The extensions of sound files are: 1. WAV, which is a sound file format developed by Microsoft; 2. MIDI, which is a unified international standard for digital music/electronic synthesized instruments; 3. MP3, which can be High-quality, low-sampling rate compression of digital audio files; 4. MP4, using a2b music compression technology with "perceptual coding" as the key technology; 5. VQF, an audio compression technology jointly developed by YAMAHA and NTT; 6. OGG is a new audio compression format, similar to existing music formats such as MP3.
The operating environment of this tutorial: Windows 7 system, Dell G3 computer.
Sound file (audio file) is an important type of file in Internet multimedia. It is the original sound recorded through a sound recording device and directly records the binary sampling data of the real sound.
The general method of obtaining audio data is to use a fixed time interval to sample (quantize) the audio voltage, and convert the results to a certain resolution (for example: CDDA each sample is 16 bits or 2 bytes )storage. The sampling time interval can have different standards, such as CDDA using 44100 times per second; DVD using 48000 or 96000 times per second. Therefore, sample rate, resolution and number of channels (e.g. 2 channels for stereo) are key parameters of audio file formats.
What needs to be distinguished is that audio files and codecs are different. Although one audio file format can support multiple encodings, such as the AVI file format, most audio files only support one audio encoding.
There are two main types of audio file formats:
Lossless formats, such as WAV, FLAC, APE, ALAC, WavPack (WV)
Lossy formats, such as MP3, AAC, Ogg Vorbis, Opus
Lossy file formats are models based on acoustic psychology that are difficult or impossible for humans to hear except For example, a high-volume sound is followed by a low-volume sound. MP3 belongs to this category of files.
The compression ratio of lossless audio formats (such as FLAC) is about 2:1. There will be no data/quality loss during decompression. The data generated by decompression is exactly the same as the uncompressed data. If you need to maintain the original quality of your music, you should choose a lossless audio codec. For example, using the free FLAC lossless audio codec you can store the equivalent of 20 CDs of music on a DVD-R disc.
Lossy compression has many applications, but is not used much in professional fields. Lossy compression has a large compression ratio and provides relatively good sound quality.
Audio data format
1. WAV format
WAV format is developed by Microsoft Corporation A sound file format, also called a waveform sound file, is the earliest digital audio format and is widely supported by Windows platforms and their applications. The WAV format supports many compression algorithms, multiple audio bits, sampling frequencies and channels. It uses a sampling frequency of 44.1kHz and 16 quantization bits. Like CD, it requires too much storage space to facilitate communication and dissemination.
2. MIDI format
MIDI is the abbreviation of Musical Instrument Digital Interface, also known as musical instrument digital interface. It is a unified international standard for digital music/electronic synthetic instruments. It defines the way in which computer music programs, digital synthesizers and other electronic equipment exchange music signals. It stipulates the data transmission protocol between cables and hardware and equipment connecting electronic musical instruments and computers from different manufacturers, and can simulate the sounds of multiple musical instruments. MIDI files are files in MIDI format, and some instructions are stored in MIDI files. Send these instructions to the sound card, and the sound card will synthesize the sound according to the instructions.
3. CDA format
Everyone is familiar with the CD music format. The extension is CDA. Its sampling frequency is 44.1kHz and 16 quantization bits. It is the same as WAV, but CD storage uses the form of audio tracks, also called the "Red Book" format. It records a waveform stream, which is an approximately lossless format.
4. MP3 format
The full name of MP3 is MPEG-1 Audio Layer 3, which was merged 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 be compressed to a smaller level with very little sound quality loss (the human ear cannot detect this sound quality loss at all).
MP3, an ISO/IEC international standard, is the most popular digital audio coding and lossy compression format. Almost all terminals and software support this format.
5. MP3Pro format
MP3Pro was developed by the Swedish Coding Technology Company, which contains two major technologies: one is the unique decoding from Coding Technology Company Technology, the second is a decoding technology jointly researched by MP3 patent holder Thomson Multimedia Company of France and Fraunhofer Integrated Circuit Association of Germany. MP3Pro can improve the original MP3 music sound quality without basically changing the file size. It can compress audio files at a lower bit rate while maintaining the pre-compression sound quality to the greatest extent.
6. WMA format
WMA (Windows Media Audio) is Microsoft's masterpiece in the field of Internet audio and video. The WMA format achieves a higher compression rate by reducing data traffic but maintaining sound quality. Its compression rate can generally reach 1:18. In addition, WMA can also prevent copying through DRM (Digital Rights Management) solutions, or add restrictions on playback time and playback times, or even restrictions on playback machines, which can effectively prevent piracy.
7. MP4 format
MP4 uses a2b music compression technology developed by American Telephone and Telegraph Company (AT&T) with "perceptual coding" as the key technology. A new music format jointly announced by GMO and RIAA. MP4 uses copyright-protecting encoding technology in the file. Only specific users can play it, effectively ensuring the legality of music copyright. In addition, the compression ratio of MP4 reaches 1:15, which is smaller than MP3, but the sound quality is not degraded. However, because only specific users can play this file, its spread is far behind that of MP3.
8. SACD format
SACD (SA=SuperAudio) is officially released by Sony. Its sampling rate is 64 times that of the CD format, which is 2.8224MHz. The SACD playback frequency bandwidth reaches 100kHz, which is 5 times that of the CD format. The 24-bit quantization bit is far more than that of the CD, and the sound details are richer.
