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Optical disc authoring
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Optical disc authoring, including CD, DVD, and Blu-ray Disc authoring, is the process of assembling source material—video, audio or other data—into the proper logical volume format to then be recorded ("burned") onto an optical disc (typically a compact disc or DVD).
Process
[edit]
To burn an optical disc, one usually first creates an optical disc image with a full file system, of a type designed for the optical disc, in temporary storage such as a file in another file system on a disk drive. One may test the image on target devices using rewriteable media such as CD-RW, DVD±RW and BD-RE. Then, one copies the image to the disc (usually write-once media for hard distribution).
Most optical disc authoring utilities create a disc image and copy it to the disc in one bundled operation, so that end-users often do not know the distinction between creating and burning. However, it is useful to know because creating the disc image is a time-consuming process, while copying the image is much faster.[dubious – discuss] Most disc burning applications silently delete the image from the Temporary folder after making one copy. If users override this default, telling the application to preserve the image, they can reuse the image to create more copies. Otherwise, they must rebuild the image each time they want a copy.
Some packet-writing applications do not require writing the entire disc at once, but allow writing of different parts at different times. This allows a user to construct a disc incrementally, as it could be on a rewritable medium like a floppy disk or rewritable CD. However, if the disc is non-rewritable, a given bit can be written only once. Due to this limitation, a non-rewritable disc whose burn failed for any reason cannot be repaired. (Such a disc is colloquially termed a "coaster", a reference to a beverage coaster.)
There are many optical disc authoring technologies for optimizing the authoring process and preventing errors. Some programs can mount a disc image as a file system type, so these images appear as mounted discs. The disc image can then be tested after it is assembled but before writing to a physical disc.
Sessions
[edit]DVD and Blu-ray (sequential) discs also allow the use of multiple sessions.
Tracks
[edit]Tracks contain the information to be stored on the disc. A track is a consecutive set of sectors on the disc containing a block of data. One session may contain one or more tracks of the same or different types. Tracks can be audio information or data, which use the same format, or video information. Data can include album information and low-resolution graphics such as karaoke lyrics; however, these tracks are not compliant with the Red Book of CD audio standards.
Hardware
[edit]Authoring is commonly done in software on computers with optical disc recorders. There are, however, stand-alone devices like personal video recorders which can also author and record discs.
Software
[edit]Use of optical disc recorders require optical disc authoring software, sometimes called "burning applications" or "burner applications". Such software is usually sold with the recorder. Some operating systems come bundled with them.
Creating an optical disc usually involves first creating an optical disc image with a full file system designed for the optical disc, and then actually burning the image to the disc. Many programs create the disc image and burn in one bundled application (Quick Copy or Copy On-the-fly), such that end-users do not even know the distinction.
Disc file systems include ISO 9660 (often known simply as “ISO”) and Universal Disk Format (UDF). ISO is most common for CDs and UDF is most common for DVDs.
There are also packet writing applications that do not require writing the entire disc at once, but allow writing parts at a time, allowing the disc to be used as a random access removable medium (somewhat like a very large floppy, though with unique constraints).
Sometimes, disc images are made to make the authoring process more straightforward. Sometimes disc images are even used to emulate the presence of a CD-ROM or DVD drive with the data entirely resident on the hard disc.
For the command-line tool cdrdao, a so-called TOC file that can be authored inside a text editor is used to specify the details of the desired disc record.[1]
File systems
[edit]Optical disc file system types include ISO 9660 (often known simply as "ISO") and Universal Disk Format (UDF). ISO is most common for CDs and UDF is most common for DVDs and BDs.
ISO 9660
[edit]ISO 9660 is a format mainly used on CDs. The ISO 9660 can be extended with El Torito, Joliet, Rock Ridge, or the Apple ISO 9660 Extensions.
