MP3 format was born in Germany in 1980s. The so-called MP3 also refers to the audio part of the MPEG standard, that is, the MPEG audio layer. According to the difference of compression quality and coding processing, it is divided into three layers, which correspond to three kinds of sound files: * .mp1* .mp2/* .mp3. It should be noted that the compression of MPEG audio files is lossy compression. MPEG3-3 audio coding has a high compression ratio of10:12:1,while basically keeping the low audio part undistorted, but sacrificing the high audio part from 12KHz to 16KHz in the sound file. Music files with the same length are stored in * * .mp3 format, generally only * *110. WAV file, and the sound quality is not as good as CD format or wav format Because it has small files and good sound quality; So at the beginning of its appearance, no other audio format can match it, thus providing good conditions for the development of * * .mp3 format. Until now, this format is still all the rage, and its position as the mainstream audio format is hard to shake. But the copyright problem of MP3 music has not been solved, because MP3 has no copyright protection technology, which means anyone can use it clearly.
There are many sampling frequencies for MP3 compressed music. The sampling frequency of 64Kbps or lower can save space, and the standard of 320Kbps can also achieve extremely high sound quality. We use the MP3 encoder of Fraunhofer IIS Mpeg Lyaer3 (the best encoder at present) to encode a 3-minute song at 128Kbps, and get a 2.82MB MP3 file. The default CBR (fixed sampling frequency) technology can sample a song at a fixed frequency, while VBR (variable sampling frequency) can increase the sampling frequency to obtain higher sound quality when the music is "busy", but the generated MP3 file may not be played on some players. We set the level of VBR to be basically the same as the previous CBR file, and the generated VBR MP3 file is 2.9MB.
midi:
People who often play music should often hear the word MIDI (Musical Instrument Digital Interface), which allows digital synthesizers to exchange data with other devices. The MID file format is inherited from MIDI. MID file is not recorded sound, but a set of instructions that record sound information and then tell the sound card how to reproduce music. This MIDI file only needs about 5 ~ 1 0kb of music per minute. Nowadays, MID files are mainly used for original musical instruments, amateur performances of pop songs, game tracks and e-cards. *. * effect. Mid file playback depends entirely on the grade of sound card. * the biggest use. Mid format belongs to the field of computer typesetting. *.MID files can be written in composition software, or the music played by an external sequencer can be input into the computer through the MIDI port of the sound card to make *. Intermediate file.
WAV:
It is a sound file format developed by Microsoft, which conforms to the specification of PIFFRESOURCE exchange file format, and is used to save the audio information resources of WINDOWS platform, and is supported by WINDOWS platform and its application programs. “*。 WAV "format supports many compression algorithms such as MSADPCM and CCITT A LAW, and supports many audio bits, sampling frequencies and channels. Like CD format, the sampling frequency of standard WAV file is 44. 1K, the rate is 88K/ s, and the quantization bit is 16. Look, the quality of audio files in WAV format is almost the same as that in CD format.
amr:
Amr stands for Adaptive Multirate (Audio Codec). It belongs to audio files (i.e. sound effect files) and comes from CD, MP3, etc. It is similar to MP3, but the compression ratio is higher than MP3. At present, some phones of Nokia and Sony Ericsson have more AMR formats.
AMR ringtone format is also one of the common file formats of MMS. It can be used to make music files, and it is often used to make some sound works, such as funny sounds and animal sounds. AMR has irreplaceable advantages in showing personality. Because the capacity of AMR file is very small, the AMR audio size per second can be controlled around 1K, so AMR is widely used as the recording file format of mobile phones even if it is an audio file with the length of 1 minute.
AMR (Adaptive Multi-Rate): A commercial name provided by Nokia for ringtones in WB-AMR format (AWB), which was selected by 3GPP (3rd generation partnership project) as the broadband language decoding standard for GSM and 3G WCDMA applications. AMR proposed by European Communication Standardization Committee is the most widely used voice standard in mobile communication system. MMS also adopts this format as the sound standard. Supported models: Alcatel OT756, Siemens CX65, etc. Like ADPCM, AMR is not a special ringtone format, but a format widely recognized by major mobile phone manufacturers to save mobile phone recordings. Because the capacity of AMR file is very small-the AMR audio size can be controlled at around 1K per second, even the audio file with the length of 1 minute can meet the current technical specification of China Mobile that the multimedia message should not exceed 50K, so AMR is the only format for loading human voices into multimedia messages. But because of its small size, the sound quality of AMR format songs can be imagined. According to the author's actual operation, Alcatel OT756 and Siemens CX65 can record their own ringtones and save them as AMR format audio files, but compared with MP3 ringtones supported by OT756 or WAV ringtones supported by CX65, the volume, clarity and layering of AMR ringtones are completely different. However, as a voice ringtone, AMR also has its own advantages, that is, the convenience of production-turn on the recording function, and the recorded sound can be used as a ringtone, which is not fast. Because it is an audio file commonly used in MMS, most MMS phones that support recording function can record and play AMR ringtones, but it should be noted that being able to record and play does not necessarily mean that it can be set as an incoming ringtone. Take Panasonic G60, Samsung X608 and Sony Ericsson Z608 as examples. All three mobile phones can record AMR and play it well, but this is only a part of its recording function, which does not belong to the category of ringtones, so AMR is not supported as a ringtone.