MP4, full mpeg-4 'ts 14, is a kind of use mpeg-4 multimedia computer file formats, vice file name. MP4, to store the digital audio and digital video primarily. In addition, MP4 and comprehensible to MP4 player, MP4 player is a set of audio, video, images browsing, e-books, radio is equal to the integrative multi-functional players.
introduction
About MP4 accurate concept, it is a long story, because no matter from the MP4 brand, market, product specifications, standard and so on various aspects to say, you can use a word to describe - "random". Don't know is hype or the trend, now businessman, as long as you can touch the eyes while video player, all are called MP4, that easy. Actually, MP4 player is an able to play files to mpeg-4 equipment, it can be called PVP. Video Player, Personal (Personal Video Player) are also called Media Player, make (PMP Portable Media Player). Now to MP4 player function without specific definition, although many manufacturers are defines it for multimedia video player, but it besides listening to watch movies the basic function of music playback, outside also support the browse pictures, and even some products also can surf the Internet. But in order to emphasize portable characteristics, here we have discussed the MP4 player in portable, played video as standard, they can pass the USB or 1394 ports transfer files, very conveniently video download file to equipment in play, and shall bring LCD screen, in order to meet the needs of video playback at any time.
Working principle
MP4 player is using Digital Signal processor (DSP (Digital Signal Processer) to complete the processing transmission and decoding MP4 files tasks. In charge of data transmission DSP walkman, device interface control, file decoding playback and other activities. DSP in a very short time to finish the task, and many kinds of processing this process by which energy consumption few (this is also it is suitable for portable player a remarkable characteristic of).
First will MP4 songs files from memory out and reads the storage signal - to decoding chips to signal decoding - by digital-to-analog converters will solve it's digital signal converted into analog signals - again after conversion analog audio amplifier - retro-annual to earphone jammer, and output later is we have heard music.
Hardware structure
MP4 "core" dirty
In principle, MP4 and MP3 difference, but from hardware performance speaking, both differ very far, mainly because video playback reactive MP4
Can, Divx Xvid and etc. The broadcast mpeg-4, request the CPU and DSP higher processing power, but also to have certain of system memory, Divx encoder came early developers use frequency, encoder for 400MHz above the computer to complete the decoding, visible MP4 requirements chip has high computing performance, many MP4 luxuriant interface consumed a lot of system resources, MP4 video data and image is not only the data processor, now MP4 or many digital function and multimedia function of unity, to realize the function of forms type, for example, digital video collection, partner, DC, FM, please... Even some MP4 also support the multi-line work. So MP4 chip requires not only has high computing power, and integrated many functions.
Due to MP4 core chip making, craft level requirement is exorbitant, so average MP4 manufacturers are powerless, these core generally by traditional production, such as the Intel chips everybody, TI, Sigma design etc., even AMD has introduced a MP4 special processing chip - AU1200. At present the MP4 mainly adopts is TI the scheme and Wintel complete hardware and software solutions. Among them, TI (Texas Instruments) is mobile entertainment facilities, and intel-based desktop chip giant platform of chip giant, because TI started early, so now mostly MP4 are using TI chip solutions occupied most of the market share. Although hardware have certain rules, but software system has no unified standard, but each merchants on his own development (mostly Linux), this also is "made a big random" reason. Now most manufacturers are using TI solution, the main love visualization, and Europe and Japanese series digital manufacturers of SONY, Toshiba.
And Wintel strong-strong union, launch PMC new standard, central processing unit adopts intel-based XScale series, the software system is Microsoft's Windows make Media Center system, software and hardware have uniform standard, fully embodies the Microsoft foray into Portable Media market, ambitious, due to the system Windows Media Center, make overall structure of open, so can the operating system on the basis of expanded by application software. Wintel schemes, unified industry standards, to a certain extent to MP4 FaZhanDian clear direction. At present, the scheme of support this basically has iRiver, wei xing, samsung and innovation, etc.
TMS320DM270 chip:
TMS320DM270 internal structure: by the TMS320DM270 core, can see the chip is of a function extremely powerful chips, mainly by the ARM (80MHz), C54xDSP (90MHZ) and iMX (180MHz) three core components, including ARM7 RISC processors is mainly responsible for the external interface management, C54X DSP digital signal processor is responsible for audio in respect of various kinds of processing, and video data and iMX engine processing image data. IN addition, the integration of various function module and controller to make its also has other powerful functions, such as camera, reader, recording, AV - IN/AV - OUT etc.
