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Periphery. What is a CD-ROM

What is the difference between the Cross flash firmware for the optical drive and the “normal” one? Cross flash (crossfleshevaya) in all directories is usually marked with an asterisk - "*". She can reflash the drive regardless of what firmware is in it at the moment. "Normal" can only be correctly installed on the previous version (Iron Journal).

Does the optical drive flashing invalidate the warranty or not? It all depends on the specific seller from whom the goods are bought. If the warranty obligations (and all of its applications) do not say anything about replacing the firmware, then it will be very difficult for the store not to repair or replace an idle optical drive under warranty. For complete confidence, you can call and find out everything in the technical support service, while requiring references to the official documents of this store (because it is easier for employees to say that there will be no guarantee than to repair and waste time).

August 17, 1982 is considered the birthday of the compact disc, one of the most common types of information carriers currently available.

The development of compact discs involved Philips and Sony. Compact discs are made of polycarbonate with a thickness of 1.2 mm, coated with a thin layer of aluminum with a protective lacquer coating. Initially, CDs were positioned for digital storage of audio information.

The external size of a compact disc is determined by a special standard and is equal to 120 mm. This is the usual size that everyone is used to. There is a more compact version - 80 mm. If you look closely at your drive, you will see that in the sliding tray there is a small recess for these discs. Standard disks originally contained 650 MB of data (or 74 minutes of audio). There are several assumptions explaining this choice of the diameter and capacity of optical carriers. According to one of them, the volume of the disc was calculated in such a way that Beethoven’s ninth symphony, which is 74 minutes long, fits completely on it. It was this work that was most popular in Japan in the late seventies of the last century. According to another version, the diameter of the CD corresponds to the size of the Dutch stands for beer mugs.

CD Formats

The very first CDs were designed exclusively for listening to music in music players. But then the producers saw that CDs can be used not only to record music tracks, but also to record data. And in a short time many different formats were created, designed for different purposes. The following standards currently exist

  • CD-Audio (CD-DA)
  • CD-ROM (mode 1 and mode 2)
  • CD-ROM-XA (mode 2, form 1 and form 2)
  • CD-i, VideoCD
  • CD-Extra
  • PhotoCD
  • KaraokeCD
  • CD-RW

Many of these formats are not widely used. But the emergence of various formats has created a problem - it was necessary to have a lot of players for each format. Fortunately, manufacturers have managed to create universal players that can read all the formats presented on the disc, or that can skip tracks recorded in an unfamiliar format.

A CD-ROM is the name of a digital storage medium. In its physical device, it is absolutely identical to the CD-DA audio disc. The only difference is in the logical structure of the tracks. The disk consists of three layers: a substrate made of polycarbonate plastic, on which tracks are stamped with a press, a sprayed reflective aluminum coating and a protective layer. It is on the protective layer that the pattern is applied.

Standards for CDs

The production of any kind of CD must meet certain standards, which are known as the Red Book, Yellow Book, Green Book and so on.

  • Red Book (Red Book) - a standard that describes the method of storing sound digital information, which were created by Philips experts. All music audio CDs comply with this standard. This book served as the basis for other standards. This format assumes the ability to record two-channel audio with 16-bit pulse-code modulation (PCM) and a sampling frequency of 44.1 kHz. The system of error correction based on the Reed-Solomon code allows you to easily read discs with small scratches on the surface.
  • Yellow Book - this standard expands the Red Book by adding the specification of multimedia devices CD-ROM. Regular computer games and software are recorded in accordance with the Yellow Book.
  • Green Book (Green Book) - this standard involves a combination of the Red and Yellow Books, when the disc can contain both music tracks and programs.
  • Orange Book - this standard covers the technology of recordable and rewritable CD-R and CD-RW.
  • White Book (White Book) - the standard for video CD.

CD-R and CD-RW

Conventional CD-ROM discs were recorded on expensive equipment in enterprises. They had one drawback - Data was recorded once and could only be read. Recordable discs are more complex than standard CD-ROM discs. They have a layer of special plastic, burned by a laser. The information on the disc is recorded as a spiral track running from the center to the edge of the disc. The track can be continuous, or consist of several parts (sessions).

A maximum of 99 sessions can be recorded on a single CD.

There are two types of recordable discs: CD-R (recordable, once recordable disc) and CD-RW (rewritable, rewritable disc). How many times can I burn a CD-RW disc? A normal disk allows you to do this about 1000 times. The difference between disposable and rewritable discs lies in the use of different coatings on blanks - if dyes are used for CD-R discs, the change of which during laser burning is irreversible, then rewritable discs use materials whose change in reflective properties is not reversible.

UDF File System

For recordable CD-R, CD-RW and DVDs, a special file system UDF (Universal Disk Format) is used, which was first developed to work with flexible magnetic media. The peculiarity of this system is the ability not to close the session while recording, that is, to work with a CD like a floppy disk. Before recording, a recordable disc must be formatted in a special way in order to use it as a regular external medium in the future. UDF format applies to almost all file systems and is supported by all new operating systems.

Data capacity

A standard CD has a capacity of 650 megabytes of data, or 74 minutes of digital music. This standard has been unchanged for a long time. But then the producers found a way to increase the amount of recorded information. Due to the increase in recording density, it was possible to increase the total volume of disks - now the majority of recordable disks sold have a volume of 700 megabytes.

Burn discs

When burning discs with the help of various programs like Nero, the user sometimes does not quite correctly represent the process of “burning” the disc itself and makes mistakes that can be avoided. Here are a few concepts used in the process of burning a disc:

  • session is a special area on the disk. CDs can have sessions and tracks. Each session has one or more tracks. Each session can include a maximum of one data track, and there can be several audio and video tracks.
  • multiSession - a recording mode that allows you to record a CD, that is, add new information to the previously recorded one. Each session will contain the initial record (lead-in), then directly the data and the final information about the session (lead-out). This mode has a certain disadvantage - if one session is separated from another, each time about 15 MB is lost. In addition, some older CD-ROM models cannot read discs recorded in this mode, while others have a limit on the number of sessions they can see.
  • initial recording (Lead-In) - service area on the disk. This area marks the beginning of the recording session and contains the table of contents (TOC, Table of Contents) session, which includes information about the tracks of the session itself. It is recorded with the Lead-Out of this session. Each Lead-nI zone is approximately 9 MB;
  • final recording (Lead-Out) - a service area on the disk, similar to Lead-In, which shows the end of the recording session. Always recorded with Lead-In. The first lead-out disk takes about 13 MB, all of the following take up approximately 4 MB;
  • table of contents (TOC, Table of Contents) - contains information about the type and number of tracks, their location on the disk and the length (volume) of the entire disk. Physically, the TOC table is located in the Lead-In area. In the multisession discs, each session has its own Lead-In area and, respectively? its own table of contents is the most "correct" at the time of recording, because it contains the most recent changes.

Thus, when recording a multisession CD, a new session is recorded each time, which consists of a Lead-In area, a data track and a Lead-Out area. The Lead-In and Lead-Out areas require approximately 15 MB for each session and do not contain any useful data. Therefore, it is not recommended to write data in small chunks, since you just lose a lot of volume for recording. It is better to prepare a collection of files sufficient to fill the disc, and record everything in one session.

  • if possible, do not start other programs when writing to disk, since writing a disk is a rather resource-intensive operation, and any intervention in this process can lead to a write error and damage to the disk;
  • even if you have two CD-ROM drives and you want to transfer data from one disk to another, it is still advisable to transfer the source files to the hard disk. The performance of hard drives is much higher than the most high-speed drives;
  • if you constantly have errors when recording at high speeds, then use a lower speed. It is better to wait and get a working disk than to throw out damaged disks;
  • cD-R drives with a SCSI interface are more reliable than drives with an IDE interface. If you are quite often and professionally working with writing to discs, then choose the SCSI bus.

