compact disc
Enable an AI agent to recognise a compact disc, assess its readability and recording state, and decide how it can be played, read, copied, recorded, preserved or retired.
Research draft, second pass
A second pass drafted this model: the structure a model of this thing needs, and what is known about it in the world. The line under this one says how the second half was obtained - researched against sources, or recalled without web access, in which case nothing here was read anywhere and every claim is a lead to verify. Unreviewed either way.
Researched by: Codex + Grok
Purpose and description
Enable an AI agent to recognise a compact disc, assess its readability and recording state, and decide how it can be played, read, copied, recorded, preserved or retired.
A compact disc is a 120 mm (standard) or 80 mm (mini) polycarbonate optical disc that stores digital information as one continuous spiral of pits and lands, recovered through the substrate by a 780 nm infrared laser at constant linear velocity, originally specified by Philips and Sony for 16-bit/44.1 kHz stereo audio and later generalised to computer data and other payloads.
It can be Identify the medium and inspect its track or session organisation using compatible equipment.; Play audio tracks or read data tracks when the relevant equipment supports them.; Extract tracks or create a preservation image when authorised, recording completeness and read errors.; Record or append content when the medium, recording state and available capacity permit it.; Erase or rewrite a confirmed rewritable disc when authorised and after assessing preservation needs.; Choose appropriate handling, cleaning, storage, recovery or retirement actions from observed condition..
Distinguishing features
A compatible drive identifies the medium as belonging to the CD family; circular shape and a reflective surface alone do not distinguish it from DVD or Blu-ray.
Disc markings and drive-reported media information support classification as pressed CD, CD-R or CD-RW; record disagreements rather than inferring the type from surface colour.
Reading identifies a CD track or session layout, or the drive recognises a blank recordable CD; failure to expose ordinary files does not exclude an audio CD.
CD-family identification remains separate from content format: a disc containing music files is not thereby identified as an audio CD.
Scope
+ Identification as CD-family optical media, including uncertain or conflicting identification evidence
+ Physical form and compatibility with disc-loading mechanisms
+ Pressed, recordable or rewritable medium and its current recording state
+ Audio tracks, data tracks, sessions and links to recorded content
+ Surface condition, read results and preservation needs
+ Disc-specific constraints on playback, reading, recording and handling
- The artistic works, software or documents recorded on the disc
- The optical drive or player as equipment
- Cases, sleeves, inserts and storage furniture as separate objects
- DVD, Blu-ray and other non-CD optical media
- Copyright licences, ownership agreements and access permissions as independent records
- Digital disc images and extracted files as independent digital objects
Characteristics
- CD-family identification
- confirmed CD | suspected CD | conflicting evidence | unidentified Prevents actions based solely on appearance or an unverified label.
- Recording medium
- pressed | CD-R | CD-RW | unknown Constrains whether recording, further recording or erasure is possible.
- Physical form
- standard circular | small circular | shaped | other | unknown Affects whether a particular loading mechanism can accept the disc.
- Outer diameter
- mm Supports identification of physical format and loading compatibility.
- Recorded organisation
- blank | audio tracks | data tracks | audio and data tracks | unresolved Determines the appropriate playback, inspection and extraction methods.
- Recording closure
- open or appendable | closed or finalised | not applicable | unknown Helps assess further recording and compatibility without equating unused capacity with writable space.
- Recording capacity
- reported total and remaining capacity in sectors, bytes or audio minutes, with reporting basis Allows an agent to assess whether a proposed recording fits under the intended recording mode.
- Physical damage
- observations of scratches, contamination, cracks, warping, label damage or layer separation, with location and severity Separates potentially recoverable read problems from conditions that may make loading unsafe.
- Read verification
- untested | fully read within stated scope | partially read | unreadable on tested equipment | inconsistent Expresses demonstrated usability without treating a successful sample or failed attempt as a universal result.
- Equipment compatibility
- links to tested players or drives, with operation, result and test date Compatibility depends on the medium, recorded organisation and equipment used.
Also called
Where this came from
wikidata · CC0 1.0
Drafted structure
Bundle to layer to finding to question, as the second pass will find it: 6 bundles · 11 layers · 18 findings · 28 questions.
CD identification Establish whether the object is a compact disc and which physical and recording variant it represents.
Similar-looking optical discs can require different equipment and permit different operations.
Format evidence
Reconcile visible identifiers with evidence obtained from optical equipment.
