Digital audio formats or how sound is stored on a computer


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Digital audio formats or how sound is stored on a computer

Digital Audio Formats

Today there are about three dozen common digital audio formats. Why you need to create so many types of sound files to store one type of content and how to manage all this, you will learn from this material.

Audio format developments | Digital audio | How to Create Digital Media  Infographics Using ConceptDraw PRO | Audio Infographic

Surely many users prefer to use their home computer not only as a workhorse, but also as a multimedia center, where they can watch movies or family photos, as well as listen to their favorite music. Although compact digital players or mobile phones are certainly more suitable for listening to musical compositions, but unlike them, a computer can not only play music.

No matter how big the built-in memory of your music player is, it will most likely be difficult to store your entire music library on it. Plus, you can create, edit, organize, and search for music with your PC. Also, don’t forget that there are around three dozen common digital audio formats today, and most players are far from omnivorous and can only play a few of them.

So why do you need to create so many music formats to store one type of content? The fact is that, in the vast majority of cases, the sound is stored in “compressed” form, since one minute of uncompressed composition occupies about 10 MB on the hard disk. On the one hand, this seems not to be much, but on the other, if you are a music lover and your collection consists of several hundred or even thousands of songs, then it is clear that the sound must be compressed to reduce the space it occupies in electronic media.

Various special algorithms are used to compress music files, which subsequently determine the structure and presentation of the audio data, or so-called digital audio file formats. All audio formats can be divided into three groups: uncompressed audio formats, lossless compression, and lossy compression.

No compression
One of the most widespread formats related to this type is the well-known WAV. The sound of files with this extension is stored without compression or changes. It is true that much more space is required to store uncompressed files and therefore WAV is more widely used only in professional audio and video applications, where the sound should not have a loss of quality before processing. Keeping ordinary musical compositions in this form is unwarranted waste.

To play WAV files, you do not need any special software, as all media players understand this format, including the standard Windows Media audio player built into the Windows system.

Another format used to store uncompressed audio that is worth mentioning is Apple’s development called AIFF (Audio Interchange File Format). As you may have guessed, it is most commonly used on Macintosh computers running Mac OS X.

Lossless compression (lossless)
Lossless compression algorithms for audio files work on the principle of conventional file cabinets. They do not provide the highest level of compression (40 to 60%), while they have virtually no effect on sound quality. It is also worth noting that in this case, the encrypted data can be fully restored to its original form. Therefore, the use of lossless compression is most often used when it is important to keep the compressed data identical to the original.

The most popular audio formats in this group are FLAC (Free Lossless Audio Codec), APE (Monkey’s Audio), WMA (Windows Media Lossless), and ALAC (Apple Lossless Audio Codec). Each has its own pros and cons. For example, the APE codec offers slightly better compression gains, while FLAC is more common. In general, all true music lovers store their music collections in lossless formats, as they do not remove any data from the audio stream and the files created with these codecs can be listened to even on high-quality stereos.

To play lossless compressed formats, as a rule, third-party players (except WMA) are used, such as MPlayer, foobar, AIMP, Winamp, VLC and others, since all the necessary codecs are already built into them. Another option is to separately install an additional codec pack (for example, K-Lite), after which you can listen to files in lossless format from almost any audio player.

Lossy compression
This is the most popular group of algorithms that provides the maximum audio compression ratio (up to 10 times or more). However, unlike previous formats, the audio file loses quality here, and how much depends


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Varieties of digital audio formats.

Varieties of digital audio formats.

Audio Formats

There are several concepts of audio format.

Audio Format

The audio data presentation format in digital form depends on the quantization method of a digital-to-analog converter (DAC). The sound equipment at the present time the most common two types of quantization:

Pulse – code modulation
sigma – delta – modulation
Often bit quantization and frequency sampling point for various audio devices that record and play back as digital audio presentation format (24-bit / 192 kHz, 16-bit / 48 kHz).