The designations of 1x speeds on a CD-ROM and 1x on a DVD-ROM are not the same. The CD-ROM "x" corresponds to the transfer rate of the first standardized CD-ROM, subsequently adopted for 1x, that is 150 Kb / s, and for DVD-ROM for 1x, respectively, the transfer rate of the first DVD-ROM was adopted, that is - 1350 kb per second.

Burning to a CD-RW that has been fully formatted differs from burning to a disc that has been erased with so-called quick formatting. With fast formatting, the data is not physically erased, and at the beginning of the disc a mark is placed indicating that the disc is empty. With full formatting, the disk is clogged with zeros. Full formatting is more resistant to reading and writing. With quick formatting glitches are possible (

Created: 03/11/96
   Last Modified: 02.22.99

All rights in this document belong to the author. Reproduction of this text or its part is allowed only with the written permission of the author.

How does the CD?

A standard disc consists of three layers: a polycarbonate substrate, on which the relief of the disc is stamped, a reflective coating of aluminum, gold, silver or some alloy deposited on it, and a thinner protective layer of polycarbonate or varnish, which is applied to inscriptions and drawings. Some disks of "underground" manufacturers have a very thin protective layer, or do not have it at all, which is why the reflective coating is quite easy to damage.

The informational relief of the disk consists of a spiral path that runs from the center to the periphery, along which the hollows (pitas) are located. Information is encoded by alternating pits and gaps between them.

What recording formats are used in the CD-ROM?

The CD-ROM uses the same technology as the conventional CD-DA audio system described in the Audio Disc FAQ (CDDAFAQ.TXT file). The first standard of the CD-ROM series, describing a system of recording on a CD of arbitrary digital data, was released in 1984 by Philips and Sony under the name Yellow Book ("yellow book"); subsequent extensions are known under the names Green Book ("green book"), Orange Book ("orange book"), White Book ("white book") and Blue Book ("blue book"). All of them complement the basic CD-DA standard described in the Red Book (the "red book").

The disk contains the lead-in zone, the actual data (Program) and the lead-out zone. The introductory zone contains the table of contents of the disk (Table Of Contents - TOC), which lists the addresses of the disk tracks and their parameters. The lead-out zone acts as a limiter to the recorded area of \u200b\u200bthe disc and is necessary for full compatibility with the Red Book, although all modern CD-ROM drives and most household players do not need it.

For recording data using separate "audio tracks". These standards do not refer to the disc as a whole, but only to the format of individual tracks, and tracks of different formats can coexist on one disc. To read them, you need a player that supports either all the formats presented on the disc or skips unknowns (many players and CD-ROM drives cannot skip tracks of unknown formats).

The tracks are addressed in the MSF format (Minute: Second: Frame — minute: second: frame), where a frame is a standard CD-DA frame (2352 bytes, 1/75 sec.). Drive interfaces also use absolute addressing by frame numbers. The first track of the standard starts at 0: 2: 0 MSF.

Yellow Book defines the basic formats for writing data to a disc: CD-ROM mode 1 and CD-ROM mode 2. In both formats, within each of the frames of the track, with a volume of 2352 bytes, 12 bytes of synchronization, 4 bytes of the sector header and 2336 bytes are allocated for data recording, which is called a sector or block. Due to the presence of sync bytes and a header, it is possible to accurately find the required data block, which in a normal audio disc requires monitoring the subcode Q channel.

In the mode 1 format used in most CD-ROMs, 288 bytes are allocated from the data area for writing EDC / ECC codes (Error Detection Code / Error Correction Code), thanks to which data discs are read much more reliably than sound discs with the same workmanship. The remaining 2048 bytes are allocated for storing a block of data.

In the mode 2 format, correction codes are not used, and all 2,336 bytes of sector data are allocated for recording information. It is assumed that the recorded information either already contains correction codes or is insensitive to minor errors left over by the low-level Reed-Solomon code. This format is intended primarily for recording compressed audio signals and images.

Disk format 1, which combines sound programs and data, called Mixed Mode Disk. In this case, the first track records data, and all subsequent - audio information. Some household players, especially of previous years of release, do not distinguish the format of the tracks and try to reproduce it when they hit the data track, which can lead to damage to the amplifiers and speakers. Most modern players either ignore data tracks, or imitate their “play” without sound.

The mode 2 format in its pure form is practically not used - on its basis, the CD-ROM / XA (eXtended Architecture) formats of two versions (Green Book) were developed. In the first variant, 8 bytes of the subtitle, 4 bytes of the EDC and 276 bytes of the ECC are allocated from the data block of 2336 bytes, leaving 2,048 bytes for the data, as in the "mode 1" format; in the second variant, ECC is not used and 2324 bytes remain for data. On a single XA format track, there can be sectors of both the first and second options. The advantage of this approach is the ability to simultaneously read real-time data and audio and / or video information, without unnecessary movement between tracks.

The CD-I format (CD-Interactive - interactive CD) described in the Orange Book provides for recording video on XA tracks and playing it using a special CD-I player on a home TV in parallel with listening to a sound program. CD-I tracks are not included in the TOC, so they are not visible on equipment that does not support this format.

For compatibility with standard audio players, the CD-I Ready format was proposed ("ready to play on a CD-I player"), which uses a stretched pause before the first soundtrack to record the image, ignored by most conventional players.

For compatibility with XA disc reading equipment, the CD-Bridge format ("CD-bridge") was proposed. It is a CD-I format track that is included in the total disk contents and contains both CD-I and XA address labels.

The Orange Book also defines the technology and format of recordable CD-Rs (CD-Recordable), which can be recorded in several stages (sessions), as well as have an initial session stamped during production (the so-called Hybrid Disk). Each session contains its own Lead In, Program and Lead Out zones.

The third part (Part III) of the Orange Book describes the technology and format of rewritable CD-RW (CD-ReWritable) discs that allow you to repeatedly record and erase information on a disc.

The White Book describes the VideoCD format based on CD-Bridge and used to store moving images in AVI, MPEG, and the like. Blue Book describes the CD-Xtra format, consisting of two sessions — audio and data session.

The organization of the file system on a CD-ROM is described by the ISO 9660 standard. Level 1 of this standard includes the MS-DOS and HFS (Apple Macintosh) file system formats. Files are written continuously, in the form of sequences of adjacent sectors, the nesting of MS-DOS directories cannot exceed 8, the name length is 8 + 3 characters. Only capital letters A..Z, numbers 0..9 and the "_" character are allowed in file names and extensions. Level 2 describes a file system with long names with no character set restrictions and nesting levels up to 32. Level 3 additionally allows intermittent writing of files - for example, in the case of packet writing in several steps. The session file table of contents (VTOC - Volume Table Of Contents) is recorded at the beginning of the track with normal data blocks, unlike the TOC disc recorded in the Q subchannel of the Lead In zone.

The Rock Ridge extension describes the format of the UNIX file system. Microsoft (Windows 95 / NT) uses the Joliet system with names up to 256 characters. The system is partially compatible with ISO 9660 like VFAT for magnetic disks - in ISO, long names look like their initial characters with the addition of a sequence number in case of collisions.

A special case of the CD-R is the Kodak Photo CD format used for multisession recording of photo collections. Photo CD uses the CD-Bridge format, designed in the ISO 9660 file system. Photo CD discs can be played on special consumer-type TV players or read by computer CD-ROM drives.

The CD-Text format implies encoding textual information in bits of the R..W subcodes. It can be information about the title, the authors and the content of the disc, as well as any other text information.

How does a CD-ROM drive?

A typical drive consists of an electronics board, a spindle motor, an optical read head system and a disk loading system.

On the electronics board all control circuits of the drive, the interface with the computer controller, the interface connectors and the audio signal output are located. Most drives use one electronics board, but in some models, separate circuits are placed on auxiliary small boards.

A spindle motor is used to drive a disk with constant linear or angular velocity (CLV - Constant Linear Velocity, CAV - Constant Angular Velocity). Maintaining a constant linear velocity requires a change in the angular velocity of the disk depending on the position of the optical head. When searching for fragments, the disk can rotate at a higher speed than when reading, therefore, a good dynamic response is required from the spindle motor; the motor is used both for acceleration and for braking the disc.

