Audio CD

das CDDA-Logo
the CDDA Logo

the audio CD (audio Compact disk, digital audio CD or briefly CD-DA) is an optical mass storage, since 1979 by Philips and Sony for the digital storage of music was developed and the record as the most important medium of noted, intended for the salesSpeaking and music photographs replaced.

Table of contents

meaning

Few years after the introduction on the market that CD (1982) the digital medium already became more popular than the Vinyl record; however in the USA 1983 about 30,000 CD-Player and 800,000 audio CDs were sold. 1988 was produced for the first time 100 million audio CDs per year.

Beginning of the 90'sYears disappeared to LPs then to a large extent from the former “record shops”. Millions of buyers replaced their partial record collections developed for many decades by audio CDs and made for the music industry possible record conversions in such a way after years of the recession. The boom year of the German music industry was 1997, as the industry approximately 2.6 billion eurogained.

In Germany audio CDs - at least according to tax law - do not become when regards valuable cultural properties; to audio CDs a VAT rate of 16 per cent applies, while this for books and notes are about 7 per cent.

For instance since the turn of the century the disk companies deplore however again decreasing/going back conversions. The turnover break-downslie with up to ten per cent; German disk companies even lost 2003 a fifth of their conversion; in the year 2002 the conversion had already decreased/gone back around more as eleven per cent on less than two billion euro.

A cause for the current problems of the music industry are according to their statementabove all pirat copies so mentioned its, which are spread over exchange stock exchanges, as well as copies of audio CDs; in opinion of the music industry exceed the number of the CD blanks taped with music (2002: 267 million) those the sold music CDs (2002: 166 million) by far; like theseNumbers to have been determined are, betray the representatives of the music industry meanwhile not. Critics of the music industry accuse, the companies would have the indications of the time for example the development of a consistent selling as Internet down load - overslept and became now in damage delimitation (copy protection measures, criminal procedures approximatelyInternet music exchange stock exchanges, “robbery copiers are criminals”) practice, which does not tempt the customer in the long run to consume more music CDs.

technology and standardisation

the audio CD is one of the official CD formats, those in the so-called” multicolored books “(see Rainbow Books) to be described and the Compact disk- Logo to carry may do. The format specifications that audio CD, correctly as CD-DA designation, is 1980 under the designation” talk Book “by the ANSI (IEC-908) standardized; this standard made it possible that originally each CD-Player and each CD-ROM drive assembly could play each audio CD - so long itself the disk companiesby the standard held.

Audio CD contains no multimedia or textuellen additional information in this original form excluding audio data and. Extensions to the CD-DA such as Mixed mode CD, Enhanced CD/CD pluses, CD text, CD+G or CD+MIDI can contain however additional information.

The audio data are unkomprimiert stored. The talk Book format supports onlysimple procedure for recognizing or correcting read errors, the CIRC in such a way specified (CROSS Interleaved Reed Solomon code), and permits errors per second up to 250. Good CD-Player can” cover “also somewhat higher error numbers still (nearly) inaudibly.

The CD is 1.2 mmthickens disk with a diameter of 12 cm and/or. 8 cm (CD single), which of a polycarbonate carrier consists, on which a thin aluminum layer one lays on.

data format

the audio data are noted with a scanning rate by 44.1 kHz, 16-Bit-Samples and 2 channels; the data rate of oneAudio CD is therefore about 1 to,411,200 bit/s.

The range audio CD is with 5 cycles per second to 20 kHz, the volume range with 96 railways.

The data are stored in Frames (also “mini Frame” mentioned). Each Frame contains 33 bytes. Of it 24 is byte audio data (thusexactly 6 Stereo Samples), 8 byte contain error correction data and a “Subcode in such a way specified” - byte. The bits of the Subcode byte are named P to W. The respective bits of the successive Subcode bytes form one Subchannel in such a way specified each. The individual Subchannel is likewise named P to W.

In each case 98 Frames are combined into a block (also sector or Frame called). Each block contains thus 2352 byte audio data. This corresponds 1/75 second. The 98 Subcode bytes result in the eight Sub Channels P to W to 98 bits each. The audio CD after the talk Book standard uses onlythe Subchannel P and Q. Subchannel P contains a simple music break flag. This can be used by CD players, in order to jump over a tracing. This feature is supported however by hardly equipment.

Subchannel Q contains against it numerous information. The 98 Q-Channel-bits of a block have the following structure:

  • 2Bit synchronisation
  • 4 bits addr - indicates, in this sector contains which data of the Q-Channel.
    • 0 = no Q-Channel-data
    • 1 = position information (see below)
    • 2 = medium catalog number (e.g. UPC or EAN)
    • 3 = ISRC
    • 4..15 = reserves
  • 4 bits control bit
    • bit 0: 1:Audio data with pre-emphasis, 0: without
    • bit 1: 1: Digital copy permits, 0: Bits 2
    • forbade digital copy: 1: Data TRACK, 0: Audio TRACK
    • bit 3: 1: Four-channel audio (Quadrophonie), 0: Two-channel audio (Stereo).