CD-family confirmation
Record the basis for identifying the disc as CD-family media, including contradictory or unavailable evidence.
- What markings or drive-reported information identify this medium as a CD rather than DVD, Blu-ray or another optical format? definition
- Which observation or device produced the identification, and does it agree with the printed label? provenance
Physical variant
Identify the disc's form and relevant loading constraints.
Disc form and fit
Record dimensions, shape and attachments needed to assess acceptance by a specific loading mechanism.
- What are the disc's measured outer diameter and shape, and are any adhesive labels or adapters attached? measurement
- Does the intended tray, spindle or slot-loading mechanism explicitly support this physical variant? boundary
Recording capability Determine which recording operations the medium and its present state permit.
A blank, appendable, finalised or rewritable disc presents materially different action choices.
Medium capabilities
Establish recording capabilities inherent to the identified medium.
Recordability class
Distinguish pressed media from recordable and rewritable media using explicit identification evidence.
- Is this a pressed disc, CD-R or CD-RW, and what evidence establishes that classification? definition
- Which recording or erasure operations does the identified medium support with the intended writer? action
Current write state
Assess present recording state and capacity for the proposed operation.
Appendability and capacity
Record blankness, closure state and usable remaining capacity as distinct observations.
- Does the writer report the disc as blank, appendable or closed, and what sessions are already present? measurement
- Can the proposed recording fit and complete in the chosen recording mode without erasing content that must be retained? action
Recorded organisation Describe how recorded material is arranged and exposed on the disc.
An agent must distinguish audio tracks, data tracks and sessions to avoid incomplete playback or extraction.
Tracks and sessions
Establish the readable physical recording layout.
Layout inventory
Record reported sessions, track ordering, track types and extents, including unresolved regions.
- Which sessions and tracks are reported, in what order, and which are identified as audio or data? measurement
- Does the inventory cover the entire reported disc layout, or only the portion exposed by the current player or operating system? boundary
Content association
Connect recorded regions to content records without treating packaging claims as verified contents.
Labels and readable content
Separate printed titles, filesystem labels and inspected contents, and link each to its evidence.
- Which content identifications come from printing or packaging, and which were established by reading the disc? provenance
- Which external content records correspond to each readable track or data volume, and where is the correspondence uncertain? boundary
Condition and readability Assess physical defects and demonstrated read performance.
Visual condition and actual readability provide different evidence for safe loading, recovery and preservation.
Physical condition
Inspect the disc surfaces, centre and edge before choosing an intervention.
Damage and contamination
Locate contamination and structural or surface damage without assuming that appearance predicts data loss.
- What scratches, deposits, cracks, warping or signs of layer separation are visible on each face, the centre hole and the outer edge? measurement
- Do the observed defects justify withholding the disc from a drive pending further assessment? action
Read evidence
Record reproducible read outcomes and their coverage.
Verified readable extent
Tie successful reads, errors and inconsistencies to tested regions, equipment and methods.
- Which tracks or address ranges were read successfully, which failed, and what remains untested? measurement
- Which drive, software, settings and test date produced these results, and were repeat reads consistent? provenance
Use and preservation Choose operations appropriate to the disc's capabilities, condition and preservation needs.
Recognition and inspection must lead to concrete decisions about playback, extraction, intervention and retention.
Operation selection
Match an intended use to compatible equipment and established prerequisites.
Supported next operation
Determine whether the requested playback, data access, recording or erasure operation can proceed.
- Does the selected equipment support this medium type and recorded organisation for the requested operation? action
- Before recording or erasing, which existing tracks or sessions must be preserved, and what linked authority permits the change? boundary
Preservation decisions
Connect preservation actions to the disc's observed condition and the completeness of recovered material.
Recovery and retention
Record the next handling or recovery action and distinguish a verified preservation copy from a partial extraction.
- Should the disc next be stored, cleaned using a supported method, read with other compatible equipment or referred for specialist recovery? action
- What evidence shows that a linked extraction or disc image preserves the required tracks, sessions and metadata, and what omissions remain? boundary
Evidence and external alignment What the world already says about this thing, gathered so the model can be checked against it.
A model that cannot be lined up against existing standards, identifiers and practice cannot be adopted by anyone who already uses them.
Reported evidence
Findings from the breadth pass, kept separate from the structural claims.