A stand is attached to the axis of the spindle motor, to which the disc is pressed after loading. The surface of the stand is usually covered with rubber or soft plastic to eliminate disc slip. The disk is pressed against the stand using a washer located on the other side of the disk; stand and washer contain permanent magnets, the force of attraction which presses the washer through the disk to the stand.

The optical head system consists of the head itself and the system of its movement. The head contains a laser emitter based on an infrared laser LED with a typical wavelength of 780 nm and a power of 0.2–0.5 mW, a focusing system, a photodetector, and a preamplifier. The focusing system is a movable lens driven by an electromagnetic voice coil (voice coil) system, made in analogy with a movable loudspeaker system. Changes in the magnetic field cause the lens to move and refocus the laser beam. Due to the low inertia of such a system, it effectively tracks the vertical beats of the disk even at significant speeds of rotation.

The system for moving the head has its own drive motor, which drives the carriage with the optical head using a gear or worm gear. To eliminate the backlash, a connection with an initial voltage is used: with a worm gear - spring-loaded balls, with a gear, a pair of gears that are spring-loaded in different directions.

The disk loading system is carried out in three versions: using a special disk case (caddy) inserted into the drive receiving opening, using a sliding tray (tray) on which the disk itself is placed, and by directly inserting the disk into the drive receiving slot. In all cases, the system contains a motor for retracting / pulling out the tray, the case or the disc itself, as well as the mechanism for moving the frame, on which the entire mechanical system together with the spindle motor and the optical head drive is mounted, to the working position when the disc rests on the spindle motor stand. In some drives, the frame is fixedly mounted on the shock absorbers, and the disc is lowered by means of a movable stand located on the tray. In a number of drives (for example, Samsung 2432, 3231), the tray drive is carried out by a system for moving the head, where a transfer mechanism is provided for this.

When using a conventional tray, the drive cannot be set to a position other than horizontal. In drives that can be mounted in a vertical position, the tray design provides clamps that hold the disc when the tray is extended.

On the front panel of the drive are usually located the Eject button for loading / unloading the disc, the access indicator to the drive and the jack for connecting headphones with electronic or mechanical volume control. In some models, a Play / Next button has been added to start playing audio discs and switching between sound tracks; The Eject button is usually used to stop playback without ejecting the disc. On some models with a mechanical volume control, made in the form of a knob, playback and transition are performed by pressing the end of the knob.

Electronic volume control can support interface control. In Windows 95, there is a separate headphone output volume control in the drive properties (Control Panel -\u003e Multimedia -\u003e CD Music).

Most drives also have a small hole on the front panel, designed for emergency removal of the disk in cases where it cannot be done in the usual way - for example, if the drive tray or the entire CD-ROM fails, when power is lost, etc. Insert a pin or straightened paperclip into the hole and press gently - this removes the lock of the tray or disc case and can be pulled out manually.

What interfaces do the CD-ROM work with?

SCSI, IDE - CD-ROM is connected directly to a SCSI or IDE trunk (ATA) with a device number for SCSI or Master / Slave - for IDE. IDE CD-ROMs usually work in the ATAPI standard (ATA Packet Interface - ATA packet interface).

Sony, Mitsumi, Panasonic are the three most common interfaces supported by many sound cards and individual adapters. Mitsumi and Panasonic use a 40-pin interconnect cable, as for IDE, and Sony - a 34-pin, as for floppy drives.

There are also CD-ROMs with the so-called Proprietary Interface - the manufacturer’s own interface, supplied with an adapter and a connecting cable.

Currently, CD-ROMs are available only with SCSI and IDE interfaces.

Why does the disc rotate at different speeds when running a CD-ROM?

The information on the compact disc is recorded with a constant linear density; therefore, in order to achieve a constant reading speed, the rotation speed changes depending on the movement of the read head. The standard disk rotation speed is 500 rpm when reading from inside zones and 200 rpm when reading from outside (information is recorded from inside to outside).

What does an "n-speed" CD-ROM mean?

With a standard rotation speed, the data transfer rate is about 150 kb / s. In two-speed CD-ROMs, the disk rotates at a proportionally higher speed, and the transfer speed increases proportionally (for example, 1200 kb / s for 8-speed).

Due to the fact that the physical parameters of the disk (mass heterogeneity, eccentricity, etc.) are standardized for the main rotational speed, at speeds greater than 4-6, significant disc oscillations already occur, and reading reliability, especially for illegal production discs, may worsen. Some CD-ROMs with reading errors can reduce the speed of rotation of the disk, however, most of them can not return to the maximum speed until the disk change.

At speeds above 5000-6000 rpm, reliable reading becomes almost impossible, so the latest models of 12 and faster CD-ROMs when reading data work in CAV mode (constant angular speed), rotating the disk with the maximum possible speed. In this mode, the rate at which data is received from the disk varies depending on the position of the head, increasing from the beginning to the end of the disk. The speed indicated in the passport (for example, 24x) is reached only on the outer sections of the disk, and on the inner ones it drops to about 1200-1500 kb / s.

Why are "illegal" discs often read worse than "branded"?

The standard for compact discs determines their physical and optical parameters: the thickness and reflectivity of the aluminum layer, the depth and shape of the pits (recording elements), the distance between the tracks, the transparency of the protective layer, eccentricity, etc. Leading companies that produce compact discs have proven technologies and reliable equipment to meet these parameters; equipment and technologies of illegal manufacturers often do not provide this.

The mechanics and optics of different models of CD-ROM have different tolerances and adjustment possibilities, because of which some models can confidently read discs that are practically unreadable by other models. Also, as a result of operational wear, the drive parameters deteriorate with time, which leads to a deterioration in the reading of disks, which were read with confidence on the new drive.

Is it possible to visually determine the quality of the disk?

Approximately - you can. You need to carefully consider the working surface of the disk - it should be flat, and it should not be scratches, turbid areas, bumps or depressions, as well as "stains" on the reflective layer. Then look at the light on the disk (working side to yourself) - it may be slightly transparent, but without obvious holes in the reflective layer. The more transparent the disk, the higher the probability of its uncertain reading.

Cheap discs (especially those made in China) usually do not have a protective lacquer on the reverse side - even a small scratch on this side can lead to a complete failure to read the corresponding disk area.

What is the quality of playing audio CDs?

Playing audio discs is a side effect of the CD-ROM function, and is usually done “on a residual basis” - the simplest (often equivalent to 12 or 14-bit) DAC and an uncomplicated output amplifier. Mass CD-ROMs are significantly inferior stationary

m Hi-Fi players, some models are close to inexpensive portable players. In any case, the quality of the signal at the headphone output (front panel) is worse than that at the linear output (rear wall) - due to the additional distortion during amplification.

In addition to the quality of the DAC, many CD-ROMs do not resample the digital signal to improve the signal-to-noise ratio, nor interpolation and masking to smooth the curve and partially compensate for uncorrected errors. The lack of interpolation and masking leads to noticeable distortions and clicks when reading discs in error, while readout errors on the sound player are not so noticeable.

Many modern CD-ROMs have an additional digital audio output on the back (S / PDIF — Sony / Philips Digital Interface Format — a Sony / Philips digital interface format) that can be connected to studio or consumer equipment that has an S / PDIF input or AES / EBU, which makes it possible to reproduce sound from a disk with almost no distortion (some distortions can be introduced by a CD-ROM decoder). The output is in the form of a two-pin connector and is most often referred to as “Digital Audio”.

What is the maximum capacity of a CD?

Approximately 650 MB (* 1024 * 1024 bytes) - 74 minutes of recording, data stream - 153600 bytes / s. Such a recording duration is determined by the standard, however, with a more dense arrangement of the tracks or the pits themselves on the disc, a longer playing time or data volume can be obtained. Similar disks with deviations from the standard may be unstable read by some drives, or not read at all.

Can I use a driver from another model with IDE CD-ROM?

In most cases - yes, if the CD-ROM works in the ATAPI standard. However, some drivers may not work correctly with other models of CD-ROM.

