Sound file formats Talk (Author: Xu Jianguo, 2001 at 19:41 on January 9) compressed file format song files to make smaller, more easy to store and spread on the Internet. All of this is for a purpose - computer users who love music can easily communicate their digital music. Since music exchange is welcomed, technicians have invented better audio formats. In addition to rare parts, such as BlueMatter and WMA, try to achieve even exceeding the sound quality of the CD, most of them work towards copyright protection, smaller file size, and extension of fancy extension (such as visible cover). In order to understand most of the audio files, you should understand a few terms. Traditional audio files can be stored in a hard disk or other storage medium, we call them "discrete file" or "downloadable files". In general, this music file needs to completely download it before you appreciate it (such as MP3). You can easily copy the discrete documents of many formats, of course, copyright issues should be noted. Flow files (such as the file format used in ReaRaudio and QuickTime) are another file, you can download while downloading. Flow Media Player Download a few seconds of content temporarily stored in the buffer, and playing the content in the buffer while continuing to download, people will not pay attention to any problem. But a problem that may exist is that you may not easily save the entire file to your hard drive. It should be noted that some file formats, such as MP3 and WMA, can either a discrete file or a streaming file. If the manufacturer of the file is not limited, you can also save the Reaudio file. If some songs you just want to listen to one or two, do not want to waste the precious hard disk space, the flow file is very useful. You know, a song may be 2MB to 60MB (depending on the file format). Content providers (Record companies or songs authors) can effectively prevent piracy in streaming files, or as a lower sound quality demonstration to encourage you to download a full version of "discrete file". Online radio providing real-time flow file playback (such as Reaudio format, WMA format), but when the network is not good, due to the low speed, "burr" is generated, at this time, the server will send a signal and since then Transport at a lower rate. When more and more users use Cable Modem or DSL, high-speed connection can easily handle high-quality large stream files, flow files will be truly popular. Compression technology makes audio files easier to store and propagate. The compression of the audio file is generally an acoustic wave other than the human auditory range, or uses some of the sounds to "cover". For example, an uncompressed 50MB WAV file is compressed into an MP3, WMA or Mjuice (.mjf) file, only 5MB. There are other factors that affect people's choice of audio files. For example, a free MP3 song, it has three versions: 96kbps (96 thousand bit per second), 128kbps and 192kbps. Kbps (bit rate) indicates the amount of data per second, the higher the Kbps value, the better the sound quality, the larger the file, the longer the download time. Users generally believe that 128kbps MP3 files are closest to CD sound quality, so if you like CD, you should choose 128kbps version. If you are willing to lose a little sound quality, in exchange for a faster download speed or save more songs in your computer, you may wish to choose 96kbps. If you have a pair of picky ears and a lot of storage space, then download 192kbps MP3.
You may encounter some unfamiliar concepts, for example, when recording a WAV file, you will see different sound quality representations: Sample Rates, Sampling Accuracy (Bit Depth, Channels). The sampling frequency refers to how many times the original sound is recorded per second. It is indicated by Hz or KHz. The higher the sampling frequency, the better the sound quality, but the file is, the number of channels, the number of channels, WAV is mono (MONO) Still a double channel (Stereo). Sampling accuracy is 8, 16 or more, tells you how much information is recorded when the computer records each time the original sound. 44.1KHz, double channel, 16-bit sampling accuracy, the standard of CD sound quality we usually said. MP3 You don't have to be limited to the original format of the audio file. A player like MusicMatch Jukebo 5.1 can convert several audio formats and can even take a track from the CD. Typical proportions of MP3 format compressed music have 10: 1, 17: 1, or even 70: 1. You can save space with 64kbps or lower sampling frequencies, or use 320 kbps standard to achieve extremely high sound quality. We encode a 3-minute song with MusicMatch Jukebox 5.1 at the frequency of 128kbps, get 2.82MB MP3 file. Using the default CBR (fixed sampling frequency) technology can sampling a song at a fixed frequency, while VBR (variable sampling frequency) can increase the frequency of sampling when the music "is busy", but The resulting MP3 file may not be played on some players. We set the level of VBR