The file format determines the structure and presentation of the audio characteristics of the data when stored on a PC storage device. To eliminate redundancy of audio data using audio codecs, with the help of which compression of audio data is carried out. There are three groups of audio file formats:

uncompressed audio formats, such as WAV, AIFF
lossless compressed audio formats (APE, FLAC)
audio formats, with the use of lossy compression (mp3, ogg)
There are only modular music format files. By synthetically or sampled pre-recorded live instruments, they are, in the main, used for the creation of modern electronic music (MOD). Also here the format of MIDI can be attributed, which is not a sound recording, but in this with the help of a sequencer it allows to record and play music, using a specific set of commands in the form of text.

Sound digital media formats are used as that of mass-propagated sound recordings (the CD, the SACD), so and in a professional recording (the DAT, MiniDisc).

For surround sound systems and you can select sound formats, in a multi-channel accompaniment largely without sound for movies. Such systems have a set family of two large formats that compete the companies of the Digital Theater then Systems Inc. – DTS and Dolby Laboratories Inc. – Dolby Digital.

Also called format the number of channels in multi-channel sound systems (5. 1; 7. 1). Initially, this system was designed for the cinema, but later it was extended to home theater systems.

What formats are used to represent digital audio?

What formats are used to represent digital audio?

Audio Formats

The format is used in two different ways.

Digital Audio Formats

When using a specialized medium or recording method and special read / write devices, the concept of format includes both physical characteristics of a sound carrier: the dimensions of a cassette with a magnetic tape or disk, the tape itself, or a disc, recording method, signal parameters, encoding and error protection principles, etc. .P. When using a universal information medium of wide application, for example, a flexible computer or a hard disk, the format is understood only as a method of encoding a digital signal, the peculiarities of the arrangement of bits and words and the structure of service information; all the “low-level” part directly related to working with the media, in this case, remains under the control of the computer and its operating system.

Of the specialized digital audio formats and media, the following are the best known today:

CD (Compact Disc) is a 120mm or 90mm single sided optical laser read / write disc, containing a maximum of 74 minutes of stereo sound at 44.1 kHz sampling rate and 16 linear quantization bits. The system is offered by Sony and Philips and is called CD-DA (Compact Disc – Digital Audio). For error protection, Cross Interleaved Reed-Solomon code (CIRC) and Hamming code 8-14 modulation (Eight to Fourteen Modulation, EFM) are used. A distinction is made between stamped compact discs (CD) write-only (CD-R) and rewritable (CD-RW).
PCM decoder (PCM deck): a system for converting the digital audio signal into a pseudo-video signal compatible with popular video formats (NTSC, PAL / SECAM) and vice versa. PCM decoders are used in combination with home (VHS) or studio (S-VHS, Beta, U-Matic) VCRs, using them as read / write devices. The devices operate with 16-bit linear quantization at sample rates of 44.056 kHz (NTSC) and 44.1 kHz (PAL / SECAM) and can record a two- or four-channel digital signal. In fact, such a decoder is a modem (modulator-demodulator) for a video signal.
S-DAT (Fixed Head Digital Audio Tape – Fixed Head Digital Audio Tape) is a system similar to a conventional cassette recorder, in which recording and reading is performed by a block of thin film fixed heads in a 3.81 mm wide tape in a double-sided cassette with dimensions of 86 x 55.5 x 9.5 mm. It implements two- or four-channel 16-bit recording at 32, 44.1, and 48 kHz.
R-DAT (Rotating Head Digital Audio Tape) is a VCR-like system with cross-tilted rotating head recording. The most popular tape-based digital recording format, R-DAT systems are often referred to simply as DAT. The R-DAT uses a 73 x 54 x 10.5mm cassette, with a 3.81mm wide tape, and the cassette and tape system itself is very similar to a typical VCR. The basic belt speed is 8.15mm / s, the rotation speed of the main unit is 2000rpm. R-DAT operates with a two-channel signal (on some models, four channels) at sample rates of 44.1 and 48 kHz with 16-bit linear quantization and 32 kHz with 12-bit non-linear quantization. To guard against errors, a double Reed-Solomon code and modulation with an 8-10 code are used. Cassette capacity – 80. .240 minutes depending on speed and belt length. Domestic DAT recorders are usually equipped with a phonogram illegal copy protection system, which does not allow recording from the analog input at a frequency of 44.1 kHz, as well as direct digital copying in the presence of SCMS prohibition codes (Serial Code Managenent System). Studio tape recorders have no such restrictions.
DASH (Digital Audio Stationary Head) is a 6.3 and 12.7 mm wide magnetic tape recording system with fixed heads. Belt speed is 19.05, 38.1, 76.2 cm / sec. Implements 16-bit recording with sample rates of 44.056, 44.1 and 48 kHz from 2 to 48 channels.
ADAT (Alesis DAT) is a proprietary system for recording eight-channel audio on S-VHS videotape, developed by Alesis. It uses linear quantization of 16 bits at 48 kHz, the capacity of the cassette is up to 60 minutes per channel. ADAT tape recorders can be cascaded so that a 128-channel synchronous recording system can be assembled.