El Torito makes it possible to boot from a CD. The Joliet extension by Microsoft makes it possible to have long file names encoded in UCS-2, among other things. Rock Ridge is a system providing file-ownership, fewer restrictions on the file names, and more. Amiga extensions allow use of Amiga-specific attribute bits and comments. The Apple Extensions enables Macintosh-specific creator codes, file type, and so on.
Universal Disk Format
[edit]Universal Disk Format (UDF) is a newer filesystem that comes with additional features such as Unicode support, packet writing (UDF 1.50), and defect management on rewritable formats. Packet writing can alternatively be implemented with UDF 1.02 and Mount Rainier extensions. It allows one to use the disc like a floppy disk, that is to easily delete, create, and modify files, without having to write the whole disc again.
DVD-Video uses UDF 1.02, however Blu-Ray Disc uses UDF 2.50.
HighMAT
[edit]A compatibility technology called HighMAT allows visual material on the disc to be recognised, interpreted and supported by electronic play devices more efficiently.[2]
See also
[edit]References
[edit]- ^ "cdrdao(1) - Linux man page". linux.die.net. Retrieved 27 August 2020.
- ^ "HighMAT: a new CD format". Geek.com. 21 October 2002. Archived from the original on 21 October 2018. Retrieved 21 October 2018.
External links
[edit]Optical disc authoring
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Introduction
Definition and Scope
Optical disc authoring is the process of assembling, formatting, and writing digital content—such as data, audio, or video—to optical media including compact discs (CDs), digital versatile discs (DVDs), and Blu-ray discs, utilizing specialized software and hardware to generate discs that are compatible with standard playback devices. This workflow involves collecting source materials, converting and reorganizing them into an integrated structure, and applying format-specific standards to ensure proper readability and functionality. The scope of optical disc authoring encompasses a range of disc types, from data discs for general file storage to audio CDs compliant with Red Book standards, video DVDs adhering to DVD-Video specifications, and interactive Blu-ray discs supporting advanced multimedia features like menus and high-definition playback.[7] Unlike simple file copying, which merely transfers data without regard for playback protocols, authoring emphasizes structured formatting to achieve device compatibility and optimal performance across consumer electronics. File systems, such as ISO 9660, play a key role in enabling cross-platform readability during this process. Key applications include archival storage for long-term preservation of digital data and images, software distribution via bootable or installable media, music production for creating playable audio collections, and video production for authoring home entertainment discs.[8][9][7] Authoring requires compatible optical drives capable of reading and writing to these media formats.[10] The practice evolved from the introduction of CD-ROMs in the 1980s, with the compact disc format launched in 1982 by Philips and Sony, to DVDs developed in 1995 by the DVD Forum for enhanced capacity, and Blu-ray discs released in 2006 by the Blu-ray Disc Association to support high-definition content.[11][12][13] By the 2020s, optical disc authoring has shifted toward legacy support and niche uses, overshadowed by the dominance of digital streaming and cloud storage services.[14]Historical Development
The origins of optical disc authoring trace back to the 1970s with the development of the LaserDisc, an analog video format pioneered by Philips in collaboration with MCA and others, where the first commercial players were introduced in 1978 despite limited adoption due to its play-only nature and competition from videotape.[15][16] In 1979, Philips and Sony formed a joint task force to create a digital audio disc, culminating in the Compact Disc (CD) standard, with the first commercial CD—"The Visitors" by ABBA—pressed on August 17, 1982, in Hanover, Germany, marking the shift to digital optical authoring for audio content.[17][18] The CD era from the 1980s to 1990s expanded authoring capabilities beyond audio, with the introduction of CD-ROM for computer data via the Yellow Book standard published by Philips and Sony in 1983, which specified cross-interleaved Reed-Solomon coding and layout for reliable data storage and retrieval on 650 MB discs.[19] A key milestone was the ISO 9660 standardization in 1988, which defined a volume and file structure for CD-ROM, enabling interoperable data authoring across systems without reliance on proprietary formats.