Waitec VISION HR DVD Recorder - page 6

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 the 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 and 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 the case of a reader and especially a high-priced stand-alone reader, we would expect better control during the reading process. We tested the Waitec VISION HR 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's error correction capabilities. In addition, we used the SBC444A test disc from Philips and 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 layer 0 to layer 1. 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.

The Waitec VISION HR read the disc successfully without skips, picture stills or glitches.

• Abex TCD-541

This 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 15th track revealed a momentary freeze during playback. This track contains a scratch size of 3.0mm

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 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. 160 black dots grouped together construct an artificial fingerprint.

All audio tracks were played with the Waitec VISION HR deck. No audible read errors (clicks, skips) were detected.

• 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 black dots have a size of 300 micrometers to 800 micrometers.

All tracks played successfully.

• Abex TCD-721R

The medium has the same contents as the 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 Waitec VISION HR played successfully the first 6 tracks out of 15 in total. The 6th track corresponds to a scratch size of 1.2mm. First problems occurred with the 7th track (1.4mm) with audible "clicks" while playing.

• CD-Check

We finish this test cycle with the 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:

The drive managed to play successfully the four tracks out of the five. In the fifth track, only one attempt was clear without clicks. The remaining four produced audible clicks.

The VISION HR showed good performance in our error correction tests.