How to distinguish CD, VCD and DVD?

How to distinguish CD, VCD and DVD? DVD is very reflective, like a mirror, completely different from CD.

This CD is a series of audio tracks. If you look carefully, you can see more than a dozen tracks.

You'd better find a CD player without a computer.

CD discs can not only burn CD music discs, but also VCD SVCD data discs.

How to distinguish CD, VCD and DVD? CD and DVD say the name of the CD, and VCD says what is written in the CD! There will be some words on the surface of the CD-R, CD-RW is CD, DVD+R, DVD-RW, DVD+RW, and DVD-D9 is DVD!

Please accept it, thank you!

What's the difference between CD, VCD, DVD and CD? On the surface, DVD is very similar to CD/VCD. But in essence, there are essential differences between the two. If you think that the difference between DVD and CD/VCD is only in the playback effect, it seems a bit too simple.

1, technically speaking.

DVD/CD are all the same, because they all store the required data in a tiny groove on the track of the optical disc, and then read it by the laser beam of the optical disc drive. However, in terms of optical disc density, DVD is much larger than CD/VCD, so reading DVD data requires a laser beam with a shorter wavelength than reading CD/VCD data. Because only in this way can the laser beam be focused and positioned on the optical disc more accurately. The minimum pit length of CD is 0.834μm, and the track pitch is1.6 μ m. The infrared laser with the wavelength of 780 ~ 790 nm is used for data reading, while the minimum pit length of DVD is only 0.4μm, and the track pitch is 0.74μm, and the infrared laser with the wavelength of 635 ~ 650 nm is used for data reading.

2. When playing the image.

VCD can only reach the standard of 240 lines, while DVD can reach the standard of 720 lines, so DVD has an absolute advantage in definition.

3. In terms of data capacity

CD/VCD can only hold about 650MB-700MB of data, while DVD can hold at least 4.7GB of data. According to various combinations of single/double-sided and single/double-layered structures, DVD can be divided into four physical structures: single-sided single layer, single-sided double layer, double-sided single layer and double-sided double layer. The capacity of single-sided single-layer DVD is 4.7GB (about 7 times that of CD-ROM), and the capacity of double-sided double-layer DVD is as high as 17GB (about 26 times that of CD-ROM).

A single-sided DVD disc can have one or two recording layers. Like a CD, the laser reads the data on a single-sided disc from the bottom of the disc, and the data on a double-sided DVD disc is stored on the upper and lower sides of the disc respectively.

There are two ways to read data from a double-sided disk:

(1) After playing the program on the first side of the CD, take the CD out of the player, turn it over and put it in the player to continue playing the program on the second side;

(2) Two laser readers are installed in the player to read data from the upper and lower sides of the CD respectively, or only one laser reader is installed in the player, but after reading the first side of the CD, it can automatically jump to the other side of the CD to continue playing.

If the latter scheme is adopted, it is not necessary to take out the optical disc and turn it over after reading the first side of the optical disc.

Double-layer disk is actually two layers of disks stacked together, and the lower layer is a semi-reflective layer, through which the data of the upper layer can be read. When reading the next plate, always start from the inner ring, read from the inside out, and then read the first plate after reading the next plate. There are two ways to read the upper disk:

(1) OTP method, that is, when reading the upper disk, it starts from the outer ring and moves from outside to inside;

(2 2) PTP(ParallelTrackPath) method, that is, when reading the upper disk, it starts from the inner ring and moves from the inside out. When the laser reader reads the data on the upper and lower optical discs, its optical focus will change.

Single-layer disc and double-layer disc are composed of two substrates, and the thickness of each substrate is 0.6mm, so the thickness of DVD disc is1.2 mm. For single-sided disc, only the lower substrate contains data and the upper substrate has no data; There are data on the upper and lower substrates of the double-sided disk.

4. Functional aspects.

DVD can provide multi-track (multi-language), multi-text support, multi-angle viewing and other colorful functions, which are not available in CD and VCD.

The difference between DVD and CD/VCD is roughly the same. Although it looks simple, these differences alone are enough for DVD to completely beat CD/VCD. However, due to the price advantage of the latter two, they still have a high advantage in the market, but I believe that in the near future, DVD will officially replace CD and VCD and become the absolute mainstream.

