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Home > Hardware Reviews > Optical Storage

Friday, June 19, 2009
Blu-Ray Writing Quality Tests Vol 2

2. Testing process

For this test we used the Pioneer BDR-203BK and a Sony BWU-300S BD burners. A combination of Blu-Ray burners and BD-R/RE media were used for this test. All discs were burned at the highest allowed speed using the "Create Disc" function of Nero's CDSpeed utility, which burns the disc with data to its full capacity.

In the table below, you can see all the available media and burners we used in this test.

Media brand
Media ID
Media type / Certified speed
Nominal capacity
Burner
Write speed
Panasonic
MEIRB1 (001)
BD-R 6X
50 GB
Pioneer BDR-203BK v1.10
8X
Verbatim
VERBATIMb (000)
BD-R 2X
50 GB
2X
TDK
TDKBLDRFD (000)
BD-R 6X
50GB
8X
Moser Baer India
MBIR06 (000)
BD-R 6X
25 GB
8X
Panasonic
MEIRA1 (001)
BD-R 6X
25 GB
8X
TDK
TDKBLDRBB (000)
BD-R 4X
25 GB
8X
TDK
TDKBLDRBD
BD-R 6X
25GB
8X
Verbatim
VERBATIMc (000)
BD-R 4X
25GB
8X
Verbatim
VERBATIMe (000)
BD-R 6X
25GB
8X
Verbatim
VERBATIMw (000)
BD-R LTH 2X
25GB
2X
Verbatim
VERBATIM0 (000)
BD-RE 2X
7.5GB
2x
Verbatim
VERBATIM0 (000)
BD-RE 2X
25GB
2X
TDK
TDKBLDWfa (000)
BD-RE 2X
50GB
2X
Verbatim
VERBATIMa (000)
BD-R 2x
7.5GB
2X
Panasonic
MEIRB1 (001)
BD-R 6X
50GB
Sony BWU-300S v1.06
8X
Verbatim
VERBATIMb (000)
BD-R 2X
50GB
2X
Moser Baer India
MBIR06 (000)
BD-R 6X
25GB
6X
Panasonic
MEIRA1 (001)
BD-R 6X
25GB
8X
Verbatim
VERBATIMe (000)
BD-R 6X
25GB
6X
Verbatim
VERBATIMc (000)
BD-R 4X
25GB
4X
Verbatim
VERBATIMw (000)
BD-R LTH 2X
25GB
2X
Verbatim
VERBATIM0 (000)
BD-RE 2X
25GB
2X
Verbatim
VERBATIM0 (000)
BD-RE 2X
7.5GB
2X

As we previously mentioned, the software we used was the Opti Drive Control v1.21 by Erik Deppe and the reader was a LiteOn DH-4O1S vCP56 BD-ROM drive. The measuring speed was set at 4X.

Before testing, each disc was cleaned using air spray and special tissues. After cleaning, no dust particles or any visible signs of handling, such as minor scratches and fingerprints were identified in naked eye.

The OptiDrive Control v1.21 software has a "Disc Quality" function for Blu-ray discs. This function will scan the disc and report error parameters. For BDs the following parameters are measured:

  • LDC (Long Distance Code): number of parity errors on LDC codewords per ECC block (32 sectors)
  • BIS (Burst Indication Subcode): number of parity errors on BIS codewords per ECC block (32 sectors)

On a good disc the average LDC should stay below 13 and BIS should stay below 15, according to the author of the software.

Notice here that we have to do with the average values of these signals and not the maximum, which are present on the quality graphs as peaks. The software also reports jitter values.

Let's say a few words about the LDC and BIS signals.

For Blu-ray disc, , the Partial Response- Maximum likelihood (PRML) method is used for recovering the data from the signal.

Partial Response (PR) equalization is used to limit the effects of ISI, and then a sequence of bits is evaluated to define the most likely sequence of bits, based upon known allowed sequences. This is the Maximum Likelihood (ML) detection and uses a Viterbi algorithm to determine the ML sequence.

The Blu-Ray disc is more sensitive to burst errors compared to the DVD system. Therefore, the error correction system of Blu-Ray disc should be able to cope well with long burst errors, rather with single (random) errors.

The maximum number of errors that can be corrected depends on the number of parity symbols added. For each two parity symbols added, one error can be corrected. But Blu-Ray uses a more efficient approach to correct the burst errors. It uses a burst indicator mechanism that can detect bursts of errors before the correction starts. The advantage of this method is actually the prior knowledge of the error locations on the decoding process.

These burst indicator used in the Blu-Ray format is called picket code. The pickets are columns that are inserted in between columns of the main data at regular intervals. The main data is protected by a Reed Solomon code, while the pickets are protected by a second independent Reed Solomon code. When decoding (reading), first the picket columns are corrected. The correction information can be used to estimate the location of possible burst errors in the main data.

A BluRay Disc Error Correction Block (ECC Block) can store 64 Kilobytes of user data. This data is protected by the Long Distance Code (LDC) which has 304 code words with 216 information symbols and 32 parity symbols giving a code word of length 248.

A Blu-Ray Disc ECC block contains 4 equally spaced picket columns. The left most picket is formed by the sync pattern at the start of each row. If the sync pattern was not detected properly, that can be an indication for a burst error similar to the knowledge that a symbol of a picket column had to be corrected. The other three pickets are protected by the so-called Burst Indicator Subcode (BIS). The BIS code words are interleaved into three columns of 496 bytes each. Both LDC and BIS codes are decoded by the Reed Solomon decoder.

For additional information about the Blu-ray's error correction, modulation and quality signals read our previous Blu-ray Writing Quality article.

In the following pages we present the measurements for each disc.




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