Is it possible to read sound from a sound disc in digital form?

You can - you need a CD-ROM that supports the Read Long command and is able to find audio sectors in direct access mode (for example, many of the drives with a SCSI interface, most of the Panasonic models), and a special program - grabber - to read full audio sectors, for example, CDGRAB, CDDA, CDT, CD2HDD, CD2WAV - for DOS; WinDAC, CD Copy, CDDA32 or CD Worx - for Windows 95. WinDAC, in addition to simply reading audio tracks, allows you to simultaneously convert them to other formats using the ACM system (for example, in MPEG-3 with the Fraunhofer IIS ACM Codec installed). CDDA32 can independently convert audio into ReadAudio format.

Often these programs come with a list of CD-ROM models that support the long-reading command. Due to small differences in interfaces, some drives do not work with some of these programs, but they can work with others.

Under DOS, it is desirable to have a native driver of the CD-ROM used, or one of the universal drivers that support Read Long — for example, vide-cdd. For PIIX controllers (motherboards on Intel Triton), we can recommend the TriCD universal driver. Triones sys.

Under Windows 95, if the PIIX controller is used and the standard IDE ATAPI driver recognizes it - this often prevents normal reading of audio discs. In this case, you also need to install either your own CD-ROM driver under Win95, or a driver from Triones version 3.22 or later. You can also try installing the MKEATAPI driver from the Panasonic ATAPI CD-ROM series.

Regular DOS reader programs most often do not work in a Windows DOS session — in this case, you need to use native programs — with either the GUI or the console programs (CDDA32).

One of the main problems with reading audio discs is the synchronization error between frames. They arise mainly because the majority of CD-ROM drives are focused on reading data discs (Data CDs), and the ability to read “raw” sound frames is a side function. Due to the fact that in the format of the Data CD sector there is always a header containing its address and type, the drive can confidently find the desired sector without accurately tracking the information of the Q subchannel in which

cD-DA frame addresses are written. As a result, a drive correctly positioned on a data sector is often unable to do this for a CD-DA frame; in some cases, the reason is the internal buffer, in which the read frames fall without the timestamp read from Q subchannel. A program that reads frames will then receive data shifted forward or backward — by several samples or even entire frames.

Many drives that do not know how to position themselves correctly on sound frames, nevertheless, give satisfactory results with careful continuous reading when the program manages to take data from the buffer at about the same rate at which they arrive there. Violation of this balance - a slow processor, frequent task switching, device contention on one interface, repeat reading due to a malfunction, etc. - leads to repositioning and errors.

To combat synchronization errors, most programs have a mode in which the correctness of the docking of neighboring sectors is checked by reading them with overlapping. When using a CD-ROM with a larger buffer size, the likelihood of errors is reduced, and on drives with correctly implemented reading they do not occur at all.

When reading audio discs on different hardware, using different programs and even when re-reading, the beginning of the audio data in the file can be shifted - due to the same impossibility of precise positioning on the desired sector of the track in most drives.

Synchronization problems as a result of positioning are often mistakenly referred to as jitter. In fact, the term jitter is used to denote the jitter of the phase of a digital signal due to rapid fluctuations in the flow velocity generated by the operation of phase-locked loop (PLL) circuits, generator instability, noise, pickup, etc. In a sense, sync violations are also phase errors of a higher level, but applying the term jitter to them is not entirely correct.

In OS / 2 "Merlin" and Windows 98, Digital Transfer mode is implemented, when a digital reading is used to play a CD, the result of which is reproduced through the Wave channel of the sound card. In cases where the quality of the DAC and amplifier cards is higher than in the CD-ROM, this can give a significant improvement in sound; However, the parameters of most simple sound cards are much worse than in the middle-class CD-ROM. In addition, the digital transmission mode is enabled only for those drives that are capable of reading audio frames in real time, though not quite perfectly.

Some drives, following copyright protection agreements, can read the sound sectors in modified form (for example, using smoothing polynomials); with a single copy, these differences are almost imperceptible by ear.

How to know the ability of the drive to carefully read the sound sectors?

In the general case, only by experiments, since this is not reflected in the drive specification. Read Long support is available in most drives, but only a few are able to accurately position themselves on them in direct access mode (without software synchronization)

The drive check consists in repeated (two to four times) reading without software synchronization of the same sound tracks (preferably long, 10-15 minutes each) from the beginning and end of the disc, preferably with the active parallel operation of other programs and the load on the hard drive, followed by binary file comparison. If the lengths of the files, and their contents from time to time match, the drive works extremely neatly.

In some cases, the beginning of the track in the file may have a variable offset, but the remaining parts of the files are completely the same - such a drive can also be considered quite accurate. If the length and content are different, you can try changing the driver, installing MKEATAPI.MPD, changing the reader (you can start with DAC 2.3 / DOS or WinDAC 1.33 by Chris Schmelnik). If this does not lead to success, only software synchronization can help, and even then not always, since some drives can output the results of an interpolator, which on low-quality disks will vary from reading to reading.

In the extreme case, when there are clicks and failures even with software synchronization, you can try the CD Worx program that reads the tracks in virtual memory. By eliminating parallel calls to the hard drive, this may help to read the track or part of it clean enough, but the free RAM volume should be enough to accommodate the entire readable sound. In the case of exhaustion of physical memory, pumping (swapping) to the hard drive begins, which again fails in the reading process, and also requires considerable (from tens of minutes to several hours) time to transfer the sound from the paging file to the WAV file.

Even if reliable repeatability of reading results is achieved, it is necessary to confirm or exclude the possibility of the drive deliberately distorting the read data. To do this, the resulting files must be compared with files read on other drives with proven repeatability, taking into account, if necessary, the possible variation in the initial offset and file lengths.

For the following drives, the ability to accurately read sound sectors has been proven experimentally:

Acer: 620A (firmware 201N and later), 624A Panasonic: CR-584, 585 and on; Pioneer suffix "B" is desirable: DR-511 (A24X), not all firmware; DR-502S (A02S) Sony: CDU711, 811 Samsung: SCR-2030, 2430 Teac: 532

Less reliably (failures can occur during pauses in the process of reading and re-reading blocks) the following drives work:

Samsung: SCR-2432, 3231

Why is an audio disc that plays well in a CD-ROM hard to read?

When playing audio discs for uncorrected errors, the mechanism of substitution of the next correct signal samples or interpolation is turned on, when the erroneous samples are calculated according to the correct ones so that they form a smooth curve with them. This eliminates clicks and obvious interference, although it introduces some distortion into the sound, hardly noticeable or completely imperceptible in devices of such quality as a CD-ROM. When reading the same disk, most drives give the frames directly after the decoder, bypassing the interpolator, and the uncorrected errors in this case appear as cracks and dips in the sound. The interface does not provide for marking individual error samples in a frame - the drive can mark only the entire frame as valid or as erroneous. A number of drives always returns a sign of the correct frame, if there were no synchronization failures when reading, regardless of whether there are uncorrected errors in the frame.

What is the lifetime of a CD?

This time for discs made and used in full compliance with the technology is approximately estimated at several decades. However, the comparative youth of even the CD-DA and CD-ROM technologies, not to mention the CD-R and CD-RW, does not allow to take into account all possible factors (various violations of the production technology and recording, clouding of the polycarbonate transparent layer, oxidation of the reflective foil as a result of diffusion oxygen from organic layers, the penetration of air oxygen and moisture through the ends of the disk, etc.), so the real figure is estimated at about 10-15 years. In the case of low quality discs, there is a decrease in the reliability of reading stamped discs after 5-6 years of operation, and recordable discs after one or two years.

Why does the reliability of many drives deteriorate with time?

This is mainly caused by two reasons: contamination of the focusing lens and degradation of the laser emitter (LED).

The lens is most often contaminated as a result of dust and tobacco smoke. You can use special cleaning discs to clean your lenses, but some of them have hard brushes that can scratch the plastic lenses. The lens is cleaned more carefully by disassembling the drive and washing it with a natural cotton swab moistened warm water  with soap, followed by wiping with the same dry swab. It is necessary to handle the lens with extreme care in order not to damage its soft plastic and suspension parts.

