MPEG standard video compression coding technology mainly adopts inter-frame compression coding technology with motion compensation to reduce temporal redundancy, DCT technology to reduce spatial redundancy of images, and entropy coding to reduce statistical redundancy in information representation. The comprehensive application of these technologies greatly improves the compression performance.
MPEG- 1
The MPEG- 1 standard was officially released in 1992. The number of this standard is ISO/IEC1172, and its title is "Coding of moving images and their accompanying sounds in digital storage media with bit rate of about 1.5Mb/s".
MPEG- 1 layer 1 digital cassette
MPEG- 1 layer 2 DAB, VCD, DVD
MPEG- 1 Layer 3 Internet, MP3 music
MPEG- 1 audio layer 1
Features: Simple coding. The audio compression scheme used in digital cassette tape, 2-channel and VCD is MPEG- 1 Layer 1. ..
Advantages: Compared with time domain compression technology, the compression method is much more complicated, the coding efficiency and sound quality are greatly improved, and the coding delay is also increased accordingly. It can achieve "completely transparent" sound quality (EBU sound quality standard)
Disadvantages: High bandwidth requirements.
Application field: VoIP
Royalty method: free of charge
Remarks: MPEG- 1 audio compression coding is the first international standard for data compression in high definition audio, which is divided into three levels:
-Layer 1(Layer 1): simple coding, used for digital cassette recording tapes.
-Layer 2: The algorithm has medium complexity and is used in digital audio broadcasting (DAB) and VCD.
-Layer 3: The coding is complex, which is used for the transmission of high-quality sound on the Internet, such as MP3 music compression with 10 times.
Musicam (MPEG- 1 Audio Layer 2, MP2)
Type: audio
Manufacturer: MPEG
Bandwidth required: 256 ~ 192 kbps (compressed by 6 ~ 8 times)
Features: The complexity of the algorithm is moderate, and it is used for digital audio broadcasting (DAB) and VCD, with two channels. MUSICAM is widely used in the production, exchange, storage and transmission of digital programs such as digital studios, DAB and DVB because of its appropriate complexity and excellent sound quality.
Advantages: Compared with time domain compression technology, the compression method is much more complicated, the coding efficiency and sound quality are greatly improved, and the coding delay is also increased accordingly. It can achieve "completely transparent" sound quality (EBU sound quality standard)
Disadvantages:
Application field: VoIP
Royalty method: free of charge
Remarks: Same as MPEG- 1 audio layer 1.
MP3(MPEG- 1 Audio Layer 3)
Type: audio
Manufacturer: MPEG
Bandwidth required:128 ~112 kbps (compressed 10 ~ 12 times).
Features: Complex coding, used for high-quality sound transmission on the Internet, such as MP3 music compression 10 times, 2 channels. MP3 is a hybrid compression technology based on the advantages of MUSICAM and ASPEC. At that time, the complexity of MP3 was relatively high, which was not conducive to real-time coding. However, due to its high-level sound quality at low bit rate, MP3 has become the darling of soft decompression and network playback.
Advantages: High compression ratio, suitable for Internet communication.
Disadvantages: When MP3 is at 128KBitrate or below, there will be obvious high-frequency loss.
Application field: VoIP
Royalty method: free of charge
Remarks: Same as MPEG- 1 audio layer 1.
MPEG-2
The MPEG-2 standard was published in 1994, including the system part numbered138181,the video part numbered 138 18-2 and the video part numbered12.
MPEG-2 coding standards hope to include coding standards in various fields such as digital TV and image communication. MPEG-2 is divided into five profiles according to different compression ratios, and each profile is divided into four image formats according to different image clarity, or called level. There are 20 combinations of five levels and four levels * * *, but some combinations are unlikely to appear in practical application, and the commonly used combination is 1 1. These 1 1 combinations are used in different occasions, such as MP@ML (master level and master level) with studio quality standards for SDTV and MP@HL (master level and high level) for American HDTV Major League.
MPEG-2 audio layer
Type: audio
Manufacturer: MPEG
Bandwidth required: same as MPEG- 1 Layer 1, Layer 2 and Layer 3.
Features: MPEG-2 uses the same codec as MPEG- 1, and the structures of layer 1, layer 2 and layer 3 are the same, but it can support surround sound of 5. 1 and 7. 1 channels.
Advantages: Support 5. 1 channel and 7. 1 channel surround sound.
Disadvantages:
Application field: VoIP
Commission method: charged separately.
Remarks: MPEG-2 adopts the same codec as MPEG- 1 sound, and the structure of 1 layer, layer 2 and layer 3 is the same, but it can support 5. 1 channel surround sound and 7. 1 channel surround sound.
MPEG-4
1began to study MPEG-4 in July 1995, and 10 was approved as a formal standard by ISO/IEC in October. The official standard number is ISO/IEC 14496, which not only aims at video and audio coding at a certain bit rate, but also pays more attention to the interactivity and flexibility of multimedia systems. This standard is mainly used for videophone, videoe-mail, etc. The transmission rate is required to be low, 4800-6400 bit/s, and the resolution is 176 * 144. MPEG-4 uses very narrow bandwidth, and obtains the best image quality with the least data through frame reconstruction technology and data compression. With the high compression rate and high image reproduction quality of MPEG-4, MPEG-2 video files in DVD can be converted into smaller video files. After this processing, the video quality of the image has not been greatly reduced, but the volume can be reduced several times, so it is very convenient to save the programs on DVD with CD-ROM. In addition, MPEG-4 is also very useful in family photography and video recording, as well as real-time video playback on the Internet.
MPEG-7
MPEG-7 (its origin is 1+2+4=7, because there is no MPEG-3, MPEG-5, MPEG-6) began to learn at 1996+00. Exactly speaking, MPEG-7 is not a compression coding method. Its official name is' Multimedia Content Description Interface', and its purpose is to generate a standard for describing multimedia content. This standard will provide a certain degree of freedom for the interpretation of information meaning, which can be transmitted to and accessed by devices and computer programs. MPEG-7 is not aimed at a specific application, but at the picture elements standardized by MPEG-7, and will support as many applications as possible. The starting point of establishing MPEG-7 standard is to classify images and sounds through many parameters and query their databases, just as we query text databases today. It can be applied to digital libraries, such as image cataloging, music dictionaries and so on. Multimedia query service, such as telephone directory; Select broadcast media, such as radio and TV channels; Multimedia editing, such as personalized electronic news service, media creation, etc.
MPEG-2 1
MPEG put forward the concept of "open core" at the MPEG conference in June 199, and the MPEG conference in February19 decided that the official name of MPEG-2 1 was "open core" or "digital audio-visual framework", aiming at integrating standards to support coordination technology and manage multimedia business, and understanding how to integrate different technologies.