What is a VCD?

VCD is the abbreviation of "video disc", which is a CD containing sound, video and pictures. VCD is very similar to CD turntable. VCD contains 74/80 minutes of video and audio on a 650MB/700MB CD, and can store video and audio with different video and audio quality. VCD uses the standard compression format MPEG. Use a pressure standard called mpeg to store video and audio. Almost all computers with CD-rom, DVD-rom and software can play vcd. It can also be marked with menus and chapters like a DVD.

A player that can play VCD

-Standard VCD player (very popular, such as Super Jieba).

-Almost all standard DVD players

-PS(Playstation) can also be played with VCD-addon (PS 2 does not support VCD).

-Sega can also play vcd with vcd-sddon.

-Almost all personal computers use CD-r om/DVD-r om and software players.

What is a DVD?

The English full name of DVD is Digital Video Disk, that is, digital video disk or digital video disk. It uses MPEG2 compression technology to store images. Some people also call DVD a digital multifunctional disk, which combines computer technology, optical recording technology and film and television technology to meet people's demand for large storage capacity and high efficiency storage media. DVD is not only widely used in audio/video field, but also will promote the development of publishing, broadcasting, communication and other industries. It has a wide range of uses, as can be seen from its five specifications:

DVD-ROM- CD of computer software, similar to CD;

DVD-video- home audio-visual CD, similar to LD or videocd.

Dvd-audio-music disc, similar to music CD;

DVD-r (or DVD-write-once)- A write-once DVD similar to CD-r;

DVD-RAM (or rewritable DVD)- An optical disc that can be read and written many times, and its use is similar to that of MO.

From the following aspects, we can see that DVD is superior to CD and VCD:

1, large capacity, fast reading: most DVDs are the same size as ordinary CDs, with a diameter of about 12 cm (also 8 cm). They consist of two base layers with a thickness of 0.6 mm each. Multi-faceted and multi-layer technology is adopted, that is, each CD can store two layers of information, and each CD can have up to four storage spaces. DVD improves the storage capacity per unit area by using more concentrated red laser. In addition, using shorter wavelength laser and denser information pits, the maximum reading rate of single-layer DVD can reach 1 1.08 Mbit/sec, which is equivalent to an eight-speed optical disc drive.

2. High-resolution video: The resolution of DVD using MPEG2-2 standard image compression technology can reach 720×480, far exceeding that of VCD (352×240). MPEG2 has the ability to flexibly adjust the video reading rate, so it can save a lot of information storage space while maintaining the original image quality. In addition, the built-in mailbox of DVD player and the display mode of pan scanning can also adjust the aspect ratio of 16:9 or 4:3 TV.

3. Sound quality of high fax: ∶DVD can convert analog information with more accurate sampling accuracy, expand the traditional two channels to 5. 1 channel, and let people really enter the multi-channel world.

Physical format 120mm CD storage capacity (GB) 80mm CD storage capacity (GB)

DVD-ROM

DVD- video single side and single layer

Single-sided double-layer

Double-sided monolayer

Double-sided double-layer 4.7

8.5

9.7

17 1.4

2.6

3.9

5.3

DVD-R

DVD-RAM single-sided and double-layered

Double-sided double layer

Single-sided double-layer

Double-sided double-layer 3.9

7.8

2.6

5.2 1.2

2.4

0.7

1.4

Can VCD DVD play CD? You can play

What's the difference between CD, CD-ROM, VCD and DVD-Video and DVD-ROM? VCD (video disc) refers to video disc. Cd-rom (compact disk-read only memory), DVD is the abbreviation of [digital video disk-read only memory], which is translated into digital video disk in Chinese. Strictly speaking, this kind of DVD should be called DVD-Video (DVD for short), which is a read-only DVD and must be played by a special DVD player. DVD-ROM is a direct-reading optical drive, which can read CD, VCD, DVD, CD-R and CD-RW.

How to distinguish VCD from DVD and CD-ROM? There is no video image on the CD, and the VCD has a small capacity, so it can hold movies. . . But it didn't contain much, so it was replaced by a DVD with a larger capacity.

