Surface error scanning




Optical media can predictively be scanned for errors and media deterioation well before any data becomes unreadable.

A higher rate of errors may indicates deteriorating and/or low quality media, physical damage, an unclean surface and/or media written using a defective optical drive. Those errors can be compensated by error correction to some extent.

Error scanning software includes Nero DiscSpeed, k-probe, Opti Drive Control (formerly "CD speed 2000") and DVD info Pro for Windows, and QPxTool for cross-platform.

Support of error scanning functionality varies per optical drive manufacturer and model.

Error typesedit

There are different types of error measurements, including so-called "C1", "C2" and "CU" errors on CDs, and "PI/PO (pairity inner/outer) errors" and the more critical "PI/PO failures" on DVDs. Finer-grain error measurements on CDs supported by very few optical drives are called E11, E21, E31, E21, E22, E32.

"CU" and "POF" represent uncorrectable errors on data CDs and DVDs respectievly, thus data loss, and can be a result of too many consecutive smaller errors.

Due to the weaker error correction used on Audio CDs (Red Book standard) and Video CDs (White Book standard), C2 errors already lead to data loss. However, even with C2 errors, the damage is unhearable to some extent.

Blu-Ray discs use so-called LDC (Long Distance Codes) and BIS (Burst Indication Subcodes) error parameters. According to the developer of the Opti Drive Control software, a disc can be considered healthy at an LDC error rate below 13 and BIS error rate below 15.

Comments

Post a Comment

Popular posts from this blog

Optical Disc manufacturing

Optical discs are made using replication. This process can be used with all disc types. Recordable discs have pre-recorded vital information, like manufacturer, disc type, maximum speeds, etc. In replication, a cleanroom with yellow light is necessary to protect light sensitive materials and to prevent dust from corrupting the data on the disc. A glass master is used in replication. The master is placed in a machine that cleans it as much as possible using a rotating brush and deionized water, preparing it for the next step. In the next step, a surface analyzer inspects the cleanliness of the master before photoresist is applied on the master. The photoresist is baked in an oven to solidify it. Then, in the exposure process, the master is placed in a turntable where a laser selectively exposes the resist to light. At the same time, a developer and deionized water are applied to the disc to remove the exposed resist. This process forms the pits and lands that represent the data on the
Read more