superiority
(1) Content-based interactivity
MPEG-4 provides multimedia data access tools based on content, such as index, hyperlink, upload, download and delete. Using these tools, users can conveniently and selectively obtain the content related to their own objects from the multimedia database, and provide the functions of content manipulation and bit stream editing, which can be applied to interactive home shopping, digital effects of fading in and out, etc. MPEG-4 provides an effective natural or synthetic multimedia data coding method. It can combine natural scenes or objects into synthetic multimedia data.
(2) Effective compressibility
MPEG-4 is based on higher coding efficiency. Compared with other existing or coming standards, it is based on higher visual and auditory quality at the same bit rate, which makes it possible to transmit video and audio over low-bandwidth channels. At the same time, MPEG-4 can also encode synchronous data streams. The multi-view or multi-channel data stream of a scene can be efficiently and synchronously synthesized into the final data stream. This can be used for virtual 3D games, 3D movies, flight simulation exercises and so on.
(3) Universal accessibility
MPEG-4 provides robustness in error-prone environment to ensure its application in many wireless and wired networks and storage media. In addition, MPEG-4 also supports content-based scalability, that is, content, quality and complexity are divided into many small blocks to meet the different needs of different users and support transmission channels and receivers with different bandwidths and storage capacities.
These characteristics will undoubtedly accelerate the development of multimedia applications, and the application fields that benefit from them are: Internet multimedia applications; Radio and television; Interactive video games; Real-time visual communication; Interactive storage media applications; Studio technology and TV post-production; Virtual conference using facial animation technology; Multimedia mail; Multimedia application under the condition of mobile communication: remote video monitoring; Remote database service through ATM network and so on.
MP4 is an audio format, which has nothing to do with MPEG-4, just as MP3 has nothing to do with MPEG-3. In terms of technology, MP4 uses MPEG-2 AAC technology, abbreviated as A2B or AAC technology. Its characteristics are more perfect sound quality and higher compression ratio (15: 1-20: 1). MPEG-2 AAC can provide high-quality audio coding with optional range of 1 ~ 48 channels when the sampling frequency is 8 ~ 96 kHz. AAC is the abbreviation of advanced audio coding, which is suitable for the coding of multi-channel ultra-high quality audio signals from the telephone voice quality with a bit rate of 8kbps to 160kbps, and allows multimedia coding and decoding. It adds some functions that MP3 does not have, such as perfect stereo reproduction, bit stream effect sound scanning, multimedia control, noise reduction, etc., so that the sound quality of CD can be perfectly reproduced after audio compression.
A2B technology mainly consists of the following three parts. First, at & amp； T's audio compression technology patent can improve AAC compression ratio to 20:1without losing sound quality; Second, secure database, which can create a specific key for your A2B music file and put this key into its database, only A2B players can play music with this key; Third, protocol authentication, including copy license, allowable copy quantity, total duration of songs, playable time of songs, and business sales license.
MP4 format (also called MPEG-4) is a kind of MPEG format, and it is a compression method of moving images. Through this compression, smaller files can be used to provide higher image quality, which is one of the most popular video file formats (especially in the network). The advantage of this format is that it can cover not only the low frequency band but also the high frequency band. At present, the most popular compression methods of MP4 are DivX and Xvid.
DivX is a digital multimedia compression format, which compresses movie audio through MP3 and video through MPEG-4 technology. DivX was developed by DivXNetworks.
When it comes to DivX, we can't help but talk about MPEG, which is the abbreviation of moving picture expert group. This expert group was established in 1988, and is responsible for establishing audio and video standards for CDs, including MPEG- 1, MPEG-2 and MPEG-4. Respectively adapt to different bandwidth and digital image quality requirements. MPEG- 1 is believed to be the most widely contacted, because it is widely used in the production of VCD and the network application of downloading some video clips. VCD can be compressed in MPEG- 1
XviD is based on OpenDivX. Xvid supports multiple coding modes and is an open source MPEG-4 video codec. Quantization, range control, motion search, curve and many other coding technologies are very powerful for users. For today's market, Xvid's competitor is DivX. But Xvid is open source, and DivX is only free.