[20] In 1995, the Universal Disk Format (UDF) emerged from the Optical Storage Technology Association (OSTA) to support rewritable media, providing packet-writing capabilities that facilitated incremental authoring on CD-RW and later formats.[21] The 1990s and 2000s brought DVD expansion, with DVD-Video and DVD-ROM standards finalized in December 1995 by the DVD Forum—a consortium including Toshiba, Sony, and Philips—allowing authoring of interactive menus, subtitles, and multi-angle content through collaborative specifications developed by industry groups.[22] The decade's high-definition rivalry between Blu-ray (backed by Sony and the Blu-ray Disc Association) and HD DVD (promoted by Toshiba and the DVD Forum) intensified authoring demands for larger capacities, ending in February 2008 when Toshiba conceded after key studio support shifted to Blu-ray, enabling 25-50 GB discs with advanced authoring features protected by the Advanced Access Content System (AACS) encryption standard.[23] From the 2010s to 2025, optical disc authoring has faced decline amid the rise of digital distribution and streaming platforms, reducing consumer demand for physical media production. In February 2025, Sony ceased production of recordable Blu-ray media, further emphasizing the format's transition to legacy and specialized applications.[24][25] However, it endures for archival storage, where discs offer long-term durability against digital obsolescence, and in professional video workflows, such as 4K UHD Blu-ray mastering for cinema releases requiring precise layer structuring and metadata embedding. Recent applications include tools for retro gaming preservation, where enthusiasts author custom discs to replicate and safeguard vintage CD-ROM and DVD-based titles from the 1990s and 2000s against media degradation. Post-2000, the rise of open-source authoring software, such as cdrtools and dvd+rw-tools integrated into Linux distributions, has sustained accessibility by providing free alternatives for burning and verification without proprietary licenses.Fundamentals of Optical Discs
Types of Optical Media
Optical disc authoring involves selecting appropriate media types based on content requirements, such as data volume and intended use, with formats evolving from compact discs (CDs) to higher-capacity digital versatile discs (DVDs) and Blu-ray discs (BDs).[26] These media are categorized primarily as read-only, recordable (write-once), and rewritable, each employing distinct physical characteristics and layer structures to store data via laser-readable pits and lands on a reflective surface.[27] Read-only formats are pre-manufactured for mass replication and cannot be altered by end-users, making them ideal for commercial distribution of software, audio, and video. The CD-ROM, introduced in the 1980s, offers a capacity of 650-700 MB and supports both data and audio content, using a single-layer aluminum reflective coating with pits stamped into a polycarbonate substrate.[26] DVD-ROM builds on this with higher density, providing 4.7 GB for single-layer discs and 8.5 GB for dual-layer variants, where the second layer uses a semi-reflective coating to allow laser penetration for reading both levels.[28] Blu-ray ROM further advances capacity to 25 GB per single layer and 50 GB for dual-layer discs, leveraging a blue-violet laser (405 nm wavelength) for finer pits and multi-layer stacking up to four layers in some configurations, enabling high-definition video storage.[29] Recordable formats allow one-time writing for permanent archiving or distribution, using organic dye layers that the laser alters to mimic read-only pits. CD-R discs employ this write-once mechanism with capacities matching CD-ROM at around 650-700 MB, where the dye (typically cyanine, phthalocyanine, or azo compounds) changes opacity when heated.[30] DVD-R and the competing DVD+R formats offer 4.7 GB single-layer capacity, with DVD+R designed for enhanced compatibility across DVD players and drives through features like defect management and higher write speeds.[31] BD-R extends this to 25 GB single-layer, 50 GB dual-layer, and up to 100 GB triple-layer using multiple dye-based recording layers, suitable for large data backups.[32] Rewritable formats enable multiple write-erase cycles through reversible material changes, facilitating iterative authoring and testing. CD-RW uses a phase-change alloy layer (often silver-indium-antimony-tellurium) that toggles between crystalline (reflective) and amorphous (less reflective) states via laser heating, maintaining 650 MB capacity but with lower initial reflectivity (15-25%) compared to read-only media.