Introduction to Audio Formats

  
First, let's clarify the concept of digital audio, which is a sequence of data used to represent the strength of sound, which is sampled, quantized, and encoded by analog sound. Simply put, digital audio is encoded in a digital audio format, and the different digital audio devices we use generally correspond to different audio file formats. Common digital audio formats are:
1. WAV format, a sound file format developed by Microsoft Corporation, also known as waveform sound files, is the earliest digital audio format, widely supported by the Windows platform and its applications. The WAV format supports many compression algorithms, supports multiple audio bits, sampling frequency and channel, uses 44.1kHz sampling frequency, and 16-bit quantized bits. Like CD, the storage space is too large for communication and propagation.
2. MIDI is the abbreviation of Musical Instrument Digital Interface, also known as musical instrument digital interface, is the unified international standard for digital music/electronic synthetic instruments. It defines the way computer music programs, digital synthesizers, and other electronic devices exchange music signals. It specifies the protocols for data transmission between cables and hardware and devices connected to electronic instruments from different manufacturers. It can simulate the sound of a variety of instruments. A MIDI file is a file in MIDI format, and some instructions are stored in the MIDI file. Send these commands to the sound card, and the sound card synthesizes the sound according to the instructions.
3. Everyone is familiar with the music format of CD, the extension CDA, its sampling frequency is 44.1kHz, 16-bit quantization digits, the same as WAV, but CD storage uses the form of audio track, also called " The Red Book format, which records waveform streams, is an almost lossless format.
4. MP3 full name is MPEG-1 Audio Layer 3, which was incorporated into the MPEG specification in 1992. MP3 can compress digital audio files with high sound quality and low sampling rate. In other words, audio files (mainly large files, such as WAV files) can compress files to a lesser extent with little loss of sound quality (the human ear can't detect this loss of sound quality at all).
5. MP3Pro was developed by Sweden's Coding Technology Company, which contains two major technologies: one is from the decoding technology unique to Coding Technology, and the other is from the MP3 patent holder France Thomson Multimedia and A decoding technique jointly studied by the Fraunhofer Integrated Circuit Association of Germany. MP3Pro can improve the sound quality of the original MP3 music without substantially changing the file size. It is able to maintain the sound quality before compression with maximum compression of audio files at a lower bit rate.
6. WMA (Windows Media Audio) is Microsoft's masterpiece in the field of Internet audio and video. The WMA format is designed to reduce data traffic but maintain sound quality for higher compression ratios. The compression ratio is typically 1:18. In addition, WMA can also prevent copying through DRM (Digital Rights Management) scheme, or limit the playing time and playback times, or even limit the playing machine, which can effectively prevent piracy.
7. MP4 is a kind of a2b music compression technology developed by AT&T, which is based on "perceptual coding". It is jointly released by American Network Technology Corporation (GMO) and RIAA. New music format. MP4 uses copyright-protected encoding technology in the file, which can only be played by specific users, effectively ensuring the legitimacy of music copyright. In addition, MP4 has a compression ratio of 1:15, which is smaller than MP3, but the sound quality has not decreased. However, because only certain users can play such files, their spread is far from MP3.
8. SACD (SA = SuperAudio) was officially released by Sony. Its sampling rate is 64 times that of the CD format, which is 2.8224MHz. The SACD playback frequency bandwidth is up to 100 kHz, which is 5 times that of the CD format. The 24-bit quantized bits are far more than the CD, and the details of the sound are more abundant and clear.
9. QuickTime is a digital streaming media launched by Apple in 1991. It is aimed at video editing, web site creation and media technology platforms. QuickTime supports almost all mainstream personal computing platforms and can provide real-time digitization via the Internet. Information flow, workflow and file playback. The existing versions are QuickTime 1.0, 2.0, 3.0, 4.0, and 5.0. In version 5.0, a number of new technologies such as players that support the highest A/V playback quality are also integrated.
10. VQF format is an audio compression technology jointly developed by YAMAHA and NTT. Its compression ratio can reach 1:18, so the file size of VQF after compression is 30% to 50% smaller than that of MP3 under the same conditions. It is more convenient for online communication, and the sound quality is excellent, close to CD sound quality (16-bit 44.1kHz stereo). However, VQF did not disclose technical standards and has not been popular yet.