If the Q-Channel contains position information, these are coded as follows:

  • 8-bit: TRACK number
  • 8-bit:Index POINT
  • 24 bits: Sector address (relative to the TRACK beginning)
  • 8-bit: reserved (0)
  • 24 bits: Absolute sector address
  • 16 bits: (carriage return character) check total

there the Q-Channel different data contained can contain, cannot not each sector its item data. Most CD players show then an interpolated valueon, if a sector does not contain item data or the verification with the check total of the Subchannels indicates a read error. According to talk Book standard however 9 from 10 sectors item data must contain, so that when playing CD very rapidly new item data are available.

The Subchannel R toW are unused with pure audio CDs and by most audio CD players are ignored. Extended formats, like CD text or CD+G code there their complementary data.

On audio CD can be stored up to 99 TRACKs. A TRACK usually corresponds thereby to a music piece. Each TRACK can in addition by index POINTs to be further partitioned (for example for the sets of a symphony or airs within an opera), today's Player support this function however frequently no longer, since them were used only on few CDs.

A standard-conformal TRACK must at least 4 seconds (300 sectors)long its, index POINTs must likewise at least. four seconds distance from each other have. Between the TRACKs is the TRACK Pre Gap, which must have a length of at least two seconds with standard-conformal audio CDs and which audio quiescent level must have. Many audio CDs contain however TRACK, those smoothlyinto one another turn into, without an audible break between them exists.

The addressing of the sectors leans thereby against the targeted application as clay/tone carrier: The sectors become in the format minute:Second:Block addresses. To the simplification of the announcement these data BCD-coded on thatCD stored. The value for seconds is on 0-59, the block number on 0-74. There is thus possible for block addresses from 00:00.00 to 99:59.74, which for the originally conceived play time of 74 minutes is sufficient. It is fixed that the first TRACK is to begin with sector 00:00.00.Certain ranges that CD are however before the first TRACK and need therefore negative sector numbers. These are stored with an offset by 100 minutes, so that they fall into the unnecessary address ranges from 80:00.00 to 99:59.74. Many CD diagnostic programs are able, these sectorsto select and their contents (e.g. to represent the TOC).

The sectors audio CD do not contain a header. It is not possible thus to head for and pick aimed individual sectors out. In order to recognize, which sector straight is read, the drive assembly must read in one, sometimes even several sectors and thoseData of the Q-Channels evaluate. This explains the quite high access time when optional heading for for instance another TRACK.

Low level format

the data bits are not pressed directly in pit and country on the CD. Instead the data become over a 8-zu-14-Kodierung into so mentioned“Channel bit” changed. In addition the Channelbits of a data byte is by 3-bit-lange tracing (English.gap) from each other separated, so that per data byte the place is needed by 17 Channelbits.

The 33 bytes of a Miniframes correspond to 33*8 = 264 data bits. On that CD become however 33*17= 561 Channelbits stored. To these then still 24 Channelbits come to the synchronisation and 3 “merge bits so mentioned”, thus 588 Channelbits per Miniframe.

Details in addition, how the data on that are stored CD, see in the article Compact disk.

history

thoseLength of the recording audio CD is to have been specified allegedly by of Sony vice-president Norio Ohga with the argumentation, CD must seize up to 75 minutes music, since this corresponds for instance to the length of Beethovens of ninth symphony. Also the conductor harsh ore of Karajan is uppushed a minimum length, in order to be able to play important works of the music noly-break. Philips scientists are to have favored against it CD with smaller diameter and shorter Spieldauer. Originally should the CD even on 1973 a developed format, which video Long Play disk (VLP, laser vision) to be based.In the long run of Sony however apparent succeeded vice-president.

„The bent “scanning rate of 44.1 kHz came off by an interesting circumstance. The digital audio data needed a storage medium, which had to be reliable and available. For this a video recorder of the system U-Matic became - which at that time of SonyTime in study-uppercalibrate far was common - uses, since this was able to store accordingly high frequency digital signals durably on magnetic tape. Special converters (PCM-1610 and PCM-1630) existed, which audio data with 16 bits digitized and a “video” - signal produced, that by the U-Matic-video recorder notedwill could. Per video picture line 96 bits could be coded. With 294 usable lines and 50 (half) pictures per second (PAL video signal) 96*294*50 = 1411200 could be stored in such a way bits per second. With 2x16 bit per SAM-polarizes arose so a scanning rate of 44100 values per second.


