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Home > Hardware Reviews > Optical Storage

Tuesday, November 10, 2009
Sony DVDRW DRX-S70U-W

3. Reading of defected CDs

This series of tests checks the drive's ability to correct/conceal possible erroneous data after reading artificially scratched / defective audio discs.

Using a CD-R in best shape to do the DAE test is generally not a safe way to test the drive's error correction capabilities. If your drive would not read audio CDs error free from an error free disc, you would probably bring the drive back to the vendor. It is far more interesting to see how a drive is behaving under critical conditions (which will also tell something about the DAE quality on CDs that have manipulated C2 error information on purpose). For that a special test CD like the ABEX discs from ALMEDIO can be used, that can be used to do a comparison between different drives. The ABEX test disc is actually an AudioCD that has artificial scratches and other physical disc error patterns on its surface.

Using a special software, we compare two audio files using FFT analysis. The first audio file has been extracted by a normal audio disc without physical error patterns on it . The second one is the result of the extraction of the ABEX test discs which hold the same audio tracks, but it also has specific defects on its surface. The similarity factor of the the two tracks unveils the error correction capabilities of the drive.

The differences between the two compared tracks are translated to a signal (noise) illustrated in the following graphs. Each graph tells a lot about the abilities of the drive. The quality of the optical system (and/or of the error correction capabilities of the firmware) is shown in at which time index the error start. The error hiding qualities are shown when the wedge gets bigger. The X position of a grid line is always a start of a new minute position on the CD (in play time, up to 74 min). The Y axis shows the dB(A) value of the error in the extracted file. The 0 dB(A) baseline at the top is marked slightly different. So the graph shows a range of 6 dB(A) down to -120.0 dB(A). Each line represents 6 dB(A) of volume (6 dB(A) louder means that the sound is double as loud).

- ABEX TCD-721R

 

Errors total Num : 850849
Errors (Loudness) Num : 55658 Avg : -75.8 dB(A) Max : -21.9 dB(A)
Error Muting Num : 2794 Avg : 1.1 Samples Max : 34 Samples
Skips Num : 0 Avg :0.0 Samples Max 0 Samples
Total Test Result 76.7 points(of 100.0 maximum )

The drive's performance on this disc can be commented using the graph above. Error correction is good here, starting at the point where the defect is starting to grow, but error hiding mechanisms are average. We can tell that by the noise that almost all the time exceeds that -60 db(A) level, especially after the 32min mark where the scratch on the surface of the disc becomes bigger.

- ABEX TCD-726R

Errors total Num : 734
Errors (Loudness) Num : 162 Avg : -85.9 dB(A) Max : -58.2 dB(A)
Error Muting Num : 3 Avg : 1.0 Samples Max :1 Samples
Skips Num :0 Avg :0,0 Samples Max 0 Samples
Total Test Result 89.4 points(of 100.0 maximum)

The majority of the DVD burners we have tested so far had managed to accurately read the specific disc. The Sony drive reported some errors here but they should not make it out to your speakers, since they are below the -60 dB.

- CD-Check Audio Test Disc

The CD-Check Test Disc is another tool for evaluating the Sound Reproduction / Error correction capabilities of a CD player. The disc offers a signal combination with disc error patterns to rate the drive's abilities to read music and reproduce it completely. Five tracks on the disc contain a sequence of progressively more difficult tests. These tracks are referred to as Check Level-1 through Check Level-5.

The tracks are reproduced through a software multimedia player (e.g. Windows Media Player). Each level is considered as passed, if the tone is smooth, continuous without interruptions, skipping or looping. The higher the Check Level passed, the more reliable the sound reproduction of the tested drive.

Error Level 1 2 3 4 5
Sony DRX-S70U-W 5/5 5/5 5/5 0/5 0/5

An average good performance for theSony drive , as it successfully played only the first 3 tracks.




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