Kinds and varieties
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- Pressed audio CD (CD-DA / Red Book)
- CD-ROM (Yellow Book data disc)
- CD-R (write-once dye recordable)
- CD-RW (phase-change rewritable)
- Video CD and Super Video CD (White Book)
- Enhanced CD / CD Extra / mixed-mode (audio plus data sessions)
- Mini CD (80 mm audio or data)
- Shaped or business-card CD (non-round, limited drive compatibility)
- Which of these kinds and varieties hold for the sense of compact disc this model covers, and on what evidence? provenance
Identifiers and schemes
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- Wikidata - Q34467 - Item for compact disc as a storage medium.
- IEC - IEC 60908 - CD digital audio system standard (Red Book in IEC form).
- ISO/IEC - ISO/IEC 10149 - Physical CD-ROM (read-only 120 mm optical data disk).
- ISO - ISO 9660 - CD-ROM volume and file structure, not a disc serial.
- GTIN / EAN-13 / UPC - retail barcode on the package or on-disc print - Identifies a commercial release, not the physical disc format.
- Label catalogue number - issuer-assigned album/single cat. no. (varies by label) - Primary identifier in discographies; not standardised globally.
- CD-R ATIP - Absolute Time in Pre-groove manufacturer/dye codes - Identifies recordable media stock and writer timing, not pressed titles.
- Table-of-contents disc ID - CDDB / Gracenote / MusicBrainz disc ID from track offsets - Fingerprint of a particular pressing's TOC, not a printed code on the disc.
- Which of these identifiers and schemes hold for the sense of compact disc this model covers, and on what evidence? provenance
Standards and regulation
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- IEC 60908 Compact disc digital audio system - International Electrotechnical Commission (Philips/Sony Red Book in IEC form)
- ISO/IEC 10149 and ECMA-130, Data interchange on read-only 120 mm optical data disks (CD-ROM) - ISO/IEC; Ecma International
- ISO 9660 Volume and file structure of CD-ROM - ISO
- Philips/Sony Rainbow Books (Red, Yellow, Orange, Green, White, Blue) - Philips and Sony, licensed as Compact Disc Digital Audio and related marks
- OSTA MultiRead - Optical Storage Technology Association, so CD-ROM drives can read lower-reflectivity CD-RW
- Serial Copy Management System (SCMS) on consumer digital outputs - specified in the CD-DA ecosystem
- U.S. Audio Home Recording Act of 1992 - SCMS and royalty scheme for consumer digital audio recorders, not a disc geometry standard
- ISO 18927 (imaging materials - recordable compact disc systems - method for estimating life expectancy based on effects of temperature and relative humidity) - ISO
- Which of these standards and regulation hold for the sense of compact disc this model covers, and on what evidence? provenance
Real-world use
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- Pressed retail music albums and singles played in home, portable, and car CD decks
- 1990s-2000s distribution of PC software, games, drivers, and encyclopedias as CD-ROM
- Consumer and office burning of CD-R/CD-RW for photos, documents, and short-term backup
- Library, radio, and archival holdings of commercial audio CDs as the circulating or preservation copy
- Embedded and industrial playback (kiosks, older medical/imaging carts, some test equipment) where a disc is still the install or update medium
- DJ and broadcast playback from audio CDs or CDJs, now largely displaced by files but still encountered
- Which of these real-world use hold for the sense of compact disc this model covers, and on what evidence? provenance
Typical measurements
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- Outer diameter - 120 (standard) or 80 (mini) - mm
- Thickness - 1.2 - mm
- Centre hole diameter - 15 - mm
- Mass - about 15-20 (120 mm) - g
- User data capacity - 650 (74 min) or 700 (80 min); 800 uncommon/nonstandard - MB (decimal marketing) / MiB in computing
- Red Book playing time - 74 or 80 - min
- Audio coding - 16-bit, 44.1 kHz, 2-channel linear PCM (~1411 - kbit/s
- Read laser wavelength - 780 - nm
- Track pitch - 1.6 - µm
- Scanning velocity (CLV) - 1.2-1.4 - m/s
- Reflectivity (pressed / CD-RW) - ≥70 pressed; ~15-25 CD-RW - %
- Which of these typical measurements hold for the sense of compact disc this model covers, and on what evidence? provenance
Failure modes and hazards
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- Scratches, cracks, and hub-area breakage that interrupt tracking or shatter in a high-speed PC drive
- Corrosion or pinholing of the aluminium reflector and poor lacquer ("disc rot", including historic bronzing on some pressings)
- CD-R dye fade and oxidation from heat, humidity, and light; brand-dependent life from a few years to a few decades, unsuitable as a sole archive