Digital audio file formats wav, mp3, aiff, ogg, flac, m4a

Digital audio file formats wav, mp3, aiff, ogg, flac, m4a

digital audio formats

The last five years gave a great boost to the development of portable and stationary audio systems, and with this support for a variety of digital audio formats.

DIGITAL AUDIO FORMATS

Small pocket devices have a large internal memory and fixed audio equipment has become even smarter and more demanding. That is why, now, we can not save space on the player and download songs that weigh between 15 and 30 MB each, but at home, listen to digital music in a quality equal to the sound of an analog vinyl.

Description of popular digital audio formats
However, the most widespread audio formats still have their pros and cons, and even in an urgent matter like digital audio, a “panacea” has not yet been found. Classic digital audio formats are divided into “compressed” and “uncompressed” streams, as well as “lossless” formats, which exclude loss of sound.

Description of digital audio formats Description of digital audio formats

Wav audio format
The waveform audio file format (WAVE, WAV – “in waveform”) is a file format for storing a recording of an uncompressed digitized audio sequence. In general, this is the most common format for working in the studio and in broadcasting. allows you to get the most honest sound quality. For example, the standard audio CD format is an LPCM audio stream, with parameters: 2ch (stereo), 44-100Hz, 16bit.

Mp3 audio format
MPEG-1/2 Audio Layer 3: (MP3) is the most popular digital format for storing compressed audio. The MP3 format uses a special algorithm designed to greatly reduce the size of the original file. This format allows you to keep the audio close to the original sound, but thanks to a variety of settings, extremely small size.
Compared to the standard audio CD format, a file in MP3 format and a bit rate of 128 kbps will be approximately 1/11 the size of the original file.

FLAC audio format
FLAC (Free Lossless Audio Codec) is a popular free codec designed for lossless compression of audio data. What does that mean? Unlike lossy audio codecs such as MP3 or OGG, the FLAC audio codec does not remove any information from the audio stream. This format is ideal for audiophiles who create their own music collections and listen to music on high-quality equipment.

Ogg audio format
OGG is a format that has not gained great popularity, but is nonetheless used by a fairly large audience. The OGG format, similar to MP3, compresses audio with loss of quality, but is fundamentally different in practical conversions. This made it possible to get better quality with a smaller file size and to display this codec as absolutely independent. In addition to similar formats that convert lossy audio, OGG has the ability to adjust container properties.

Aiff audio format
The Audio Interchange File Format (AIFF) is a fairly universal audio file format developed by Apple, which is used to store audio data. Like its counterpart, the WAV format, it is uncompressed audio and is widely used in professional recordings and music production.
The .aiff and .aif files created by Apple Loops are used by GarageBand and Logic Audio music editors.

M4a audio format
Apple Losseles (also known as Apple Lossless Encoder, ALE or Apple Lossless Audio Codec, ALAC) (m4a) is another Apple development. This audio format refers to uncompressed audio, which provides lossless playback. It is a fairly specific format, which is mainly supported by products of the creator company, and in some cases, as in the iPhone system sounds, where it is possible to use exclusively the m4a format.

