Why is the movie player called mp4?

Mp4-related definition MP4, full name MPEG-4 Part 14, is a multimedia computer file format using MPEG-4, with an extension of .mp4, which mainly stores digital audio and digital video. In addition, MP4 can be understood as MP4 player, which is a multifunctional player integrating audio, video, picture browsing, e-books and radio. MP4 is bigger than MP3. The exact concept of MP4 is a long story, because the brand, market, product specifications and configuration standards of MP4 can all be described in one word-"chaos". I don't know if it's hype or fashion. Now, in the eyes of merchants, all players that can access video are called MP4, which is simple and intuitive. In fact, MP4 player is a device that can play MPEG-4 files. It can be called PVP (Personal Video Player) or PMP (Portable Media Player). At present, there is no specific definition of the function of MP4 player. Although many manufacturers define it as a multimedia audio-visual player, it supports music playing, browsing pictures and even some products can surf the Internet besides listening to movies. However, in order to emphasize the characteristics of portability, the MP4 players we discuss here will all be portable and play videos. They can transfer files through USB or 1394 port, download video files to devices for easy playing, and should have their own LCD screen to meet the needs of playing videos at any time. MP4 file format Audio MP4 format: AAC MP4 is originally an audio format, which has nothing to do with MPEG-4, just like MP3 has nothing to do with MPEG-3. MP3 is the abbreviation of MPEG- 1 Audio Layer 3; MP4 is MPEG-2 AAC, which is a complete audio compression format, adding new functions such as perfect stereo reproduction, multimedia control and noise reduction. Most importantly, MP4 realizes digital copyright protection through special technology, which is incomparable to MP3. Video MP4 format: Most MPEG-4 MP4 players on the market are biased towards multimedia players, and those that can play AAC can be said to be rare. Some media even described MP4 as the abbreviation of MPEG4-4, which was a fallacy in the past, but this fallacy has become a truth after the constant hype of merchants. Now, if you go to the computer city and hear the word MP4, it is definitely the concept of a multimedia player that can play video format, not a walkman that can play audio MP4 AAC. This strange phenomenon is not without reason. As mentioned above, AAC has copyright protection function, which is why many record companies support AAC. In order to make their players support AAC, they have to support the payment of certain copyright fees or patent fees. In addition, the source of AAC is also a problem, which is not as public as MP3, and there are few online sources. Therefore, the development of audio MP4 player is not mature at present. In view of the above situation, many businesses simply "come back to life". Equating MP4 with the abbreviation of MPEG-4 just corresponds to the law that MP4 is the next generation MP3, which not only supports the music playing function of MP3, but also has powerful MPEG-4 video playing ability. In addition, it makes sense to equate MP4 with MPEG-4 just after "3". MPEG-4 encoding and format The encoding format supported by MP4 player can be said to be "chaos in chaos". Except PMC, the software systems are all designed by the manufacturers themselves, because there is no unified standard for the hardware platform, which is the fundamental reason for the uneven decoding compatibility and stability of MP4 players. In addition, MPEG-4 coding system has produced many formats. Except PMC, the decoding compatibility of MP4 is related to hardware, which greatly increases the difficulty of decoding. There are many video formats, such as AVI, ASF, MPG and WMV, and there are also many coding algorithms: MPEG- 1, MPEG-2 and MPEG-4, which are supported by most MP4 players. There are many derived coding algorithms: DivX, XviD, H.263, MS MPEG-4 3688, Microsoft Video 1, and Microsoft RLE. All kinds of MP4 players are called MP4, which is actually MP3 playing video. This player is actually not MP4, but MP3 in essence. Video playback is only its subsidiary function, also called MP4, which is purely commercial speculation. This player has great limitations: the screen is very small (0.8~ 1.8 inches), the flash memory capacity is small, and it supports specific formats (MTV, MP4, MPV and DMV, etc.). ), and most of them use low-end screens such as organic light-emitting diodes and CSTN, so they can only be called MP3 which can accurately play videos. The representatives are DEC F 12R, Golden Colorful King, 3E 1000 and Pisa Colorful Airship. MP4s, such as hard disk MP4s, are the mainstream of development at this stage, and the number of products also occupies an absolute advantage. Simply put, the concept of hard disk MP4 is to take the hard disk as a medium and watch it with you. A big belly can hold the whole world, and you don't have to worry about running out of space when using a hard disk. Generally speaking, hard disk MP4 also integrates many other functions, such as digital camera, video camera, tape recorder and digital companion ... This evaluation includes 1 1 hard disk MP4. Compared with hard disk MP4, flash MP4 uses flash memory as the storage medium, so it can be viewed everywhere. This MP4 generally supports the expansion of internal flash cards, usually SD cards. There are two MP4s of this type in this evaluation, namely Govideo PMP- 120 and JXD-680. Flash memory MP4 is much smaller, lighter and several times cheaper. MP4 without display Some manufacturers think that the 3.5-inch screen of MP4 is too small to play high-quality video, and the flash memory of 128~256M of MP4 also makes people unable to enjoy blockbusters. Therefore, these manufacturers have designed a hard disk MP4 with no screen, which can be output to TV and other screens through AV-OUT and other output terminals, using a 2.5-inch hard disk. MP4 does not emphasize mobility and is much smaller than the traditional DVD player. There are only a few models on the market. This MP4 has a capacity of tens of G, but the price is similar to that of flash memory MP4. For example, Le Cheng MP4. Audio processing In the aspect of audio processing, TI mainly adopts its own TLV320AIC23B encoder. It is a high-performance and low-power stereo audio codec chip with built-in headphone output amplifier. The input mode supports MIC and LINE, and the input/output has programmable