[33] DVD-RW and DVD+RW provide 4.7 GB rewritable storage with similar phase-change technology, supporting up to 1,000 rewrites.[34] BD-RE matches BD-R capacities, including 100 GB triple-layer, using advanced phase-change materials for durability in repeated use.[32] Hybrid and specialized formats address niche applications, often combining technologies for specific uses. DVD+R DL (dual-layer recordable) achieves 8.5 GB by stacking a dye layer over a semi-reflective one, allowing write-once recording across both.[35] MiniDisc, a magneto-optical format primarily for audio, stores 74-80 minutes of compressed sound (about 150-170 MB equivalent) on 68 mm discs, using a magnetic field with laser heating to alter a rare-earth transition metal alloy layer.[36] Professional formats like stamped DVD-ROM variants (e.g., for replication mastering) use pre-etched pits similar to consumer read-only discs but optimized for high-volume production runs.[4] Capacities and speeds have evolved significantly to meet growing data needs in authoring. Early CDs operated at 1x speed of 150 KB/s, while modern Blu-ray writers reach 16x (72 MB/s) for efficient large-file transfers.[37] Layer structures progressed from single-layer pits in CDs to multi-layer configurations in DVDs and BDs, where additional semi-transparent layers enable denser packing without increasing disc size.[29]Basic Data Encoding and Layers
Optical discs store digital data through physical variations on a polycarbonate substrate coated with a reflective layer, typically aluminum. These variations consist of microscopic pits—indentations approximately 0.125 micrometers deep for CDs—and lands, the flat areas between them. When a laser beam strikes the disc, pits scatter and absorb more light, resulting in lower reflectivity that represents binary 0s, while lands reflect the light more directly back to the photodetector, signifying 1s. This binary encoding forms the basis of data representation across formats like CDs, DVDs, and Blu-ray discs.[26][27][38] Reading data involves a low-power laser directed at the disc's underside, with the reflected light intensity modulated by the pit-land pattern to reconstruct the binary stream. For CDs, an infrared laser at 780 nm wavelength is used; DVDs employ a red laser at 650 nm for higher density; and Blu-ray discs utilize a violet laser at 405 nm to achieve even finer resolution. Writing data on recordable media (e.g., CD-R, DVD-R) uses a higher-power laser to heat an organic dye layer, causing it to become opaque or translucent and mimic the reflectivity changes of stamped pits and lands. In rewritable media (e.g., CD-RW, DVD-RW), the laser induces phase changes in a metallic alloy layer—alternating between crystalline (reflective, land-like) and amorphous (absorptive, pit-like) states—allowing data overwriting through repeated heating and cooling cycles.[39][40][41][42][39] Discs can feature multiple layers to increase capacity without enlarging the physical size. Single-layer discs have one reflective data layer; dual-layer variants, common in DVDs and Blu-ray, incorporate a semi-transparent reflective layer for the first data layer, allowing the laser to penetrate to a fully reflective second layer below. Multi-layer discs, such as BDXL Blu-ray formats, extend this to three or four layers by stacking additional semi-transparent recordings, with the laser focusing at different depths via objective lens adjustments. Error correction ensures data integrity against defects like scratches; CDs use Cross-Interleaved Reed-Solomon Code (CIRC) combined with Eight-to-Fourteen Modulation (EFM), which converts 8-bit data to 14-bit symbols to balance run lengths and aid clock recovery while enabling correction of burst errors up to 2.5 mm. DVDs and Blu-ray employ more robust schemes, including layered Reed-Solomon codes and advanced interleaving for higher densities.[27][43][44][45][46] Data is organized in a continuous spiral track starting from the inner radius and winding outward to the edge, with a pitch of about 1.6 micrometers for CDs. This spiral groove guides the laser beam via tracking mechanisms, such as three-beam or differential phase detection. In rewritable discs, the groove incorporates a wobble—a sinusoidal deviation at around 1 kHz for CDs or frequency-modulated for DVDs—to encode absolute time and speed information, facilitating precise head positioning without dedicated servo tracks.[47]Authoring Process
Content Preparation