Degradation (dimming) of a laser emitter occurs when a low-quality LED is used in the drive, or it operates in the limit mode. In some cases, the situation can be improved by increasing the radiation power by a trimming resistor, which is present on the heads of most drives, but after a while the power will again fall below the norm. An excessive increase in power also reduces the reliability of reading discs, and also accelerates the degradation of the radiator.

Another possible reason is the wear of the mechanical parts of the drive and the deterioration of positioning accuracy, but this happens mostly only in very simple and cheap drives, where no measures have been taken to eliminate the backlash of the transmission mechanism.

To read video discs, support is needed from the drive itself and its driver, as well as the decompression program (player) of the video format. Some combinations of the drive, controller, driver and program unpacking with each other. You can try to change the driver or unpacking program. There are also cases where when installing a CD-ROM on one channel from the HDD, video discs are played much slower.

  What is a DVD?

Initially, Digital Video Disk is a digital video disk, then Digital Versatile Disk is a digital multi-purpose disk. The recording system is like a CD, but it has a much higher recording density, which gives the capacity of the simplest disc about 4.7 GB.

DVDs can be double-layered, containing two different information layers, located at different depths and read independently, as well as double-sided. The introduction of the second layer is associated with some overhead for the independent processing of the layers, and increases the disk capacity by 1.8 times, and the organization of the second side doubles the capacity. Thus, the double-layer double-sided disk has a capacity of 17 GB.

Currently, DVDs are mainly focused on recording movies with integrated localization (soundtracks and subtitles in various languages, from which the player automatically selects the desired language). The minimum capacity disc holds a 133-minute MPEG-2 movie.

DVDs with arbitrary data are denoted DVD-ROM, recordable - DVD-R, rewritable - DVD-RAM. DVD-R have a maximum capacity of about 3.9 GB, DVD-RAM - 2.6 GB.

What are the reasons for the poor performance of Samsung-631 CD-ROM drives?

In addition to the low quality of the mechanism itself and the readout system, in these drives, there is insufficient clamping of the disk to the spindle, causing the discs to slip during acceleration and deceleration. The reason for the weak clamping is the large gap between the spindle magnet and the metal disk, which is attracted by the magnet. Michael Svechkov (2: 460 / [email protected]) recommends sticking a steel washer 1-2 mm thick to the magnet, picking it up so that the gap between the magnet and the metal disc is minimal, but with the thinnest discs they should not touch each other, otherwise the tray ejection system will be disrupted.

Why is a CD-ROM labeled Creative defined as MATSHITA?

MATSHITA - abbreviated to eight characters (identifier size limit) is the name of the concern Matsushita Electric Co., the most well-known trademarks of which are Panasonic, Technics and National. Creative does not manufacture its own CD-ROM drives, ordering them from a number of manufacturers; most often under the brand Creative models are found Panasonic and Samsung.

Where can I find software, drivers and information on the CD-ROM?

ftp.panasonic.co.jp - MKEATAPI.MPD (file 58x_95) http://www.aha.ru/~alegr - CD2HDD http://sunny.aha.ru/~gw/ - CD2WAV and CD2SB http: // members.aol.com/mbarth2193 - CDCOPY http://www.ncf.carleton.ca/~aa571/index.html - CDDA http://www.tfh-berlin.de/_s570959/cdworx.html - CD Worx http : //members.aol.com/schmelnik/dac.html - WinDAC

http://www.faqs.org - large collection FAQ

A large selection of CD-ROM materials is available at www.cdrom-guide.com.

Extensive information on computer hardware in Russian is available at www.ixbt.ru.

Many thanks to all who sent answers, recommendations, comments and tips for this FAQ.

Text FAQ in alternative encoding is available for FReq at 2: 5000 / [email protected]  by the name of CDROMFAQ. The Audio Disc FAQ (CD-DA) is located in the CDDAFAQ file, and on recordable discs and CD-R drives - CDRFAQ. The full FAQ package and descriptions are available at ftp://spider.nrcde.ru/pub/text/tech/emtcfaqs.zip and through the FAQ page at http://spider.nrcde.ru. The package is also distributed by FIDO fileecho XHRDDOCS.

How is a CD set up?

A standard disk consists of three layers: a polycarbonate substrate, on which a disk relief is stamped, a reflective coating of aluminum, gold, silver or other alloy deposited on it, and a thinner protective layer of polycarbonate or varnish, on which inscriptions and drawings are painted. Some disks of “underground” manufacturers have a very thin protective layer, or do not have it at all, which is why it is fairly easy to damage the coating.

The informational relief of the disk consists of a spiral track that runs from the center to the periphery, along which there are recesses (pitas). Information is encoded by alternating pits and gaps between them.

What are the recording formats used in the CD-ROM?

The CD-ROM uses the same technology as the conventional CD-DA sound system. Issued by Philips and Sony, standards for recording arbitrary data on CDs are known as Yellow book  ("Yellow book"), Green book  ("Green book"), Orange book  ("Orange Book"), White book  ("White book") and Blue book ("Blue Book"); they all complement the basic CD-DA standard described in Red book  ("Red Book").

For recording data using a separate "sound box". These standards do not refer to the disk as a whole, but only to the format of individual tracks, and the tracks of various formats can coexist on one disk. To read them, you need a player that supports either all the formats on the disc, or allows unknown ones (many CD-ROM players and CD-ROM drives do not know how to skip overlays of unknown formats).

The Yellow Book defines the basic formats for writing data to a disc: CD-ROM mode 1 and CD-ROM mode 2. In both formats, each bypass frame has a capacity of 2352 bytes, also called sectors, 12 bytes of synchronization are allocated, 4 bytes of sector header and 2336 bytes for data recording. Due to the presence of the sync bytes and the title, it is possible to accurately find the required data sector, which is extremely difficult in a regular audio disc.

In the mode 1 format used in most CD-ROMs, 288 bytes are allocated from the data area for writing EDC / ECC codes (Error Detection / Error Correction Code), thanks to which the data discs are read more reliably than sound discs in the same quality of manufacture. The remaining 2048 bytes are allocated for data storage.

In the mode 2 format, the correction codes are not used, and all 2336 bytes of the sector data are allocated for recording information. It is assumed that the recorded information either already contains the correct codes or is insensitive to minor errors left after the correction by the low-level Reed-Solomon code. This format is intended mainly for recording compressed audio signals and images.

The format disk mode 1, on which sound programs and data are combined, is called Mixed Mode Disk. At the same time, data is recorded on the first pass, and on all subsequent ones - sound information. Most sound players do not distinguish between the format of the tracks and, when hit by the data transfer, they try to reproduce it, which can lead to damage to the amplifiers and speakers.

The format mode 2 in its pure form is not practically used - on its basis the CD-ROM / XA format (eXtended Architecture) of two options (Green Book) is developed. In the first version, a data block of 2336 bytes is allocated 8 bytes of subtitle, 4 bytes of EDC and 276 bytes of ECC, leaving 2,048 bytes for the data, as in the “mode 1” format; in the second version, ECC is not used and 2324 bytes remain for data. The sectors of both the first and the second variants can meet on the same path of the XA format. The advantage of this approach is the possibility of simultaneous reading in real time data and sound and / or video information, without unnecessary movement between the tracks.

File format CD-I (CD-Interactive - intepaktivny CD), as described in Orange Book, ppedusmatpivaet videoizobpazheniya recording file format for dopozhki XA and vosppoizvedenie VARIATIONS ppoigpyvatelya using a special CD-I on an everyday TV's paralleling with pposlushivaniem programs will sound. The tracks of the CD-I format are not included in the disk contents (TOC), so they are not visible on the equipment that does not support this format.

For compatibility with standard sound players, the CD-I Ready format was proposed (“ready to play on a CD-I player”), which uses a wired pause before the first sound pattern, and I use a red-rotor that is used by the ipodices unit and I have an ipodshop device that was used by the player and the player is using a real-time recording device that is used by the player and the player is using a real-time recording device.