CD: pure music

VCD: video elementary CD

DVD: high definition video disc

EVD: high-definition digital movies and TV

MPEG4: compressed high-density video disc

MP3: Compressed pure music

DVD has the characteristics of high density, high image quality, high sound quality, high compatibility and high reliability. High density: The diameters of DVD and CD are both 120mm, but the capacity of CD is 680MB, which can only store 74 minutes of VHS-quality dynamic video images, while the capacity of single-sided single-layer DVD recording layer is 4.7GB If it is played at an average data rate of 4.69Mbps, which is close to the requirements of broadcast video quality, it can store the whole movie of 133 minutes and 20 seconds. The capacity of double-sided and double-layer CD is as high as 17GB, and one CD can accommodate four movies. This requires the use of more advanced technical means in DVD to improve the information recording density, thus increasing the disc capacity. The following table lists several technical means to improve the recording density of optical discs. Technical means: the numerical aperture of CD/VCD DVD mirror is NA 0.45 0.6, the error correction coding redundancy is 3 1% 15.4%, the channel coding modulation mode is 8/ 17 modulation, and the laser wavelength is 8/ 16 modulation, λ 780 nm, 650 nm/635 nm spot diameter/kloc-0. 0.08 μ m track spacing10.6 μ m 0 At present, the DVD-Video products adopt MP@ML in the 1 1 specification of MPEG-2 (i.e. 720 pixels/line× 576 lines/frame, 30 frames/second for NTSC TV). PAL standard TV 720 pixels/line× 488 lines/frame, 25 frames/second, maximum data transmission rate 15Mbps), reaching broadcast video quality (its horizontal resolution is greater than 500 lines). In order to achieve higher picture quality and clarity, we can also choose the corresponding high-order specification in MPEG-2. The system code stream of DVD consists of three parts: the main video code stream (MPEG-2/MPEG- 1 compressed code stream), the sub-video code stream (up to 32 code streams can be recorded and played for dialogue in 32 languages and the display of karaoke subtitles) and the audio code stream (up to 8 code streams can be recorded and played, supporting sounds in 8 languages). The maximum data rate of the whole system code stream can reach 10.08Mbps, and DVD has many new functions, such as multi-ending (enjoying different story development), multi-angle (viewing pictures from nine angles), zoom and parental control (cutting out pictures that are not suitable for children). There are three options for the aspect ratio of the picture: panoramic scanning, 4:3 normal screen and 16:9 widescreen. PCM Dolby AC-3 audio sampling frequency 48KHz/96KHz 48KHz 48KHz sampling accuracy 16/20/ 24 bit compressed data data rate 768Kbps~ ~ minimum 32Kbps main code stream: minimum 64Kbps 2.304Mbps maximum 48Kbps maximum 384Kbps number of channels in an audio code stream 1 5. 1 7. 1 Maximum number of audio streams DVD standard stipulates that Dolby AC-3 and/or linear PCM audio systems are mandatory for NTSC TV systems (such as the United States and Japan); For PAL TV systems (such as Europe and China), MPEG audio format and/or linear PCM audio system are mandatory. Table 3 gives the technical parameters of three audio systems. 1992, Dolby Laboratories released AC-3 digital surround sound system, which used six completely independent channels (left, right, middle, left surround, right surround, subwoofer for short, 5. 1 channel) and a full-band (~ ~20KHz) high-precision realistic sound field to produce very good live digital surround sound effects. High compatibility: DVD player, DVD player and DVD-ROM/R/RAM can play CD; Both DVD player and DVD-ROM/R/RAM can play VCD discs. Dvd-rom/r/ram can also read CD-rom. High reliability: DVD adopts RS-PC (Reed Solomon product code) error correction coding mode and 8/ 16 signal modulation mode to ensure reliable data reading. The block length of error correction code (ECC) is 16 recording sectors (38,688 bytes), corresponding to the length of 82.5344mm on the track; If the original bit error rate is 10-3, after error correction, the bit error rate can be less than 10-20, which is far lower than the bit error rate required by the computer. In order to effectively prevent the software from being copied, with the active participation of the Motion Picture Association of America, agreements were reached with Toshiba, Sony and other 1996, 12 home appliance and computer companies on the copyright and anti-piracy of DVD software. 1996 10, the DVD Technical Federation composed of all parties announced the garbled technology used in DVD software and hardware and the measures to distribute software according to six regional codes, which realized the protection and reliable use of software copyright.