Tuesday, June 26, 2012

The features of DVD(compared with CD and VCD)

DVD is of high density, definition, acoustic fidelity, compatibility and reliability.

1. High Density:
DVD and CD discs has a diameter of 120 mm, but CD disc has a capacity of 650 MB which can only store a 74 minute long Dynamic video image with a quality equals to VHS. While the single DVD record side has a capacity of 4.7 GB, which can store a film of 133minutes 20 seconds that can be played at a standard average data rate of 4.96Mbps as the TV video quality. Generally speaking, a video of an hour long usually takes up at least 2GB space. The capacity of double sides and double layers DVD can be as much as 17 GB, which can store four films.

2. High Definition:
DVD is compressed under an active image compress standard MPEG-2(ISO/IEC13818) with a changeable system code rate from 1 to 10.7 Mbps. At present, DVD uses MPEG-2 is the MP@ML of the 11 specifications. That is NTSC Standard TV 720 pixels / line × 480 lines / frame, 30 frames / sec; PAL standard TV 720 pixels / line × 576 lines / frame, 25 frames / sec data transfer rate up to 15Mbps, some image standard can reach up to the level of TV broadcasting standard with a horizontal resolution of 500 lines. To obtain a higher definition, advanced specifications of MPEG-2, the system code stream is composed by the main video stream (MPEG-2/MPEG-1 compact code stream) sub-image code stream (at most 32 code stream can be recorded; this can be used to show the dialogue of text movies and the subtitles of karaoke) and video code stream (at most 8 code streams that supports 8 languages) three parts. The maximum data rate of the whole system code stream can be 10.08mbps. DVD also has a multi-outcome (to enjoy a variety of different story development), multi-angle (up to 9 images, and parental control of viewing angle (also known as: Child locks, shield the screen not suitable for children) and other functions. Screen length and width than the alternative: pan & scan, 4:3 normal screen and wide screen 16:9, etc.

3. HD:
DVD has eight isolated audio code stream, it is enough to reach the effect of Three-dimensional high-fidelity digital surround sound. The specification of DVD regulates that the NTSC TV system shall use Dolby Digital and Linear PCM audio systems. The following table offers the technical parameter of the three audio systems. in 1992, Dolby Laboratories in the United States issued a Dolby Digital surround sound system to six fully independent channels (left, right, middle, left surround, right surround and subwoofer, referred to as 5.1 channel) and full-band ( ~ 20KHz) high-precision real sound field, resulting in a very good spot high-fidelity digital surround sound.

PCM Dolby digit MPEG-2
sample frequency 48KHz/96KHz 48KHz 48KHz
sample accuracy 16/20/24bit compact data compact data
data rate 768Kbps ~
Min 32Kbps,
 max 448Kbps
primary code stream:Min 64Kbps,
 max 384Kbps
number of channel for per code stream 1 5.1 7.1
Maximum number of code streams 2~8 Max 8 Max 8

4. High Compatibility:
DVD has a powerful compatibility. DVD-ROM can read data of CD and the DVD palyer can play VCD and CD discs, the DVD burner can also burn CD discs.

DVD Forum defines a number of compatible DVD (DVD-Multi) specifications, ensuring the consumer DVD and PC DVD environment, players, audio devices, video devices and drives, recorders and CD-ROMs, recordable CDs playback, sound recordings, video and reading, recording and other functions compatibility. More compatible with DVD logo shown:

5. High Reliability:
DVD uses RS-PC (Reed Solomon Product Code) error correction coding methods and 8/16 bit signal modulate method to ensure the reliability of data read out. The block length of ECC is about 16 record sector units (38688 bytes), the correspondent length of 82.5344 mm on the optical track. If the origin error coding rate is 10-3, the current error coding rate can be 10-20 after code error correction, which is much lower than standard computer error coding rate tolerance 10-12. In order to prevent software being copied, with the occupation of American Motion Picture Association, Toshiba and Sony in all 12 consumer appliance company reached the unanimous agreement on DVD software press rights and pirate proof with computer companies in July, 1996. In October 1996, the DVD technology union declares that DVD shall adopts Unicode technology and the publishment by six area code to ensure the reliability of use and protection of software right. 

For more information: http://www.powerdatarecovery.com/cd-dvd-resources/the-features-of-dvd.html

No comments:

Post a Comment