For compatibility with the XA disc reading equipment, the CD-Bridge format (“CD-bridge”) was proposed, representing the CD-I format included in the total table of contents of the CD-I format, containing adress labels of both formats - CD-I and XA.

The Orange Book also defines the format of recordable CD-R (CD-Recordable) discs, which can be recorded in several receptions (sessions), as well as have an initial session stamped during manufacture (the so-called Hybrid Disk is a hybrid disk). Each session contains an introductory recording (Lead In), the actual data and an output recording (Lead Out).

The White Book describes the VideoCD format, based on CD-Bridge and used for storing moving images in AVI, MPEG and similar coding. Blue Book describes the CD-Xtra format, consisting of two sessions - audio and data session.

The file system organization on a CD-ROM describes the ISO 9660 standard. Level (level) 1 of this standard includes the formats of the MS-DOS and HFS file systems (Apple Macintosh). MS-DOS directory nesting cannot exceed 8, and the name length is 8 + 3 characters. Level 2 describes a file system with long names and a nesting level of up to 32. Rock Ridge extension describes the format of the UNIX file system.

A special case of a CD-R is the Kodak Photo CD format used for multisession recording of collections of photographs. Photo CD uses the CD-Bridge format, formatted in the ISO 9660 file system. Photo CDs can be played with special players on a home TV or read by computer CD-ROM drives.

How is the CD-ROM drive installed?

A typical drive consists of an electronics board, a spindle motor, an optical read head system and a disk loading system.

On the electronic board all control circuits of the drive, the interface with the computer controller, the connectors of the interface and the output of the audio signal are placed. Most drives use one electronic board, but in some models, separate circuits are placed on auxiliary small boards.

A spindle motor is used to drive a disk at a constant or variable linear speed. Maintaining a constant linear velocity requires a change in the angular velocity of the disk, depending on the position of the optical head. When searching for phrases, a disk may turn at a faster speed than reading, therefore a good dynamic characteristic is required from the spindle motor; the engine is used for both the acceleration and the braking of the disc.

On the axis of the spindle motor, the stand is closed, after which the disk is pressed after loading. The surface of the stand is usually covered with rubber or soft plastic to prevent slipping of the disc. The drive to the stand is carried out with the help of a washer, located on the other side of the drive; the stand and the washer contain permanent magnets, the force of which is applied by the puck through the disk to the stand.

The optical head system consists of the head itself and the system of its movement. A laser emitter based on an infrared laser LED, a focusing system, a photo- receiver and a preamplifier are placed in the head. The focusing system is a movable lens driven by an electromagnetic voice coil (voice coil) electromagnetic system, made in analogy with a mobile speaker system. A change in the magnetic field strength causes the lens to shift and the laser focus is refocused. Due to the low inertia of such a system, it effectively tracks the vertical beats of the disk even at significant rotational speeds.

The system for moving the head has its own drive motor, which drives the carriage with the optical head with the help of a gear or a gearbox. To eliminate the backlash, the connection with the initial stress is used: when the gearbox is worn - the sprung balls, while the gears are sprung into pairs of different springs.

The disk loading system is carried out in two versions: using a special case for a disk (caddy) inserted into the receiving hole of the drive, and using a sliding tray (tray) on which the disc itself is put. In both cases, the system contains the engine that drives the tray or the case, as well as the frame transfer mechanism, on which the entire mechanical system is locked together with the spindle motor and the optical head drive, while the disc rests on the spindle motor stand.

When using a conventional tray, the drive cannot be installed in a position other than the horizontal one. In drives that can be mounted vertically, the tray design includes locking pins that hold the drive when the tray is extended.

On the front panel of the drive, there are usually located the Eject button for loading / unloading the disk, the indicator of the device turning and the jack for connecting headphones with an electronic or mechanical volume controller. In the series of models, a Play / Next button has been added to start playing audio discs and transition between audio tracks; The Eject button is usually used to stop playback without ejecting a disc. On some models with a mechanical volume control made in the form of a handle, play and transition are performed by pressing the controller's end.

Most of the drives also have a small hole on the front panel, which is designed for accidental disc ejection in cases where it cannot be done in the usual way - for example, when exiting the tray or the entire CD-ROM, when the power is lost, etc. In the hole, you need to insert a pin or a lamellae and gently press - while this locks the tray or disc case, and it can be pulled out manually.

What interfaces do the CD-ROM work through?

SCSI, IDE - CD-ROM is connected directly to the SCSI or IDE trunk (ATA) with the device number for SCSI or Master / Slave - for IDE. IDE CD-ROMs usually work with the ATAPI standard (ATA Packet Interface - ATA Packet Interface).

Sony, Mitsumi, Panasonic - three most popular interfaces supported by many sound cards and separate adapters. Mitsumi and Panasonic use a 40-pin interconnect cable, as for IDE, and Sony - a 34-pin, as for floppy drives.

There are also CD-ROMs with the so-called Proprietary Interface - the manufacturer's own interface, supplied with an adapter and a connecting cable.

Currently, CD-ROMs are available only with SCSI and IDE interfaces.

Why does a CD rotate at a different speed when running a CD-ROM?

The information on the CD is recorded with a constant linear density, therefore, in order to achieve a constant reading speed, the rotation speed changes depending on the read head movement. The standard disk rotation speed is 500 rpm when reading from internal zones and 200 rpm - when reading from external ones (information is recorded from the outside).

What does “n-speed” CD-ROM mean?

At the standard rotation rate, the data transfer rate is about 150 kb / s. In two-speed and faster CD-ROMs, the disk spins at a proportionately higher speed, and the transfer speed rises proportionally (for example, 1200 kb / s for the 8-speed one).

Due to the fact that the physical parameters of the disk (mass imbalance, eccentricity, etc.) have been standardized for the main rotation speed, at speeds greater than 4-6, significant disk oscillations already occur, and reading reliability, especially for illegal production discs, may worsen. Some CD-ROMs with read errors can reduce the speed of disk rotation, however, most of them cannot return to the maximum speed until the disk is changed.

At speeds above 4000-5000 rpm, reliable reading becomes almost impossible, so the latest models of 10- and higher-speed CD-ROMs limit the upper speed limit. At the same time, at the external tracks, the transfer speed reaches the nominal one (for example, 1800 kb / s for 12-speed models, and as far as internal traffic drops to 1200-1300 kb / s.

Why are "illegal" discs often read worse than "brand"?

Standard on compact discs determines their physical and optical parameters: the thickness and reflectivity of the aluminum layer, the depth and shape of the pit (recording elements), the distance between the tracks, the transparency of the protective layer, eccentricity, etc. The leading companies that produce compact discs have developed technologies and reliable equipment to comply with these parameters; equipment and technologies of illegal manufacturers often do not provide this.

The mechanics and optics of various models of CD-ROM have different tolerances and trimming capabilities, which is why some models can readly read discs that are not readable by other models. Also, as a result of operational wear, the parameters of the device deteriorate with time, which leads to a deterioration in the reading of the disks, which are read reliably on the new device.

Is it possible to visually determine the quality of the disk?

Approximately - you can. It is necessary to carefully consider the working surface of the disk - it should be level, and there should not be any carpeting, turbid areas, bulges or depressions, as well as “dilutions” on the reflective layer. Then look at the disk in the light (by the worker to himself) - it can be slightly transparent, but without obvious holes in the reflective layer. The more visible the disk, the higher the probability of its unconfirmed reading.

Cheap discs (especially those made in China) usually do not have a protective lacquer on the reverse side - even a small scratch on this side can lead to a complete failure to read the corresponding area of \u200b\u200bthe disc.

What is the quality of playing audio CDs on a CD-ROM?

Playing audio discs is a side effect of a CD-ROM function, and is usually done “by residual principle” - a simple (often 12 or 14-bit) DAC and an uncomplicated output amplifier. Mass CD-ROMs are significantly inferior to stationary Hi-Fi players, some models are approaching low-cost portable players. In any case, the quality of the signal at the headphone output (front panel) is worse than that at the linear output (rear wall) - due to additional distortions during amplification.

