Optical discs and landmarks

How do you differentiate between CD and DVD formats, such as DVD-ROMs with different DVD-Rs or DVD + Rs? Can the DVD drive you have purchased read all kinds of discs? Which format should I choose best for my job?

The following article gives you an overview of the development stages of optical disk format and structure of each format. It does not cover everything but refers to the most common format and more 'secret' information about the old disk.

CD (COMPACT DISC)

Appearing more than 12 years ago (October 1982), today's CDs are very popular and its future is still bright, although DVDs have appeared. The first format of the CD is the audio CD. In 1984, the standard for the CD-ROM was released, allowing for the storage of applications and data to run on the computer. Since then, many extensible formats have appeared, such as CD-ROMs, CD-Is, Enhanced CDs, and Video CDs. These formats are physically identical to audio CDs but contain other formatting data such as text, images, video, and so on. They are produced for specialized use in a specific device. computers, game machines.

The CD is a collaboration between Philips and Sony. Philips researches on lasers and Sony researches on digital music. But before that, there were three inventions that were considered as the basis for the CD:

Pulse Code Modulation (PCM): digital audio encoding on CDs, invented by Alec Reeves in 1937 in London, England.

Error Correction Code: A bug fix mechanism invented by Irving Reed in 1960.

Lasers: invented by Arthur Schawlow and Charles Townes in 1958.

There are 3 main CD formats:

Audio CDs are the original CD format and all other CD formats are based on this format. Audio CDs can also be used for CD-Graphics or CD-Text and CD-Extra (adding PC data beyond audio data).

CD-ROMs are based on audio CDs to hold PC data (applications and games).

CD-ROMs XA is a multimedia format of CD-ROMs, basically CD-I, Video CD and Photo CD. The CD-I Bridge format allows CD-ROMs and CD-ROMs to be played on CD-I players.

AUDIO CD (COMPACT DISC DIGITAL AUDIO - CD DA)

Digital CD for stereo recording, released by Philips and Sony in 1982. (Plate and analogue audio cassettes). Audio CDs come in three formats: CD-Graphics, CD-Text and Extra CD. See Table 1.

CD-GRAPHICS (CD-G)

This format adds six signal channels in audio CD format to contain additional graphics and simple text files that can be displayed while playing music. There is also a CD-G application called Karaoke (CD-G Karaoke) for playing on portable CD players, which requires a TV for displaying images and lyrics. See table 2.

CD-TEXT

Also added 6 signal channels in audio CD format. Readers supporting CD-Text can display up to 21 lines with 40 graphical and numerical symbols. The specifications of this format apply to JPEG images. CD-Text is an audio CD format that adds information about the album, title, artist ...

ENHANCED CD (CD-EXTRA)

Also rooted in audio CDs, but CD-Extra has two disk areas (multiple disk regions originating from the CD-R format, allowing data to be written multiple times). Each area has three parts: lead-in, data area and lead-out.

Area 1 can contain 98 tracks of audio data in the same format as audio CDs. Zone 2 contains data in CD-ROM format XA and is required to have a certain file structure and directory using the ISO 9660 file system (if it can be read on a Mac, it must use the HFS file system). : autorun.inf file; CDPLUS directory; PICTURES directory; and the DATA option folder.

HDCD (HIGH DEFINITION / HIGH DENSITY COMPATIBLE DIGITAL)

This is also an extension of the audio CD developed by Pacific Microsonics. This standard restricts additional information to the track so that this channel is complementary to the audio channel. HDCD samples 20-bit audio samples (audio CDs are 16-bit), so they sound more natural and natural. An audio CD player can play HDCDs, but a dedicated HDCD player will produce better sound.

CD-ROM (COMPACT DISC - READ ONLY MEMORY)

The audio signal is the first digitized, followed by the data. In 1984, Philips and Sony introduced the CD-ROM format. This standard is compatible with optical drives used on PCs. Physically, CD-ROMs are like audio CDs, but they contain data of two different formats. While audio CDs can only be read at a single speed, the CD-ROM can read at up to 56X. The CD-ROM has a more sophisticated detection and fixing mechanism than audio CDs (in addition to a separate recognition and repair layer), which is understandable because if the audio CD is defective, the audio will be incomplete, With CD-ROM, wrong data is difficult to accept.

Other CD-ROM audio CD formats are available at two important points:

The data on the CD-ROM is divided into sectors, including user data and other data for control and error correction.

Data on the CD-ROM is stored as a file. So every CD-ROM needs a file format so that the PC can access the data easily and quickly.

When the first CD-ROMs came out, the main applications were often encyclopedias and large text databases. After this, the graphics, audio, and video are also saved on the CD-ROM. The CD-ROM is also used to store software and is a solution for storing large files.

CD-ROM XA (EXTENDED ARCHITECTURE)

This is an improved format introduced by Philips, Sony and Microsoft in 1988 to better synchronize text, audio, and video. Mode 2 sectors can contain both audio and interleaved data that can be read simultaneously. The XA CD-ROM utilizes 256-color image format, Adaptive Delta Pulse Code Modulation (ADPCM) audio codec. The physical architecture of Mode 2 of the XA CD-ROM has two additional formats: Mode 2 Form 1 and Mode 2 Form 2. XA Mode 2 Form 1 has the same error detection and correction mechanism as Mode 1 disks. higher compatibility. XA Mode 2 Form 2 removes a layer of error correction data to provide more room for data. In essence, this format is not widely used and has not really attracted the followers. There are three basic CD formats based on the physical architecture of the XA CD-ROM: Photo CD, Video CD and Extra CD. Currently, there are only two popular formats: Video CD and Extra CD.

Needless to say, our common CD-ROMs use Mode 1 and the ISO 9660 / Joliet file system for Windows and other operating systems. Windows can also read the XA Mode 2 file structure, but Mode 1 is still used for many purposes. Single-mode and HFS (Hierarchical File Structure) CD-ROMs are less common. There are also Hybrid CD-ROMs containing both ISO 9660 and HFS filesystems for both platforms to read, executables (.exe) have two separate versions for two operating systems but multilanguage files convenient to use.