9. QuickTime
QuickTime is a digital streaming media launched by Apple in 1991. It is oriented to video editing, Web website creation and media technology platform, QuickTime It supports almost all mainstream personal computing platforms and can provide real-time digital information flow, workflow and file playback functions through the Internet. The existing versions are QuickTime 1.0, 2.0, 3.0, 4.0 and 5.0. Version 5.0 also incorporates many new technologies such as players that support the highest A/V playback quality.
10. VQF format
VQF format is an audio compression technology jointly developed by YAMAHA and NTT. Its compression rate can reach 1:18, so it is the same In this case, the compressed VQF file size is 30% to 50% smaller than MP3, which is more convenient for online transmission. At the same time, the sound quality is excellent, close to CD sound quality (16-bit 44.1kHz stereo). However, VQF has not disclosed technical standards and has not yet become popular.
11. DVD Audio format
DVD Audio is a new generation of digital audio format, with the same size and capacity as DVD Video. It is a music format DVD disc with a sampling frequency Selectable for "48kHz/96kHz/192kHz" and "44.1kHz/88.2kHz/176.4kHz", the number of quantization bits can be 16, 20 or 24 bits, and they can be freely combined. Although the low sampling rates of 192kHz and 176.4kHz are dedicated to 2-channel playback, they can be recorded into up to 6 channels. The sound recorded in 2-channel 192kHz/24b or 6-channel 96kHz/24b can accommodate more than 74 minutes of recording, with a dynamic range of 144dB, and the overall effect is outstanding
12, MD format
Everyone is familiar with Sony’s MD (MiniDisc). The reason why MD can store 60 to 80 minutes of stereo music sampled at 44.1khz on a small disk is because it uses the ATRAC algorithm (Adaptive Acoustic Transformation Coding) to compress the sound source. This is an audio decoding system based on psychoacoustic principles. It can compress the audio of CD records to about 1/5 of the original data volume without significant loss of sound quality. ATRAC utilizes the psychoacoustic characteristics of human hearing (spectral masking characteristics and temporal masking characteristics) and the human ear's limited ability to resolve signal amplitude, frequency, and time. When encoding, components that are insensible to the human ear are not encoded or transmitted, so that It is possible to correspondingly reduce the amount of data stored, thus ensuring sound quality and reducing the size.
13. RealAudio format
RealAudio is a file format launched by Real Networks. The biggest feature is that it can transmit audio information in real time, especially at high network speeds. Under slower conditions, data can still be transmitted relatively smoothly, so RealAudio is mainly suitable for online playback on the network. There are three main RealAudio file formats: RA (RealAudio), RM (RealMedia, RealAudio G2), and RMX (RealAudio Secured). The commonality of these files is that the sound quality changes with different network bandwidths, ensuring that most people Under the premise of hearing smooth sound, listeners with wider bandwidth can get better sound quality
14. VOC format
VOC files, in DOS programs and games This kind of file is often encountered. It is a digital sound file generated with the Sound Blaster card. It has a similar structure to a WAV file and can be easily converted to each other through some tool software.
15. AU format
AU file, which is mainly used for multimedia sounds on the Internet. AU files are digital sound files under the UNIX operating system. Since the early Web servers on the Internet were mainly based on UNIX, this kind of file became the only standard sound file used on the WWW.
16. AIFF format
AIFF (.AIF) is a sound file format developed by Apple and is supported by Macintosh platforms and applications.
17. SVX format
Amiga sound (.SVX): The sound file format developed by Commodore is supported by the Amiga platform and applications and does not support compression.
18, snd format
MAC Sound (.snd): A sound file format developed by Apple Computer Company. It is supported by the Macintosh platform and various Macintosh applications and supports certain compression.
19, S48 format
S48 (stereo, 48kHz) adopts MPEG-1 layer 1, MPEG-1 layer 2 (referred to as Mp1, Mp2) sound compression format, Because it is easy to edit and cut, it is widely used in radio stations.
20. AAC
AAC is actually the abbreviation of Advanced Audio Coding. AAC is an audio format jointly developed by Fraunhofer IIS-A, Dolby and AT&T. It is part of the MPEG-2 specification. The algorithm used by AAC is different from that of MP3. AAC improves encoding efficiency by combining other functions. AAC's audio algorithm far exceeds some previous compression algorithms (such as MP3, etc.) in terms of compression capabilities. It also supports up to 48 audio tracks, 15 low-frequency audio tracks, more sampling rates and bit rates, multiple language compatibility, and higher decoding efficiency. In short, AAC can provide better sound quality while reducing the size of MP3 files by 30%. h;b%
Digital audio has become mainstream due to its excellent sound quality, lossless transmission, and the ability to perform various editing and conversions, and is used in various aspects.
21. OGG format
OGG format is a commonly used audio format on the Internet. Usually software will use it
The full name of Ogg should be OGG Vorbis is a A new audio compression format, similar to existing music formats such as MP3. But one thing is different: it is completely free, open and patent-free. OGG Vorbis has a very outstanding feature, that is, it supports multi-channel. With its popularity, it will not be a dream to use a Walkman to listen to DTS-encoded multi-channel works in the future.
Vorbis is the name of this audio compression mechanism, and Ogg is the name of a project that intends to design a completely open multimedia system. Currently, only the OggVorbis part of the plan has been implemented.
The extension of Ogg Vorbis file is .OGG. The design format of this file is very advanced. OGG files created now can be played on any player in the future, so the file format can continue to improve in size and sound quality without affecting older encoders or players.
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