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Home > Hardware Reviews > Optical Storage

Friday, October 22, 2010
Optiarc AD 7260S review

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. For example, a drive that will start error correction quite early indicates either bad optics and error correction. However, if the corrected data (wedges) stay below -60 dB(A) , this means that the drive has sufficiently hidden these errors and they most probably be unaudible, especially if they are surrounded by loud music.

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 : 806412
Errors (Loudness) Num : 46634 Avg : -74.1 dB(A) Max : -37.2 dB(A)
Error Muting Num : 2965 Avg : 1.1 Samples Max : 7 Samples
Skips Num : 0 Avg :0.0 Samples Max 0 Samples
Total Test Result Optiarc AD-7260S C2 Accuracy : 99.6 %
76.9 points (of 100.0 maximum)
Total Test Result LiteOn iHAS524 76.8 points (out of 100.0 maximum )
Total Test Result Optiarc AD-7240S 76.9 points (out of 100.0 maximum)

The drive's performance with 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, and error hiding mechanisms should be considerded as adequate. The average value for the errors is not high , although some wedges reachde the -37.3 dB(A). This means that some distortion (clicks, pops) could reach your speakers in the specific areas if you playback this file.

- ABEX TCD-726R

Errors total Num : 339
Errors (Loudness) Num : 12 Avg : -66.0 dB(A) Max : -57.4 dB(A)
Error Muting Num : 0 Avg : 0 Samples Max : 0 Samples
Skips Num : 0 Avg : 0.0 Samples Max 0 Samples
Total Test Result Optiarc AD-7260S C2 Accuracy: 100.0 %
93.3 points (of 100.0 maximum)

Total Test ResultLiteOn iHAS524

100 points (out of 100.0 maximum)
Total Test Result Optiarc AD-7240S 100 points (out of 100.0 maximum)

Surprisingly, the drive did not mahage to get a '100' score with this disc, which is generally easier for most DVD burner to habdle compared to the TCD-712R (scratched) test disc of the previous test. The reason is a wedge that appeared early enough and before the defected area, at around the 10min mark. This behavior could be attributed to bad optics and error correction.

 

- CD-Check Audio Test Disc

CD players have built-in D/A converters that turn the digital data on a CD into analog signal - what we hear as music. Ideally, all the digital data should be converted to the analog format. In reality, many factors cause digital data to be lost and sound reproduction to detoriate.

CD players handle this data loss using a sophisticated error correction system that allows them to recover it. However, when the data loss is greater than a system;s recovery ability, some of the signal is lost. It is then that the CD player uses compensation methods such as interpolation, data substitution or signal muting to make this loss as anaudible as possible. However, this results in altered and often distorted sound.

The level of sound distortion depends on the amount of data loss. Initially, music may sound brittle and there may be subtle problems with stereo imaging or dynamics. Over time, disc skipping, clicks, pops in the signal or audible signal muting may result. CD-CHECK contains a special signal (tone), designed for early detection of the most subtle forms of distortion. 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
Optiarc AD-7260S
5/5
5/5
5/5
5/5
0/5
LiteOn iHAS524 5/5 5/5 5/5 0/5 0/5
Optiarc AD-7240S
5/5
5/5
5/5
5/5
0/5

An adequate performance for the Optiarc AD-7260S , as it successfully played the first 4 tracks.




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