Philips DVP720SA DVD Player - page 7

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.

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 Philips DVP720SA with a number of pressed DVD-Video and AudioCD test discs. The ABEX series from Almedio can provide 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 Philips DVP720SA read the disc successfully, and no skips, picture stills or glitches were noticed. This good behaviour 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 Philips DVP720SA 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 from 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 of black dots in total, construct the artificial fingerprint.

All audio tracks were played in the Philips DVP720SA 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 micrometers to 1000 micrometers, while the black dots have a size of 300 micrometers to 800 micrometers. No audible clicks or skips was noticed during playback, indicating very good performance.

• Abex TCD-721R

Same contents as with the Abex TCD-726, but different defect. A scratch sized from 0.4mm to 3.0mm is 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 Philips DVP720SA managed to play up to track No 9 which has a defect size of 1.8mm. The rest of the songs with larger defects produced audible clicks, albeit low leevel.

• CD-Check

We finish this test 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:

Philips had good behavior with this disc also. The first four tracks were played flawlessly while the last one failed, producing some audible clicks. The overall performance of the DVP720SA in our CD error correction tests is very good.