Content preparation is the foundational stage in optical disc authoring, where digital assets are assembled, formatted, and organized to ensure seamless integration with the target medium's specifications. This process involves gathering various media files, converting them to compatible formats, and planning the overall disc structure to meet standards like those for CD, DVD, or Blu-ray. Proper preparation minimizes errors during subsequent writing and enhances playback reliability across devices.[48] File gathering begins with collecting source assets, including audio tracks, video clips, and data files, from diverse origins such as hard drives or external storage. For audio content destined for CD-DA discs, files like WAV must be converted to uncompressed 16-bit PCM at a 44.1 kHz sampling rate to comply with the Red Book standard, which defines the format for compact disc digital audio as two-channel signed linear pulse-code modulation. Similarly, video for DVD authoring requires conversion to MPEG-2 format, the specified codec for DVD-Video streams, ensuring compatibility with players that decode at resolutions up to 720x480 or 720x576 pixels. Data files, such as documents or software, are assembled without alteration if already in standard formats, but executables or archives may need verification for integrity using checksums.[49] Structure planning follows, focusing on defining the disc layout, including directory hierarchies and interactive elements for video discs. Directory structures adhere to a hierarchical tree model, limited to eight levels deep in basic implementations, to organize files logically— for instance, placing audio tracks in a root-level folder or video segments in subdirectories. For DVD and Blu-ray video discs, menus are designed to provide navigation, often using proprietary formats like IFO files for DVDs to specify button highlights and transitions, or the BDMV directory structure for Blu-rays, which includes playlist files (.mpls) and clip information (.clpi) to link menus to content. These layouts are sketched using diagramming tools or authoring previews to simulate user flow, ensuring menus support features like chapter selection without exceeding disc capacity limits.[48] Compatibility considerations are critical to enable broad accessibility, particularly for cross-platform use between Windows, macOS, and Linux systems. Authors must adhere to file system constraints, such as ISO 9660's 8.3 filename format (eight characters for the name, three for the extension) to maintain DOS-era compatibility and prevent recognition issues on older hardware. For audio data discs containing MP3 files, embedding ID3 tags for metadata like artist names and track titles enhances usability in media players. Preparation aligns with ISO 9660 limits on path depths and character sets, avoiding Unicode in basic modes to ensure universal readability.[48][50] Tools integration supports these steps through basic editing and simulation capabilities integrated into authoring workflows. Video clips can be trimmed using timeline-based editors to precise durations, while compression tools reduce file sizes— for example, applying bitrate limits to MPEG-2 streams for DVD to fit within 4.7 GB capacity. Audio files undergo normalization to prevent clipping, and layouts are previewed in simulation mode to test menu interactions and playback sequences without physical disc burning. These preparatory edits ensure assets are optimized before final assembly.[51] Special cases require tailored preparation, such as for bootable discs or hybrid media. Bootable CDs and DVDs incorporate the El Torito specification, an extension to ISO 9660, by embedding a bootloader image—typically a 1.44 MB floppy or hard disk emulation—into the Boot Catalog at sector 17 of the volume descriptor, allowing BIOS-initiated loading of operating systems or diagnostics. Hybrid CDs, designed for Mac/PC compatibility, combine ISO 9660 for Windows with HFS for Macintosh, using tools to generate shared file views where the same assets appear in both file systems without duplication, facilitating cross-platform distribution of software or multimedia.[52][53]Writing and Burning