to be basically the same as the sound quality of the previous CBR file, and the generated VBR MP3 file is 2.9MB. You can download to MP3 files on most music websites, such as http://www.mp3.com with http://www.emusic.com. However, it should be known that you have no authorized MP3 files in accordance with Riaa (Recording Industry Association of America). Windows Media Audio Microsoft's Windows Media Audio 7 (.wma file) is a compressed discrete file or stream file that provides an opportunity outside of MP3. The main advantage of WMA relative to MP3 is that its sound quality is better at lower sampling frequencies. In April 1999, NSTL (http://www.nstl.com) found that 51% of the audience thinks with an old version of WMA recorded songs with 64kbps, 29% of people think 128kbps MP3 More better, 19% abstains. WMA's authors say the new WMA file (version 7) sounds better. This means that our 3-minute songs can record a smaller than 1.43MB WMA files in 64kbps without obvious distortion. The WMA file is recorded in 5kbps, 8kHz to 192kbps, 44MHz sampling frequency. RealjukeBox 2 is one of several multi-purpose media players. You can use it to listen to the Internet radio, burned CD, and enjoy a variety of music files. Another advantage of WMA is that the content provider can join anti-copy protection in the DRM (DigitalRights Management) scheme such as Windows Media Rights Manager 7. You can download and play a WMA file, but if it is protected, you have to complete another step. For example, your browser may even download another site to download a license file, this license may also value a dollar bill for free, or it is only the lock of the file to let you listen to a specific number or time. Many consumers have an objection to this, but the members of Microsoft and other SDMI (Secure Digital Music Initiative claim to protect music in the future. A site that provides a WMA file is http://www.musicblitz.com.
WAV Microsoft's ordinary WAV format has a high sound quality, but because there is no compression, the audio per minute accounts for about 10MB of storage space. We use MusicMatch Jukebox to transfer the previous 3-minute song to the WAV file of the CD sound quality, with 31.08MB. The WAV file has no copyright protection, the only reason for the release of people in this format is the length of it. However, in Windows sound tips (such as ""), it has completed it. It can also be used to temporarily store songs to CD-R on the hard disk. Download WAV website has http://www.wavplace.com. Apple's AIFF (AUDIO INTERCHANGE FILE FORMAT) and AU format developed for UNIX, and WAV very much, although these documents cannot be universal, but many players support them. ReaRaudio RealNetworks is the name of the largest streaming media. Its file format is more confusing: RA (Reaudio), RM (RealMedia, Reaudio G2), RMX (Reaudio Secured), and more. Many websites collect these files to "Real". If your RealPlayer software can't handle this format, it will remind you to download a free upgrade package. Many music websites are like a listening version of the REAL format of the song, such as http://www.emusic.com. In the audio file, the length of the file is critical. Windows Media is committed to generate better sound quality than MP3 with a smaller file; RealNetworks starts replacing the G2 format to a more dependent RealAudio 8. The main disadvantages of Reaudio is that most users are still using 56Kbps or lower rate modems, so typical playback is not the best sound quality. Some download sites will prompt you to choose the best REAL file based on your MODEM. RealNetworks launched Real Audio 8 and claims that new formats are not light energy to provide CD sound quality at 64kbps, and also save money online because it produces the same sound quality as G2 with a narrower bandwidth. Liquid Audio record company or composer can make their songs into the secure LQT (Liquid Track) format of Liquid Audio, then sell these songs over 800 websites (such as Amazon). Consumers can download a free paragraph, or bought at a price of 1 to 2 dollars and listened to the free player Liquid Player 5 (http://www.liquidaudio.com). Liquid Player 5 can record the tracks on CD-R to create a CD played on other CDs. You can even use a special file to play your LQT file on other computers. The LQT file uses a compressed format, but it is more than the MP3 file because of the MP3 files. Anyway, it provides music with CD sound quality, and you can see text, pictures or lyrics while listening to music. MIDI MIDI (Musical Instrument Digital Interface) allows digital synthesizers and other devices to exchange data; the MID file format is inherited by MIDI. The MID file is not a recorded sound, but tells the sound card how to reproduce a set of instructions. Such a MID file is only about 5 to 10 kB per save. Today, the MID file is mainly used in the original instrument works, the amateur performance of popular songs, game tracks, and e-greamers. .Mid files can be found at http://www.midi.net.