MP4 battery
MP4 batteries commonly used lithium ion battery composite. The battery has small. Capacity, high. Light weight etc. Buy should note or key consideration of your battery capacity, of course, is capacity, the higher the better.
TI about MP4 system plan:
TI's tms320dm270 scheme is MP4 at present the most advanced solutions, with good quality and one of video format compatible good special card, the horizontal evaluation is using the most MP4 scheme. MP4 internal core framework mostly used central processor with DSP coordination work manner, generally the CPU and DSP is integrated together. Digit Signal Processor) DSP (mainly responsible for video decoding and coding, And the central processor mainly deal with file management, access, and use interfaces, peripheral component control etc. In addition, some function module will increase the special chip, such as DC control module and display control module, etc.
Audio processing
Audio processing aspect, TI mainly adopts the development of oneself TLV320AIC23B encoder, it of a high performance of low power consumption stereo audio Codec chip, built-in headphone output amplifier, support MIC and LINE IN two kinds of input methods, input/output has programmable gain control. AIC23 internal integration frequency-field (ADC) and digital-to-analog (DAC) circuit, output SNR can be achieved respectively 90dB and 100dB, can be in 8K ~ 96K frequency range provide 16/20/24/32-bit sampling. Sound relatively sterling, fidelity of high, treble loud, bass real net. This horizontal evaluating MSI MEGAWVIEW 561 is used this kind of audio decoding chips.
Video display
Video shows that can is through NTSC or PAL to external output, also can be the output to bring a LCD screen, now MP4 adopts screen basically has: CSTN, TFT LCD screen and LPTS etc, about these three screen the characteristic and effect of the knowledge of the respect, please refer to the Pacific earlier in the article: the literacy movement, portable media player, MP4 comprehensive doubts ".
Access management
Current main hard disk MP4 by the HITACHI, FUJITSU and TOSHIBA from the 1.8 inches for hard disk, occasionally a notebook hard disk by 2.5 inches, But for managing cost, also have on market by small capacity and narrowing the volume flash MP4, but for MP4 for flash memory as medium, using from the current technology background and market price terms, although flash disk don't compare with the advantages of (stability, low energy consumption, shockproof sex), but is not the path flash memory. Since the previous HITACHI released 0.8 inch of little hard disk to a embarrassing situation since the MP4 brings new hope.
Power management
About the problem, as power sources, as is always the right buttons, general MP4 MP4 can only support the hard disk video broadcast a blockbuster time negroponte, this is absolutely and insufficient, especially for built-in lithium battery MP4, this is extremely convenient, for the battery endurance is too short to be equal to lost carry-on see meaning. However, this time from connect evaluation more than 10 paragraph MP4 kind of saw battery for conserving, MP4 problem with removable lithium battery, useful, the more pleasurable AA dry cell is a continuous play among video eight hours and 11 hours.
species
Called the MP4 video playback bioengineering.medicine.hygienist MP3
This player is not actually are, in essence, MP4 video playback is merely MP3, its annexes function, called the MP4, purely commercial hype. This player limitations greatly small screens (1.8 inches), 0.8 ~ flash memory capacity small, support a specific format (MTV, MP4, MPV and etc.), and most DMV is adopted CSTN OLED and low-end screen etc, so accurately, this can only be called can play video MP3 just. Representatives are: DEC F12R, king, JinBang dazzle colour 3E E1000 and PISA dazzle colour airship, etc.
Hard disk type MP4
Is simply take the hard disk as media carry-on look. Tatu accommodate the world, had never worry not enough disk space. Hard disk MP4 generally has integrated many other function, for example, digital camera, video camera, LuYinBi, digital partner... But the mp4 than mainstream flash memory mp4 much more expensive, often without consideration. No 1000
Flash memory type MP4
Contrast hard disk type MP4, MP4, is to flash memory type to storage media carry-on view, the MP4 generally support by inter-tangential flash card extend, are generally SD card or TF card. Flash memory type MP4 relatively small, lightweight much cheaper than common MP4 several times.
No screen to MP4
Some vendors think MP4 3.5 inch screen is too small, played high quality video appear cold Chen, in addition to flash type MP4 128MB ~ 16GB, also is not large, so these manufacturers enjoy designed a kind of no screen hard disk MP4, the MP4 can pass AV - moments, chromatism weight even HDMI etc output output to TV screen mode, and USES is 1.8 ~ 2.5 inches little hard disk, on bulk slants big, but for this not emphasize mobility MP4 speaking, volume than the tradition on DVD confidential cabinet many, there has been a lot of, the MP4 generally contain dozens hundred G capacity, but price than flash type MP4 expensive. For example, love visual MP4.
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