The burning process in optical disc authoring relies on a laser diode to physically alter the disc's recording layer, enabling data storage through changes in reflectivity. For write-once media such as CD-R, the laser emits high-power pulses to heat an organic dye layer, causing it to deform or bubble and form non-reflective regions that simulate the pits found on pressed discs, while the read laser later detects these as low-reflectivity areas. In rewritable media like CD-RW, the laser induces phase changes in a metal alloy layer between crystalline (reflective) and amorphous (non-reflective) states, allowing data overwriting. This laser writing occurs in a spiral track, with precise control of pulse timing and power to ensure accurate pit/land transitions, as specified in recording standards for compatibility with playback devices.[54] To maintain a continuous data stream during writing and prevent interruptions that could render the disc unusable, drives incorporate buffer underrun protection mechanisms. These systems monitor the drive's internal buffer and temporarily suspend laser writing if data inflow slows—such as due to system bottlenecks—resuming seamlessly once the buffer refills, thereby avoiding coasters (failed discs). Technologies like Sanyo's BURN-Proof exemplify this approach, enabling reliable burns even on older hardware without halting the rotation prematurely. Writing speeds are calibrated relative to standard rates: CDs use constant linear velocity (CLV), varying rotation to achieve a fixed 1.25 m/s linear speed and 150 kB/s data rate at 1x; DVDs often employ zoned CLV (ZCLV) or CAV hybrids, accelerating from inner to outer zones for faster overall throughput, such as up to 8x (10.8 MB/s) on DVD+R. Overburning extends capacity beyond nominal limits (e.g., 700 MB for 74-minute CDs) by writing into the lead-out area, though it risks compatibility issues with some readers.[55][56][57] Various write modes dictate how data is transferred to the disc, balancing efficiency and flexibility. Disc-at-once (DAO) records the entire content in one uninterrupted pass, ideal for seamless audio or video without gaps; track-at-once (TAO) writes individual tracks sequentially with pauses, adding run-out blocks between them for later editing; packet writing, often paired with the Universal Disk Format (UDF), supports incremental additions in small fixed or variable packets, mimicking removable storage for drag-and-drop operations. Error management integrates real-time correction using cross-interleaved Reed-Solomon (CIRC) codes, which detect and fix burst errors up to 3.5 mm long during encoding, while defects trigger skip/retry mechanisms to relocate data to alternate areas.[54][58][56] Finalization completes the authoring by appending structural metadata, ensuring the disc functions as a closed unit readable by consumer devices. This includes etching the lead-in area with the table of contents (TOC), which catalogs track starts, lengths, and modes (e.g., audio or data), followed by the lead-out area of unrecorded space signaling data's end. In multisession contexts, each session receives its own lead-in and lead-out, but finalization of the last session writes a comprehensive TOC for full compatibility.[56][54]Verification and Finalization
Verification in optical disc authoring ensures the integrity of recorded data by reading back the entire disc to detect read errors and employing software tools for byte-for-byte comparisons against source files or disc images.[59] This process typically involves authoring software like ImgBurn, which verifies disc readability and matches data against an original image file to confirm accuracy.[59] For comprehensive checks, tools such as Nero DiscSpeed perform surface scans to identify damaged sectors, categorizing areas as good, damaged, or bad based on error thresholds.[60] Error analysis focuses on quantifying and classifying defects using standardized metrics. In CDs, the Cross Interleaved Reed-Solomon Code (CIRC) employs C1 and C2 decoders for correction: C1 handles initial parity checks with a (32,28) code using four P parity bytes, while C2 applies a (28,24) code with Q parity bytes after interleaving delays.[56] C1 error rates of 10–99 per second are acceptable, 100–220 indicate poor quality, and rates exceeding 220 are unacceptable; any C2 errors are unacceptable as they signify uncorrectable frames.[60] For DVDs, parity inner errors (PIE) and parity inner failures (PIF) are evaluated, with PIE rates under 20 considered excellent and PIF averages below 0.5 acceptable; tools like Opti Drive Control provide detailed scans to detect dye degradation or physical defects.[60] These analyses adhere to standards like ISO/IEC 10149, which defines block error rates (BLER) for CD media at a maximum of 220 per second.[61] The finalization process closes the disc to prevent additional writes, writing a protective lead-out area and fixing the table of contents (TOC) in the lead-in for standalone playback compatibility.