Philipsalso the right of the Lizenzierung of the” CD “possesses - Logos, which appears on each CD; the patent lying to reason ran out however between 2002 and 2003 .

In particular on older CDs it is indicated whether the individual photograph steps (admission, mixture, Premaster) similarly or digitally providedare. In addition the abbreviations AAD, ADD and DDD are used.

excessive CDs

there the specification certain tolerances of the physical format (for instance the track location) contained, is possible it to accommodate by Ausreizen of these tolerances (closer letter of the traces) more data on CD,as original was intended. This is however used only rarely by pressed audio CDs. CD blanks for describing (which have the same fundamental structure as audio CD) often are however in such a way manufactured that they exhibit 80 minutes play time (to sector 79:59.74). From almost all CD players such becomeCDs problem-free played.

A further increase of the track density permits a still longer play time (90 and/or. 99 minutes). It comes however to problems, since for it sector addresses must be used, which were reserved by the talk Book standard for negative sector addresses. There many CD drive assemblies only the sectors over90:00.00 as negative sector addresses understand, are 90-Minuten-Rohlinge so mentioned (thus the sectors to 89:59.74 contained) on these drive assemblies still playable. The 99-Minuten-Rohlinge in such a way specified requires however a certain “intelligence” from drive assembly electronics, in order to recognize whether a negative sector address or one at the end that CDis meant. In practice a heuristic is usually used, which functions as follows: A purposeful selection of addresses zw. 90 and 99 the data at the CD beginning (negative addresses), a continuous selection supplies to that with CD with rising addresses against it recognized and it will become withTransition from minute of 89 to 90 the sectors at the end that CD selected.

Due to the problems, which 90 - and 99-Minuten-Rohlinge cause, it is to be rather advised against these since one cannot be safe whether they can be read later on another drive assembly again.

copy protection/Un-CD

something similar the DAT - standard contains the audio CD after the talk Book standard a copy protection procedure, whereby only in the Table OF CONTENTS (TOC) indicates a bit the copy protection. Additionally a similar bit is in each Q-Sub-Channel-block, which can indicate three conditions:Copy-protected (always set), copy (bit alternating over the Sub Channel blocks) and not copy-protected (always ungesetzt). Theoretically these flags should be spent correctly on the digital exit with a HiFi CD Player. However with most computer components these flags are ignored.

Since approximately 2001 also audio CDs become in Germanysold, the one copy protection going beyond it contain. It will likewise misleading called CD, do not correspond however to the talk Book standard, are therefore no genuine audio CDs and can no longer in all CD-Playern be played; thus the copy protection in such a way specified becomes one „playing protection “, from that CD one „Un-CD “. The evasion one „effective copy protection “is after amending copyright (new copyright law (UrhG), into force since 13. September 2003) no longer permissible (§ 95 A UrhG). However the question arises whether for audio CDs the usedCopy protection procedures at all the demand for an effective copy protection fulfill, since many CD of drive assemblies can correct these errors automatically. A judicial decision to the copy protection of the audio CDs is still pending.

So modified audio CDs must however after § 95 D UrhG since that 1. November 2003 throughthe manufacturer to be marked clearly. The IFPI (international Federation OF the Phonographic Industry) introduced an appropriate Logo for copy-protected audio CDs. The Heise magazine publishing house operates also a data base, in which for copy-protected and potenziell playable music CDs cannot be searched.

There is numerousCopy protection procedure with different protection and efficiency in use; the copy protection MediaMax CD3 von SunnComm can be deactivated under the operating system Microsoft Windows for example simply by the pressing of the SHIFTs - key, since hereby the CD autostart is switched off. One knows three different kinds of copying contactors for audioCDs differentiate.

