Blu-ray Disc recordable

, there are five versions of BD-RE and four versions of BD-R formats. Each version includes three Parts (a.k.a. Books): Basic Format Specifications, File System Specifications, Audio Visual Basic Specifications. Each part has sub-versions (e.g. R2 Format Specification includes Part 3: Audio Visual Basic Specifications Ver.3.02, Part 2: File System Specifications Ver. 1.11, Part 1: Basic Format Specifications Ver. 1.3). In spite of having the "Blu-ray" brand, "BDXL" (or "BD-XL") is separate from the original "BD" format, meaning existing Blu-ray drives that predate the release of BDXL (mid-2010) do not support BDXL. Even Blu-ray drives released after that date may not necessarily support BDXL unless explicitly stated. == Capacity ==

A single-layer Blu-ray disc (BD-R and BD-RE) has a capacity of 25,025,314,816 bytes, which are 23,866 MiB. A dual-layer Blu-ray disc (BD-R DL and BD-RE DL) has 50,050,629,632 bytes, which are 47,732 MiB. This is exactly twice the capacity, unlike dual-layer DVDs, which only have less than twice the capacity as single-layer DVDs. This area is referred to as the "Volume Space" in the UDF specification, and stores the file system, names of files and folders, and the file contents. The same area is referred to as the "program area" on the CD. Other information such as where the disc sessions and tracks are located and their length are stored outside this area. If the spare area is enabled, 256 MiB (268.435.456 bytes) are taken away from the "Volume Space" and reserved for the spare area. Within the "Volume Space", the capacity that can be occupied by the content of files is also slightly reduced by file system overhead and by slack space as well, but the amount of slack space is trivial given that file systems on optical discs use a low cluster size (also referred to as "logical sector size") of 2 KiB (2048 bytes), matching the size of a single physical sector on optical discs. With packet writing, the file system overhead is larger. The spare area is where the drive stores addresses for unreadable sectors so they are replaced with new data in case. This is known as defect management and is handled internally by the drive, not by the computer's operating system. On some earlier formats, including the CD-RW and DVD±RW, defect management has to be handled by the UDF file system, meaning by the computer, also referred to as the "host" system. ==Speed==

, the following speeds are seen in Blu-Ray specifications for R/RE discs: Write verification is a feature of formatted Blu-ray media, officially called "Defect Management". Similar functionality existed on DVD-RAM and on Mount Rainer-supporting disc drives, but BD-R is the first write-once media with such functionality. If not deactivated, the correctness of the written data is verified immediately after being written. Poorly readable data can be written again to an area of spare blocks, but the writing speed is halved during the entire writing process because only half of the disc rotations are for writing. Defect management can be deactivated by burn programs using a feature called "Stream Recording" which enables full nominal write speed. Whether defect management is beneficial with mediocre media depends much on the individual medium and the drive's firmware. It works well with narrowly located bad spots but tends to fail more often than stream recording if the drive perceives reduced read quality on the whole medium. It may be desirable to deactivate write verification on undamaged media to save time when mass-producing physical copies of data, since errors are unlikely to occur on physically undamaged media. == Pricing ==

(approximate pricing): • BD-R/RE drive US$50 and above • 6× single-layer BD-R disc (25 GB) US$0.42 each in quantity; • 10× single-layer BD-R disc (25 GB) CN¥2.04 each in quantity; • 6× double-layer BD-R disc (50 GB) US$1.64 in quantity; • 2× single-layer BD-RE disc (25 GB) US$0.82 in quantity; • 2× double-layer BD-RE disc (50 GB) US$3.15 in quantity; • 4× BD-R XL disc (100 GB) US$5 in quantity; • 4× BD-RE XL disc (100 GB) US$11 in quantity; ==Recording mechanisms ==

Instead of the pits and lands found on prepressed/prerecorded/replicated discs, BD-R and RE discs contain grooves which contain a wobble frequency that is used to locate the position of the reading or writing laser on the disc. BD-R has an Optimum Power Calibrations (OPC) / Test Zone, which is used to calibrate (finely adjust) the power of the writing laser before and during writing, and it also has a Drive Calibration Zone (DCZ) at the outer edge of the disc, for optional high speed calibration. The calibration is necessary to allow for slight manufacturing defects, greatly reducing or completely eliminating rejected discs and drives, reducing costs and eliminating potential waste. The information below describes the different types of recording layers that may be used on BD-R and BD-RE discs. HTL (high to low) "Normal" BD-R discs use a composite (or, in the case of BD-RE, a phase-changing alloy) that decreases its reflectivity on recording, i.e. "High To Low". Sony, for example, uses an inorganic composite that splits into two laminar components with low reflectivity. Composites used may include BiN, Ge3N4, and Pd-doped tellurium suboxide. A pair of layers with copper alloy and silicon that combines on recording may alternatively be used. Similar to CD-RW and DVD-RW, a phase transition alloy (often GeSbTe or InAgTeSb; copper silicate (CuSi) or other alloys can also be used, like Verbatim's proprietary MABL) is used for BD-RE discs. Melting the material with a very high power beam turns it into an amorphous state with low reflectivity, while heating at a lower power erases it back to a crystalline state with high reflectivity. In BD-RE discs, the data layers are surrounded by a pair of dielectric Zinc Sulfur-Silicon Dioxide layers. An adhesive spacer layer and a semi-reflective layer are used for multi-layer discs. The recording and dielectric layers are all deposited using Sputtering. BD-R LTH (low to high) BD-R LTH is a write-once Blu-ray Disc format that features an organic dye recording layer. "Low To High" refers to the reflectivity changing from low to high during the burning process, which is the opposite of normal Blu-rays, whose reflectivity changes from high to low during writing. The advantage of BD-R LTH is it can protect a manufacturer's investment in DVD-R/CD-R manufacturing equipment because it does not require investing in new production lines and manufacturing equipment. Instead, the manufacturer only needs to modify current equipment. This is expected to lower the cost of disc manufacturing. Old Blu-ray players and recorders cannot utilize BD-R LTH; however, a firmware upgrade can enable devices to access BD-R LTH. Panasonic released such a firmware update in November 2007 for its DMR-BW200, DMR-BR100 and MR-BW900/BW800/BW700 models. Pioneer was expected to ship the first LTH BD drives in Spring 2008. Sony upgraded the PlayStation 3 firmware enabling BD-R LTH reading in March, 2008. In 2011, France's Ministry of Culture and Communication conducted a study on the suitability of data archival of LTH (low to high) discs compared to HTL (high to low) discs. The data they collected indicated that the overall quality of LTH discs is worse than HTL discs. == Recording modes ==

A BD-R has three recording modes: SRM (sequential recording mode), SRM+POW (sequential recording mode + pseudo-overwrite), and RRM (random recording mode). On each BD-R, this mode can only be set once, and is set before writing any data. SRM is also known as SRM-POW (SRM without POW). It is the fastest mode and does not reserve a 256 MiB overhead. SRM+POW can simulate overwriting on write-once media by mapping physical data blocks to different logical blocks, meaning blocks exposed to the operating system, a feature used by UDF version 2.60. Unlike with packet writing (used from UDF 1.50 to 2.50), this is done by the drive rather than the operating system. The operating system only needs to specify where it wants the new data to appear, and the drive handles the rest. A BD-RE is randomly writable. ==See also==