[62] In a session, this involves completing the lead-in, program area, and lead-out, designating it as the final session to make the disc non-appendable and readable by standard players.[62] For CDs, finalization writes the TOC with track details into the lead-in, ensuring recognition by audio and ROM drives.[56] Playback testing simulates use on target devices to validate functionality, such as menu navigation on DVD players, and addresses regional restrictions where applicable.[63] Video discs incorporate region codes during authoring—e.g., Region 1 for North America—to limit playback to compatible players, requiring verification that the code aligns with intended distribution areas.[63] A brief check may verify file system elements like volume descriptors in ISO 9660 or UDF to ensure structural integrity.[56] Common issues include buffer underruns during closure, leading to incomplete TOC writes, and incompatible finalization that renders discs unreadable on certain players due to improper lead-out formatting.[64] Insufficient disc space—e.g., less than 5 minutes in HQ mode for DVDs—can halt finalization, particularly on write-once media like DVD-R.[64] Remedies involve re-authoring the content with adjusted parameters or using alternative software to retry closure, ensuring adequate power supply and compatible media throughout.[64]Sessions and Track Management
Multisession Capabilities
Multisession capabilities in optical disc authoring enable the incremental addition of content across multiple writing sessions on the same disc, particularly on write-once (e.g., CD-R, DVD-R, BD-R) or rewritable (e.g., CD-RW, DVD-RW, BD-RE) media. Each session operates as an independent unit, featuring its own lead-in area (containing the table of contents or equivalent descriptors), a data zone for tracks, and a lead-out area to signal the end of that session. This structure allows users to write, verify, and close individual sessions without finalizing the entire disc, preserving space for future additions.[65] In single-session authoring, the disc is fully closed after writing, with a comprehensive table of contents (TOC) written to the lead-in, preventing any further data addition and ensuring broad compatibility. Multi-session authoring, however, keeps the disc appendable by omitting a final lead-out or including pointers to potential future sessions, updating the TOC during subsequent writes to incorporate all prior sessions into a unified view. This approach facilitates flexible workflows, such as adding files over time, but requires compatible hardware and software to recognize and access the complete disc structure.[66] Support for multisession recording originated with compact discs (CDs) under the Orange Book standards (Part II for CD-R, published in 1990), which extended the earlier Yellow Book CD-ROM specification to enable multiple sessions on recordable media. For DVDs, multisession is less prevalent but enabled via the Universal Disk Format (UDF) file system, as outlined in ECMA-167 (3rd edition, 1997), allowing incremental recording on formats like DVD-R and DVD+R, though often requiring packet-writing extensions for finer control. Blu-ray Disc rewritable media (BD-RE) and sequential recording mode for BD-R further advance this, supporting multiple sessions per the Blu-ray Disc Association's physical format specifications, though BD-R sessions are typically limited compared to rewritable variants.[66] The authoring process for multisession discs begins with preparing content for the first session, writing it using tools that specify an open or multi-session mode (e.g., the--multi flag in cdrecord for CDs, which leaves the disc appendable). After verification, the next session is written at the calculated offset from the previous lead-out, with the authoring software querying the disc's session information to ensure continuity. For example, on CDs, offsets are determined via commands like cdrecord --msinfo to locate the start of the next writable area. This iterative process repeats until the disc is finalized or capacity is exhausted.[65]
Limitations include significant overhead from repeated lead-in and lead-out areas, which reduces usable capacity per session—typically by several megabytes on CDs and more on higher-density formats. Compatibility challenges persist, as older or legacy drives often read only the first session, treating subsequent content as inaccessible or erroneous. Audio CDs, bound by Red Book standards, generally remain single-session to ensure universal playback, while data-oriented discs benefit most from multisession features.[66]