CDs & DVDs in Ghana

A standard disc consists of three layers: a polycarbonate substrate, on which the disc relief is stamped, a reflective coating of aluminum, gold, silver or other alloy sprayed onto it, and a thinner protective layer of polycarbonate or varnish, on which inscriptions and drawings are applied. Some discs of "underground" manufacturers have a very thin protective layer, or do not have it at all, which makes the reflective coating quite easy to damage. The informational relief of the disc consists of a spiral path going from the center to the periphery, along which grooves (pits) are located. Information is encoded by alternating pits and spaces between them. What recording formats are used in the CD-ROM? The CD-ROM uses the same technology as the conventional CD-DA sound system. The standards for recording arbitrary data on compact discs released by Philips and Sony are known as Yellow Book, Green Book, Orange Book, White Book ) and Blue Book ("blue book"); they all complement the basic CD-DA standard described in the Red Book. Separate " CDs & DVDs in Ghana audio tracks" are used for data recording. The mentioned 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 the same disc. To read them, you need a player that either supports all the formats on the disk, or allows unknown ones (many CD-ROM players and drives cannot skip tracks of unknown formats). The Yellow Book defines the basic formats for writing data to disk: CD-ROM mode 1 and CD-ROM mode 2. In both formats, inside each of the track frames, 2352 bytes in size, which are also called sectors, are allocated 12 bytes of synchronization, 4 bytes of the sector header and 2336 bytes for writing data. Due to the presence of the syncronization and header bytes, it is possible to accurately find the required data sector, which is extremely difficult in an ordinary audio disc. In the mode 1 format, used in most CD-ROMs, 288 bytes are allocated from the data area for recording EDC / ECC codes (Error Detection Code / Error Correction Code), thanks to which data discs are read much more reliably than audio discs with the same workmanship. The remaining 2048 bytes are reserved for storing data. In the mode 2 format, the correction codes are not used, and all 2336 bytes of data in the sector are allocated for writing information. It is assumed that the recorded information either already contains the correction codes, or is insensitive to minor errors left after the correction with the low-level Reed-Solomon code. This format is intended primarily for recording compressed audio signals and images. A mode 1 disk that combines sound and data is called the Mixed Mode Disk. At the same time, data is recorded on the first track, and sound information is recorded on all subsequent ones. Most audio players do not distinguish the format of the tracks and, when they hit the data track, try to reproduce it, which can damage amplifiers and speakers. The mode 2 format is practically not used in its pure form - on its basis the CD-ROM / XA (eXtended Architecture - extended architecture) formats of two versions (Green Book) have been developed. In the first version, 8 bytes of the sub-header, 4 bytes of EDC and 276 bytes of ECC are allocated from a data block of 2336 bytes, leaving 2048 bytes for data, as in the "mode 1" format; in the second option ECC is not used and 2324 bytes are left for data. On the same track of the XA format, the sectors of both the first and the second options can be met. The advantage of this approach is the possibility of simultaneous reading in real time of 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 format tracks and playing it back with a special CD-I player on a household TV in parallel with listening to sound. Tracks in CD-I format are not included in the disc table of contents (TOC), so they are not visible on hardware that does not support this format. For compatibility with standard audio players, the CD-I Ready format ("ready for playback on a CD-I player") has been proposed, which uses an extended pause before the first audio track, which is used by most conventional players to record the image. For compatibility with the device for reading discs in the XA format, the CD-Bridge format ("CD-bridge") was proposed, which is include https://jiji.com.gh/cds-and-dvds