The German computer magazine c't has 3 articles on HD-discs in the newest issue No. 15/2006, now on the newsstands in Europe. If you can get it, it's well worth looking at!!
The first article is a short introduction to the questions (particularly the what and why) addressed in the 2 longer articles.
The second article takes a look at 2 players they imported from the US (there are no home high-defintion drives currently available in Germany): Toshiba HD-A1 (HD-DVD) and Samsung BD-P1000. I won't say much about this test, other than that the technical quality of the BluRay sample movies was not that great: with the exception of one trailer, they didn't do justice to the bandwidth available. Both players had various warts and compatibility problems, but I won't go into this here.
The third article is the most interesting (at least for me
). They tested 2 BluRay burners with the presently available media types. I'll try to summarize the results in a similar style to the DVD tests.
The BluRay discs are the first comsumer optical media where the recordable discs and recorders were lauched at the same time as the players- that means (hopefully) that things like DVD booktypes won't show haunt us with compatibility problems. It also means the the rewritables (BD-RE) come with builtin defect management (like DVD-RAM) and should be more reliable than DVD or CD rewritables.
I'll say a few words about the physical construction and data structure of a BD-R because this affects what quality tests should examine. This information is also taken from the c't article. The primary source is the series of White Papers available at www.blu-raydisc.com
The physical structure of BD-media is different from CDR and DVD, in that the information layer is only ca. 0.1 mm from the lower surface. The upper (support) layer is ca. 1.1 mm. This has several consequences for the manufacturers that can potentially affect quality:
- the lower layer is too thin for pressing and really too thick for spincoating- needs special techniques
- this lower layer is also sensitive to scratching, which is why most manufacturers use some kind of hardened coating
- the asymmetric construction means that the discs are susceptible to bowing (distortion)
The information layer consists of phase-change material (e.g. GeSb) for rewritables and (at present) various inorganic material types for write-once media. Organic pigments are in development- these will be cheaper to produce but more susceptible to temperature and humidity.
The error correction mechanisms are based on recording blocks with 64 kiB data and 14.2 kiB other codes. Special "picket" symbols aid in the localization of "burst errors" (a sequential group of errors) that normally result from scratches or spots. There are 2 specified limits for burst errors that allow the error correction to still function correctly:
- no more than 8 burst errors (Burst Count = BC
) are allowed per recording block
- the sum of all burst errors in a recording block (Burst Length = BL
) should not exceed 600
In addition, individual errors may occur (e.g. from poor media or faulty burning). The resulting "Random Signal Error Rate" (RSER10K
) should not exceed 2 per 10000 recording blocks!
As with CD and DVD, the actual information bits are encoded in the land/pit transitions. To avoid too many sequential 1's or 0's, the information is encoded in so-called channel bits (8 data bits -> 12 channel bits). For DVD's, these vary in length between 3T and 14T (where T is the basic time unit). These are shown, for example, in the timing analysis (TA) graphs for Plextor drives and (lately) in the DVDScan jitter tests for newer LiteOn drives. For BD, variation is between 2T and 8T.
The variation in length of the pits and lands determines the jitter
, which should be < 6.5%. The difference in the DC offset between short (2T) and long (8T) signals determines the asymmetry ASYM
(10% to +15%), which should not vary much on a disk.
c't sent their test discs to Audiodev in Sweden who analyzed them with the new CATS B600 BDR Pro analyzer. As usual, c't combined the various measurements into a quality index (the details are not specified). As with DVD's, an index of 100 is perfect, >= 75 is very good (++), >= 50 is good (+), >= 25 satifactory (0) and >=0 is adequate (-). A negative index (--) means that uncorrectable errors occured or other signal aspects were greatly out of spec.
) on to the test results.
There are presently 5 brands (and 4 manufacturers) available or in preproduction. All come as both write-once (BD-R) and rewritable (BD-RE). The Fuji media is made by Matushita (Panasonic), Verbatim (Mitsubishi) are preproduction samples.
c't burned samples of all media with both drives (except the Verbatim: Pioneer only). The Pioneer-burned disks were measured by Audiodev, subjected to a cliamtic stabilty test with 100 hours at 80° C and 85% rel. humidity and tested again at selected radial positions. Because of the tight schedule, the Panasonic discs were also tested at selected positions only.
The results (index and grade) are summarized in the following table. All discs were burned at 2x CLV (9 MiB/s). In contrast to DVD's, c't did not specify a "mechanical index" for the unburned discs. I hope they add this information in subsequent tests.
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disc manuf. ID Pioneer Panasonic Pioneer
BD-RE25 Sony SONY (001) 87 / ++ 85 / ++ 73 / +
BD-RE25 TDK TDKBLDWBA (000) 70 / + 61 / + 72 / +
BD-RE25 Panasonic MEI (001) -61 / -- 67 / + -103 / --
BD-RE25 Verbatim VERBATIM0 (000) -94 / nr na -266 / nr
BD-R25 Sony SONY (001) 21 / - 67 / + 78 / ++
BD-R25 TDK TDKBLDRBA (000) -7 / -- 84 / ++ 64 / +
BD-R25 Panasonic MEI (001) -103 / -- 58 / + -199 / --
BD-R25 Verbatim VERBATIMa (000) -69 / nr na -34 / nr
- In all, the quality and compatibility is very good for this early stage in the product cycle.
- The best results were attained by the Sony and TDK BD-RE.
- Most discs exceeded the jitter margin but did not show pronounced extrema in the curves.
- Bowing generally remained within spec, even after the climate test
- A tendency to increasing RSER10K with radius indicates problems with the uniformity of the applied lower layer.
- Pioneer had problenms with some discs. Firmware update will probably help.
- The Verbatim media are preproduction samples and were not graded. The poor climatic showing of the BD-RE is due to increased jitter and needs work prior to volume production
- The Panasonic drive did better than Pioneer and is able to read and write CD's as well thanks to the dual lenses in the PUH.Drives
See the general discussion above.
There isn't much additional information here this time. There are no details available regarding DVD burns.
The Panasonic drive is only available as an OEM unit.
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Burn Quality Reading Noise
BD-R / BD-RE DVD R/DL DVD / CD BD / DVD
Model + Firmware
Pioneer 1.10 - / + + / -- + / na ++ / +
Panasonic B100 + / + ++ / + + / + ++ / ++
So, that was a while in the making, but because this is the first look at this kind of drive, there is some background information that won't need repeating in the future.