  • Illegal TOC: With this procedure (normally in an additional session, there the second session a copy first contains) the TRACK positions are returned on illegal positions, like for example on a block in Lead in. Since HiFi Player normally only the first session regard(Talk Book), this protection concerns only computer drive assemblies. Since however into many newer Playern, particularly into DVD Playern, computer hardware is inserted, it comes there also ever more frequently to problems. A modification of these illegal TOC expresses itself with a TRACK list changing when each inserting that CD.There the TOC within the intended range, for improvement of the legibility is written, a multiplicity of different (and to wrong) TOC several times one behind the other is put down.
  • Intentional read errors: By manipulation of the CROSS Interleave Reed Solomon code (CIRC) become an approximately at places of the piece of music with linear rise of the levelfew Samples falsifies. Die Parität wird jedoch über den korrekten Block berechnet. Thus with the selection of the block the respective Samples is marked as defective. Computer drive assemblies, which do not have a special audio mode, return the incorrect data, while HiFi drive assemblies are particularly prepared for such errors and thoseincorrect data (often linear) interpolate. Since the level in the place rises linear, this error on HiFi Playern is not to be audible. However it is to be noticed that in many blocks the error correction is already expenditure-provoked. Each small scratch on the surface can provoke genuine read errors.One buys as it were audio CD, which is already from the beginning zerkratzt (although one cannot see scratches on the surface).
  • Wrong q Subcodes: This copy protection is used rather rarely, since also HiFi Player thereby can have problems. It is based on the fact that CD-Player the CD similarlyhow play a LP in a course, in which these follow „the groove “. Only with the TRACK selection or when jumping over individual places effectively a certain block is looked for. With audio CDs the respective position is noted in each Q-Subcode to a block. If one there oneeasily deviating position registers (in disorder throw ELT), cannot be searched any longer accurately, which does not disturb however HiFi Player (it is Player with shock Resistance). Computer drive assemblies against it are usually block-by-block addressed and must look for the position on that very often again CD. This is then not more possible, since the positions are through in and suppl. throw ELT, and therefore a few blocks one reads before or later. This expresses itself in short repetitions or missing bits (usually around 0.05 seconds long).

contents and formats

the marketing partitioning into large, well-known of the record LPs and smaller Singles were taken over also with that audio CD. The following contents-dependent formats developed:

  • CD (albums, compilations): Clay/tone carrier with 12 cm diameters and about 45-80 minutes of music/clay/tone material
  • single: Clay/tone carrier with 8 cm diameters and about 1-4 TRACKs. Play time of order of magnitude12-15 minutes (music).
  • Maxi/Maxi - single: Clay/tone carrier with 12 cm diameters, but only about 1-5 TRACKs

beside it developed Promo CD, one clay/tone carrier with twelve or eight centimeters of diameter for advertising purposes, which is usually distributed free of charge. Sometimes it contains the whole album, which are appliedis, sometimes in addition, only very few TRACKs or only cutouts of the whole TRACKs. Target groups for Promo CDs are as multiplicators working humans or institutions, for example radio - stations or DJs.

CD-Player

the first playback unit (CD player) for audio CDs, Sony CDP-101, became 1. October 1982 presented and at the price of 168.000 Yen (at that time approximately 625 US Dollar) sells.

the first audio CDs

the first audio CDs placed the disk label PolyGram to 17. August 1982 before; it acted thereby around

economics that audio CD

against the purchase of audio CDs and for the Download over P2P - networks in the Internet often one states, audio CDs are a too expensive Konsumgut- the hearing habits of the consumers changed: One has in former times still consciously music heard - for example one let the record player run and heard from the armchair a symphony - hears one today, in the age of very small playing devices such as MP3-Player or Discmen, with each opportunity music, approximately on the way to the work, with the Joggen or during working. The consumers are thus no longer as strong as in former times ready, for something, which is consumed besides, such high prices to pay. That one among friends musicexchanges and that for this reason the pro person purchases from music CDs it removes is a logical consequence of it.

Also against the composition of a CD selling price criticism becomes loud. According to the IFPI, the world union of the clay/tone carrier industry, the licenses for the music make “usually for more than one third of theSelling price to the Detailhandel out ", and necessarily is also a risk reallocation, i.e. a transverse subsidization of successful CDs in favor of of other productions, “only 15 - 20% of all new publications play their costs”.[1] The moreover it is stated that the pure material and manufacturing costs of oneCD practically with zero would lie.

Price composition of a CD music album in Germany:[2]

Cost centre portion in per cent
of labels 26%
selling 23%
trade 20%
value added tax 14%
artist 7%
GEMA 6%
production 4%

the labels (music companies) pay additionally a separate amountto the artists. One assumes the artist receives altogether 15% of the CD retail price.

In view of the falling popularity that audio CD and the problem of the “robbery copiers” alternatives are considered. One argues that it with a price of 50 cent for the Download of a particularSongs would be possible that the music company takes approximately 40% of the price, while the artist likewise earns more with 20% - the costs of distribution and manufacture can be saved, because the commodity is supplied over Internet; and the GEMA remuneration would be omitted, because deliveries upthe purchase by tapable data media were planned or set already into force. With 20 Songs to ever 50 cent would in most cases less pay the customer, than with the purchase material audio CD. To good the latter proponents of a consistent Download Musikhandels think that by thoseLowering of the consumer price the legal purchase was set in motion by music.[3]

See also: DVD, DVD audio, super audio CD, XRCD, copy protection, photograph procedure (CD), Freedb, Subcode, ISRC, [[CD+G]]

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