ABOUT DIGITAL AUDIO FORMATS

ABOUT DIGITAL AUDIO FORMATS

Digital Audio Formats

Today, there are several digital audio formats that are superior in quality to compact discs and are available on both physical media and the Internet. What are advanced sound lovers listening to now? Let’s find out.

Digital Audio Formats

The capabilities and quality of the CD-DA format were initially limited by the capabilities of CD as a medium. Legend has it that the standard 74-minute compact disc capacity was chosen in order to be able to record long classical pieces without splitting into two discs. And to be absolutely precise, this figure appeared thanks to Beethoven’s Ninth Symphony: it lasts exactly 74 minutes. Another default parameter was the 44.1 kHz sample rate. This figure defines the upper limit of the reproduced frequency range. For a CD that had to reproduce frequencies up to 20 kHz, this was the lowest possible carrier frequency. As a result, the only field of maneuver was the bit depth, the level of which was 16 bits. With regard to sound recording, bit depth determines its dynamic range and resolution.

The CD cannot be copied into the memory of the computer in the usual way, since we usually copy files. To save a CD-DA, you need a special program, a program that allows you to convert data recorded on an audio disc to PCM format (WAV file). A properly organized CD-DA ripping process allows you to get a completely identical digital copy on your hard drive. Audio CDs are generally saved on a computer as a large FLAC audio file (also WAV, WV, or APE) with a CUE index card or as separate tracks.

As the best digital audio format, the CD did not last that long, just over ten years. In the mid-nineties, the first format appeared that allows for better sound quality. HDCD was an improved version of CD-DA. Their difference consisted in a special recording algorithm that made it possible to save additional data on the sampling depth in a standard CD format. With an HDCD decoder, the output signal received not 16, but 20 bits, which did not give the standard of 96, but up to 120 dB of dynamic range and a very noticeable increase in recording resolution. At the same time, devices without an HDCD decoder played discs like normal CD-DAs. Interestingly, when saving such a disk on a PC in the same way,

The next leap in terms of sound quality came at the beginning of the new millennium. Two HD audio formats were introduced to the audiophile audience at once, appearing almost simultaneously. DVD-Audio, a further development of the traditional recording method and promoted by Panasonic and Toshiba. It is capable of recording 24-bit / 192 kHz in stereo mode and 24-bit / 96 kHz in multi-channel mode.

The SACD format competed with it, which, by the way, looked much less like a normal CD, although it was called “super CD”. Super Audio CD, developed by Sony, was based on the revolutionary DSD encoding algorithm. This digitizing method assumed one-bit sampling at an ultra-high frequency of 2.8224 MHz. The encoding and decoding principles of a DSD stream are much simpler than in high-bit formats and are essentially closer to the principles of analog technology. At the same time, the SACD format retains all the advantages of the advanced digital format and has output characteristics comparable to DVD-Audio in both sound quality and number of channels.

Both DVD-Audio and SACD were designed with a high level of copy protection, but inquisitive minds have already won over both formats, so if desired, the content of both disc types can be saved to a PC as images. ISO (without changing the structure and original codec) or FLAC tracks in 24-bit / 96 kHz or 24-bit / 192 kHz. Almost simultaneously with the DVD-Audio and SACD formats, another original format for publishing high-quality music was born: DAD 24/96. DAD stands for Digital Audio Disk, but it is essentially a DVD-Video with a high-quality still image and sound that can be played on any standard DVD player or PC.

Obviously, with this approach, Blu-ray media, with its HD sound formats, recorded in high quality without compression, is quite applicable for recording music in high quality. However, at the moment there are few such publications, and a special version of the BD-Audio format has every chance of not seeing the light of day, as the sale of high-quality audio material is already very active on the Internet. Anyone who does not want to convert DVD-Audio, DAD and SACD discs to the FLAC format on their own can officially buy albums already converted in 24-bit / 96 kHz or 24-bit / 192 kHz quality.