Formats: what is digital sound Part 2
Historically, digital sound was undoubtedly the initiative of company engineers who adopted Philips-developed Audio-CDs, also called CDDA – Compact Disk Digital Audio.
As a result, digital audio media led to a massive transition in recording studios to digital DAT tape recorders and digital editing equipment with S / PDIF and other interfaces. And then digital sound began to penetrate deeper into our lives from CD players, and as it was transmitted via S / PDIF, it became digital switches, equalizers, and noise reduction systems. Today this series ends with Dolby Digital surround sound processors.
Who needs it
CDDA’s sound quality is satisfactory for most end users, ie listeners, but the amount of data required to present sound in this way is critical. As a result, several compressed digital audio formats appear, one of which is the old MS ADPCM, and among which are quite acceptable Sony ATRAC, PASC or Fraunhoffer MP3. Each of the encoding methods has an important characteristic – the bit rate, with which the compressed information enters the decoder when the audio signal is restored.
For example, when you talk on a cell phone, the sound of your voices is digitally converted and compressed, degrading its performance. Various algorithms compress speech hundreds of times, preserving the basic characteristics.
Let’s move on to specific audio file formats and audio compression formats. The most common format today is, of course, MP3. However, historically, to understand the evolution of sound formats, it is necessary to start with a different type of file, with the extension .WAV.
Variety of formats
Wav
It is the primary format for many, many digital audio playback systems and is used as a standard audio file format on personal computers. In addition, it has a strong set of specifications, which has grown considerably lately. Its full name is Microsoft RIFF / WAVE – Resource Interchange File Format / Wave – Resource Interchange File Format / Waveform, and it was created by Microsoft and Intel engineers. In turn, WAV is short for Waveform Audio File Format.
Apple AIFF
This type of file is standard for Apple Macintosh systems and sound processing systems based on it. Apple AIFF stands for Audio Interchange File Format: an audio interchange file format, it is somewhat similar to WAV. Its peculiarity is that it allows additional information to be placed next to the sound wave, in particular WaveTable samples (examples of the instrument sound together with synthesizer parameters), which improves the quality of the final result. Although today Apple computers are capable of playing files in almost any format, including MP3.
RAW
Yes, this is not just the image format in which some digital cameras take pictures. In fact, RAW is the call. “Pure Digitization”, which does not contain a title and only contains a sequence of samples of a sound wave. Typically, the scan is stored in 16-bit format.
MP3
The most popular compression format today is MP3. The MP3 (MPEG Layer 3) format was developed, after several intermediate formats, by the Fraunhofer Institute in Germany. Actually, the .MP3 format is based on fooling the human ear. After some research, it turned out that human hearing tends to adapt to the appearance of new sounds, which is expressed in an increase in the hearing threshold. Therefore, some sounds are capable of masking (that is, making them subjectively inaudible) others. So in this format, some of the sounds that, according to the corresponding theory, are made inaudible, are simply removed from the general sound. The resulting “semi-finished product” is then encoded using the Hoffman method. Be sure to note that in MP3 format, programs that compress the sound of the original are not standardized, that is, each competent programmer can implement their own compression scheme. And only decoders meet the standards, which leads to the fact that the quality of MP3 playback does not always depend on the player that plays this file. Due to the different skills and predilections of implementers of various encoders, some of them are better at handling symphonic music, some with rock and metal, some with rap and rave, etc.
