Sony DVP-NS330 DVD Player - page 3

Error Correction Tests

Here, we try to simulate one of the most interesting problems faced by the average user while using a DVD player, the reading accuracy of a DVD player when accessing a defective or scratched DVD or CD disc. Of course, the performance of the drive here has to do with the quality/precision of the 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.

Our experience from PC CD/DVD readers shows that some drives just skip the read errors at full reading speed, producing unreliable results, while some others dramatically slow down reading speed and perform read retries to maintain reading accuracy over the problematic areas. To our disappointment, firmware upgrades for the drives do not always positively affect the error correction performance of a reader.

In the case of a reader and especially a high-priced stand-alone reader, we do expect better control during the reading process. We tested the Sony DVP-NS330 with a number of pressed DVD-Video and AudioCD test discs. The ABEX series fromAlmedio offer a good picture of the error correction capabilities of a CD/DVD reader. In addition, we used the SBC444A test disc from Philips and the CD-Check test disc from Digital recordings.

DVD-Video

• Abex TCD-545

This 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 check for high quality picture and sound. The disc contents is a MPEG-2 NTSC DVD-Video file. Apart from the disc contents, 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. Fingerprints are sized from 0.065mm to 0.075mm.

Although a graphical presentation of the transfer rate when reading the test disc is always enlightening, it is not an easy task when you test a non-PC DVD player. As a result, we used the test disc as a normal DVD-Video disc and checked whether it is recognized and played correctly, with detailed navigation through the tracks and forward/reverse operations. Note that the size of the defects increases as we sequentially play the tracks.

The Sony DVP-NS330 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. We proceed to the next test disc, the Abex TCD-541.

• Abex TCD-541

This disc is exactly the same as the Abex TCD-545 tested previously, except that the defect is a scratch of dimensions varying from 0.4mm to 3.0mm, increasing by steps of 0.2mm/step.

The Sony DVP-NS330 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 the specific disc.

AudioCD

• Abex TCD-726

This is an AudioCD disc used for measurement and adjustment of the error correction ability and tracking/focusing servo characteristics of a player against the defects included in 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 the black dots are sized of 0.4mm to 1.0mm. Last, the simulated fingerprints are small gathered dots, of diameters sized from 65 micro-meters to 75 micro meters. 160pcs black dots in total construct the artificial fingerprint.

All audio tracks were played in the Sony DVP-NS330 deck. No audible read errors (clicks, skips) were reported.

• Philips SBC 444A

The test concept with the Philips SBC 44A is the same as in the previous test disc. Interruptions on the information layer vary from 400 micrometer to 1000 micrometer, while the black dots have a size of 300 micrometer to 800 micrometer. The test results of the previous test were confirmed, with the player reading the discs accurately.

• Abex TCD-721R

Same contents as with the Abex TCD-726, but different defect. A scratch sized of 0.4mm to 3.0mm is oin 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 Sony DVP-NS330 played successfully the first 7 tracks out of the 15 in total. The 8th track corresponds to a scratch size of 1.4mm. First problems occurred in the 8th track (1.6mm) with audible "clicks" while playing, followed by sound skips and playback interruptions in the 10th track (2.00mm). The remaining tracks were not playable at all.

This behavior has been met with many other PC CD players, where drives successfully corrected/concealed read errors coming from local scratches up to 1.8mm, approximately. Of course, some rare exceptions give us hope and raise our expectations from a player.

• CD-Check

We finish this testing cycle with the CD-Check disc from Digital Recordings. Five audio signals (5 tracks) in combination with disc error patterns to rate the player's ability to read music and reproduce it completely. The five tracks contain a sequence of progressively difficult tests.

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 2): 1.125mm scratch

Check level 5 (track 2): 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:

The Sony DVP-NS330 successfully handled (played) the first 3 tracks, which correspond to a scratch sized up to approximately 1.125mm. Notice that the same player managed to correct more seriously defective areas on the Abex TCD-721R test disc (up to 1.4mm). 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 drive "faces" the same scratch 4 times per cycle, making playback more difficult. Don't forget that error correction/ concealment procedures can be effected by statistical factors, and thus, repeating the same test does not always give exactly the same results.

Summarizing, we could say that Sony DVR-NS330 returned average behaviour in the error correction tests.