almedio offers a good picture of a CD/DVD reader error correction capabilities. In addition, we used SBC444A test disc from Philips and CD-Check test disc from Digital Recordings.
is a single-sided, dual layer (S-2 type, OTP) disc with 8.5GB capacity. The
disc can be used for checking the layer switching operation from layer1 to
layer 0. The disc also includes test pictures and test signals for Dolby Digital,
linear PCM (48kHz/24bit, 96kHz/24bit) and others to examine high
quality pictures and sound. The disc content is a MPEG-2 NTSC DVD-Video
file. The TCD-545 includes defects on
the disc area (black dots and fingerprints). The size of the black dots varies
from 0.4mm to 1.0mm. and fingerprints from 0.065mm to 0.075mm.
LiteOn LVW-5005 read the disc successfully, and no skips, picture stills or glitches were noticed. This good behavior is also prominent amongst most PC DVD recorders/players. Now, we shall proceed to the next test disc, the Abex TCD-541.
disc is exactly the same as the Abex TCD-545 tested previously, except that
the defect is a scratch in size ranging from 0.4mm to
3.0mm, increasing by 0.2mm /per step.
The LiteOn LVW-5005 showed very good performance again. All chapters of the DVD-Video were played correctly. Here we should say that not all PC DVD/CD players are able to read that specific kind of discs.
is an AudioCD disc used for measurement and adjustment of the error correction
ability and tracking/focusing servo characteristics of a player against
possible defects on some CDs. Three kinds of defects are included
on this disc, :interruption in information layer, black dots and fingerprints.
The interruptions are fabricated by intentionally varying the lengths of pits
in the disc fabrication area. Their size varies from 0.5mm to 1.0mm. The diameter
of black dots is from 0.4mm to 1.0mm. The simulated fingerprints
are, in turn, small gathered dots, of diameters sized from 65 micrometers to
75 micrometers. 160pcs black dots altogether construct an artificial
All audio tracks were played in LiteOn LVW-5005 deck. No audible read errors (clicks, skips) were reported.
Philips SBC 444A
The test concept with Philips SBC 44A is the same as in the previous test disc. Interruptions on the information layer vary from 400 micrometers to 1000 micrometers, while black dots have size of 300 micrometers to 800 micrometers. Once again the LiteOn device read the contents of the disc without any problems.
The medium has the same contents as Abex TCD-726, but a different
defect- a scratch sized of 0.4mm to 3.0mm on the disc's surface. Error
symptoms expected when playing this disc are noise, sound skips, same sector
repeatedly played, start of tune cannot be detected, etc.
The LiteOn LVW-5005 played successfully the first 9 tracks out of 15 in total. The 9th track corresponds to a scratch size of 1.8mm. First problems occurred at the 10th track (2.0mm) with audible "clicks" while playing.
Such a behavior has been encountered in case of many other PC CD players, where drives successfully corrected/concealed read errors coming from local scratches up to 1.8mm, approximately. Obviously, some rare exceptions give us hope and arouse our expectations of a player.
We finish this testing cycle with CD-Check disc from Digital Recordings. Five audio signals (5 tracks) are combined with disc error patterns to rate the player's ability to read and reproduce music completely. The five tracks contain a sequence of tests of progressively rising difficulty .
Check level 1 (track 1): Standard manufacturing errors
Check level 2 (track 2): 0.375mm scratch
Check level 3 (track 3): 0.750mm scratch
Check level 4 (track 4): 1.125mm scratch
Check level 5 (track 5): 1.500mm scratch
Any clicks, interruptions or looping during audio reproduction indicate failure of a Check level (audio track). Below you can see the test results:
LiteOn LVW-5005 successfully handled (played) the first 3 tracks, which
to a scratch up to approximately 1.125mm, at the end of the track. Notice
that the same player managed to correct more seriously defective areas on the
test disc (up to 1.8mm). The explanation here must be related to the way the
scratched areas are positioned on the surface of each disc. The Abex TCD-721R
places the scratched area on a single part of the disc. On the other hand,
the CD-Check disc "slices"
the disc circle in four equal sectors and each scratch is placed along the
margins of each sector (four equal scratches on the disc). As a result, the
the same scratch 4 times per cycle, making playback more difficult.
You should bear in mind, however, that error correction/ concealment
procedures may be affected by statistical factors, and thus, repeating
the same test does not always give exactly the same results.
Summarizing, we can say that LVW-5005 performed well in our error correction tests.