What are the characteristics of the MP3 format?
1. MP3 is a data compression format.
2. It discards data in the pulse-coded modulation (PCM) audio data that are unimportant to human hearing (similar to JPEG is a lossy image compression), MP3 thus achieving a much smaller file size.
3. MP3 audio can be compressed according to different bit speeds, providing a range of trade-offs between data size and sound quality. The MP3 format uses a mixed conversion mechanism to transform the time-domain signal into a frequency-domain signal.
4.32-Band Multiphase Integrator Filter (PQF).
5.36 or one tap improved discrete cosine filter (MDCT); Each sub band size can be at 0 ... 1 and 2 ... 31 Independent choice.
6. MP3 not only has extensive client-side software support, but also has a lot of hardware support such as Portable media Player (MP3 player) DVD and CD player.
MP3 is a lossy digital audio compression format. The full name is Mpeg-1 audio Layer 3, where MPEG is the abbreviation of the Moving Picture Experts Group, MP3 meaning the dynamic image Expert group. The so-called "lossy compressed audio format" is the digital audio use of the sound loss of the compression mode, in order to reduce the size of the file to meet the needs of replication, storage, transmission. The compression rate of the MP3 can reach 1:12, but it does not sound distorted in the ear, MP3 as it removes the sound from the digital audio beyond the hearing range of the human ear without altering the main sound. In addition, MP3 can upload, download any other format of the computer files, with mobile storage capabilities.
MP3 is actually a function-specific small computer. In its small fuselage, with memory (memory card), display (LCD display), central processing Unit [MCU (microcontroller) or decoding DSP (digital signal processor), etc.
When the micro-operating system is loaded, the MCU starts to control the operating system and performs the various functions it specifies. For MP3, the main function is to play MP3 music. Playback process is MP3 music file decoding process, MCU using its own CPU computing power to assume the heavy MP3 music file decoding task. When MP3 music download to MP3 generally stored in the fuselage built-in flash or hard disk, MP3 in the process of playback, MCU from the storage medium read it out, buffered in RAM, after decoding play out. Since the signal is a digital signal, the analog devices such as headphones cannot be played, then a number/mode converter (DAC) is needed to transform the digital signal into an analog signal, and the music can be played through the headphones.
MP3 products are commonly used in USB2.0 interface, USB2.0 is divided into two kinds: USB2.0 full Speed (full-speed) and USB2 0 Hi Speed (high speed). USB2.0 Full Speed transfer rate is 12Mbps (megabits per second), equivalent to 1.5mb/s. Currently, most MP3 are of this type of interface. USB2.0 Hi Speed The theoretical transmission rate can reach 480Mbps, which is equivalent to 60mb/s, which means that the dress full of a 128MB MP3 only need 2 seconds! But for a variety of reasons, the actual transmission rate is far from reaching this value, MP3 the general transmission rate has not exceeded $number, but can reach a few trillion per second, this speed is fast enough.
In addition, the early MP3 used mostly USB1.1 interface, its general transmission rate is 1.5Mbps, which is equivalent to USB2.0 (Full speed) 1/8.
MP3 is a low-power small audio device, MP3 and its power supply design is also very important. Design is not good, not only the power consumption is not said, but also may cause interference in the audio signal.