In addition to the quality of the DAC, most CD-ROMs do not redistribute the digital signal to improve the signal-to-noise ratio, nor interpolation and masking - to smooth out and partially compensate for uncorrected errors. The lack of interpolation and masking leads to noticeable distortions and clicks when reading discs in error, while reading errors are not so noticeable on the audio player.

Many modern CD-ROMs have an additional digital audio output on the back (S / PDIF - Sony / Philips Digital Interface Format - a Sony / Philips digital interface format), which can be connected to a studio or home appliance with an S / PDIF input or AES / EBU, which allows you to play sound from a disc practically without distortion (some distortion can be made by a CD-ROM decoder).

What is the maximum capacity of a CD?

Approximately 650 MB (* 1024 * 1024 bytes) - 74 minutes of recording, data stream - 153600 bytes / s. Such a recording duration is determined by the standard, however, with a tighter location of the walkways or the pit itself on the disc, a longer playing time or data volume can be obtained. Such discs with deviations from the standard may be unstable read by some drives, or not read at all.

What is CD-R and CD-E?

The system of one-cd (CD-Recordable - recordable CD) and multi-crown (CD-Erasable - erasable CD) CD recording. The terms CD-R and CD-E denote both the recording devices and the discs themselves.

For a single-record recording, so-called “golden” discs are usually used, representing a conventional compact disc, in which the reflection layer is made of gold film, and the transparent plastic layer directly adjacent to it is made of material that darkens during heating. In the recording process, a laser beam heats up plastic areas, which darkens and ceases to transmit light to the reflecting layer, causing a “gap” between the “pitas” - unchanged transparent plastic areas.

To facilitate tracking of the informational part of the recording process, CD-R discs are made with auxiliary markup. When reading, tracking is performed, as usual, by the recorded distance of the pits.

Some software versions (for example, CDR Publisher) allow you to burn bootable discs. To boot from such disks, the computer BIOS should support this feature (latest versions of the AWARD and Phoenix BIOS).

Why do noise appear when recording pure WAV on a CD-R?

Perhaps the reason is that some sound editors (for example, Cool Edit and Sound Forge) put their service information at the end of the WAV file, formatting it as an additional record in full accordance with the RIFF format. However, the software of some CD-Rs ignores the length of the sound fragment, traversing the rest of the file after the header as a single sound fragment, as a result of which the service information gets to the disk in the format of digital sound and reproduces like noise or clicks at the end of programs. To eliminate this phenomenon, it is necessary either to prohibit sound editors from storing the service information in the WAV file, or to remove it with the help of other programs.

During the multisession recording of individual sound tracks, at the beginning and at the end of each session, the input and output zones are formed, hit on which during reproduction causes the appearance of a random signal. Audio discs are recommended to be recorded in one session, backing up with creating a complete audio file if the CD-R software does not allow combining files in the recording process.

In addition to the above, interference on recorded audio discs may occur due to instability of the data stream in the CD-R (internal buffer overflow or interruption of the stream), deviations from the parameters of the recorded signal, laser mode, or the speed of the disk, the disk, or the disk, or the disk / disk, or the disk, or the disk, or the disk, or the disk, will not work. the fault of the players, unable to confidently read the specific copies of the disks. In the case of poor-quality recording of data disks, the situation is often saved by large amounts of correction codes provided in CD-ROM formats.

Can I use a driver from another model with IDE CD-ROM?

In most cases - yes, if the CD-ROM works in the ATAPI standard. However, some drivers may not work properly with other models of CD-ROM.

To read video CDs, you need support from the side of the drive itself and its driver, as well as the video player's unpacking program (player). Some combinations of the drive, the controller, the driver and the packaging program are incompatible with each other. You can try to change the driver or program unpacking. There are also cases when installing a CD-ROM on one channel from the HDD video discs are reproduced much slower.

You can - you need a CD-ROM that supports the Read Long command and is able to find audio sectors in direct access mode (for example, many of the drives with a SCSI interface, most Panasonic models), and a special program - grabber - for reading full audio sectors, eg CDGRAB, CDDA, CDT, etc. Often, such programs include a list of CD-ROM models that support the long-reading command. Due to minor differences in interfaces, some disk drives do not work with some of these programs, but can work with others.

One of the main problems when reading audio discs is synchronization errors between sectors. They occur when the program reading the disk does not have time to issue the command to read the next sector before the overflow of the internal CD-ROM buffer and the data from the beginning of the sector will be lost. In this case, the CD-ROM is forced to perform positioning, and the frame structure of the audio discs makes it impossible to start reading exactly from the right place. As a result of such failures in the programmed file, there are drops or the appearance of a few extra samples of the signal. For the battle with synchronization errors, some programs have a mode in which the matching of adjacent sectors is checked. When using a CD-ROM with a larger buffer size, the probability of errors is reduced.

Violations of synchronization as a result of positioning are often mistakenly called "jitter". In fact, the term jitter is meant to denote the fermenting of the phase of a digital signal due to rapid fluctuations in the flow rate, generated by a change in the speed of rotation of the disk and its vertical beating. In a sense, the violations of synchronization are also phase errors of a higher level, but the use of the term jitter is not quite correct for them.

What are the reasons for the poor performance of Samsung-631 CD-ROM drives?

In addition to the low quality of the mechanism itself and the readout system, in these drives there is an insufficient pressing of the disk to the spindle, which makes the disks slip during acceleration and braking. The reason for the weak clamping is a large gap between the spindle magnet and the metal disk, which is attached to the magnet. Michael Svechkov (2: 460 / [email protected]) It recommends to glue a steel washer with a thickness of 1-2 mm to the magnet, choosing it so that the gap between the magnet and the metal disk is minimal, but with the thinnest disks they should not rub together, otherwise the work of the tray ejection system will be broken.

CD Record / Read Drive (optical drive)   - a device designed to read and write information from optical storage media (compact discs). The process of reading / writing information from a disk is carried out using a laser.

The following types of drives exist:

Any of these drives consists of:

  • electronics boards. Here you can find a processor, a ROM, which contains a utility program, a laser head control circuit, power chips for controlling motors, and an interface with a computer controller.
  • spindle motor. It serves to drive a disk at a constant linear or angular velocity.
  • optical system with read head. The system consists of a head and a system for moving it. A laser emitter based on an infrared laser LED, a focusing system, a photodetector, and a preamplifier are located in the head.
  • drive control systems. Loading, unloading, playing is performed with a single button (Eject).

What does a cd look like?

A CD-ROM disk is an optical information carrier in the form of a plastic disk with a hole in the center, the process of which is written and read information by means of a laser. The prototype of such a disc is a phonograph record. The volume of a CD-ROM is up to 700 MB, the diameter is 120 mm, the disk thickness is 1.2 mm. The disk is made of polymer and covered with a metal film (Fig. 2.4). The "father" of the CDs is the head of Sony Japanese Norio Og.



Fig. 2.4.

A standard DVD CD looks the same, but its size is 4.7 GB for single-sided discs and 9.4 GB for double-sided discs.

How to handle CDs?

A compact disc is a reliable storage medium designed for its long-term storage. According to some estimates, the lifespan of modern CDs may be about 100 years. However, this period largely depends on the conditions of storage and use of the carrier. Damage to the disk can lead to errors when reading files and data. Here are some guidelines for handling CDs that will help avoid such troubles.

  • Inscriptions on recordable discs may be made only with special markers.
  • Do not bend the disc. This may cause cracks or the disk may simply break.
  • Do not heat the disc. It is made of plastic and is deformed when heated.
  • Do not scratch the disc. Inhomogeneities can cause read errors.
  • Do not expose the disc chemically. active substances. The surface of the plastic disk substrate and the reflective layer may be damaged by alcohol, acetone and various cleaning solutions.
  • A contaminated disc can be washed with warm soapy water or a non-aggressive surfactant (shampoo, laundry detergent), or specially manufactured liquids.
  • Keep your disc collection in dark places. RW discs, unlike R-discs, are less susceptible to the harmful effects of sunlight, but do not abuse it.