11. DVD Audio is a new generation digital audio format that is the same size and capacity as DVD Video. It is a DVD format for music formats with sampling frequencies of “48kHz/96kHz/192kHz” and “44.1kHz/88.2kHz/176.4kHz”. Alternatively, the number of quantization bits can be 16, 20 or 24 bits, and they can be freely combined. The low sampling rate of 192 kHz and 176.4 kHz is dedicated to 2-channel replay, but it can be up to 6 channels. With 2-channel 192kHz/24b or 6-channel 96kHz/24b recording, it can accommodate more than 74 minutes of recording, with a dynamic range of 144dB, and the overall effect is outstanding.
Sony's MD (MiniDisc) is familiar to everyone. It is. The reason why MD can store stereo music of 44.1khz in 60-80 minutes in a small disk is because the ATRAC algorithm (adaptive acoustic conversion coding) is used to compress the sound source. This is a set of acoustic decoding system based on psychoacoustic principle, which can compress the audio of a CD record to about 1/5 of the original data volume without significant loss of sound quality. ATRAC utilizes the psychoacoustic characteristics of the human ear (spectral masking characteristics and temporal masking characteristics) and the limited resolution of the human ear to the amplitude, frequency and time of the signal. When encoding, the components that are not felt by the human ear are not encoded and are not transmitted. It is possible to reduce the storage of certain data amounts accordingly, thereby ensuring the sound quality and reducing the volume.
13. RealAudio is a file format introduced by Real Networks. The biggest feature is that it can transmit audio information in real time. Especially in the case of slow network speed, data can still be transmitted smoothly, so RealAudio mainly Suitable for online playback on the web. The current RealAudio file format mainly includes RA (RealAudio), RM (RealMedia, RealAudio G2), and RMX (RealAudio Secured). The commonality of these files is that the quality of the sound changes with the network bandwidth. Most people hear a smooth sound, so that a wider bandwidth listener gets better sound quality.
14. Liquid Audio is a website that offers paid music downloads. It provides copyright protection for music by using its own unique audio encoding format in music. Liquid Audio's audio format is called LQT. If you want to play music in this format on your PC, you must use one of the Liquid Player and Real Jukebox players. These files are also not convertible to MP3 and WAV formats, so this makes audio files in this format not shared and burned to CD. If you have to burn a Liquid Audio file to a CD, you must use a burning software and CD burner that supports this format.
15. Audible has four different formats: Audible 1, 2, 3, 4. The Audible.com website mainly sells audio books on the Internet and protects the goods and files they sell through one of four Audible.com proprietary audio formats. Each format primarily considers the audio source and the device being listened to. Formats 1, 2, and 3 use different levels of speech compression, while Format 4 uses a lower sampling rate and the same decoding method of MP3, resulting in clearer speech utterances and more efficient downloading from the Internet. Audible uses their own desktop player, which is the Audible Manager, which allows you to play Audible files stored on your PC or transferred to a portable player.
16. VOC files, which are often encountered in DOS programs and games, are digital sound files generated with Sound Blaster cards. They are similar in structure to WAV files and can be easily converted to each other through some tool software.
17. AU files, which are mainly used for multimedia sounds on the Internet. The AU file is a digital sound file under the UNIX operating system. Since the Web server on the Internet was mainly based on UNIX, this file became the only standard sound file used on the WWW.
18. AIFF (.AIF) is a sound file format developed by Apple that is supported by the Macintosh platform and applications.
19. Amiga Sound (.SVX): The sound file format developed by Commodore, supported by the Amiga platform and applications, does not support compression.
20. MAC Sound (.snd): A sound file format developed by Apple Computer Corporation that is supported by the Macintosh platform and a variety of Macintosh applications to support some compression.
21.S48 (stereo, 48kHz) uses MPEG-1 layer 1, MPEG-1 layer 2 (referred to as Mp1, Mp2) sound compression format, because it is easy to edit, cut, so it is widely used in radio stations.
22. AAC is actually an abbreviation for Advanced Audio Coding. AAC is an audio format jointly developed by Fraunhofer IIS-A, Dolby and AT&T, which is part of the MPEG-2 specification. The algorithm used by AAC is different from the MP3 algorithm. AAC combines other functions to improve coding efficiency. AAC's audio algorithms far surpass the previous compression algorithms (such as MP3, etc.) in compression capabilities. It also supports up to 48 tracks, 15 low frequency tracks, more sample rate and bit rate, multi-language compatibility, and higher decoding efficiency. In short, AAC can provide better sound quality than 30% smaller than MP3 files.
23. Digital audio has become the mainstream with excellent sound quality, no loss of transmission, and a variety of editing and conversion, and is applied to all aspects. //This article from the computer software and hardware application network www.45it.com reproduced please specify
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