gain adjustment. AIC23 integrates analog-to-digital conversion (ADC) and digital-to-analog conversion (DAC) circuits, and the output signal-to-noise ratio can reach 90dB and 100dB respectively. It can provide 16/20/24/32 bit sampling in the frequency range of 8 K to 96 K, with pure sound quality, high fidelity, loud treble and clean bass. This audio decoding chip is used in MSI MEGAWVIEW 56 1. Video display Video display can be output to the outside through NTSC or PAL format, and can also be output to its own LCD screen. At present, MP4 mainly uses LCD screens such as CSTN, TFT and LPTS. For the knowledge about the characteristics and effects of these three screens, please refer to an earlier article in the Pacific: Literacy Campaign, Portable Media Player MP4 completely dispels doubts. At present, the mainstream hard disk MP4 of access control management adopts Hitachi, Fujitsu and Toshiba's 1.8 inch hard disk, and occasionally uses 2.5 inch notebook hard disk. In order to save costs, there are MP4s with small capacity and reduced volume flash memory on the market, but for MP4s, all of them are based on flash memory. Judging from the current technical background and market price, although flash memory has incomparable advantages (stability, low energy consumption and good earthquake resistance), flash memory is not the right way. Since Hitachi released the 0.8-inch micro hard disk last year, it has brought new hope to MP4 in an embarrassing situation. Power management: Just like the film source, the power supply has always been the dead end of MP4. The general hard disk MP4 can only support a long video playing life, which is absolutely not enough, especially the MP4 with a built-in lithium battery, which is extremely inconvenient, because the battery life is too short, which means that it loses the meaning of watching with you. This time, however, MP4 exceeding 10 saw a new hope for battery problems. Some MP4s use removable lithium batteries and AA dry batteries. What's more gratifying is that some can play videos for 8 hours continuously, 1 1 hour. Advantages of MP4 player It can directly play high-quality video and audio, and can also browse pictures, which can be used as mobile hard disk and digital bank. Some products also have some very novel and practical functions. For example, AV420 can record video, and it can store the signals of DVD, TV and other devices in the hard disk in MPEG-4 format. The upcoming MP4 player of CIMC Wei Chao Power Company supports PIM management and wireless network functions, which can play more roles after the popularization of wireless environment. Moreover, most MP4 players we see now have professional video functions such as video conversion, and have perfect video input/output ports, so the video files we carry can be played on many occasions. Although this is not of greater practical significance for some users who only use the player on the road, it is very useful for some users who often make video presentations, because MP4 players can be easily connected to output devices such as projectors and televisions. From the point of view of personal use, the biggest advantage of MP4 player is its small size, easy to carry, and it can play videos with you at any time. However, there is more than one product that meets these conditions, and PDA is a competitor. Although it is impossible to directly compare the functions of the two, there is no essential difference between them only from the video playback function of this machine, but the PDA has more functions and the price is relatively cheaper. If you don't often use MP4 player, it's ok to choose PDA instead of MP4. MP3 player, as its name implies, is a music playing tool that can play MP3 format. MP3 is the abbreviation of MPEG Audio Layer 3. MPEG compression format is a set of standards for images and sounds formulated by moving picture experts group, among which MP3 is a new audio signal compression format standard designed for compressing sound signals. MP3 is a format that uses the third layer audio compression mode in the international standard MPEG to compress sound signals. Chinese is also called "computer network music". The third layer of audio compression in MPEG is much more complicated than the first and second layers of coding, but its sound quality is higher than that of the first and second layers, even comparable to that of CD. The sampling frequency of CD is 44. 1MHz, and the data volume is 1.4Mbps, while the corresponding MP3 data volume is only 1 12kbps or 128kbps, which is1/kloc-0 of the original data volume. That is to say, a traditional CD can now store 10 times or even more music, but for the human ear, the music effect is no different. MP3 itself is a computing method of compression and decompression, which is used to process high-speed sound information. The sound quality of the sound file it generates is close to that of CD, but the file size is only one twelfth of that of CD. If a CD can store about 12-20 songs in CD format, if it is stored in MP3 format, it can store about 100 songs, which is its charm. The original goal of MP3 is to reduce the file size to facilitate data transmission on the network, and to keep playing MP4 (also called MPEG-4) similar to the original one, which is a kind of MPEG format and 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). It is a compression standard for ultra-low bit rate moving images and languages. Used for real-time image transmission with transmission rate lower than 64Mbps. It can not only cover the low frequency band, but also develop to the high frequency band. MP4 provides a broader platform for multimedia data compression, which defines a format and an architecture, rather than a specific algorithm. It can make full use of various multimedia technologies, including some tools and algorithms of compression itself, as well as technologies such as image synthesis and speech synthesis. MP4 has aroused widespread concern since it was put forward. At present, the most popular compression methods of MP4 are DivX and XviD. For DVD programs processed by MP4 technology represented by DivX or XviD, the video and audio quality of images has not been greatly reduced, but the volume has been reduced to a fraction of the original size, so it is very convenient to save the generated files with two ordinary discs with 650MB capacity. If the requirements are lowered a little, a disc can hold movies for more than 100 minutes, and the picture quality at this time is obviously better than that of VCD.