What is a flash drive?

A USB flash drive (flash drive) is a device designed to “memorize” (accumulate and store) information - text documents, pictures, photos, music, video. It has a small size (just like a lighter) and connects to a computer through a special hole in the system unit. This hole is called a USB connector. A compact disc is also an external storage device. However, the flash drive has a number of advantages, thanks to which it is slowly squeezing DVD disks out of use (as once these disks have replaced floppy disks).

New term

USB flash drive (flash drive) - a storage device that uses flash memory as a carrier and is connected to a computer or other reader through a USB interface. In other words, USB Flash Drive (flash drive) is a type of external storage medium for a computer (Fig. 2.5).



Fig. 2.5.

Flash drives are so popular in the first place because they are very easy to use. They open on any computer (and even on many modern TVs), and no special programs are required to work with them. Modern flash drives are capable of “storing” a large amount of data (an order of magnitude larger than compact discs), moreover, they are reusable, that is, they are capable of overwriting information a thousand times. USB flash drive, unlike the CD, is not subject to scratches and dust, resistant to vibration, shock, falls. It works silently, has a small weight and size, which is very convenient if you need to constantly carry it with you. Some special flash drives have such an additional function as protection of information. This may be a fingerprint verification or password that must be entered to open the contents of the flash drive. In addition to the advantages of a flash drive, there are several disadvantages. The lifetime of a flash drive is 5–10 years. At the same time recording speed decreases with time. Another disadvantage of the flash drive is the sensitivity to electrostatic discharge. Electric shock, such as from charging your wool sweater, can cause the flash drive to burn out and lose information on it. Getting wet in the rain can also be fatal to a flash drive, especially if there was an attempt to plug in a still wet device.

Flash Memory Cards and Card Reader

A memory card (or flash card) is also a device for storing and storing information. But you shouldn’t confuse it with a flash drive: with the similarity in assigning a memory card, they do not look like flash drives (Fig. 2.6).


Fig. 2.6.

Memory cards are used in most models of modern phones, cameras and camcorders. Often, data from a memory card — photos, videos, or music — needs to be transferred to

In the period 1994-1995, the basic configuration of personal computers no longer included floppy disk drives with a diameter of 5.25 inches, but instead, the installation of a CD-ROM drive having the same external dimensions was considered standard.

The abbreviation CD-ROM (Compact Disc Read-Only Memory) is translated into Russian as a permanent storage device based on a CD. The principle of operation of this device is to read numerical data using a laser beam reflected from the surface of the disk. Digital recording on a CD differs from recording on magnetic disks by very high density, and a standard CD can store approximately 650 MB of data.

Large amounts of data are characteristic of multimedia information (graphics, music, video), so CD-DOM drives are classified as multimedia hardware.

The main disadvantage of standard CD-ROM drives is the inability to write data, but in parallel with them there are CD-R (Compact Disk Recorder) recording devices and CD-RW multiple recording devices.

The main parameter of CD-ROM drives is the speed of reading data. It is measured in multiples. The reading unit in the first production samples, which was 150 Kb / s, was taken as the unit of measurement. Thus, a double-read drive provides 300 KB / s performance, 600 KB / s quadruple speed, and so on. Currently, CD-ROM readers with 32x-48x performance are the most common. Modern samples of write-once devices have a performance of 4x-8x, and multiple recording devices - up to 4x.

Video card (video adapter)

Together with the monitor, the video card forms the video subsystem of a personal computer. The video card was not always a component of the PC. At the dawn of personal computer technology, there was a small, dedicated on-screen memory area in which the processor entered image data in the general area of \u200b\u200bRAM. A special screen controller reads data about the brightness of individual points on the screen from the memory cells of this area and, in accordance with them, controls the scanning of the horizontal beam of the monitor's electronic gun.

With the transition from black-and-white monitors to color and with an increase in screen resolution (the number of dots vertically and horizontally), the video memory area was not enough to store graphic data, and the processor could not cope with the construction and updating of the image. Then there was a selection of all operations related to the management of the screen, in a separate unit, called the video adapter. Physically, the video adapter is made as a separate daughter board, which is inserted into one of the slots of the motherboard and is called a video card. The video adapter took over the functions of a video controller, video processor and video memory.

During the existence of personal computers, several video adapter standards have changed: MDA (monochrome); CGA (4 colors); EGA (16 colors); VGA (256 colors). Nowadays, SVGA video adapters are used, which can optionally provide reproduction of up to 16.7 million colors with the possibility of arbitrary selection of screen resolution from the standard range of values \u200b\u200b(640x480, 800x600,1024x768,1152x864; 1280x1024 pixels and more).

Screen resolution is one of the most important parameters of the video subsystem. The higher it is, the more information can be displayed on the screen, but the smaller the size of each individual point and, thus, the smaller the apparent size of the image elements. The use of high resolution on a small monitor leads to the fact that image elements become illegible and work with documents and programs causes fatigue of organs of vision. The use of low resolution leads to the fact that the elements of the image become large, but there are very few of them on the screen. If the program has a complex control system and a large number of screen elements, they do not completely fit on the screen. This leads to lower productivity and inefficient work.

Thus, for each size of the monitor there is its own optimal screen resolution, which the video adapter must provide.

Table Monitor screen resolution

Most modern applications and entertainment programs are designed to work with a screen resolution of 800x600 or more. That is why today the most popular monitor size is 15 inches.

Color resolution (color depth) determines the number of different shades that a single point of the screen can take. The maximum possible color resolution depends on the properties of the video adapter and, first of all, on the amount of video memory installed on it. In addition, it depends on the set screen resolution. With a high resolution of the screen, each point of the image has to be allocated less space in the video memory, so that the color information is forced to be more limited.

Depending on the set screen resolution and color depth, the required amount of video memory can be determined by the following formula:

where P is the required memory capacity of the video adapter;

m - horizontal screen resolution (points);

n is the vertical resolution of the screen (points);

b is the bit color coding (bit).

The minimum requirement for color depth today is 256 colors, although most programs require at least 65,000 colors (High Color mode). The most comfortable work is achieved with a color depth of 16.7 million colors (True Color mode).

Working in full color True Color mode with high screen resolution requires significant video memory size. Modern video adapters are also capable of performing image processing functions, reducing the load on the central processor at the cost of additional video memory. Until recently, video adapters with a memory capacity of 2-4 MB were considered typical, but already today, 16 MB is considered common.

Video acceleration is one of the properties of the video adapter, which consists in the fact that some of the image building operations can occur without performing mathematical calculations in the main computer processor, and purely in hardware, by converting data in the video accelerator chips. Video accelerators can be part of a video adapter (in such cases they say that the video card has hardware acceleration functions), but can be supplied as a separate board installed on the motherboard and connected to the video adapter.

There are two types of video accelerators - flat (2D) and three-dimensional (3D) graphics accelerators. The former are most effective for working with application programs (usually office applications) and are optimized for the Windows operating system, while the latter are focused on the work of multimedia entertainment programs, primarily computer games and professional three-dimensional graphics processing programs. Usually in these cases different mathematical principles of automation of graphic operations are used, but there are accelerators with functions of both two-dimensional and three-dimensional acceleration.

Sound card

The sound card was one of the most recent enhancements to the personal computer. It connects to one of the motherboard slots in the form of a daughter card and performs computational operations related to the processing of sound, speech, and music. Sound is reproduced through external speakers connected to the sound card output. A special connector allows you to send a sound signal to an external amplifier. There is also a microphone jack, which allows you to record speech or music and save them to your hard disk for further processing and use.

The main parameter of the sound card is the bit depth, which determines the number of bits used when converting signals from analog to digital and vice versa. The higher the bit depth, the smaller the error associated with digitization, the higher the sound quality. Today’s minimum requirements are 16 bits, and 32-bit and 64-bit devices are the most common.

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