- Damage to the label face, which sits much closer to the data layer than the polycarbonate read face
- Warp from heat (cars, attics) causing focus/tracking failure
- Unreadable or nonstandard TOC, including early-2000s copy-controlled CDs that fail in PCs and some car heads
- CD-RW reflectivity below what an older audio player will accept
- Broken polycarbonate edges are sharp; discs are not a chemical ingestion standard hazard in normal use
- Which of these failure modes and hazards hold for the sense of compact disc this model covers, and on what evidence? provenance
Regional variation
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- Spelling: optical media are "disc" in the Philips/Sony and IEC usage; "disk" is the usual magnetic-media spelling in US computing, so mixed catalogues confuse the two
- Japan commonly issued 8 cm CD singles; Europe used 12 cm maxi-CD singles with extra tracks; US retail leaned less on the CD single
- Copy-controlled CDs (CCCD) were pushed hardest in some European and US major-label releases in the early 2000s and are now a known playback incompatibility class
- Video CD was a mass movie format in parts of Asia and less so in North America, where DVD arrived as the consumer video disc
- Japanese mini-LP CD reissues (cardboard sleeves, obi) are a packaging practice, not a different physical format
- Super Audio CD (a neighbour format) had relatively stronger audiophile/Japanese retail presence than Red Book CD, which remained global
- Which of these regional variation hold for the sense of compact disc this model covers, and on what evidence? provenance
Neighbouring kinds and how to tell them apart
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- DVD - Same 120 mm × 1.2 mm outline, but 650 nm laser, smaller pits, different data-layer depth, and typical single-layer capacity around 4.7 GB; a CD drive cannot read a DVD.
- Blu-ray Disc - 405 nm laser and much higher areal density (25 GB single-layer typical); physically similar disc but incompatible optics and file systems.
- Super Audio CD (SACD) - Looks like a CD; hybrid discs carry a Red Book layer a CD player can use, plus a DSD layer that only an SACD-capable pickup can read.
- MiniDisc - 64 mm magneto-optical disc in a cartridge, typically ATRAC-compressed; not pit-and-land CD and not playable in a CD transport.
- LaserDisc - About 300 mm analog (later digital-audio) optical videodisc; same "laser reads a disc" idea, incompatible size, modulation, and players.
- Vinyl LP / 7-inch - Analog mechanical groove, not optical pits; identified by a stylus, 33⅓/45 rpm, and lack of a laser-readable polycarbonate sandwich.
- DVD-Audio - MLP/high-resolution audio on DVD physical media, not Red Book 16/44.1; a CD player will not play the DVD-Audio layer.
- Which of these neighbouring kinds and how to tell them apart hold for the sense of compact disc this model covers, and on what evidence? provenance
Sources
- IEC 60908: Compact disc digital audio system - International Electrotechnical Commission - Physical and logical specification of CD-DA: 16-bit/44.1 kHz stereo audio, CIRC, EFM, frame structure, and player/disc parameters later treated as the Red Book in IEC form.
- ISO/IEC 10149 / ECMA-130: Data interchange on read-only 120 mm optical data disks (CD-ROM) - ISO/IEC and Ecma International - Yellow Book physical CD-ROM: 120 mm disc geometry, sectoring (Mode 1/Mode 2), and interchange of read-only data discs.
- ISO 9660: Volume and file structure of CD-ROM for information interchange - International Organization for Standardization - The dominant volume/file system on data CDs, including the interchange limits that later extensions (Joliet, Rock Ridge) work around.
- The Compact Disc Handbook, 2nd ed. (Ken C. Pohlmann) - A-R Editions - Engineering account of pit/land readout, CIRC, capacities, and the Rainbow Book family as used in audio and data practice.
- Compact disc (Q34467) - Wikidata - Stable public identifier for the artefact class and links to related optical-disc items.
What the second pass must settle
- Does the registry intend this entry to include shaped promotional CDs, small-format CDs and hybrid media containing a CD-readable layer?
- Which authoritative format references and drive reports should resolve conflicting identifications of CD variants and recording states?
- What inspection criteria should require withholding a cracked, warped or otherwise damaged disc from a drive?
- Which read-verification methods and acceptance criteria are appropriate for audio playback, file recovery and preservation imaging respectively?
- Which cleaning and storage guidance is supported for each medium construction, including discs with adhesive labels or visible layer deterioration?